sealed system problems!!!!

[supared1]

hello all,
first of all i'm newbie (to the site and industry) and would like to wish everyone a very happy and leak free 2011, the main reason for this post is to pick your brains and hopefully get some advice, i have recently moved ino my new home and immediately checked the heating and hot water systems, i have an unvented system (megaflo) and a sealed heating system (red expansion vessel).
Now to the point, all the downstairs radiators were only warm except one which remained cold 😕 investigating i found the filling loop was left open and the pressure was up to 2.5 bar so i reduced the pressure via the bypass/overflo and switched off the filling loop, this seemed to slighly warm the cold radiator only slightly, so i switched off all the rads (lockshield) except that one to try and balance them and no luck, but i noticed that the boiler was switching off even though the therm/heating was on and the house was cold, oh and the boiler is a halstead best 50 and has no problem with hot water, its just the heating thats baffling me.
I have also noticed that there is a gate valve just above the pump and before the mid pos valve which leads to the return i'm pretty sure thats a bypass but to me it seems to take the majority of the heated water from the boiler straight back into the return.
many thanks for just reading this because i know its a bit long winded but any advice would be greatly receaved.
Many Thanks.

 

[franky]

I think you might of got your words mixed up? Did you release the pressure though the pressure relief valve the bypass goes between the flow and returns?
When you turn on the boiler does the flow pipe heat up real quick? Check the pump is running
The bypass is this fully open and might be creating the loop back to the boiler telling it to turn off?

 

[supared1]

Hi, and thanks for replying so soon, yes I got a bit confused.com there, I used the preesure relief valve to bring the pressure to 1 bar and the bypass valve above the pump that leads to the return is fully open, this could explain why the boiler is switching off. But I've tried the valve open and shut but the cold rad still doesn't warm up, the rads upstairs are red hot and they're only slightly open at the lockshields

 

[franky]

Right just leave the bypass slightly open and forget about it. Sorry didn't read the bit about the downstairs rads look for a zone valve. Is your house divided so if you look at your programmer does it say heat1 heat2 hot water?

 

[supared1]

Hi sorry franky i typed out a reply on my phone but there must have been a problem in sending, right after another night tinkering i'm still no nearer to solving it.
The bypass is only just open and i'll leave it like that as you said, the flow pipe heats up really quickly so i know thats not an issue, there are no zones valves as far as i can see and the programmer is basic with no heat 1 or heat 2, i was convinced it was a balancing issue but tried that and i thought airlocks were not likley on sealed systems????? i might need to start flushing out rads but not sure the missus would appreciate that on our lovely new carpet...

 

[franky]

Right so its fine upstairs just downstairs is the problem?
You've turn off all the rads on the top floor but it didn't heat up downstairs or improve?
Did you check the pump ?
It should pump round there sound like a bit of a blockage something must be restricting the flow if theres no motorised vales to split upstairs and down stairs
You can always stick a pipe on the drain off open it up for a while see if you can drag the hot water to it

 

[tipintim]

You must have zone valve

 

[oldplumber]

close/turn off all top floor rads, and all bar one ground floor rad, then on boiler, heating on demand via room stat and close lockshield on working rad and then crack open, hopefullly rad should warm up and check its bleed of air, repeat for next rad and so on. If upstairs rads working ok then blockage down stairs ?, if it doesnt work add a sludge remover and leave in for 2 weeks, and run system on ground floor only for a while to help it clear out, then drain down, flush thro and have another go. Finally it could be a failing pump giving a gravity cct to the top floor only hence your problem so pump change needed. try the flushing first as its cheaper than a new pump. have fun.

 

[T.T]

I had a similar problem with one radiator not getting hot, is the TRV side working properly? Try taking off the head and pushing down on the pin.
If so, try gentley knocking the return pipe on rad' with a wrench as rust can block the pipe work. I know it's not a very technical approach but it has worked for me in the past.

 

[supared1]

hi all and thanks for all the great advice, i turned off all the upstairs rads and left the downstairs open which helped all but one of the rads (but they are still not as hot as think they should be) then i turned off the the other downstairs rads except the one that wouldn'd work and it got a little warm like there is minimal flow through it, it seemed as though the pump didn't think that was a good idea and there was a lot of noise as if there was no flow, i believe that the previous owners lived abroad for the winter months and maybe the rads havent even been used! i'm not sure but there is defo no zone valve and initially thought it could be the pump not being good enough with it being in the loft and the flow being rubbish downstairs but i think it could be a blockage in which case i'll flush through myself, i was under the immpression that a sludge build up was rare in sealed systems? if it turns out to be sludge how do you add sludge remover to a sealed system?

 

[franky]

Sludge can happen in a sealed system just do the job properly hire a powerflusher and chemicals and you'll not have to worry

 

[GQuigley67]

sludge in sealed system is not rare, its almost unavoidable. You can add sludge remover to system by partially draining down and adding it into the top of towel rail if you have one by removing the air point or via the filling loop with an injector.

 

[oldplumber]

buy an aerosol version and inject it in via a rad bleed valve or pour the cheaper version in via a towel rail end stopper, cheap connectors at screw fix. NB let the system pressure off first and drian down a bit to give u some room for the sludge remover.

 

[supared1]

Great!!! i'll crack it tommorow, i know i'm a novice but i wasn't aware of the aerosol version, i'll get the old bugger heated up if it's the last thing i do. although i haven't done a flush through yet so i may just give that a go for good measure. thanks again everyone.

 

[MickySkinn]

Hi, just curious how you got on/what method you used?