How to install an indirect heating boiler?


Many peo­ple, hav­ing prob­lems with cen­tral hot water sup­ply in an apart­ment or house, decide to install an indi­rect heat­ing boil­er. It is con­sid­ered eco­nom­i­cal and con­ve­nient to use. But how is the indi­rect heat­ing boil­er con­nect­ed? There are sev­er­al basic meth­ods that are suit­able for both an apart­ment and a coun­try house.

What’s this?

Indi­rect heat­ing boil­er — a con­tain­er of a cubic or cylin­dri­cal shape, inside which a heat exchang­er is installed, in most cas­es made in the form of a spi­ral coil. A coolant from the heat­ing sys­tem pass­es through it, with the help of which the water in the tank is heat­ed. Such sys­tems are well suit­ed for small hous­es.

The water heater in most cas­es does not have its own heat source. It uses the ener­gy of exter­nal heat­ing. It can be a cen­tral sys­tem or a sep­a­rate boil­er. There­fore, for each case, its own scheme for con­nect­ing an indi­rect heat­ing boil­er is used.

Heating connection

Such water heaters are mount­ed to the heat­ing and water sup­ply sys­tem. For every­thing to work well, you need:

  • sup­ply cold water to the bot­tom of the unit;
  • ensure hot out­let from above.

In this case, heat­ing is sup­plied in such a way that the coolant moves down. It turns out that the hot stream enters through the upper pipe, and the cold one exits through the low­er one. It is through this con­nec­tion that it will be pos­si­ble to achieve high effi­cien­cy.

Connection via 3‑way valve

This type of con­nec­tion is based on two cir­cuits:

  • heat­ing;
  • heat­ing.

By using a three-way valve, an even dis­tri­b­u­tion between the two lines is ensured. The main pri­or­i­ty is the water sup­ply sys­tem, and only then the heat­ing.

At the same time, there is no need to con­trol the valve — every­thing works auto­mat­i­cal­ly. For this, a ther­mo­stat is pro­vid­ed, which, when cooled, switch­es the valve, and water from the heat­ing sys­tem is sup­plied to the heater. When the tem­per­a­ture in the heater ris­es to the desired lev­el, the direc­tion of flu­id move­ment again changes, and it is sup­plied to the radi­a­tors.

In most cas­es, the instal­la­tion of an indi­rect heat­ing boil­er is car­ried out in this way. The fact is that the sys­tem is sim­ply indis­pens­able in the case of using a large amount of water in the house.

Impor­tant! When set­ting the ther­mo­stat oper­a­tion lim­its, it is nec­es­sary to take into account to what mark the liq­uid in the boil­er will heat up. There­fore, it is rec­om­mend­ed to set the tem­per­a­ture on the device slight­ly low­er than on the heat­ing unit. Oth­er­wise, the lat­ter will have to work almost con­stant­ly on the water heater.

Use of two pumps

Anoth­er good option is to install a check valve and two pumps. In this case, each node is con­trolled by its own pres­sure gen­er­at­ing unit. The con­nec­tion of the indi­rect heat­ing boil­er to the boil­er is car­ried out in par­al­lel with oth­er nodes, but it has pri­or­i­ty.

Cir­cu­la­tion pumps are installed in front of the water heater and heat­ing sys­tem. For con­trol, a tem­per­a­ture sen­sor is used, which sends appro­pri­ate sig­nals to the devices.

Such a sys­tem is con­sid­ered very suit­able for heat­ing based on two boil­ers. At the same time, one of them com­plete­ly trans­fers ener­gy to the radi­a­tors, and the sec­ond has an out­let to the water heater.

If the liq­uid in the water heater cools down, the coolant is sent for heat­ing, and when the tem­per­a­ture ris­es to the desired lev­el, it switch­es to heat­ing. A non-return valve is used so that the coolant flows do not mix with each oth­er.

And there is no need to wor­ry that this will affect the heat­ing of the room. Water in such boil­ers heats up quick­ly — less than an hour. And because the room just does not have time to cool down.

Connection with hydraulic switch

Con­nect­ing the boil­er to a dou­ble-cir­cuit boil­er using pumps is often car­ried out using a hydraulic arrow. Typ­i­cal­ly, such cir­cuits are built into mul­ti-loop sys­tems.

Basi­cal­ly, this option is used if there are sev­er­al heat­ing seg­ments. It can be a hot water boil­er, radi­a­tors, under­floor heat­ing and so on.

Here the hydraulic mod­ule and man­i­fold are con­fig­ured. This will remove pos­si­ble pres­sure drops in dif­fer­ent parts of the net­work.

Of course you can install bal­anc­ing valves. But this requires spe­cial skills and expe­ri­ence. In addi­tion, it may be dif­fi­cult to use in the future.

Return circulation

This scheme is imple­ment­ed if the third input is placed in the tank. It is to him that the recir­cu­la­tion of the coolant is con­nect­ed. The main pur­pose of this sys­tem is to increase the rate of sup­ply of heat­ed water. As planned, it should be sup­plied instant­ly — when the tap is opened. Thus, there will be no over­flow of liq­uid at the moment when the drain occurs.

It turns out that a looped high­way is being cre­at­ed, along which the flow is con­stant­ly mov­ing. It is con­trolled by a cir­cu­la­tion pump.

For prop­er oper­a­tion, an indi­rect heat­ing boil­er is installed, and some addi­tion­al com­po­nents, includ­ing:

  1. Check valve. It is installed at the inlet to the water heater. This pre­vents the coolant from enter­ing the cold pipeline when the pres­sure ris­es as a result of over­heat­ing of the water.
  2. Auto­mat­ic air vent. It is locat­ed in front of the check valve. This ele­ment is nec­es­sary to pre­vent exces­sive air from enter­ing the pump before it starts.
  3. Safe­ty valve. Pro­tects the heater from pres­sure surges.
  4. Expan­sion tank. This com­po­nent will main­tain a con­stant pres­sure even when the taps are closed.

Impor­tant! In the expan­sion tank, the pres­sure should not exceed the val­ues ​​that are set for the safe­ty valve.

The indi­rect heat­ing boil­er is con­sid­ered the most eco­nom­i­cal unit of the entire fam­i­ly of heaters. At the same time, there are sev­er­al options for con­nect­ing it to dif­fer­ent net­works. You just need to com­pare with the already installed heat­ing and choose the right one.


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