Pressure Release Valve (calorifier)

[Heckler]

In a perfect world - no it shouldn't, but mines been doing it for 5yrs now, never got any worse. A few drops now and then are no problem.

My 381 came to me with a 6 bar valve on it, it used to blow off occasionally but the red hot water pipe blew off regularly too!
I changed it for a 2 bar one and set the pump pressure at 20psi. It still blew off when the water got hot. I put an accumulator on, it still blows off. I gave up and now have a bottle for it to go in to.
Stu

 

[grumpygit]

You must fit a small accumulator tank to act as an expansion tank to allow the water to expand as it is heated. This will solve the problem.

If you don't have an expansion or accumulator tank it will blow off through the pressure relief, and without that it will blow a pipe or joint. 20 ltrs of water heated to 80 degs will increase pressure by 0.5 bar (all circa figures). Some tanks have a one way valve in the cold supply into the tank, this will stop you using the accumulator on the cold side as an expansion. So if you wish it not to blow off, you need to fit an expansion tank to the hot side of your system. If you don't you will have to live with wasting water into the bilge.