Baxi 105HE

I will give a quick run down of set up then explain the problem.

Terraced house, combi fitted upstairs in bedroom. 3 rads upstairs, 6 down (was four added 2) boiler approx 3-4 years old. Hot water works fine and so does the central heating upstairs.

Trouble is the rads downstairs hardly get hot, well only about half as hot as the ones upstairs. Ive turned the ones off upstairs and all this does is shuts the boiler down quicker i e getting to its maximum heat quick and knocking off. I even swapped all trvs and lockshields and flushed the system hot and cold, ive also checked the manifold downstairs which seems clear. (all pipework 8 or 10mm)

The boiler seems to go up in pressure to say 2.5 bar.

Any tips, the only other thing i can see a problem is from the boiler its running away in 22mm to i assume an upstairs manifold then down stairs to another manifold. But on inspection ive found between this 22 from upstairs to downstairs theres a section of 15mm. Now my only thoughts are that this piece of 15mm is causing a restriction and the central heating water isnt getting to downstairs quick enough thus raising pressure and not circulating to downstairs.

Any advice would be great, im a RGI and the property is my mothers but im at a loss to find the problem. Only thing i was gunna try next was to replace the piece of 15 mm with 22 and add a magnaclean in case any other debris stopping it from getting to downstairs rads.

I would fully open all the lockshields downstairs, then close the trv's if fitted to all but one rad, then do the same to the rest, if this works then you'll have to re-balance the system. If it does'nt work i would suspect sludge or the pump not working properly. Is the water clean from the lowest point ? and does it have inhibitor in ?

Also look to see if there is a balancing valve on the hot water cylinder return as this could be pinching all the flow.

Further to this a bypass might be fully open allowing flow to shoot round there?

superdupergasman said:

Also look to see if there is a balancing valve on the hot water cylinder return as this could be pinching all the flow.

Further to this a bypass might be fully open allowing flow to shoot round there?

Click to expand...

Combi Mind you, went out to one the other week and whoever converted the Y plan to combi left the heating by-pass in (gate valve fully open)

gigz said:

I would fully open all the lockshields downstairs, then close the trv's if fitted to all but one rad, then do the same to the rest, if this works then you'll have to re-balance the system. If it does'nt work i would suspect sludge or the pump not working properly. Is the water clean from the lowest point ? and does it have inhibitor in ?

Click to expand...

Have tried isolating upstairs rads inc trvs and lockshield valves to no avail only thing that happens is the chb usually shuts down sooner than it should (no flashing lights, fault lights etc).

Ive hot and cold flushed it, it has had fast cleanse and also inhibitor in to no avail.

Return filter will be blocked

Well that was another thought Slugbaby

Here's what you are looking for

I had cleaned it out 4 months earlier, it was chocka, so bad you couldn't even work out that there was a filter there. When I took the pic I was attending to a different issue and decided to check it and get a pic for the forum

Yeah i no where its at, didnt think that would be the cause like but will give it a go. I suppose this could be why the pressure seems to rise high thus being a blockage will give it a bash cheers.