How to make manual and automatic recharge of the heating system

When faced with repair work, going on a long trip or becoming a victim of an emergency, many people wonder whether it is necessary to drain the water from the heating system? In most cases, the answer is positive, although there are also situations where it is possible to fix a problem or make repairs with radiators filled with liquid.

Although the draining procedure is not particularly complicated, following the operating rules is an important nuance. If you violate the procedure, you can flood the floors in your own home with water. And if the drainage is carried out in a multi-story building, then neighbors may also suffer from incorrect actions.

Signs of a critical coolant shortage

Not all owners of private houses monitor the technical condition of their water heating; it works - and that’s okay. When a hidden leak occurs, the system continues to function for some time until the amount of coolant drops to a critical level. This moment is monitored by the following criteria:

1. In an open system, the expansion tank is first emptied, then the main riser rising from the boiler is filled with air. Result: cold batteries when the supply pipeline overheats; turning on the maximum speed of the circulation pump does not help.
2. The lack of water during gravity distribution manifests itself in a similar way; in addition, the gurgling of water in the riser can be heard.
3. On a gas heater (open circuit), frequent starts/turns of the burner are observed - clocking, the TT boiler overheats and boils.
4. The lack of coolant in a closed (pressure) circuit is reflected on the pressure gauge - the pressure gradually decreases. Wall-mounted models of gas boilers automatically stop when they fall below a threshold of 0.8 Bar.
5. Floor-standing, non-volatile units and solid fuel boilers continue to regularly heat the remaining water in a closed system until the volume vacated by the coolant is filled with air. The circulation will stop, overheating will occur, and the safety valve will operate.

Important clarification. When a TT boiler operating in an open gravity system boils, there will be no explosion, since the coolant communicates with the atmosphere. The water heated by the heater will evaporate, and then a fire will start in the boiler room. Although the described process takes a lot of time, such situations are far from uncommon.

We will not explain why the system needs to be recharged - this is an obvious measure to maintain the functionality of the heating. All that remains is to choose a method for replenishing the heating network.

Advantages and disadvantages

The use of distilled water as a coolant has both positive and negative sides.

The first include:

• accessibility and low cost;
• non-toxic, so safe for others in case of leakage;
• does not require special storage conditions and compliance with safety rules when filling;
• protects heating pipes from corrosion, scale and various deposits;
• has a greater heat capacity compared to other heat carriers (when cooled by 70 degrees, a heat transfer of 20 Kcal occurs).

The disadvantage is the fact that the distillate freezes at temperatures from -10 to -12 ᵒC Celsius. So, when the heating system is turned off in winter, the pipes will inevitably freeze and fail.

If you do not plan to live in a country house in winter, then it is more rational to choose antifreeze as a coolant that does not freeze.

Selecting a refueling option

Several methods are used to replenish the coolant supply:

1. Manual recharge is the cheapest and most versatile option, suitable for all types of wiring.
2. Automatic replenishment from the water supply is practiced only in systems operating under pressure.
3. To fill a closed network with non-freezing coolant, a manual pressure test pump is also used. The design of an automated circuit with an electric pumping station connected to a container with antifreeze is practiced in industrial boiler houses.

At home, antifreeze is pumped into the heating network using a pressure test pump

Note. If the radiator network and heated floors are filled with antifreeze, simple replenishment is done with a small hand pump. But most often, filtered tap water is used in the heating system, because of the price of non-freezing coolants (especially harmless propylene glycol).

The operating principle of the automatic make-up unit is based on the operation of a pressure reducing valve that responds to a decrease in pressure in the heating network. When it drops below the set value, the valve mechanism opens and releases water from the main line. A pumping station operates in a similar way, pumping antifreeze from a separate tank.

Unit with gearbox (left) and station pumping coolant from the tank (right)

Let us take the liberty of recommending the use of a manual recharge scheme. Causes:

1. The unit consists of 2-3 inexpensive elements and will never turn on without the knowledge of the homeowner.
2. No matter how reliably and efficiently the heating network is installed, there is a possibility of leakage and valve operation.
3. Situation: pipe break, prolonged leakage of coolant in the absence of the owners. A completely autonomous “smart” recharge will flood the entire house, ruining the flooring and causing expensive repairs.
4. Imagine an identical situation in an apartment building - a leak from an individual system and the activation of automated replenishment will flood the neighbors below.
5. Fine sand will accumulate under the valve seat and the element will lose its seal over time. Under pressure from the water supply of 4-7 bar, spontaneous replenishment will begin. The most harmless scenario is the release of excess coolant through the fuse on the boiler safety group.

To eliminate the consequences of the described troubles, it is better to allocate a little time for personal control over your heating. Having discovered signs of loss of coolant, you will make your own decision - to recharge the system immediately, look for a leak, or make repairs. For a negative example of using such automation, watch our expert’s video:

Filling heated floors

Warm floors have their own characteristics. They are not filled all at once, but one contour at a time. If you fill everything at once (and they have different lengths), then there will definitely be air in the long circuits, which is almost impossible to remove from there. Therefore, we proceed as follows.

