Classification of water heating schemes for hot water supply systems in buildings. DHW connection diagrams
Hot water heaters and heating heaters installed at consumer heating points need an annual audit and periodic repairs. At the end heating season heaters must be checked for tightness and, if a pressure drop is detected, remove the rolls and inspect the tube sheets.
The hot water heater in fig. 1 - 26 is connected to the heating network in parallel with the heating system, therefore this connection scheme is called parallel.
The hot water heater consists of a body and a tube bundle. In steam heaters upper part steam enters the housing, and condensate is removed from the lower part of the housing. The heated water passes through the pipes. In water-to-water heaters, network water enters the housing from one side and exits from the other. Toward the network water inside the tubes, water moves, going to the hot water supply system.
Hot water heaters can work with water pressure in cases and tubes up to 10 at (g), and heating - in cases 7 at and tubes 10 at.
The absence of a hot water heater greatly simplifies and reduces the cost of equipping the consumer's heating point. The consumer receives deaerated and softened water for tapping, which eliminates corrosion processes in hot water supply systems.
Autoregulation of hot water heaters according to the described scheme can only be operable with parallel and mixed switching schemes. This can be either a direct-acting regulator of the PP type, or an indirect-acting regulator with a relay device of the RD-Za or RDM type. Adjustment of regulators in two-stage schemes is described in ch.
Switching of hot water heaters from a sequential scheme to a mixed one occurs when the outdoor temperature rises, for example, for Moscow to 4 C.
When calculating hot water heaters, first of all, the permissible pressure loss in local water DYA is established.
For the manufacture of hot water heaters, brass tubes 16X0 75 mm are used. The ends of the tubes are rolled into tube sheets. The heater consists of separate sections, interconnected by branch pipes and coils. The number of sections and their diameter are selected depending on the heat consumption.
Currently, hot water heaters are manufactured without lens compensators. Heaters for heating with brass tubes must have lens compensators, since in them hotter network water passes inside brass tubes, which have a higher coefficient of linear expansion than a steel case.
Heating units and hot water heaters must be equipped with automatic regulators, metering and control devices.
In closed systems, hot water heaters are connected to the heating network mainly in parallel, mixed and sequential schemes, which are used both for dependent and independent connection of the heating system. The use of a particular scheme is determined by the ratio of the maximum load of hot water supply to calculated heating, applied in the region by the temperature schedule of the central regulation of heat supply, adopted in subscriber tego-consuming installations by the auto-regulation system.
When paying utility bills, many people are surprised to see the phrase “water heating” on the receipt. In fact, this innovation was adopted back in 2013. According to Government Decree No. 406, in the presence of a centralized water supply system, payment must be made at a two-component tariff.
Thus, the tariff was divided into two components: the use of cold water and heat energy. Now the calculation is made separately for two resources: water for hot water supply and thermal energy. That is why a column appeared in the receipts, which means the amount of thermal energy spent on heating cold water. However, many believe that heating fees are charged illegally, and they write complaints to housing and communal services. To verify the legitimacy of this type of accrual, you should learn more about this service.
The reason for this innovation was the additional use of energy. Risers and heated towel rails connected to the hot water supply system consume thermal energy, but this expense was not previously taken into account in the calculation of utility bills. Since payment for heat supply can only be charged in heating season, air heating due to the use of a heated towel rail was not paid as a utility service. The government found a way out of this situation by dividing the tariff into two components.
Equipment
If the water heater fails, the hot water bill will not increase. In this case, authorized employees of the managing organization are obliged to repair the equipment as a matter of urgency. But since the repair requires payment, this amount must still be paid by the tenants. While the heating bill will remain the same, there will be an increase in the repair and maintenance charges. This is because water heaters are part of the property of homeowners.
Concerning non-standard situations when, for example, part of the apartments in high-rise building has access to hot water, and the second - only to cold, questions regarding payment for heating are resolved on an individual basis. As practice shows, tenants are often required to pay a fee for common property which they do not use.
Component "thermal energy"
If everything is quite simple with the calculation of payment for cold water (it is carried out on the basis of an established tariff), then not everyone understands what is included in the cost of such a service as heating.
The amount for paying for such a service as water heating is calculated taking into account the following components:
- established tariff for thermal energy;
- expenses necessary for the maintenance of a centralized hot water supply system (from central heating points where water is heated);
- cost of thermal energy loss in pipelines;
- expenses necessary for the implementation of transportation hot water.
The calculation of payment for utility services for hot water supply is made taking into account the volume of water used, which is measured in m 3.
As a rule, the amount of required thermal energy is determined on the basis of the general house values, which are shown by hot water meters and consumed thermal energy. The amount of energy used in each room is calculated by multiplying the volume of water used (determined by the meter) by the specific heat energy consumption. The amount of energy is multiplied by the tariff. The resulting value is the amount needed to pay for what is written on the receipt as “water heating”.
How to calculate on your own in 2018-2019
Water heating is one of the most expensive utilities. This is due to the fact that during heating it is necessary to use special equipment operating from the mains. To make sure the receipt shows the correct amount due, you can do the calculations yourself and compare the amount received with the amount shown on the receipt. To do this, you need to find out the amount of payment for thermal energy, established by the regional tariff commission. Further calculations depend on the presence or absence of metering devices:
- If you have a meter installed in your apartment, then you can calculate the consumption of thermal energy, focusing on its indicator.
