Expansion tank for closed heating: selection and installation


tank next to the stove

The heat­ing sys­tem of pri­vate hous­es, in addi­tion to the boil­er itself and the heat­ing cir­cuit, includes sev­er­al aux­il­iary ele­ments.

They include the expan­sion tank.

This impor­tant ele­ment of the sys­tem is a nec­es­sary device that increas­es reli­a­bil­i­ty.

What is the function of expansion tank for heating system?

The pur­pose of the device lies in its name.

The heat­ing cir­cuit and the boil­er are designed for a cer­tain pres­sure. But the heat­ed coolant increas­es in vol­ume, there­fore it exerts more pres­sure. It’s in the end can lead to leaks at weak points.
The pres­sure increase must be com­pen­sat­ed by the ele­mentwhich accu­mu­lates in itself part of the liq­uid.

This is a com­mon func­tion, char­ac­ter­is­tic of all types of this device.

Types of expansion tanks

Depend­ing on the type of heat­ing sys­tem used tanks, they are divid­ed into 2 types.

open typeopen tank

Such a tank used for out­door heat­ing
with­out forced cir­cu­la­tion
. He is con­tain­er with­out top. At the bot­tom of the tank there is a hole, a heat­ing pipeline is con­nect­ed to it with a thread.

In some hous­es, you can still find a con­tain­er, it copes with its func­tion, while being quite out­dat­ed and has a num­ber of dis­ad­van­tages:

  • the need to place the tank at a height;
  • evap­o­ra­tion of liq­uid from the con­tain­er;
  • accel­er­a­tion of cor­ro­sion process­es in dif­fer­ent parts of the heat­ing sys­tem due to the con­tact of the coolant with air;
  • large tank sizes.

In con­nec­tion with these dis­ad­van­tages, closed expan­sion tanks are now becom­ing more and more pop­u­lar.

Learn more about the advan­tages and dis­ad­van­tages of heat pumps here.

Do your chil­dren often sneeze for no rea­son, and your wife spends a lot of mon­ey on var­i­ous mois­tur­iz­ers? Pay atten­tion to all the pros and cons of a humid­i­fi­er.

Closed type or membrane

These tanks are used for heat­ing sys­tems with forced cir­cu­la­tion. Capac­i­ty Closed tank typecom­pen­sates for the pres­sure surge not only when the coolant is heat­ed, but also when the cir­cu­la­tion pump is turned on.

It is also called mem­brane tank due to the nature of the inter­nal struc­ture. it a spher­i­cal or flat reser­voir, which is divid­ed into two cav­i­ties inside by a rub­ber mem­brane:

  • one is filled with coolant through a thread­ed pipe;
  • the oth­er — with an inert gas or air.

The sec­ond con­tain­er has a nip­ple that reg­u­lates gas pres­sure. The com­part­ments are not con­nect­ed to each oth­er.

The prin­ci­ple of oper­a­tion of a closed tank is sim­ple:

  • excess hot coolant enters one of the cham­bers, the vol­ume of which increas­es;
  • the pres­sure in the gas com­part­ment ris­es, which makes it pos­si­ble to com­pen­sate for the volt­age in the heat­ing sys­tem.

When the coolant cools, the process in the tank goes in the oppo­site direc­tion.

Principle of operationThere are 2 types of closed-type con­tain­ers, depend­ing on the mem­brane:

  1. In some the mem­brane is made in the form of a diaphragm that can­not be changed. These con­tain­ers are cheap­er.
  2. In the sec­ond type of closed devices the mem­brane is remov­able and looks like a pear.

The choice depends on the capa­bil­i­ties of the buy­er. It should be not­ed that dam­age to this rub­ber ele­ment is quite rare.

Before buy­ing a tank, you need to decide on its vol­ume.

Volume calculation

You can cal­cu­late the vol­ume of the tank your­self using sev­er­al online cal­cu­la­tors, or by Different volumesa fair­ly sim­ple for­mu­la:

Vtank=(Vsys­tems *k)/(1‑Pmin /RMax)where

Vtank — tank vol­ume;

Vsyst — the total vol­ume of the heat­ing sys­tem, includ­ing all radi­a­tors, under­floor heat­ing, boil­er, etc.;

k — coef­fi­cient of expan­sion of the liq­uid, for water its val­ues ​​​​depend­ing on heat­ing from 10about up to the max­i­mum tem­per­a­ture of the coolant are indi­cat­ed in the table below;

Pmin is the ini­tial pres­sure in the ves­sel;

PMax — the max­i­mum pos­si­ble pres­sure in the tank, which is cal­cu­lat­ed accord­ing to the set­tings of the safe­ty valve, tak­ing into account the dif­fer­ence in the heights of the loca­tion of the tank tie-in and the valve.

