Boiler pressure question

[Killy Bing]

Head means alot in plumbing.

especially when replacing vented cylinders

 

[IDCHAPPY]

I like head

 

[SimonG]

I like head

Easy tiger

 

[acecharly]

Head means alot in plumbing.

especially when replacing vented cylinders

With domestic supply head means alot i agree, but on a heating circuit does the weight of water coming down balance the water your pumping up?

 

[Andyswad]

Ok just an update, put tissue round radiator valves last night all of them and this morning one of them is soaked. I mean totally. Could this be the cause?

Almost certainly, there is a difference between pressure and volume, you do not always need to lose a lot of water for the pressure to drop

 

[taxes]

Just a comment from an elderly DIY guy. Half a Bar is on the low side but is perfectly adequate for a height of 15 feet ( measured vertically from the level of the pressure gauge to the top of the highest point of the heating system). There must be a leak of some sort but it may not be visible water. I could be that the warmth of the system is evaporating the small leak before you can see it. It might even be an air leakage st the highest point of the system, but very unlikely.Top up the pressure to, say 2.5 bar (some systems have the pressure relief valve set at 3 bar) and then run your finger round all the radiator connections. If the pressure still drops, check your highest radiators to see if they need bleeding. I can't see that the size of the expansion vessel could be involved, as the sole object thereof is to prevent the systems's pressure relief valve blowing unnecessarily. If you have an old style isolating valve (wheel operated) the gland nut is often suspect and needs regular tightening. Best of luck.

One thought. When you had the new boiler installed, did you change the radiators? If you did, the fitting engineer is responsible for finding the leak. You could try turning off (at both entry and exit valves) ALL the radiators except one and seeing if the pressure drop continues. If not turn one radiator on at a time and check each time. Although the continuing nature of the problem suggests a pipe/radiator fault, try turning off the boiler, letting the water cool and then turn off the water feed and returns from the boiler to the system top up the pressure and see what happens.

 

[chris watkins]

With domestic supply head means alot i agree, but on a heating circuit does the weight of water coming down balance the water your pumping up?

No, not unless you are talking about circulating head in relation to the pump (circulator).
Head in this case is the weight of water acting on the air charge inside the expansion vessel & one should equal the other when cold. Therefore what pressure is required on the gauge to get water to the upper most point of the system (plus a bit) should equal the air charge of the expansion vessel.
Then the vessel will be able to accommodate the maximum amount of expanded water as the system heats up.