Water heaters: a lecture with consequences – what they are and how they work?

Stand-alone hot water is more reliable, more flexible, and ultimately more economical. There is minimal heat loss, easy installation of an automatic water heater with minimal impact on walls and ceilings during installation.

Why they never turn off hot water in the West?

Leito is a beautiful time! Scheduled Blackouts of hot water. And in the cottage – water from a well or borehole. Le de naya! All season…

Journalists, who enjoy nagging remind from time to time with annoyance: but in the West the scheduled water outages for preventive maintenance are usually 6 hours per year!

But herein lies the catch: in the West, we’re talking about shutting off water in general, cold water, not hot water. Because there is no centralized hot water supply and there are no associated consumer problems, problems of maintaining and operating these cumbersome ramified systems, staff maintenance, large heat losses in long water pipelines and so on. We can call our centralized hot water supply an echo of totalitarianism…

All over the world houses are connected only to the cold water main, and it is heated to the right temperature and in the right quantity by modern automatic water heaters.

For residents of country houses is the best solution to the problem of hot water. Yes, and residents of our urban homes should think about it: is it worth it all year round to depend on such an unreliable, unstable and of poor quality service, as a centralized hot water supply?

Water is flowing, the meter is running…

Hot water in the household, it turns out, not so much need. Let’s look at the figures of the German statistics there are no similar statistics in America, because cold and hot water consumption meters in our households are still very rare .

So, in Germany, it is believed that one person is enough for 140 liters of water per day. You need hot water in the bathroom 52 liters , in the bathroom 43 liters of water statistically most of it is spent by the toilet bowl, and 15 liters of hot water are more than enough for washing and shaving , for washing dishes 9 liters – that’s if you do not use a dishwasher , for cleaning 8 liters .

For the other positions toilet, washing in an automatic washing machine, washing dishes in a machine, care of potted plants and garden, cooking – you initially need cold water. Total: one person per day requires hot water flowing from the faucet, 74 liters, that is, about half of the claimed 140 liters. And if you use a dishwasher, it’s only 65 liters.

This need for hot water is easily provided by modern water heaters, electric or gas. You only need to choose the best model, based on the composition of your family. Here we start to choose.

Water heaters can be electric or gas. Let’s start with the electric ones. They are divided into flow-through and storage.

Flow-through water heaters

In flow-through water heaters, water passes through a heating element, and hot water of a given temperature flows out of the tap immediately. Their advantages – compact size, mobility easy installation or reinstallation in a new place .

The difficulties of using flow-through water heaters include their high power. The power range of flow-through heaters – from 3.7 kW this provides 2.2 liters of hot water per minute to 24 kW 13 liters per minute , depending on demand.

Use a flow-through water heater can be used only where the electric network is designed for high power, otherwise a too powerful device will simply “cut off” the electricity in the apartment. Water heaters with a capacity of more than 12 kW require a three-phase network, while in the home more often used single-phase.

Accumulation water heaters

If you can’t afford the conditions that flow-through water heaters have for the electric network, then you should pay attention to storage water heaters. These are thermally insulated tanks in which a sufficiently large volume of water is heated and the automation maintains its temperature. It’s like a thermos with electric heating.

For the operation of such a water heater requires a relatively small power of 1.2 to 6 kW. When you open the tap, the preheated water flows out of the tank and is replaced by a portion of cold tap water, which immediately heats up. You can choose the volume of the tank from 10 to 150 liters or more, depending on the needs of the family.

Lessons on saving money

– When you leave home, set your electric storage water heater to minimum.

– Use a shower instead of a bath. In Germany, so do the wealthy people, because in terms of money taking a hot bath costs about 150 euros.

– Do not leave hot water on when rinsing dishes or shaving, brushing teeth. Use a glass or basin.

The variety and special features of the models of flow-through and storage water heaters is even bewildering. How to decide what you need?

Hydraulics promises: You open more, you heat more

Flow-through water heater is simple: the water flows through a tube, which heats the heating element, and the relay turns on heating when the tap water comes out, and turns off when the tap is closed.

At the same time it is a clever and ingenious device.

To begin with, flow-through water heaters can be hydraulic or electronic. In hydraulic water heaters, the water temperature depends on how much the faucet is open, that is, the flow. Thanks to the perfect design the hydraulic heaters have a low trip threshold. That is they turn on even with a small flow of water and a pressure of 0.3 bar or more.

Hydraulic heaters are also good, because they have no direct contact between the water and the heating element. Because here the heating element is soldered to the outside along the entire length of the spiral copper heat exchanger tube inside which the water flows this technology is patented by BSH .

Thanks to the absence of direct contact of a heating element with water, the high thermal conductivity of copper, the high speed of water flow and overheating protection system maximum water temperature of 60 degrees Celsius it does not form scale.

So the water hardness requirements are not stringent. Hydraulic heater – robust and reliable. They have a two-level safety system: in case of overheating the two sensors shut off power to the device.

Electronics are interested in: how much exactly in degrees?

But in electronic water heaters the temperature of the outgoing water does not depend on the temperature of the incoming. At the output is maintained at a constant set temperature regardless of pressure fluctuations and changes in water flow.

This is monitored with high precision electronics. Such water heater can be used and for heating of warm water from other sources the temperature of incoming water can reach 50 degrees of Celsius and it will not damage the device .

In electronic models, the heating element is placed in water. Water flows through the heat-resistant plastic coil and the heater is suspended inside in the form of movable stainless steel spirals.