- If there is no meter, calculations should be made based on the established normative indicators(established by the energy-saving organization).
If there is a common heat energy consumption meter in a residential building and individual meters installed in apartments, the calculation of the amount for heating is calculated based on the readings general appliance accounting and further proportional distribution for each apartment. If such a device is not available, the amount required to pay for heating is calculated based on the standard energy consumption for heating 1 m 3 of water in reporting month and testimony individual counter water.
Where to file a complaint
If the legitimacy of the appearance of an additional line “water heating” in the receipts is in question, in order not to overpay for heating, it is recommended that you first contact the Criminal Code with a request to explain what this item means. The appearance of a new line in the receipt is legal only on the basis of the decision of the owner of the MKD premises. In the absence of such a decision, a complaint should be written to the GZhI. After filing a claim with the Criminal Code, you must provide a response with explanations within thirty days. In case of refusal to justify why such a service is prescribed in the receipt, a complaint should be filed with the prosecutor's office with a lawsuit in court. In this case, if you have already paid the amount indicated on the receipt, Article 395 of the Civil Code of the Russian Federation will serve as the basis for the claim. If a refund is not required, but you still have to pay for services that you are not getting, file a claim to exclude the "heating water" line. In this case, it is worth referring to Article 16 of the Law "On Protection of Consumer Rights".
In some cases, it is necessary to install storage tanks to equalize the load of hot water supply, and also, as a reserve, in case of a break in the supply of coolant. Reserve tanks are installed in hotels with restaurants, baths, laundries, for shower nets in production, etc. Therefore, a parallel circuit can be without a battery, with a lower storage tank and with an upper storage tank.
Parallel scheme for switching on a hot water heater
The scheme is used when Q max hot water / Q o ?1. The consumption of network water for subscriber input is determined by the sum of expenses for heating and hot water supply. The water consumption for heating is a constant value and is maintained by the flow regulator PP. The consumption of network water for hot water supply is a variable value. The constant temperature of the hot water at the outlet of the heater is maintained by the temperature controller RT, depending on its consumption.
The circuit has simple switching and one temperature controller. The heater and the heating network are calculated for the maximum DHW consumption. In this scheme, the heat of network water is used insufficiently rationally. The heat of return network water, which has a temperature of 40 - 60 ° C, is not used, although it allows covering a significant share of the DHW load, and therefore there is an overestimated consumption of network water for subscriber input.
Scheme with an upstream hot water heater
In this scheme, the heater is switched on in series with respect to the supply line of the heating network. The scheme is applied when Q max hot water / Q o< 0,2 и нагрузка ГВС мала.
Dignity of this scheme is the constant flow of the heat carrier to the heating point during the entire heating season, which is maintained by the flow regulator РР. It does hydraulic mode thermal network stable. Underheating of the premises during periods of maximum DHW load is compensated by the supply of network water elevated temperature into the heating system during periods of minimum water intake or in its absence at night. The use of the heat storage capacity of buildings virtually eliminates fluctuations in indoor air temperature. Such compensation for heat for heating is possible if the heating network operates according to an increased temperature schedule. When the heating network is regulated by heating schedule, there is underheating of the premises, so the scheme is recommended for use at very low DHW loads. This scheme also does not use the heat of the return network water.
With single-stage heating of hot water, a parallel circuit for switching on heaters is more often used.
Two-stage mixed hot water supply scheme
The estimated consumption of network water for hot water supply is somewhat reduced compared to a parallel single-stage scheme. The 1st stage heater is connected sequentially to the return line through the network water, and the 2nd stage heater is connected in parallel with respect to the heating system.
In the first stage, tap water is heated back network water after the heating system, which reduces the thermal performance of the second stage heater and reduces the consumption of network water to cover the load of hot water supply. The total flow of network water to the heating point is the sum of the flow of water to the heating system and the flow of network water to the second stage of the heater.
According to this scheme, public buildings with a large ventilation load of more than 15% are connected. heating load. Dignity scheme is an independent heat consumption for heating from the heat demand for hot water supply. At the same time, fluctuations in the consumption of network water at the subscriber input are observed, associated with uneven consumption of water for hot water supply, therefore, a flow regulator RR is installed, which maintains a constant flow of water in the heating system.
Two stage sequential circuit
The network water branches into two streams: one passes through the RR flow regulator, and the second through the second stage heater, then these streams are mixed and fed into the heating system.
At maximum temperature return water after heating 70?С and the average load of hot water supply, tap water is practically heated to the norm in the first stage, and the second stage is completely unloaded, because. the temperature controller RT closes the valve to the heater, and all the network water flows through the flow controller PP into the heating system, and the heating system receives heat more than the calculated value.
