Electric water heaters, originally intended for private houses, are now increasingly found in city apartments. Thanks to the practice of summer shutdowns of hot water remaining from Soviet times, millions of urban residents each year face a choice: to start hardening with cold showers, to wash in the old-fashioned way with a ladle, boiling water on a gas stove, or not to wash at all.
Or - buy and install an electric water heater.
Prices for water heaters start at quite affordable amounts, which pushes many towards the last solution to the problem, but the adage “a cheapskate pays twice” is true in this case as well. Low power and small volume of a cheap water heater will not allow not only taking a shower, but even washing with comfort. And its simple design will lead to rapid failure.
Therefore, you need to choose a water heater according to its parameters, having a good idea of why and how you will use it. It is also a good idea to find out the hardness of the water you are going to heat before making a choice.
Characteristics of electric water heaters
By type, water heaters are divided into storage and flow.
Storage water heaters heat a certain volume of water to a predetermined temperature, which is stored in the boiler and is consumed as needed. When heated water is consumed, cold water enters the boiler, the temperature in the boiler drops, which leads to the automatic activation of the heating element.
Instantaneous water heaters heat the flow of water flowing through them.
Both types have their own advantages and disadvantages.
Storage water heaters take up a lot of space and have a limited boiler volume - as soon as it is used up, cold water will flow from the tap. Their power is low, and they are unable to heat the flowing stream of water. It can take up to several hours to reheat the entire volume of water.
But even the smallest storage water heater can be adapted for parsing water by several consumers - until the accumulated hot water runs out, it will flow with the required pressure from any tap in the apartment.
Instantaneous water heaters are easy to install, compact and can even be placed directly above the sink. But to quickly warm up the flow of water required in everyday life, they must have a decent power, which is not always acceptable.
So, for taking a shower, a flow of about 10 l / min is required. To heat the water flowing at such a rate by 30 degrees, the heater must have a power of about 20 kW, which immediately makes it impossible to use such heaters in most apartments and private houses. The maximum permissible power in apartments in apartment buildings is 7 kW, and this is only in houses with electric stoves. In houses with gas stoves, 3-4 kW are allocated for an apartment, and even less in old buildings.
In addition, if the pressure in your water supply network is not constant, then the outlet temperature of the instantaneous water heater will change all the time. The pressure has increased, the pressure has increased, and the water is flowing cold. The pressure has dropped - the water is scalding hot. Few models are able to accurately regulate the outlet temperature, so you will often have to turn the mixer valve.
The volume of the tank is of great importance for storage water heaters. The larger the volume, the more members of your family will be able to wash, take a shower or a bath without a long wait for the boiler to warm up after previous use.
But keep in mind that the larger the volume of the tank, the longer it will take to heat it, since the power of the heating elements of most water heaters is approximately the same and rarely exceeds 3 kW.
The inner lining of the hot water tank is necessary to protect it from corrosion.
Stainless steel tanks provide the best protection, but they are also more expensive than others. The weak point of stainless steel tanks is the welded seam, which is most often made with metal that is subject to corrosion.
Enamelled and glass-ceramic coated tanks are similar in performance and also provide good protection - the myth of the destruction of the protective layer under the influence of temperature changes is nothing more than a myth (of course, if you do not pour boiling water into a frozen tank).
Another thing is that the quality of the coating can be different and the glass-ceramics of a well-known manufacturer are not at all the same as the glass-ceramics of an unnamed "Chinese".
As for the rest, enamel and glass ceramics are seriously inferior to "stainless steel" only in one thing - resistance to mechanical damage. The heater tank itself, as a rule, is separated from the body by a layer of soft thermal insulation, which can protect the tank from damage, but with strong impacts, microcracks may appear on the coating, which subsequently develop corrosion. Therefore, when buying a heater with an enamelled tank, you must carefully inspect the case for dents and subsequently protect the heater from impacts.
Many manufacturers install a magnesium anode to protect the tank from corrosion, which interacts with the oxygen of the water and protects the inside of the tank. This element will protect the tank even if the coating is damaged, but it requires periodic replacement - once every 1-2 years, regardless of the condition of the protective coating.
If you want the heater to work for a long time and without unnecessary hassle, be sure to pay attention to the presence of a "dry" heating element. Especially if you have hard water - in this case, a "dry" heating element is simply necessary.
In conventional models, the heating element is located directly inside the boiler and is in direct contact with the heated water. At the same time, scale settles on it, which can quite quickly lead to the failure of the heater, to the leakage of the heating element and to the fact that all the accumulated water will be on the floor.
To avoid this, you can periodically clean the heating element from scale (2 times a year with hard water, once every 1-2 years with normal water).