The collector is completely assembled. All circuits are blocked on the return line except one. The pump is turned on, and through the supply, this circuit is filled with the heating system until clean coolant flows out of the drainage hole without a sign of air. After this happens, the circuit closes. All the others are filled in in the same way.

Here it is advisable to have another hose in order to direct it into a bucket of coolant to avoid its spillage.

After this, the drainage hole is closed, all circuits are opened and the operation of the heated floor is checked. It is important to pay attention to the fact that the radiator network system can be filled with coolant against its movement. You cannot do this with heated floors; you only need to fill it from the straight side, because otherwise the coolant will not move through the rotameters.

Manual recharge scheme

The simplest option for filling the system is implemented in 90% of double-circuit wall-mounted boilers, where a cold water supply pipe is a priori connected. A manual valve is installed inside the housing, connecting this line with the heating return line. Often, a boiler feed tap is found on solid fuel heat generators with and without a water circuit (for example, heating units of the Czech brand Viadrus).

Reference. On some models of gas heaters equipped with a DHW heat exchanger (in particular, Beretta), instead of a manual tap, manufacturers install an automatic make-up valve with an electromagnetic drive. If the coolant pressure drops below 0.8 Bar, the boiler itself draws water to the required level.

In wall-mounted double-circuit heat generators, the make-up valve is located at the bottom, where the pipelines are connected
. To assemble a classic make-up unit suitable for any type of system, you will need the following parts:

• tee with side outlet DN 15-20, corresponding to the material of the heating main pipe - fitting for metal-plastic, polypropylene, and so on;
• poppet (spring) check valve;
• ball valve;
• couplings, fittings.

The purpose of the check valve is to prevent water from the heating network from flowing back into the water supply system. If we are talking about pumping antifreeze using a pump, you cannot do without a valve. The fittings are installed in the order listed:

1. The tee cuts into the heating return after the circulation pump.
2. A check valve is connected to the outlet pipe of the tee.
3. Next is a ball valve.

Advice. If there is no fine filter at the entrance of the water supply to a private house, it is advisable to provide one on the make-up line. The element will protect the heating system from the entry of fine sand and rust particles that accumulate on the check valve plate and in the seats of three-way valves.

The operating principle of the unit is simple: when the tap is opened, water from the centralized main flows into the heating pipelines, since its pressure is higher (4-8 Bar versus 0.8-2 Bar). The filling process of a closed system is monitored by a boiler or safety group pressure gauge. If you accidentally exceed the pressure, use the Mayevsky tap on the nearest radiator and bleed off excess water.

To control the amount of coolant in the expansion tank of an open heating network located in the attic of the house, the tank must be equipped with 2 additional tubes with a diameter of ½ inch:

1. The control line, ending with a tap in the boiler room, cuts into the side wall at approximately half the height of the tank. By opening this valve, you can determine the presence of water in the tank without climbing into the attic.

   
   During the replenishment process, air bubbles escape through the tank lid, the maximum level is monitored by the flow of water from the upper fitting through the pipe

2. The overflow tube is inserted 10 cm below the tank lid, the end is discharged into the sewer or simply onto the street under the roof overhang. Being in the furnace room and opening the feed tap, you should see this pipe; when water flows from there, filling stops.

Comment. If you are interested in calculating the minimum volume of the expansion tank, follow the dedicated link.

The circuit with a check valve and shut-off valve is also applicable for filling solar systems (solar collectors) and geothermal circuits of heat pumps with antifreeze. How to use the boiler make-up valve is described in the video:

Saline solution

For open-type heating systems with natural coolant circulation, one of the possible coolant options is a concentrated solution of table salt, calcium chloride or other mineral salts. It is used to prevent heating circuit pipes from freezing in winter. Moreover, the stronger the salt concentration, the lower the freezing temperature of the solution.

Technical characteristics of the brine:

• rather low heat capacity - a solution with a salt concentration of 30% gives off 2700 J/kg deg;
• low viscosity;
• very high corrosion activity - steel pipes “burn out” very quickly from constant contact with salt;
• no toxins;
• coefficient of thermal expansion – 0.03%/deg;
• low price of salt.

Automatic make-up unit

If you are firmly confident in the reliability and quality of the system, you can install an automated circuit that adds water from the cold water pipe. What you need to buy:

• pressure reducing valve (simpler - reducer);
• 3 ball valves;
• 2 tees;
• pipe for the bypass device.

Important point. The water entering the reducer must be pre-cleaned with a coarse strainer, otherwise the valve will quickly become clogged. If such a filter is not provided at the entrance to the building, install it in front of the make-up unit.

In this diagram, the pressure gauge shows the pressure on the side of the heating network; bypass and taps are needed to service the recharge module

The main executive element of the circuit - the gearbox - consists of the following parts:

• fine filter on the inlet pipe;
• spring seat valve with rubber seals;
• pressure regulator handle with a printed scale, range – 0.5…4 Bar (or higher);
• manual shut-off valve;
• check valve at the outlet.