If the return water has a temperature after the heating system 30-40?С, for example, at a positive outside air temperature, then the heating of water in the first stage is not enough, and it is heated up in the second stage. Another feature of the scheme is the principle of coupled regulation. Its essence lies in setting the flow controller to maintain a constant flow of network water to the subscriber input as a whole, regardless of the load of hot water supply and the position of the temperature controller. If the load on the hot water supply increases, then the temperature controller opens and passes more network water or all the network water through the heater, while the water flow through the flow controller decreases, as a result, the temperature of the network water at the inlet to the elevator decreases, although the coolant flow remains constant. The heat that is not supplied during the period of high load of hot water supply is compensated during periods of low load, when the elevator receives a flow of increased temperature. There is no decrease in the air temperature in the rooms, because the heat storage capacity of building envelopes is used. This is called coupled regulation, which serves to equalize the daily uneven load of hot water supply. AT summer period when the heating is turned off, the heaters are switched on sequentially using a special jumper. This scheme is used in residential, public and industrial buildings with a load ratio Q max hot water / Q o ? 0.6. The choice of scheme depends on the schedule of central regulation of heat supply: increased or heating.
advantage sequential scheme compared to a two-stage mixed one is the alignment of the daily heat load schedule, best use coolant, which leads to a decrease in water consumption in the network. The return of network water with a low temperature improves the effect of district heating, because. steam extraction can be used to heat water reduced pressure. The reduction in network water consumption under this scheme is (per heating point) 40% compared to parallel and 25% compared to mixed water.
Flaw- inability to complete automatic regulation thermal point.
Two-stage mixed scheme with limitation of the maximum input water flow
It has been used and also makes it possible to use the heat storage capacity of buildings. In contrast to the conventional mixed circuit, the flow regulator is installed not before the heating system, but at the inlet to the point of supply water withdrawal to the second stage of the heater.
It maintains the flow rate below the set value. With an increase in water intake, the RT temperature controller will open, increasing the flow of network water through the second stage of the hot water heater, while reducing the flow of network water for heating, which makes this scheme equivalent to a sequential circuit in terms of the estimated flow of network water. But the second stage heater is connected in parallel, so maintaining a constant water flow in the heating system is provided by a circulation pump (an elevator cannot be used), and the pressure regulator RD will maintain a constant flow of mixed water in the heating system.
Open heating networks
Schemes for connecting DHW systems are much simpler. Economical and reliable operation of DHW systems can only be ensured with the availability and reliable operation water temperature controller. Heating installations are connected to the heating network according to the same schemes as in closed systems.
a) Scheme with a thermostat (typical)
Water from the supply and return pipelines is mixed in the thermostat. The pressure behind the thermostat is close to the pressure in the return pipeline, so the DHW circulation line is connected after the water withdrawal point after throttle washer. The washer diameter is selected based on the creation of resistance corresponding to the pressure drop in the hot water supply system. Max Flow water in the supply pipeline, which determines the estimated flow rate for the subscriber input, takes place at the maximum load of DHW and minimum temperature water in the heating network, i.e. in a mode where the DHW load is entirely provided from the supply pipeline.
b) Combined scheme with water intake from the return line
The scheme was proposed and implemented in Volgograd. Used to reduce fluctuations variable flow water in the network and pressure fluctuations. The heater is connected to the supply line in series.
Water for hot water supply is taken from the return line and, if necessary, is heated in the heater. At the same time, the adverse effect of water intake from the heating network on the operation of heating systems is minimized, and the decrease in the temperature of the water entering the heating system must be compensated by an increase in the temperature of the water in the supply pipeline of the heating network in relation to the heating schedule. Applies to load ratio? cf \u003d Q cf hot water /Q o\u003e 0.3
c) Combined circuit with water withdrawal from the supply line
With insufficient power of the water supply source at the boiler house and to reduce the temperature of the return water returned to the station, this scheme is used. When the return water temperature after the heating system is approximately equal to 70?С, there is no water intake from the supply line, hot water supply is provided tap water. This scheme is used in the city of Yekaterinburg. According to them, the scheme makes it possible to reduce the amount of water treatment by 35 - 40% and reduce the consumption of electricity for pumping the coolant by 20%. The cost of such a heat point is more than with the scheme a), but less than for closed system. This loses the main advantage. open systems– protection of hot water supply systems from internal corrosion.
The addition of tap water will cause corrosion, therefore the circulation line of the DHW system must not be connected to the return pipe of the heating network. With significant water withdrawals from the supply pipeline, the consumption of network water entering the heating system is reduced, which can lead to underheating of individual rooms. It doesn't happen in the schema. b) which is its advantage.
Connection of two types of load in open systems
Connection of two types of load according to the principle unrelated regulation shown in figure A).
In the scheme unrelated regulation(Fig. A) heating and hot water installations operate independently of each other. The consumption of network water in the heating system is maintained constant by means of the flow regulator PP and does not depend on the load of hot water supply. The consumption of water for hot water supply varies in a very wide range from the maximum value during the hours of the highest drawdown to zero during the period when there is no drawdown. The temperature regulator RT regulates the ratio of water flow from the supply and return lines, maintaining a constant temperature of the water for hot water supply. The total consumption of network water for the heating point is equal to the sum water consumption for heating and hot water supply. The maximum consumption of network water occurs during periods of maximum drawdown and at a minimum water temperature in the supply line. In this scheme, there is an overestimated flow of water from the supply line, which leads to an increase in the diameters of the heating network, an increase in initial costs and increases the cost of heat transport. Estimated consumption can be reduced by installing hot water accumulators, but this complicates and increases the cost of equipment for subscriber inputs. In residential buildings, batteries are usually not installed.
