- Placement and mechanical installation
- Typical strapping scheme
- Harness for seasonal use
- Water intake when the supply is turned off
- Recirculation piping
- Strapping without mixer
Today we will try to classify the well-known information about the installation of electric storage water heaters. We will consider the schemes of hydraulic piping, its functions and draw conclusions – which installation will be technically correct and which will not.
Placement and mechanical installation
It is well known that an electric boiler in a pressurized water supply system is absolutely insensitive to the level difference between itself and the draw-off points. Nevertheless, there are requirements for the installation height. It should not be too large, so as not to introduce unnecessary difficulties in the process of securing the tank, and at the same time not too low, so that there is no tangible “theft” of space.
Please note that the section of the wall from 30 to 50 cm immediately under the boiler should be free of communications and other stationary objects: here the tank shut-off valves and other elements of its piping are mounted. If the tank is installed in a caisson or a niche, or its piping is hidden, provide for the presence of revision doors in the false wall for direct access to the rough plumbing.
Another small subtlety: for most water heaters, the terminals are located immediately behind the control unit for less noticeable wiring of communications. Therefore, the installation height of the tank should be such that the entire control unit is, on average, just below the shoulders.
Typical strapping scheme
Let’s immediately stipulate a few simple rules for plumbing in the context of installing a boiler. First of all, the use of flexible connecting pipes is undesirable. The threaded branches of the tank must be immediately turned with corners to the wall, and then lowered along it (or passed through) with the subsequent installation of two taps. To drain hot water, it is allowed to use PP-R fittings, for example, a threaded corner transition with MRV.
But at the cold water inlet, it is better to pack a bronze corner “nut-fitting” on a Teflon cord. As with the turn of the hot tap, remember to count the turns beforehand so that the corners look straight into the wall after packing. A metal connection is required to install the safety group, usually it has two internal threads.
Then you can completely switch to plastic pipes. Immediately after the tank taps are turned down, two ball valves in a plastic housing are installed. Ten years ago, shut-off valves in this place were not given much importance until the opinion was finally established that the tank should be serviced at least once every 2-3 years. In order for all other points of the water intake to remain operational for this time, the heater is localized with taps. By the way, a hot tap is clearly necessary only when heating devices operate in parallel and to protect against backflow through direct-acting mixers..
Typical piping of a storage water heater: 1 – shut-off valves at the water supply inlet; 2 – ball valves of the water heater; 3 – security group; 4 – storage water heater
That’s all: this is the simplest wiring diagram, which can be supplemented with perhaps an elementary mechanical filter. Strictly speaking, an electric boiler can work without strapping at all, with only one safety group. But, as we will see later, additional fittings make the use of the water heater much more convenient..
Harness for seasonal use
In apartments, boilers are most often installed as a forced measure for the period of scheduled repairs of the heating network. Most of the time the water heater is idle and, although it is recommended to keep it filled, the constant flow of water can cause deposits to build up in the tank. Therefore, a system should be provided for disconnecting the tank from the water supply system, which is quite simply implemented by a pair of ball valves or one three-way valve.
If you use ball valves, install one of them up to the point where the hot outlet is tapped into the water supply system. This tap is closed in the summer to prevent water from flowing into the mains. The presence of a tap on the hot outlet is strictly necessary to limit the flow in the winter.
1 – shut-off valves at the water supply inlet; 2 – three-way valve; 3 – security group; 4 – storage water heater
One three-way valve, installed at the point of connection to the hot line, also solves the problem of switching between modes. It is noteworthy that it is on three-way taps that it is most simple and profitable to implement a system with several water heaters connected by a parallel pipeline..
Water intake when the supply is turned off
Most storage water heaters are of a closed type and do not drain water by gravity. However, there are a number of piping additions that make it possible to draw water in the absence of pressure. These add-ons make it most easy to empty the tank if it is removed for service..
First of all, the theory: the hot branch pipe of the tank reaches the very top of the container, the cold one is located at the bottom under the diffuser cover. The water is drained out precisely through the cold pipe, and air is sucked into the container through the long hot pipe..
Storage water heater design: 1 – cold water supply; 2 – heating element; 3 – tank; 4 – hot water intake; 5 – thermal insulation; 6 – case
The simplest solution is to plunge a tee into the hot bend to the point where the ball valve is installed. Using these two taps, you can provide the tank with air suction and use hot water from the “cold” pipeline. But this approach is not entirely safe: forgetting to turn off the air intake valve, you risk flooding your home when pressure appears in the cold water supply system.
The problem is solved in two ways. The first is the installation of a check valve on the air intake valve at the hot input. The problem is that there is almost always a small amount of water in the high tube of a filled tank, so the system does not work very stable – the water column prevents the valve from opening even if there is a relative vacuum in the tank. You have to bleed water from the tube manually when you first open the system.
1 – tee; 2 – check valve; 3 – valve for air suction
It is also possible to install a check valve bypassing the cold supply shut-off valve. In this case, the valve is installed opposite to the normal flow of water, blocking its entry into the tank when pressure is applied. As before, this task can be solved with even fewer 3-way valves..
One of the most interesting innovations in plumbing of the XXI century is the addition of a small pump to the network, which constantly pumps water through a closed circuit of hot water supply. The bottom line is that you don’t have to wait for cooled water to flow out of the system. Although at first glance it seems too costly (electricity for the pump + constant heat losses), with the right implementation (daily timer and good thermal insulation of the pipes), the economic benefit from such a system grows in proportion to the removal of the draw-off points from the boilers.
First, about the layout of the pump. It is installed on a line that duplicates the hot water supply pipe to the last draw-off point. The opposite end of the recirculation line is connected either to a special branch pipe of the boiler, or directly to the cold water supply. A check valve is used to separate flows at this point..
Connection of a storage water heater with circulation: 1 – water heater taps; 2 – safety group with a check valve; 3 – valve for air suction when draining the tank; 4 – hot water consumers; 5 – circulation pump; 6 – check valve; 7 – daily timer; 8 – storage water heater
The pump is controlled by a daily timer, which turns on recirculation only during the hours of maximum demand, for example from 5 to 9 and from 18 to 23 hours. Hot water intake is possible from any point of the recirculation loop, but the further along the channel, the more the water cools. Often, a flow-through heated towel rail is cut into the recirculation system. To be able to turn off the latter when not needed, use a three-way valve in the tie-in to the shorting jumper.
Strapping without mixer
In conclusion, we will tell you about the best way to connect the boiler in a bath or summer shower, where there is no normal mixer. Of course, you can regulate water heating with a thermostat, but the storage heater is not flexible enough in this matter..
Connecting a water heater without a mixer: 1 – thermostat valve; 2 – water heater taps; 3 – security group; 4 – valve for air suction when draining the tank; 5 – water heater
To solve the problem, a shorting jumper is installed between the boiler inlets, equipped with a thermostatic valve for heating radiators. It is designed to pump a small amount of cold water. It is better to install the thermostat right next to the tank so that the water has time to mix normally during the flow through the pipes. A similar system works equally well when powered both from a tank and from a pressure water supply.
Of course, for the convenient use of the temperature control system, you will have to get used to it a little. This is made easier by the tank thermostat and the scale of divisions on the thermostat..