Or purchase a heater with a "dry" heating element - the design of such a heater does not provide for contact of the heating element with water, it is located in a metal flask or tube. Of course, the scale does not disappear anywhere, it settles on the outer surface of the flask. But due to the greater thickness of the metal and the larger area of contact with water, this does not lead to rapid burnout, therefore, heaters with a "dry" heating element can work ten times longer than their counterparts with a "wet" heating element.
The rated power determines how quickly the heater will heat the water. For a storage heater - the more power, the faster the entire tank will warm up and hot water will flow from the tap again. And if for a heater with a small tank (15-30 l) the difference in heating time for low-power and powerful heaters is 10-30 minutes, for volumetric heaters (80-100 l) the difference in heating time can already be several hours. If the wiring and permissible power allow, it makes sense to install two smaller ones of the same power instead of one large 3 kW heater - this will halve the waiting time for hot water if it suddenly runs out.
Some heaters are equipped with two heating elements and have an accelerated heating mode. When a large volume of cold water comes in and a sharp drop in temperature, both heating elements can be turned on, increasing the rate of water heating. And in the mode of maintaining the temperature, only one heating element works. This mode of operation of the heater reduces the load on the network. Heaters equipped with automation are able to independently connect / disconnect the second heating element.
For an instantaneous heater - the more power, the greater the head of heated water it can provide.
An instantaneous water heater with a capacity of 3 kW will be able to heat only a thin stream of water “to warmth” - about 1.5 l / min. You will still be able to wash and brush your teeth, but something else is no longer there.
A 5-7 kW instantaneous water heater can be used for washing dishes, but the shower will not be very comfortable - both the water is cool and the pressure is weak.
There are instantaneous heaters of greater power on sale, but, unfortunately, their installation will require separate wiring - and sometimes three-phase. However, if you are the happy owner of a three-phase power supply with a large allowable power consumption, then installing a 15-20 kW instantaneous water heater will provide you with hot water with normal pressure in almost unlimited quantities.
When buying a heater for a city apartment - especially a storage heater and especially on the lower floors - pay attention to the maximum allowable water pressure for the selected heater. Despite the pressure standard of 4 bar, in urban water supply networks, the pressure can reach up to 7 bar. Either select a heater with a maximum allowable pressure of 8-10 bar, or provide a pressure reducer at its inlet.
At the maximum heating water temperature should pay attention when choosing a storage heater. The higher the heating temperature, the less hot water will have to mix with cold water to achieve warm water. But at the same time, the higher the risk of burns when the hot water tap is fully open.
A water heater - both flowing and storage - carries many dangers. To avoid flooding, electric shock or hot water burns, pay attention to all safety features:
- The regulator (limiter) of the heating temperature allows you to set the maximum water temperature and avoid scalding when inadvertently opening the tap.
If children can use the tap, and the maximum heating temperature is above 80 ° C, a regulator is necessary - the temperature should be set no higher than 75-80 ° C.
- Protection against overheating turns off the heating element in case of danger of water boiling. Usually, the heater automatics turns off the heating element much earlier, but if it breaks down, only the overheating protection will save the flow heater from damage to the heating element, and the storage heater from rupture of the tank.
- Residual current device protects against electric leakage into heated water. It is strongly not recommended to use a heater that is not equipped with an RCD.
- The safety valve acts as a check valve, preventing water from flowing out of the storage heater, and also relieves excess pressure.
Since the water intake in the storage heater is carried out from above, and cold water immediately enters the hot place, the tank always remains full. In the absence of a check valve and the cessation of water supply, the tank may remain without water, which will lead to the failure of the heating element.
A safety valve (with a branch) protects the tank from excessive pressure in the water supply. However, this is not a panacea: if the pressure in the system is much higher than the required one, then a fairly strong stream of water will always flow through the tube with a noticeable noise. There is little pleasant in this, therefore it is recommended to add a pressure reducer at the inlet.
Electric water heater selection options
If you need a heater to provide one point with hot water, and the wiring allows you to connect electrical appliances with a consumption of 5-7 kW, choose among instantaneous water heaters. If you want the heater for showering, check out the shower head option.
If you live in a city apartment and do not want to depend on seasonal water outages, choose among storage heaters with a volume of up to 50 liters - this will be enough to wait out the shutdown.
If the wiring does not allow you to connect powerful devices, but you also don’t have the opportunity or desire to tinker with the connection and wiring of the storage heater, choose among low-power flow heaters - the pressure, of course, will be weak, but this is better than nothing.
If you are afraid of leaks, choose a heater with a "dry" heating element and a maximum water pressure of 8 bar and higher. Having a magnesium anode on your chosen model will provide additional protection, but keep in mind that it needs to be replaced periodically.
If you live outside the city and you need a water heater to provide hot water for a family of 2-3 people, choose among storage heaters with a volume of 50-100 liters. For a family of 4-5 people, the volume of the tank will need more - 100 - 150 liters.
If you do not have any restrictions on wiring and power consumption, you can install a powerful instantaneous heater and forget about the lack of hot water in the tap.