In the scheme related regulation(Fig. B) the flow regulator is installed before connecting the hot water supply system and maintains a constant total water flow for the subscriber input as a whole. During the hours of maximum water intake, the supply of network water for heating is reduced, and, consequently, the heat consumption. To prevent hydraulic misalignment of the heating system, the elevator jumper is turned on. centrifugal pump, maintaining a constant flow of water in the heating system. The undelivered heat for heating is compensated during the hours of minimum drawdown, when most of network water is sent to the heating system. In this scheme building construction buildings are used as a heat accumulator, leveling the heat load curve.
With an increased hydraulic load of hot water supply, most subscribers, which is typical for new residential areas, often refuse to install flow controllers at subscriber inputs, limiting themselves only to installing a temperature controller in the hot water supply connection unit. The role of flow regulators is performed by constant hydraulic resistances (washers) installed at the heating point during the initial adjustment. These constant resistances are calculated in such a way as to obtain the same law of change in the consumption of network water for all subscribers when the load of hot water supply changes.
There are three main schemes for connecting heat exchangers: parallel, mixed, serial. The decision to apply this or that scheme is made by the design organization on the basis of the requirements of SNiP and the supplier of heat coming from their energy capacities. In the diagrams, the arrows show the passage of heating and heated water. In the operating mode, the valves located in the jumpers of the heat exchangers must be closed.
1. Parallel circuit
2. Mixed scheme
3. Sequential (universal) circuit
When the DHW load significantly exceeds the heating load, hot water heaters are installed on heating point according to the so-called one-step parallel circuit, at which the hot water heater is connected to the heating network in parallel with the heating system. The constancy of the temperature of tap water in the hot water supply system at the level of 55-60 ºС is maintained by the RPD direct-acting temperature controller, which affects the flow of heating network water through the heater. When connected in parallel, the consumption of network water is equal to the sum of its costs for heating and hot water supply.
In mixed two-stage scheme the first stage of the DHW heater is connected in series with the heating system on the return line of the heating water, and the second stage is connected to the heating network in parallel with the heating system. At the same time, tap water is preheated by cooling the network water after the heating system, which reduces heat load second stage and reduces the total consumption of network water for hot water supply.
In a two-stage sequential (universal) scheme, both stages of the DHW heater are connected in series with the heating system: the first stage - after the heating system, the second - before the heating system. The flow regulator, installed in parallel with the second stage of the heater, maintains a constant total flow of network water to the subscriber input, regardless of the flow of network water to the second stage of the heater. During hours of maximum DHW loads all or most of the network water passes through the second stage of the heater, is cooled in it and enters the heating system with a temperature below the required one. In this case, the heating system receives less heat. This undersupply of heat to the heating system is compensated during the hours of low loads of hot water supply, when the temperature of the network water entering the heating system is higher than required at this outdoor temperature. In a two-stage sequential scheme, the total consumption of network water is less than in mixed scheme, due to the fact that it uses not only the heat of network water after the heating system, but also the heat storage capacity of buildings. Reducing network water costs helps to reduce unit cost external heating networks.
The scheme for connecting hot water heaters in closed heat supply systems is selected depending on the ratio of the maximum heat flow to hot water supply Qh max and the maximum heat flow to heating Qo max:
| 0,2 ≥ | Qhmax | ≥ 1 - one-stage scheme |
| Qomax |
| 0,2 < | Qhmax | < 1 - two-stage scheme |
| Qo ma |
Two DHW schemes for a country private house - which one to choose?
What needs to be done so that hot water flows immediately after opening the tap?
Depending on the method of heating water hot water supply systems (DHW) for private country house subdivided into:
- DHW with instantaneous water heater.
- DHW with a storage water heater (boiler).
Hot water supply scheme with instantaneous water heater
As an instantaneous water heater, you can use:
- geyser hot water supply;
- heating circuit DHW double-circuit heating boiler;
- electric water heater.
- plate heat exchanger connected to the heating circuit.
Flow water heater starts to heat the water at the moment the water is being parsed when the hot water faucet is opened.
All the energy spent on heating is transferred from the heater to the water almost instantly, for very a short time movement of water through the heater. In order to obtain water of the required temperature in a short period of time, the design of an instantaneous water heater provides for limiting the flow rate of water. The water temperature at the outlet of the instantaneous heater is very dependent on the water flow — the amount of hot water flowing from the faucet.
For a normal supply hot water only one horn in the shower, the power of the instantaneous water heater must be at least 10 kW. You can fill the bathroom in a reasonable time from a heater with a capacity of more than 18 kW. And if, when filling the bath or operating the shower, you also open the hot water tap in the kitchen, then for comfortable use of hot water, you will need an instantaneous heater power of at least 28 kW.
For heating an economy class house, a boiler of lower power is usually sufficient. So, power double-circuit boiler choose based on hot water demand.
The DHW scheme with an instantaneous water heater cannot provide comfortable and economical use of hot water in the house for the following reasons:
- With low hot water consumption The instantaneous water heater does not turn on at all and does not heat the water. To obtain water of the required temperature, it is often necessary to spend more water than necessary.
- Each time the tap is opened, the instantaneous water heater restarts. Constantly turning on and off reduces the resource of its work. Each time hot water appears with a delay, only after the heating mode has stabilized. Frequent heater restart reduces efficiency and increases energy consumption. Part of the water goes uselessly down the drain.
