Power flush or chemical

[mad_angler1]

Hi all, after some advice on the parents ch system, iv been plumbing for years and working in the industry for a bit, work with electric and water now but have installed as few systems but never done any thing with poor circulation problems, the system seems to be blocked, its a 12 YO boiler (WB 28cdi) with radiators of similar age,pipe work much older, a few rads would be a few years younger though.

The problem is no rad gets fully hot, hot at tops but cold bottom, i spent yesterday checking the system over and the flow from the boiler is nice and hot but i noticed the return to the boiler it never really getting hot, middle warm at there most, the boiler is shutting down earlier than i would expect based on the return temp as well, then a few minutes later it fires back up, In the end i shut down evert rad TRV's and tested each rad on its own and it was the same just hot at top nothing on the return at all.

the flow pipes to all the rads get nice and hot but hardly anything on the return, I'm guessing this is sludge, no air in the system so i know its not that, could the internal by pass be kicking in due to the restriction causing the boiler to shut down early ?

as for cleaning what to recommend, X800/F5, does the 28cdi have an Aluminium heat exchanger ? as looked as DS40 ? also was looking at hiring a power flush matching but not sure whether to go just for cheaper and a full mains system flush

Ian

 

[steadyon]

Has the system ever worked correctly since the boiler was installed? If not, then it could be something as simple as all lock shield valves closed down too far and simple radiator balancing could be enough. You could try opening each lock shield fully (noting 1/4 turns open for each before you start) then running the system. If that makes a significant difference, re-balance. If it doesn't, restore each lock shield to its previous setting.

You could try taking a medium sized radiator off, flushing it through with mains water outside, re-installing and seeing if that makes a difference to that radiator. If lots of sludge comes out while flushing and it gets evenly warm when put back, does sound like sludge.

Otherwise, it might be worth checking that the pump is operating properly and is not worn.

I don't know for sure whether the heat exchanger is aluminium, but don't think it is. However, to be on the safe side use a cleaner which is safe on aluminium, even if it means leaving it in a bit longer.

 

[AWheating]

combi?
is the pump running well?
is there a bypass on the system?
is it micro bore?
take a small downstairs rad off and give it a flush on a hose pipe to see what comes out. if theres lots of crud then the system could well need a good powerflush.

 

[mad_angler1]

thanks for the quick reply, been over again today for a good dig around, a few answers first of all, the pipes work is original and is some years old, no really sure but all copper and pre dates the boiler, the boiler was replaced by BG in 2001 they they bought the house, rads changed a few years later.

Boiler WB 28cdi Combi
Pipe work leaves the boiler at 22mm head off into the loft for about a meter and a half then goes to 28mm for some strange reason, it heads down the house for about 7m, then drops back to 22mm for a few feet where it comes to a T, the 22mm branches left and right of another 2m to 4 out put legs at the end on each side, return flow to the boiler is dentical, not sure what to call the ends, it an end fitting with 4 tails on each, not sure if its 8mm or 10mm, looked like 8mm TBH.

flow seems good, no strange noises from the pump, its on setting 3 at the boiler, the flow pipe work is hot in the loft at the 8mm branches, the return on the other hand does not gain much temp as all. this is the same at the rads, flow is hot but return is barely warm.

after some checks today, 2 small radiators in the ground floor toilet and 1st floor airing cupboard are bouncing hot top to bottom, 2 large rads in the 1st floor bedrooms and reasonably hot as well but everything else on the ground floor is having problems, ,tops of the rads get hot but bottoms remain cool, drained one rad down with the intention of removing but in the end ran out of time, the water was clear, no black, smells of inhibiter, iv added x400 and am going to run if for a week.

its not worked well for a few years but they have put up with it,i have noticed they have a lot of Big rads in the house, far larger than i would normally notice in homes, I'm wondering if the rads are well over sized and the boiler can't cope. there are a total of 7 large double rads with 2 small 400x600 and a tall towel rail in the bath room.

as i said iv now added x400, i have also balanced it better, iv closed the valve rite down on the two small rads and the ones up in the bedrooms that are on the shortest pipework,

i think i will calculate the rads KW this week and work out load.

 

[kay-jay]

Where the main circuit joins the microbore it is called a manifold. This is likely to be the point at which the sludge is settled and causing blockage.

Have a check with a magnet to see if there is any attraction as slufge us magnetic but your pipework isn't

 

[mad_angler1]

Thanks all for the info, had a chat with a lad at work today thats ex BG heating installer, did 15 years with them then had enough, get the impression he don't like micro bore, should be 15mm and nothing else, he put a bet on it being the manifolds being the likely location of problems and every thing he said echo'd what been posted here, he told me to fire it up for an hour tonight then get a rubber hammer and give every rad a beating, not to hard though, then give the manifolds a good few taps to loosen up what may have built up there.

well i did it and its made a massive difference, every rad is not hot top and warm to hot at the bottom, the return at the rads now feels warm compared to cold before, the main flow return in the loft now is warm to hot as well so all good.

i intend now to let the x400 work its stuff till the weekend then give everything one last beating and then drawdown and flush it through via the fill loop.