Help please, Radiators won't get warm

Astrozombies

Hi folks, I'm very stuck here...2 days so far. I'll try to remember everything we have tried.

Right, a long time ago, when we moved in, the house was single pipe system. Someone came in and changed pipework and all worked great for a few years.

I decided to plaster the long walk in the living room so removed the old radiator and stood it up outside to drain.

Plastered wall. Went to Refit rad and it had been nicked. Didn't bother replacing for years... Till Sunday.

Bought 2 radiators, fitted both to wall, 1 in gap between old rad valves and other further along the wall.

Drained system, fitted new valves to pipework and attached rad 1. Extended the pipework and plumbed in rad 2.

Opened water and checked for leaks... All clear.

All old radiators start getting hot, bleed them all and all piping hot in half hour except 2 new ones.

Turned all old radiators off so hot water could only go to New ones, nothing.

Decided to drain a bit of water out from drain on paper by new rad, water comes out of hose warm/hot.

New rads bled till water only coming out. Still won't get hot.

After being on for a few hours the first in the run for a bit warm, added one got slightly aired at the top but stayed cold at the bottom.

I'm totally stuck and probably missed out some stuff but any help/questions appreciated

knightstyle

Tell us more about the system, is it pumped?  Is the pump running?  Has the system been balanced?

Astrozombies

Pump is running and tried balancing the system but have up when a valve peg snapped.
Turned all the rads off so the only place for hot water to go was the new ones.
The radiator that was there originally used to get red hot so can't see why the new one in the same place won't.
All other radiators are getting hot as they always have.

Jeepers_Creepers

Astro, could you sketch out the way you plumbed in these two rads? Are they in series or parallel with each other? (I'm guessing 'series' as this would involve less pipework?)

It does, tho', just sound like a valve hasn't opened properly - did you fit 4 new ones or reuse two of the old?

You say one rad gets a wee bit warm after a few hours of running - I suspect the end valve of the other rad (assuming they are in series). 

If they are plumbed in series and you are certain that your actual plumbing is ok, then shut off the valves on one rad (have the other rad's fully open) and remove the rad (I'd remove the colder rad as the problem is more likely to be there). Then open each exposed valve in turn, aiming in to a shallow dish. Do they both flow easily and fully? (One will be supplied directly from the system, and the other via the second rad. If one doesn't flow fully, the problem is at that end. If that end is the other rad, then you need to repeat the process and remove the other rad as well. 

Anyhoo, could you sketch and photograph what you've done with the pipes? 

Oh, and is it a vented or sealed (pressurised) system you have?

TELLIT01

Is it possible that the valve at the outlet end of the radiator is closed?  The radiator would still fill OK and would get slightly warm over a number of hours simply due to hot water in the rest of the system.

Astrozombies

Jeepers_Creepers said:

Astro, could you sketch out the way you plumbed in these two rads? Are they in series or parallel with each other? (I'm guessing 'series' as this would involve less pipework?)

It does, tho', just sound like a valve hasn't opened properly - did you fit 4 new ones or reuse two of the old?

You say one rad gets a wee bit warm after a few hours of running - I suspect the end valve of the other rad (assuming they are in series). 

If they are plumbed in series and you are certain that your actual plumbing is ok, then shut off the valves on one rad (have the other rad's fully open) and remove the rad (I'd remove the colder rad as the problem is more likely to be there). Then open each exposed valve in turn, aiming in to a shallow dish. Do they both flow easily and fully? (One will be supplied directly from the system, and the other via the second rad. If one doesn't flow fully, the problem is at that end. If that end is the other rad, then you need to repeat the process and remove the other rad as well. 

Anyhoo, could you sketch and photograph what you've done with the pipes? 

Oh, and is it a vented or sealed (pressurised) system you have?

Sorry for the crappy scratch but you get the drift?

I THINK it's a vented system but not sure.
How would I find out?
Thanks for any and all help and advice.

I've checked outlet valve and it's open. Everything SHOULD be working from my looking and trying to work it out.

Jeepers_Creepers

Ah, so 'parallel'? Good - the rads should operate independently. 

4 new valves? 

Ok, shut off boiler and pump. Now fully close off the LH rad and remove it. Now open each valve in turn (water!). Both should flow generously. I suspect one won't. 

If your boiler has a pressure gauge on it, you have a sealed/ pressurised/ unvented system. I suspect you have vented - there's a small plastic tank in the loft?

Astrozombies

Yes, vented then.
4 new valves.



Them ones on both radiators.
Thanks.
I'll let you know how I get on.

Jeepers_Creepers

When you replaced these valves, how did you stop water coming out the pipes - drain down the whole system?

A possibility is an air lock in one of these pipes - if your system is vented. We can explore that when you try opening the valves in to a container :-)

(These are seemingly bi-directional TRVs, so not a case of them being on the wrong end... Can you see a direction arrow on the chrome side, with arrowheads pointing both towards the rad and down to the pipe?)

Astrozombies

Drained the system down to pity these on, opened the system to check for leaks then turned rads on.
Yes, these can go on any side of the radiator.

Everything following freely on the first one.

jbainbridge

Possibly an airlock?

I managed to fix a similar problem by closing each valve in turn and bleeding the radiator.