- It is impossible to recirculate the water in the house wiring pipes. Hot water from the tap appears with some delay. The waiting time increases as the length of the pipes from the water heater to the point of water analysis increases. Part of the water at the very beginning has to be uselessly drained into the sewer. Moreover, this is water that has already been heated, but managed to cool down in the pipes.
- Scale deposits build up quickly on a small surface inside the heating chamber of an instantaneous water heater. Hard water will require frequent descaling.
The temperature and pressure of water in the pipes are very dependent on the amount of water flow. For this reason when another tap is opened, the water temperature and pressure in the DHW system change very much. It is not very comfortable to use water even in two places at the same time.
Ultimately, the use of an instantaneous water heater in the DHW system leads to an unreasonable increase in water consumption and volume of sewage, to an increase in energy consumption for heating, as well as to insufficiently comfortable use of hot water in the house.
A DHW system with an instantaneous water heater is used, despite its shortcomings, due to relatively low cost and small size of equipment.
The system works better if install a separate individual instantaneous water heater near each point of water analysis.
In this case, it is convenient to install electric flow heaters. However, such heaters during the analysis of water at the same time in several places can consume significant power from the mains (up to 20 - 30 kW). Usually, the power grid of a private house is not designed for this, and the cost of electricity is high.
How to choose an instantaneous water heater
The main parameter for choosing an instantaneous water heater is the amount of water flow that it can heat.
- from the tap of a sink or washbasin 4.2 l/min (0,07 l/s);
- from a bathtub or shower faucet 9 l/min (0,15 l/s).
For example.
Three points of analysis are connected to one instantaneous water heater - a sink in the kitchen, a washbasin and a bath (shower). To fill only the bath, you must select a heater that is capable of delivering at least 9 l/min. water with a temperature of 55 about C. Such a water heater will also ensure the use of hot water simultaneously from two taps - in the sink and washbasin.
Using hot water at the same time in the shower and washbasin will be comfortable if the heater performance is already at least 9 l/min+4,2 l/min=13,2 l/min
Manufacturers in technical specifications usually indicate maximum performance instantaneous water heater, based on water heating for a certain temperature difference, dT, e.g. 25 about C, 35 about C or 45 about C. This means that if the temperature of the water in the water supply is +10 about C, then at maximum performance water will flow from the tap with a temperature of +35 about C, 45 about C or +55 about C.
Be careful. Some sellers in advertising indicate the maximum performance of the device, but "forget" to write for what temperature difference it is determined. You can buy a geyser with a capacity of 10 l/min., but it turns out that at this flow rate it will only heat the water by 25 about C., i.e. up to 35 about C. Using hot water with such a column may not be very comfortable.
Suitable for our example geyser or double-circuit boiler with a maximum capacity of at least 13.2 l/min at d T=45 about C. The power of the gas apparatus with these hot water parameters will be about 32 kW.
When choosing an instantaneous water heater, pay attention to one more parameter - minimum performance, consumption l/min at which the heating is turned on.
If the water flow in the pipe is less than the value specified in the technical characteristics of the device, the water heater will not turn on. For this reason, often use more water than is necessary. Try to choose a device with the lowest possible minimum performance, for example, no more than 1.1 l/min.
Electric instantaneous water heaters designed for domestic use have a maximum heater power of about 5.5 - 6.5 kW. At maximum performance 3.1 - 3.7 l/min heat water by d T=25 about C. One such water heater is installed to service one water point - a shower, a washbasin or a sink.
DHW scheme with a storage heater (boiler) and water circulation
A storage water heater (boiler) is a heat-insulated metal tank of a rather large volume.
AT lower part most often, two heaters are built into the water heater tank at once - an electric heating element and a tubular heat exchanger connected to a heating boiler (). The water in the tank is heated most of the time by the boiler.
Electric heater turns on as needed, during the shutdown of the boiler. Such a boiler is often called indirect heating boiler.
Hot water in an indirect heating boiler is consumed from the top of the tank. In its place, cold water from the water supply immediately enters the lower part of the tank, is heated by a heat exchanger and rises.
In the European Union, hot water systems in new homes in without fail equipped with a solar heater - collector. To connect solar collector another heat exchanger is installed in the lower part of the indirect heating boiler.
DHW scheme with a layered heating boiler
AT recent times the hot water system with a layered heating boiler is gaining popularity, the water in which is heated by an instantaneous water heater. In such a boiler there is no heat exchanger, which reduces its cost.
Hot water is drawn from the top of the tank. In its place, cold water from the water supply immediately flows into the lower part of the tank. The pump pumps water from the tank through the flow heater, and is supplied immediately to the upper part of the tank. Thereby, hot water at the consumer appears very quickly- no need to wait until almost the entire volume of water warms up, as happens in an indirect heating boiler.
Rapid heating of the top layer of water, allows you to install a smaller boiler in the house, as well as reduce the power of the instantaneous heater, without sacrificing comfort.
The Galmet SG (S) Fusion 100 L layered heating boiler is connected to the DHW circuit of a double-circuit boiler or to a geyser. The boiler has a built-in three-speed circulation pump. Boiler height 90 cm, diameter 60 cm. Manufacturers produce double-circuit boilers with a built-in or remote layered heating boiler. As a result,the cost and dimensions of the equipment of the DHW system are somewhat less,than with an indirect heating boiler.