But limescale is not formed, firstly, due to properties of the plastic surface, secondly, the heater coil vibrates in the water flow and constantly shakes off scaling particles, and thirdly, the scale is shaken off due to thermal expansion of the coil material when heated. A thermostat system protects against bubbles in the water. A special damping chamber protects against pressure surges and water hammer.

The peculiarity of this design is that it imposes stringent requirements on water quality if the permissible specific conductivity of water is exceeded, as well as in the presence of rust particles the electric heater protection may activate .

But it is most likely that the water in your area will meet the necessary requirements, you can consult your local water authority about this.

At the same flow-through heaters with electronic control provide a higher level of comfort when using. They save energy compared to hydraulic flow heaters by about 20 percent. And, in addition, they have a longer life.

Hot or fine?

Now we are enough clarified on the subject to choose a hydraulic or electronic flow-through water heaters among the now familiar ones. The choice depends on the parameters of the water system in your home, as well as the desired level of comfort. Remember? Electronic heater is much more comfortable, but it is also more demanding to the hardness and conductivity of water.

Finally you have chosen the most suitable for you principle of operation of the heater. It remains to choose the model of the right capacity. And it’s not a simple question at all.

The capacity of the heater depends on its power. It is measured in liters per minute and indicated on the housing of the device.

Naturally, the more powerful the device, the thicker will be the stream of water of a given temperature from the tap. Still, be specific about how much hot water you need to get from your water heater per minute?

It depends on your requirements. It’s one thing if you need hot water just for washing your hands, washing your face and shaving, but you need much more water and a higher temperature for the kitchen sink, washing dishes. And the consumption of hot water for showers and bath tubs is completely different.

There are simple empirical formulas that link the heater capacity and its output. To obtain water at 37 degrees Celsius washing, showering the capacity in liters per minute is equal to the capacity of the appliance divided by 2.

That is, if the power is 12 kW, the device will deliver 6 liters of water per minute. This is not much, enough to wash your hands or wash and shave.

And to get water with a temperature of 50 degrees washing in the kitchen, washing dishes power in kilowatts should be divided by 3.

To be absolutely exact, let’s remember that the hydraulic heaters, unlike electronic, give on an output not a concrete set temperature, and provide a temperature difference, and water temperature on an output depends on initial temperature of water.

The formula is as follows: the temperature difference obtained is equal to the capacity of the water heater divided by the flow of water in liters per minute and all this must be multiplied by the coefficient of 14. The result is in degrees Kelvin, and if you subtract 273 from the figure obtained, you get the desired temperature difference in degrees Celsius.

Power 12 kW is good enough for a sink, acceptable for a shower and certainly not acceptable for a bath. But the capacity of 21-24 kW and above is suitable for any application. The main thing – that the power grid in your home corresponded to this capacity often – with three-phase connection .

It is not enough to put 25-amp fuses and RCD ground fault interrupter for 25 or even 40 amps. It is necessary that the wiring itself is able to withstand the high current required by a powerful water heater.

For example, a copper wire with a cross section of 1 square millimeter allows for a current density of 10 amps. So, for 24-27 amps you need to install wiring with a reserve, made of copper wire cross section of 3 square millimeters.

We will heat if there is a lot of water

They heat a large volume of water at once and automatically maintain its temperature in an insulated tank. Using the hot water faucet, we give access to the tank from below a new portion of cold water, which does not mix with the already heated thanks to special dissipaters.

For different models of such heaters requires from 1.2 to 6 kW, most often 2 kW is enough. According to their design they are divided into open, or non-pressurized, and closed, or pressurized.

The pressure water heaters have casings made of durable materials often steel . This is necessary to keep the pressure created by the thermal expansion of heated water. Unpressurized boilers can have a lighter plastic housing, because the thermal expansion of excess water is “bled” through a special tube, for example, in the sink.

In addition, according to the method of installation and capacity of boilers can be wall-mounted small capacity less than 15 liters , wall-mounted average capacity 30-120 liters and floor capacity of 200 liters or more .

In pressure boilers, the inner surface of the steel tank has a durable coating of special enamel. Boilers have a three-layer coating. It provides protection against corrosion.

Until the magnesium anode dissipates, the rust won’t go away

As an additional protection against corrosion in pressure boilers there is a witty device – a magnesium anode. Magnesium anode life depends on many circumstances: the quality of water, the operating temperature of the boiler, the intensity of its use.

On the average once in 2 years to check the condition of the magnesium anode and if necessary to replace it. It’s much easier than replacing a corroded tank that’s gone bad. All the more so that the anode is located at the top of the boiler, and when checking or replacing it does not even need to drain the tank.

In both designs, the tank is insulated with a porous material. Still, small heat losses are inevitable. To compensate for heat loss, the automatic system periodically turns on the heating and maintains the water temperature in the tank at a predetermined level.

At an outside temperature of +20 degrees and a given water temperature of +65 degrees it takes 450-900 watts per day, depending on the capacity. Accumulation water heaters are equipped with a thermostat, temperature indicator and LED indicator.

Some models have a mode to prevent freezing, it is very useful in the country house. This mode is indicated by a “snowflake” icon on the control panel, it keeps the heating to a minimum to prevent the water in the tank from freezing at minus temperatures indoors.

In addition, there are single-circuit and double-circuit boilers. The second circuit can be useful in areas where there is a reduced nightly electricity tariff. A dual-circuit water heater automatically turns on when the cheap night tariff comes on and heats water “in reserve”.

So, the storage water heater – is a convenient, reliable and trouble-free device for hot water supply.