Note. There are more expensive models of make-up reducers with a built-in pressure gauge that measures the pressure on the side of the heating system. Since this device is already in the safety group or boiler, there is no point in spending extra money and duplicating it. The exception is the situation when the make-up is installed far from the heat source (read the next section).

As you can see, the pressure reduction machine already contains all the necessary elements - a filter, a check valve and a regulator. All that remains is to assemble a simple circuit with a bypass and service taps designed for removing and servicing the gearbox.

Operating the valve is simple - use the regulator to set the minimum pressure threshold in the heating network, open the direct line taps, and close the bypass. How to properly adjust the automatic valve is shown in a short video:

Advice. If you plan to install a coarse filter in front of the gearbox, provide an additional service tap in order to clean the mesh without turning off the water in the entire house.

To organize the automatic addition of antifreeze to the system, you can adapt a “hydrofor” - a water station with an electric pump designed for water supply from a well. The pressure switch of the unit must be reconfigured to a minimum pressure of 0.8 Bar, a maximum pressure of 1.2...1.5 Bar, and the suction pipe must be directed into a barrel with non-freezing coolant.

The appropriateness of this approach is highly questionable:

1. If the “hydrofor” works and starts pumping up antifreeze, you will still have to look for and eliminate the cause of the problem.
2. If the owners are absent for a long time, replenishment will also not save the situation in the event of an accident, since the size of the container is limited. The pumping station will extend the heating operation for some time, but then the boiler will turn off.
3. Placing a large barrel is dangerous - you could flood half the house with toxic ethylene glycol. Non-toxic propylene glycol is too expensive, as is spill cleanup.

Examples of organizing automatic refueling from containers of different capacities
. Conclusion. Instead of additional pumps and automatic gearboxes, it is better to purchase an electronic unit of the Xital type. After a relatively inexpensive installation, you will be able to control the heating operation via a cell phone or computer and quickly respond to emergency situations.

How to connect to the heating system

With a closed circuit, there is not much difference where to connect the make-up pipeline - to the supply or return. We recommend using the classic proven method - the insertion point should be located on the return line next to the boiler, after the circulation pump and expansion tank. Causes:

• the unit is located in the combustion room, next to the equipment and instruments;
• pumping water into the return line is immediately reflected on the pressure gauge installed in the supply behind the boiler;
• the insert is located at the lowest point, the flow is distributed in 2 directions - into the boiler and radiators, the air is squeezed out evenly.

Classic scheme for inserting a recharge module

The piping of solid fuel units involves the installation of a condensation protection circuit with a three-way valve. You cannot make makeup in front of this valve - cold water will immediately close it and the boiler pressure gauge will begin to lag in readings. Cut inside the circuit, between the 3-way valve and the heat generator.

In a similar way, the make-up flows into the return line of the open system. The second option is to add coolant directly to the tank; the disadvantage of this method is to lay the supply pipe into the attic.

The correct connection is shown on the left - inside the primary boiler circuit

Connecting the make-up line is also allowed at other points:

• to a separate fitting of a solid fuel boiler, provided by the manufacturer;
• to the bottom of the hydraulic arrow;
• to the return manifold of the distribution comb;
• to the outlet of the indirect heating boiler.

These options are usually implemented in complex and extensive systems of country cottages. Connecting the make-up to the boiler is demonstrated in the next video:

Finally, about the safe addition of coolant

When filling water or partial replenishment, follow our recommendations:

1. Replenish the heated system slowly by opening the valve a quarter of the lever stroke. In this way, it will be possible to avoid the formation of air locks and protect the boiler heat exchanger from temperature shock.
2. Refill from scratch with the heat generator not working and the circulation pump turned off.
3. Check the pressure in the expansion tank and go through all the radiators, opening the Mayevsky valves to release air.
4. If your boiler is equipped with modern electronics, be sure to study the instructions regarding make-up. Often it is necessary to activate a special service mode in the unit.
5. Excess pressure is easily released through the nearest air vent.

The complex system make-up module can be connected to a hydraulic separator and a comb

Reference. Cast iron heat exchangers easily crack from sudden temperature changes, and steel fireboxes become covered from the inside with condensation. The latter mixes with soot and forms a dense coating.

Injecting antifreeze with a hand pump does not have any pitfalls. Pressure testing units are equipped with their own pressure gauge, which allows you to monitor the current pressure at the insertion point.

Why do you have to add water to the system?

For the boiler to work correctly, it is necessary to maintain the recommended pressure in the system. Obviously, for this to happen, a constant volume of coolant must circulate in the water heating system. And it can change during operation even in a perfectly designed and assembled structure. Loss of coolant occurs when:

• The air is bleed through the Mayevsky valve located on the radiator. As you know, you have to open the air vent and wait until a trickle of water comes out of it.
• In automatic mode, excess pressure is released through a safety valve due to a change in the operating mode of the system. In this case, the coolant escapes into the atmosphere in a gaseous state.
• The filters are cleaned from mechanical contaminants.
• There are significant or microscopic leaks, for example through dismountable connections.
• In systems with natural circulation, water evaporates through an open expansion tank.