The water in the boiler is heated in advance, whether it is spent or not. The supply of hot water in the tank allows you to use hot water in the house for several hours.
Due to this, the water in the tank can be heated quite long time, gradually accumulating thermal energy in hot water. Hence another name for the boiler - accumulative water heater.
Long duration of water heating allows use a heater of relatively low power.
Accumulative gas water heater - boiler
Storage boilers, in which water is heated by a gas burner, are less popular in systems DHW private Houses. The device in the house of heating and hot water systems with two gas appliances - a gas boiler and a gas boiler, turns out to be much more expensive.
Cumulative gas water heater- boiler It can be beneficial to install gas boilers in apartments with central heating or in private houses with solid fuel boiler heating and water heating in the DHW system with liquefied gas.
Gas water heaters, as well as boilers, are produced with open cam combustion and with closed, with forced removal flue gases and with natural draft in the chimney.
On sale there are accumulative gas boilers, which does not require connection to the chimney. (Household gas stoves they also work without a chimney.) The power of gas burners of such devices is small.
Gas boilers up to 100 liters are designed for wall mounting. Large volume water heaters are installed on the floor.
Used in water heaters different ways ignition gas- with an on-duty wick, battery-powered electronic or hydrodynamic ignition.
In devices with standby wick a small flame burns constantly, which is first ignited by hand. Some amount of gas burns uselessly in this torch.
Electronic ignition Runs on mains power or batteries.
Hydrodynamic ignition It is started from the rotation of the impeller, which is driven by the flow of water when the tap is opened.
How to choose the volume of the storage water heater - boiler
The more volume storage water heater- the higher the comfort of using hot water in the house. But on the other hand, the larger the boiler, the more expensive it is, the higher the cost of its repair and maintenance, the more space it takes.
The size of the boiler is chosen based on the following considerations.
Increased comfort will be provided by a boiler, the volume of which is selected at the rate of 30 - 60 liters per user of water.
A high level of comfort will be provided by a water heater with a volume of 60-100 liters per person living in the house.
To fill the bath, you need to use almost all the water from a boiler with a volume of 80 - 100 liters.
How to choose the boiler power for a hot water boiler
When choosing a boiler, it is necessary to pay attention to the power of the heating element that is installed in it. For example, to heat 100 liters of water to a temperature of 55 about C in 15 minutes, a heater (heat exchanger for the boiler, built-in gas burner or heating element) with a capacity of about 20 kW.
Under real operating conditions, the temperature of the water in the boiler is equal to the temperature of the water in the water supply only when the heating is turned on for the first time. In the future, in the boiler there is almost always water already heated to a certain temperature. To heat water to the required temperature in a reasonable time, heating devices of lower power are used.
But still, it is better to check how long it will take to heat the water in the boiler. This can be done using the formula:
t = m cw (t2 – t1)/Q, wherein:
t– water heating time, seconds ( with);
m- the mass of water in the boiler, kg (the mass of water in kilograms is equal to the volume of the boiler in liters);
cw- specific heat capacity of water, equal to 4.2 kJ/(kg K);
t2- the temperature to which the water must be heated;
t1– initial water temperature in the boiler;
Q– boiler power, kW.
Example:
Water heating time by a boiler with a capacity of 15 kW in a 200-liter boiler from a temperature of 10 °C(we assume that the water entering the boiler has this temperature) up to 50 °C will be:
200 x 4.2 x (50 – 10)/15 = 2240 with, that is, about 37 min.
DHW scheme with water recirculation in the system
The use of a storage water heater in the DHW system allows you to organize the recirculation of hot water in pipelines. All hot water taps are connected to a ring pipeline through which hot water is constantly circulating.
The length of the pipe section from each point of hot water consumption to the ring pipeline should not exceed 2 meters.
The circulation pump of the DHW hot water recirculation system is small in size and has low power Recirculation of water in the DHW system is provided by a circulation pump. The power of the pump is small, a few tens of watts.
DHW pumps, unlike heating pumps, must have a maximum operating pressure of at least 10 bar. Heating pumps are often designed for a maximum pressure of no more than 6 bar. Another difference is that the DHW pump must have a hygiene certificate that allows it to be used in drinking water systems.
Water in DHW systems is constantly updated and the oxygen content in it remains high enough. Corrosive activity of hot water is high. In addition, hot water must comply with sanitary requirements for drinking water. Therefore, for making DHW pumps use corrosion-resistant non-ferrous metals or stainless steel. For these reasons, DHW circulation pumps are noticeably more expensive than those for heating systems.
In some designs of DHW pipelines, it is possible to create a natural recirculation of water, without a pump.
As a result of the circulation of water in the DHW system hot water is supplied to the points of selection constantly.
In a DHW system with a storage heater and water recirculation, the water supply mode is more stable:
- Hot water is always present at the points of selection.
- Water sampling is possible simultaneously in several places. The temperature and pressure of water change slightly with a change in flow.
- From the tap, you can take any, arbitrarily small, amount of hot water.
The recirculation circuit allows not only to increase the comfort of water supply at remote points of the house, but also gives the ability to connect to it the contours of underfloor heating in separate rooms. For example, in the bathroom, a water-heated floor will be comfortable all year round.
