What pressure should be in the expansion tank and in the main circuit

Hello. Tell me - air pressure in the expansion tank and should the water pressure in the heating system be the same or not? I have a green zone of the scale from 1 to 1.5 atm on the boiler, and 3 atm is written on the tank. I understand that if the pressure in the expander is greater, then it will not work, since water will not be able to enter it. It seems to me that the air pressure should be lower than or equal to the water pressure. Maybe I'm wrong. Please tell me.

Evgeny

Expert Answer

Eugene, you are absolutely right. For the heating system to function properly, the pressure in the expansion tank should be 0.2–0.3 atm lower than in the main circuit - otherwise, water simply cannot enter the expander. In addition, it is important that this element of the system is installed according to the rules. The best place to install the tank is considered to be the section on the return pipe between the circulation pump and the boiler.

We remind you that pumping or depressurization in the expansion tank is performed by disconnecting it from the heating system. In order not to drain the coolant, ball valves should be provided at the tank connection section.