Cold downstairs radiators

F

Female Plumber

STRESSED!!!

Hi guys... Need some pointers!!

I installed an ideal logic plus combi a few months ago... The rads upstairs get red hot but the downstairs rads are cold. The flow gets red hot but nothing through the return. They're all 1200 x 600 doubles on 15mm drops.

I've flushed it, taken rads off, replaced pipes but nothing!! I dragged some water through the TF1 and carefully balanced all the rads out.. Were lovely and hot until the boiler switched off then as soon as it fired back up the downstairs ones were cold.

With just the upstairs rads on the return gets hot to the boiler, but when I open the downstairs rads the return becomes cold!!,

I'm pulling my hair out with this one,.. Literally!!! I'm thinking air locks but why is it going again after it sorts itself???.

Thankyooouuuuuu ;)
 
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F

Female Plumber

Tried it.. No luck. But one on the hallway only has lock shields on.

When just downstairs rads on boiler shoots straight upto 83 degreees then cuts out after a few mins. Pipes have been changed just incase of blockages...
 
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The guy who installed the new boiler in my property (Holty) did a mains flush on the flow then one on the return, coming out of the valves of a radiator I'd removed. Unless the whole system is new, could the drops be blocked at all?

If you open the bleed valves on the problem rads and let some water out does the rad in question get hot?
 
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F

Female Plumber

Pumps fine.. Tested that.

I think it's air locking but I don't get how it keeps doing it. Fit loads of combis on the same system with no problems what so ever. Changed some of the pipes on the return and they were all clear and clean.

I power flushed it before putting the other nee boiler on. X800 x 2.

Any tips on keeping a system/ dropped pipes from air-locking?
 
F

Female Plumber

Also while I'm on here...

Has any one changed an automatic bypass on a vokera linea before??

When you open the hot tap the radiators get red hot - so I'm guessing it's the bypass stuck. I've changed the diverted valve and that's all ok.
 
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Also while I'm on here...

Has any one changed an automatic bypass on a vokera linea before??

When you open the hot tap the radiators get red hot - so I'm guessing it's the bypass stuck. I've changed the diverted valve and that's all ok.

The bypass has nothing to do with hot water. Normally the divert valve
is stuck shut anyway. I suppose it could be stuck open.
 
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Pumps fine.. Tested that.

I think it's air locking but I don't get how it keeps doing it. Fit loads of combis on the same system with no problems what so ever. Changed some of the pipes on the return and they were all clear and clean.

I power flushed it before putting the other nee boiler on. X800 x 2.

Any tips on keeping a system/ dropped pipes from air-locking?

I'm wondering if there is a bypass issue here and the upstairs rads are working on convection, despite the pump working - ask me how I know lol!

One problem I had with the old boiler that's just been replaced that the fitter spotted and I didn't (I know!) is that the bypass gate valve was fully open. The boiler is on the same floor as the upstairs rads and I think the return was too hot. This would have been one reason why the pilot light kept going out. Me thinks the tenant, or probably her little girl had been playing with the gate valve!

Having said that I'm not upset it's been replaced, even if I've had to spend out. I was planning to get it done in the summer and I don't think that was the only problem brewing. It started to need parts that were hard to find.
 
F

Female Plumber

Also while I'm on here...

Has any one changed an automatic bypass on a vokera linea before??

When you open the hot tap the radiators get red hot - so I'm guessing it's the bypass stuck. I've changed the diverted valve and that's all ok.

The bypass has nothing to do with hot water. Normally the divert valve
is stuck shut anyway. I suppose it could be stuck open.

So you don't think changing the bypass will help? I've changed the bobbin and innards of the diverter valve.. Where's the best place to look next?
 
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What system was in place before the combi ?
ive seen hidden zone valves under floors do this and the system would still fill down the return
 
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Also while I'm on here...

Has any one changed an automatic bypass on a vokera linea before??

When you open the hot tap the radiators get red hot - so I'm guessing it's the bypass stuck. I've changed the diverted valve and that's all ok.

The bypass has nothing to do with hot water. Normally the divert valve
is stuck shut anyway. I suppose it could be stuck open.

So you don't think changing the bypass will help? I've changed the bobbin and innards of the diverter valve.. Where's the best place to look next?

No sorry I forgot the problem is downstairs radiators.
In which case the bypass will not be the problem unless it is wide open.
Very unlikely.
Have you balanced the system?

Close all radiator valves upstairs and open valves of one radiator downstairs.
See what happens.
 
F

Female Plumber

I've done that.. Balanced it up, got it going and then after a day or so the downstairs rads go cold again. Seems like it keeps air-locking but I don't see how!!!! It's gone again so I've got to go back tomorrow and scratch my head!! It's REALLY annoying!! :(
 

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