- Why it is worth abandoning urban hot water supply
- Why is this considered a savings
- Payback period
- So which water heater to choose
- Tips for placing the water heater
Today we will tell you how to abandon the city’s hot water supply system, while not only forgetting about weak water heating forever, but also doing it as economically as possible. This article will uncover some of the pitfalls of this transition and provide a real-world ROI calculation..
Why it is worth abandoning urban hot water supply
The city’s DHW system is known to many for its poor quality of service. Using it not only often costs a pretty penny, in many apartments the water is supplied subcooled to the established norms and its temperature practically does not rise above 40-50 ° C. To this must be added a few weeks of lack of hot water during the period of scheduled summer outages, when the owners are forced to heat water for domestic and sanitary needs literally by improvised methods.
There is an alternative: refuse to supply hot water to the apartment and heat it yourself using an electric or gas water heater. At the same time, interventions in the rough plumbing are minimal, most devices have the simplest piping scheme and can be installed even after finishing work is completed.
What needs to be done:
- Contact the ESP or housing and communal services with a request to disconnect from the city DHW system. If possible for the project of the house, obtain technical specifications.
- Install a water heater and tie it.
- Provide for the possibility of installing seals on each branch of each of the hot water risers. The best option is plugs with hinges for sealing.
- In the presence of the inspector, draw up an act of disconnection and the presence of a visible rupture of the pipeline.
Why is this considered a savings
The benefits of switching to self-sufficiency in hot water seem obvious when you consider that the cost of one cubic meter includes total heat losses throughout the system. For example, consider a special case for a small apartment in the Moscow region. As of July 2015, regional tariffs for utilities are as follows:
Type of service Tariff, rub. DHW, m3 120.82 HVS, m3 30.87 Drains 21.9 Electricity at one-rate tariff, kW 5.03 Electricity in three zones, kW for 1/2/3 zones 5.58 / 4.63 / 1.43 Natural gas, m3 6.04
A family of four consumes an average of 16 m per month3 hot water, that is, pays for city hot water supply 1933.12 rubles. per month. The cost of the water itself in the DHW tariff is 493.92 rubles, the remaining 1439.20 rubles. Is the cost of heating 16 m3 water up to 50 ° C, that is, 89 rubles. 95 kopecks. for 1 m3.
As you can see, water heating installations in the urban system are not very economical, because 17.9 kW of electricity is spent in them to heat one cubic meter at a one-rate tariff or 14.9 m3 natural gas.
But will home appliances be economical enough to pay for themselves in the foreseeable future? The family of 4 mentioned above needs about 500 liters of hot water per day. This task is within the power of a pressure-flow instantaneous water heater with a capacity of 6-6.5 kW or a storage heater for 120 liters with a buffer tank and a total power of heating elements up to 3 kW.
A good and reliable storage heater will cost about 10,000–20,000 rubles, and a flow heater will cost 15,000–30,000 rubles. The flow-through will be somewhat more difficult to install, since everything that has an electrical power of more than 3 kW must be connected with a separate cable with a conductor cross-section of 4 mm2 with the obligatory organization of protective grounding and shutdown, and this is an additional 3500 rubles. For a boiler, you only need a differential machine worth 1400 rubles. and a regular socket on a separate protective group.
As for the plumbing, it is the same for both devices. Since the water heater can be embedded in almost any point of hot and cold water pipelines, to connect it you will need a set of valves and 6-8 meters of pipe, which will cost another 3000 rubles. In total, the cost of an instantaneous water heater and its installation will amount to 35,500 rubles, and a storage water heater will cost 30,400 rubles..
An example of connecting a storage water heater: 1 – valve of incoming cold water; 2 – safety valve; 3 – drain valve; 4 – valve for air when draining water; 5 – storage water heater; 6 – differential machine; 7 – to the shield; 8 – water to consumers
A storage water heater with a volume of 120 liters and a capacity of 2 kW spends 2 hours to heat water up to 50 degrees. For heating 1 m3 he needs 1000/120 x 2 x 2 = 33.33 kWh. That is, for self-sufficiency, it is necessary that the average cost of electricity for the operation of the water heater is less than 2.70 rubles.
A flow-through heater with a throughput of 3 l / min per hour will heat 180 liters of water, spending 8 kWh for this. That is, its power consumption is about 30% higher. It can be argued that a storage water heater consumes energy not only for direct heating, but also for maintaining the temperature, however, these are short-term switches and such a correction can be neglected.
In fact, only gas water heaters are economical in this respect, and they are cheaper than electric ones. With a power of 24 kW and a flow of 14 l / min, the column will warm up a cubic meter of water to 70–80 ° C in about 70 minutes, spending less than three cubic meters of gas.
So which water heater to choose
If it is possible to install a gas heater in the apartment project, this is exactly what you need to do. Even half a thousand rubles a month for hot water supply is not money, while the water is of a stable temperature, under good pressure and in full. No electric heater is capable of this..
If the house is not gasified, which happens more and more often in modern construction, the use of electric water heaters cannot be avoided. Yes, on the face of a small overpayment, but how much more comfortable life becomes! Moreover, you can not spend money on an expensive heater, but install a cheaper one.
The highest water consumption is observed in the evening and at night, when the electricity tariff is 4.63 and 1.43 rubles. for 1 kW. The average daily cost of a kilowatt for hot water supply is about 1.8 rubles. And at such a cost, the price of electric hot water supply is quite comparable to that of the city. At least hot water doesn’t cost more, and the whole system is reliable and durable. The most economical in this case are storage water heaters of large volume, connected through a contactor with a timer for operation only in the night and half-peak daily zones. Their payback period is usually about 3 years, flow-through ones will pay off in 5-7 years. If the water is supplied to the house subcooled, then the payback period will be significantly reduced, because the consumption of hot water will significantly decrease.
Tips for placing the water heater
Heaters, with the exception of non-pressure flow heaters, are prohibited to be placed in the bathroom due to electrical safety requirements. Therefore, the best place to place storage water heaters is a toilet, and for pressure flow ones – a kitchen or a niche of a kitchen set.
In both places there is a supply of both cold and hot water; you can easily cut into pipes even with tees at the connection point of the kitchen sink. Do not forget that the storage water heater must be equipped with a check valve, and the flow heater must be equipped with a mesh filter..