pressure loss on firebird combi 120

asreies

Hi All

i have a combi 120 by firebird, the expansion vessel is new and set at 1 bar ,the prv is new as well as a new aav vent ontop of the boiler.
i have isolated the central heating but still lose pressure( which is not venting through the prv,) anybody come across this before all replies greatly appreciated.

items

asreies wrote: »

Hi All

i have a combi 120 by firebird, the expansion vessel is new and set at 1 bar ,the prv is new as well as a new aav vent ontop of the boiler.
i have isolated the central heating but still lose pressure( which is not venting through the prv,) anybody come across this before all replies greatly appreciated.

Sealed heating systems have expansion vessels, only way a sealed system can vent is by bottle type vent. Not sure what you mean by venting through PRV? PRV can mean pressure release valve (safety valve close to boiler) or PRV can mean pressure reducing valve. If your heating is filled via mains water, or pressurised supply you might have a PRV in that case.

When you say isolated, if you mean turning of heating water supply after you've filled to certain pressure, then it drops, system is either not filled properly or you've got a leak.

Sounds of things, maybe you are opening up safety @ boiler to vent air manually, you've no air, or water?

Might be better to provide more info.

asreies

Hi Items

you are right in saying about the bottle vent, that is fine with no air venting out,
i was trying to indicate that there is no increase in pressure or that water is escaping via the prv( got it bagged up ,alas nothing coming by this route)it seems like a dead end as to where the water is going-is it the heat exchanger?,guessing its about half to three quarters of a kettle escaping somewhere,any ideas

items

asreies wrote: »

Hi Items

you are right in saying about the bottle vent, that is fine with no air venting out,
i was trying to indicate that there is no increase in pressure or that water is escaping via the prv( got it bagged up ,alas nothing coming by this route)it seems like a dead end as to where the water is going-is it the heat exchanger?,guessing its about half to three quarters of a kettle escaping somewhere,any ideas

Sounds like you had some maintenance, modification to heating system, might be a case where its not filled properly.

If you were loosing water through safety, you'd see it. Oil boilers generally work off supply's from attic tank, it takes around 3.5 to 4 bar pressure to open up a safety allowing water to pass, not enough pressure coming from attic tank. Safety could have damaged seal and weep but you'd see it, both with boiler on or off.

An old rusty leaking heat exchanger again like safety would be fairly obvious, once water can escape it will make its escape route bigger, rusty heat exchanger would'nt be long passing loads of water once a small weep started if you get me.

I'd fill system up, vent everything you can, leave system filling valve open. Run boiler at low temp, check for leaks in the areas where recent works took place, if you cant find anything, turn up temp and check again.

If you still cant find anything and your sure system is fully vented with water supply open, might have some leaking rad valves, pipe work, valves anything really.

How old is your system, any GB pipework?

asreies

Hi Items
changed the expansion vessel because it was flat so changed prv(had blew before so worthwhile changing, same with bottle vent.
this is what i thought would rectify the system, which is four years old.
The only mod i have made and have doubts about now is a couple of aav on two radiators,the water is supplied via a heatstore inside the boiler

items

asreies wrote: »

Hi Items
changed the expansion vessel because it was flat so changed prv(had blew before so worthwhile changing, same with bottle vent.
this is what i thought would rectify the system, which is four years old.
The only mod i have made and have doubts about now is a couple of aav on two radiators,the water is supplied via a heatstore inside the boiler

Did you fit bottle vents on pipe work going to rads, maybe troublesome rads, constant air in them?

Your water should come from either attic tank or mains water, not sure about heat store inside boiler? If your heating water is not supplied by mains, you must have some kind of filling tank located well above boiler along with well above rads.

You've done some works so where ever water is coming from, make sure it has a supply along with that supply being full of water.

Hard to tell from here, might be a case now, you might have to start isolating, pressure testing sections individually to rule out or in leaks.

Maybe you've done some works over the years and its coming back to haunt you, might be time for calling in plumber etc

Then again, sometimes silly little leaks occur, hard to find ones, gate valves with weeping glands, same with rad valves, they are both very hard to see.

From here, to me a heating system filled correctly and fully vented with water supply on, losing pressure, all points to a leak. Sure you know that, finding it might go past your own ability.

Those two rads you mention, if they were air prone as in constantly requiring venting, problem might stem from those rads, underground pipe work, pipes that leak also take in air. Modern day systems once full, require little to no venting, any venting is considered annually, not monthly or weekly.

Micky Dolenz

I can only assume your plumbing and heating are pressurised. When you say you isolated the heating, how did you do this?

asreies

shut off the flow and return isolators on the boiler,with all power off waiting to see where the water can go if everything is cold, assuming water evaporizing if left on with valves open

asreies

Thank god a leak finally showed itself,all should be fine now

Micky Dolenz

at the boiler?

asreies

funny really, it was a length of pipe in a wall,carpet started to get wet, held pressure now for 7 hours, cant understand this but boiler couldnt have been pressurised during tests.