Table. The coef­fi­cient of expan­sion of water depend­ing on the heat­ing at an ini­tial tem­per­a­ture of 10aboutFROM.

Tem­per­a­ture from 10 k val­ue, %
Up to 40 0.8
Up to 50 1.2
Up to 60 1.7
Up to 70 2.3
Up to 80 2.9
Up to 90 3.6
Up to 100 4.3
Up to 110 5.2

Since the qual­i­ty of the entire heat­ing sys­tem depends on the cor­rect cal­cu­la­tions, you should not spare mon­ey and con­tact a spe­cial orga­ni­za­tion that will take into account all the para­me­ters, which will allow you to pur­chase the most suit­able tank.
Here you can also get advice on the selec­tion and instal­la­tion of the tank.

Useful tips when choosing

When buy­ing and installing an expander, it is worth con­sid­er­ing sev­er­al nuances.

  1. When choos­ing a place for mount­ing the tank, it must be tak­en into account that it can not be installed imme­di­ate­ly after the cir­cu­la­tion pump.
  2. Com­mer­cial­ly avail­able tanks come in two col­ors: red and blue. In the first, the mem­brane is stronger, but made of tech­ni­cal rub­ber. Blue tanks are used for water sup­ply, they con­tain food-grade rub­ber, but it is less strong and durable..
  3. When installing, use spe­cial sealant.
  4. If you decide to stay at open sys­temthen the tank must be placed at the high­est point, and when installing the pipeline, observe the rec­om­mend­ed slope.
  5. The size of the tank should not be less than the cal­cu­lat­ed val­ue, a slight­ly larg­er vol­ume is allowed. When using forced cir­cu­la­tion, the capac­i­ty can­not be less than 15 liters.
  6. Antifreeze can act as a coolant. For gly­col mix­ture, it is bet­ter to choose an expan­sion tank, the vol­ume of which is twice the cal­cu­lat­ed one.

The main advice is to con­tact the pro­fes­sion­als, because the instal­la­tion of the tank only seems sim­ple. In addi­tion, you can not do with­out a spe­cial tool.


installation diagram

Scheme of installing a tank in a pri­vate house sys­tem

If you are con­fi­dent in the cal­cu­la­tions and your own strengths, the tank and all mate­ri­als are pur­chased, then you can install the con­tain­er your­self.

Of the tools you will need:

  1. Stepped and adjustable wrench­es;
  2. sol­der­ing device for plas­tic pipes;
  3. Key for the instal­la­tion of plas­tic pipes;
  4. In some cas­es, you need weld­ing machine and angle grinder.

Before instal­la­tion, it is nec­es­sary to de-ener­gize the boil­er, close the valves and drain the coolant if it is already in the pipes.

Instal­la­tion is car­ried out sub­ject to cer­tain rules.

  1. The tank must be mount­ed and installed so that it can be accessed easy access for adjust­ment and main­te­nance.
  2. The tem­per­a­ture in the room should not be below 0.
  3. On the sup­ply pipe you need to install a pre-shut-off valve that will allow you to remove the expander for main­te­nance and repair.

After installing the tank, you need to start the entire heat­ing sys­tem. If boil­ing is detect­ed in it, then the rea­son lies in the incor­rect­ly select­ed diam­e­ter of the pipes. It’s not about the tank.
The instal­la­tion of the expan­sion tank is described in the fol­low­ing video:

Prices for tanks for the heating system

The cost is deter­mined by its type and vol­ume. Small closed con­tain­ers (18–24 liters) cost about 1000–12$.
An expander with a vol­ume of 100 liters can be pur­chased for 4–60 $. Between man­u­fac­tur­ers in their major­i­ty, the price dif­fer­ence is small.

Instal­la­tion by a pro­fes­sion­al will cost you about 20 dol­lars.

When con­tact­ing trust­ed com­pa­nies or with self-assem­bly, sub­ject to all the rules, you will pro­tect the heat­ing of your home from dam­age. There­fore, the instal­la­tion of a con­tain­er is nec­es­sary, and it is worth choos­ing closed con­tain­ers.

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