whats going on ARGHHH

[obseen16]

Hi guys, forgive me if this seems rushed, i spent half hour typing this all out then the darn interweb went off and lost it all,

ill start at the beginning,

Problem: Downstairs rads dont heat up unless the upstairs rads are turned fully off.

System:
8 rads, (4 up and 4 down) downstairs rads are all drop fed in 15mm Yplan system, combined feed and vent pipe which links into the system just under the pump. Pump is on the flow pipe in the airing cupboard along with the 3port valve. boiler is on the ground floor almost directly below the airing cupboard. all pipework is 22mm and 15mm

another plumber changed the pump 3 weeks ago but it didnt solve the fault.

What i have done:
Power flushed
put a new 6meter pump on
Changed trv's
Pulled water from the return on the boiler (thinking maybe an air lock)
Pushed mains pressure up the return on the boiler
pulled water through all downstairs rads and drained to outside
drained and refilled
fine balanced the system
twiddled valves (i know...)
closed off hot water pipe with gate valve
flushed rads with mains water
blanked off vent pipe (to see if it was pulling air down and into the pump)
sucked everything out the droppers with a wet and dry vac to see if any large lumps of crud came out.
Last thing i have done - Put more fernox f3 cleaner in and said see you in 3 weeks

Its surely a circulation problem but ive tried all the above and nothing worked.

have any of your had similar problems? its really weird that its all the downstairs rads not heating up even though they are all on seperate drop feeds.
its baffled me.

hope one of you guys can help on this one.

Cheers
J

 

[dave1]

Pump maybe?

 

[gasmanrob]

Had this on a new build last week someone went through the works etc. turned out there was a strainer in the return of the boiler. Out of interest was this a back boiler conversion wonder if there is a check valve somewhere.

 

[obseen16]

Hi Dave, not the pump, been changed twice in the last month so i know its not that.... i wish it was though lol
Gasmanrob, thats an interesting thought, the boiler is an old potterton netaheat (i think) its about 14 years old, there wasnt any strainers on the visible pipework, and im a little bit reluctant to start taking boards up in the old dears house unless its really necessary.

 

[gizmolang]

Is there a manual bypass if so close it down see if that helps

 

[Billy Bob Bob]

what boilers fitted to this system?

 

[obseen16]

no byass on the system, just a towel rad with no trv instead,

the boiler is a potterton netaheat i think,

 

[Billy Bob Bob]

no byass on the system, just a towel rad with no trv instead,

the boiler is a potterton netaheat i think,

start by checking bp could be issues with the boiler not producing enough energy bear in mind its a positive pressured case seal(said seal is obsolete) and contains asbestos if its a netaheat

 

[stevetheplumber]

do the down stairs rads come on if the upstairs is shut down?

 

[jase158]

had this a while back and we had 3 engineers come out, even turned pump round to push air out, turned out there was 2 aav's in the attic which were drawing air in as we were filling system as the pipes went upstairs from boiler and then back down to downstairs rads and pump was on return

 

[Harvest Fields]

I also have the same issue but the boiler fitted is a glowworm combi and there are 5 x rads downstairs 3 of which are on 10mm, the 2 on 15mm are perfectly fine but the 10mm ones are all cold. Are your downstairs rads on 10mm pipe?

 

[Mike Jackson]

I had a similar problem a while ago and it was caused by a connection between the flow and return on the pipework under the floor. I'd try shutting all of the rads off and see what happens to prove if there is any form of connection. If there's a connection the return will still get hot. Don#t muck about for too long doing this as if there isn't a connection the pump will be pumping against a dead end.

 

[diamondgas]

Is it on an open system? Magnet check around the cold feed open vent will let you know if you're flush got rid of where most blockages arise 🙂

 

[obseen16]

Hi Guys, quick answer to all the above, the boiler kicks out the heat real good, havent gas rated it but the temperature of the flow pipe is scalding hot. the pump is on the flow but the idea of an aav before the pump is a possibility which ill investigate incase there is one and its sucking air in. all pipes are 15mm to the rads throughout the house and 22mm main flow and return pipes. if i turn the upstairs rads off then the downstairs rads heat up instantly but wont stay on if upstairs are on, i even tried balancing the system with upstairs rad lockshields only just cracked about half turn.
ive tried turning all rads off to see if theres a bypass, there definatley isnt a bypass hidden on this system. its a real puzzler ive tried just about everything i have ever been taught and nothing got it going. apparently this problem only arose 5 weeks ago.

 

[obseen16]

P.S
I tried the magnet on the cold inlet tee and on all exposed pipework after the flush and the magnet didnt stick to any of it 🙁

 

[Dannypipe]

I bet there is a by pass somewhere. Even if it's just piped in by some idiot.

What a head scratcher.

 

[obseen16]

i wish there was dannyplumb, itd make it alot easier to diagnose, definatley no bypass as the return was cool after half an hour. GRRRRR sometimes i hate heating systems more than B&* bathrooms :/

 

[Dannypipe]

Hmmmm. Well best of luck with it mate.

We all get them from time to time. You've tried most things I can think of. Eventually you'll strike gold. Please let us know what the problem was.

 

[Dannypipe]

Oh one thing. It's not an Alpha pump or similar (inteligent A rated pump).

SOme of those you need to put on a set speed to balance. I had problems with one when they first started appearing on the market.

 

[pimp]

I used to take what customers said with a pinch of salt. Is it possible that this fault has existed since the system was first fitted and not just 5 weeks? Maybe you are just one in a long line of plumbers to try to cure the problem. Sometimes considering things from a different angle can help resolve them.

 

[Centralheatking]

Sometimes things are not what they seem - now - gatevalves if there are any on the system might seem open fully but when they fail shear between the gate and the wheel head
shaft just where you cannot see.

It might be that one has sheared partly open/closed........centralheatking

 

[obseen16]

cheers for that central heatking, i was wondering if the pump valve had sheared half open but the spindles turned and stopped when the valve was fuly open so im guessing not, however i think i might take the pump off and have a look when i next go over there whilst the systems drained down. it wont hurt to look i guess 🙁