A DHW system with water recirculation constantly consumes energy for the operation of the circulation pump, as well as to compensate for heat losses in the boiler itself and in pipes with circulating water. To reduce energy consumption, it is recommended to install a circulation pump with a built-in programmable timer that turns off water circulation during hours when it is not needed. The boiler and hot water pipes are insulated.
Disadvantages of a DHW system with a double-circuit gas boiler or water heater
Cycling a double-circuit boiler in heating mode
As you know, a double-circuit gas boiler can provide a house with hot water and be a source of heat in the heating system. Preparation of hot water is carried out in the flow heat exchanger of the boiler. Read about the general disadvantages of a DHW system with a flow heater at the beginning of this article. But gas appliances there is another problem with a flow heater - this is the difficulty of choosing the maximum power of a double-circuit boiler or a hot water geyser.
Most often it turns out that the required power of the boiler for preparing hot water is much greater than the power needed to heat all the rooms in the house.
As mentioned in the article above, in order to obtain hot water of the required temperature and its maximum consumption, double-circuit gas boilers and hot water geysers have a sufficiently large maximum power, about 24 kW . or more. Boilers and columns are equipped with automation, which can reduce their power to a minimum, equal to approximately 30% of the maximum, by modulating the burner flame. Minimum dual circuit power gas boiler or column is usually equal to about 8 kW. or more. This is the minimum power of the boiler, as in DHW mode and heating.
Gas burner of a double-circuit boiler or column due to design features cannot work stably with power less than the minimum (less than 8 kW.). At the same time, to work with the heating system of a private house or autonomous heating apartments, the boiler in heating mode should very often give out a power of less than 8 kW.
For example, power 8 kW. enough to provide heat to the premises of a house or apartment with an area of 80 - 110 m 2, and in the coldest five days of the heating season. During warmer periods, the performance of the boiler should be significantly less.
Due to the fact that the boiler cannot work with a power below the minimum, there are problems with the adaptation (coordination) of the double-circuit boiler and the heating system.
In small buildings, with low heat consumption for heating, the boiler produces more heat than the heating system can accept. As a result of inconsistency between the parameters of the boiler and the system, the double-circuit boiler starts to operate in a pulsed mode, "clock"- as people say.
Work in the "clocking" mode significantly reduces the service life of boiler parts, significantly reduces efficiency.
Clocking a gas boiler or column in DHW mode
Diagram of heating tap water by a double-circuit gas boiler or water heater depending on temperature ( T about C) and consumption ( Q l/min) hot water. The thick line shows the borders of the Working area. Gray zone, pos.1 - clock zone boiler or column (switching between ON/OFF). For normal water heating by a boiler or column, on the diagram, the point of intersection of the temperature and hot water flow lines (working point) must always be inside working area, the boundaries of which are shown in the diagram with a thick line. If the hot water consumption mode is selected so that the operating point will be in the gray zone, pos. 1 on the diagram, then the boiler, the column will clock. In this zone, with a small flow of water, the power of the boiler, column turns out to be excessive, the boiler, the column turns off from overheating, and then turns on again. From the tap comes either hot or cold water.
Low efficiency of double-circuit gas boilers and columns
Double-circuit gas boilers when working with maximum power have an efficiency of more than 93%, and less than 80% when operating at minimum power. Imagine how the efficiency will decrease even more if such a boiler has to operate in a pulsed mode, with constant re-ignition of the gas burner.
Please note that a double-circuit boiler operates at minimum power most of the time during the year. At least 1/4 of the consumed gas will literally fly uselessly into the pipe. Add to this the cost of replacing prematurely worn parts of the boiler. This will be a retribution for installing cheap equipment for heating and hot water in the house.
What do you want - choose
If the power of a double-circuit gas boiler is more than 20 kW., is selected based on the maximum heating required flow hot water, then the boiler cannot provide economical and comfortable operation in mode low power heating and when heating water with a small flow rate. The same can be said about the operation of the hot water column.
Most often, in the house there is no need to prepare large streams of hot water. For many people, it is much more important to provide comfortable and economical use of hot water at a low consumption.
For such economical hosts, many manufacturers produce double-circuit gas boilers and columns with a maximum power of about 12 kW. and the minimum is less than 4 kW. Such boilers, columns will provide more economical and comfortable heating and use of hot water in an amount sufficient for taking a shower or washing dishes.
Before buying a double-circuit boiler or column, the owners need to decide which mode of hot water consumption is more profitable and comfortable - with a large flow of water or with a small one. Based on this decision, choose the power of the boiler or column. If you want both, then you will have to choose a hot water system with a boiler.
For lovers of the shower, for preparing hot water and heating houses and apartments with a heated area of up to 140 m 2, with one bathroom capacity 12 kW. They are the best way meet the needs of heating and hot water systems of small private houses and apartments.
For those who like to take a bath, as well as for houses and apartments large sizes, with an area of more than 140 m 2, I strongly advise you to use a single-circuit boiler.
Many manufacturers heating equipment release special kits, a boiler plus a built-in or remote boiler, just for such cases. Such a set of equipment will cost more, but will provide an increased service life of the equipment, gas savings and more comfortable use of hot water.
Scheme of hot water supply with a heat recuperator of sewage effluents
AT Western Europe and popular in the world various ways energy savings in the operation of a private house.
Hot water from the house after use flows into the sewer and carries away with it a significant part of the thermal energy that was spent on its heating.
Scheme for the recovery of thermal energy from sewage effluents to the DHW system To reduce energy losses in the house, a heat recovery (return) scheme is used from sewer drains to the hot water supply system of a private house.
Cold water passes through a heat exchanger before entering the DHW boiler. Effluent from sanitary appliances is sent to the heat exchanger.
In the heat exchanger, two streams, cold water from the mains and hot water from the drains, meet but do not mix. Part of the heat from hot water is transferred to cold water. Preheated water enters the DHW boiler.
In the diagram shown in the figure, only those sanitary appliances that work with a hot water flow are directed to the heat exchanger. It is advantageous to use such a recovery scheme for any method of water heating - both with a boiler and with a flow heater.
In order to recover heat from the drains of sanitary appliances, which first accumulate hot water and then drain it into the sewer (bath, pool, washing and dishwasher), apply more complex scheme with water circulation between the boiler and the heat exchanger while these devices are emptying.
For houses and apartments with permanent residence highly recommend to use DHW system with a stratified heating boiler and a double-circuit boiler, or with an indirect heating boiler and single boiler. The volume of the boiler is not less than 100 liters. The system will provide good comfort of using hot water, economical consumption of gas and water, as well as a smaller amount of wastewater to the sewer. The only disadvantage of such a system is that high price equipment.
At limited budget construction in small country country houses for seasonal living you can install a DHW system with a flow heater.
It is advisable to use a hot water supply scheme with a flow heater in houses with a kitchen and one bathroom, where the heating source and hot water taps are located compactly, at a short distance from each other. It is recommended to connect no more than three water taps to one instantaneous water heater.
The cost of such a system is relatively low. and the shortcomings of operation in this case are less pronounced. A double-circuit gas boiler or gas water heater takes up little space. Almost all necessary equipment mounted in the body of the device. For installation of a boiler with a capacity of up to 30 kW or geyser does not require a separate room.
For the preparation of hot water and heating houses and apartments with a heated area up to 140 m 2, with one shower in the bathroom, I recommend installing double-circuit gas boilers with a maximum capacity 12 kW.
In a hot water system with a geyser or a double-circuit boiler the stability of the water supply mode will increase significantly if the scheme between the heater and the points of water analysis install buffer capacity - a conventional storage electric water heater. It is especially recommended to install such a buffer storage electric water heater near disassembly points remote from the gas appliance.
Read more: In a buffer tank scheme, hot water from a geyser or a double-circuit boiler first enters the tank of an electric boiler - water heater. Thus, the tank always contains a supply of hot water. The electric heater in the tank only compensates for heat losses and maintains the required temperature of hot water during the period when there is no water draw. An electric water heater with a tank of small capacity is enough - even 30 liters, and using hot water will become much more comfortable.
Domestic hot water system with instantaneous water heater and built into the boiler or a remote boiler of layered heating will be somewhat more expensive. But here it will not be necessary to spend expensive electricity to maintain the temperature of the water, and the comfort of using water will be the same as with an indirect heating boiler.
In houses with an extensive DHW networkimplement a scheme with a storage water heater (boiler) and water recirculation. Only such a scheme will provide necessary comfort and economical operation of the DHW system. True, the initial costs for its creation are the largest.
It is recommended to buy boilers that are sold complete with a boiler. In this case, the parameters of the boiler and boiler are already correctly selected by the manufacturer, and most of additional equipment built into the boiler body.
If the heating in the house is carried out by a solid fuel boiler, then it is advantageous to install, to which and connect the DHW system with water circulation.
Otherwise, for heating water in the house, attached to a solid fuel boilerindirect heating boiler, additionally equipped with an electric heater.
It is advantageous to use an electric hot water boiler in a house with a solid fuel boiler Often, only electricity is used to heat water in a house with a solid fuel boiler. For hot water in the house, near the points of water analysis, a storage electric boiler is installed - a water heater. The hot water circulation system is not made in this embodiment. Near remote points of water analysis, it is more profitable to install your own storage heater. In this case, electricity for heating water is spent more economically.
When water is heated above 54 about C hardness salts are released from the water. To reduce scale formation If possible, heat the water to a temperature lower than indicated.
Instantaneous water heaters are especially sensitive to scale formation. If the water is hard, contains more than 140 mg CaCO 3 in 1 liter, then use for heating water instantaneous water heaters, including with stratified heating boilers, is not recommended. Even small deposits of scale clog the channels in flow heater, which leads to the cessation of the flow of water through it.
It is recommended to supply water to the instantaneous water heater through an anti-scale filter, which reduces water hardness. The filter has a replaceable cartridge that will have to be changed regularly.
For heating hard water, it is better to choose a DHW storage system with an indirect heating boiler. Salt deposits on heating element boilers do not interfere with the flow of water, but only reduce the performance of the boiler. The boiler is easier to clean from scale.
It should be remembered that prolonged heating of water to a temperature of less than 60 ° C can lead to the appearance of storage tank(boiler) with hot water bacteria harmful to human health of the species Legionella. Recommended periodically perform thermal disinfection of the DHW system, raising the temperature of the water to 70 ° C for some time.