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Rads not heating - pump and boiler seem ok

Postby shaundavies » Sat Feb 23, 2008 12:50 pm

I drainded my CHS yesterday to put somecleaner in the system.

I bled the rads before switching back on and now the rads wont heat up. The feed and return pipes are warm and the pump is noisier than usual. I have vented the pump and re-bled all the rads but sitll no heat!

Could some sludge have blocked something? could it be air in the system.

Advice would be much appreciated
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Simply Build It

Postby roger196 » Sat Feb 23, 2008 6:32 pm

Starting with the obvious, are the rad valves open? roomstat calling for heat? CH timer on at boiler?
Check the pump is working by gently holding the pipes each side about ten inches from the pump. They should feel hot, about 85C.
If pump OK, then turn off all rads except two to force water thru the system. If this works, turn off one rad and open another and keep repeating this. Bleed rads at each stage with CH off.
If this does not work, turn off both these rads, and try another two.
Let us know if any improvement.
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Postby shaundavies » Sun Feb 24, 2008 7:43 pm

Thanks Roger,

Turning off the rads and putting them on 1 by 1 seems to have flushed whatever was causing the problem out. I really appreciate the fix advice.

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Postby Oliver_murphy » Sun Feb 24, 2008 7:49 pm

I would say that you have air-locked your system. A better way of clearing this is to
1. Close down EVERY rad on the system. Select CH only only max demand, and wait until both the flow and return from the boiler get hot. Then, when you have a clear system, I.E, its flowing around the primarys, open 1 rad. Wait until its hot all over, bleed, close it again, then move onto the next one. Repeat until all rads are hot.

you then need to balance your system, write back if you need help with that,
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Postby littleredhen » Thu Feb 28, 2008 1:49 pm

THANKYOU for this advice - I was searching online desperately trying to avoid calling out an expensive plumber and this was my exact problem which seems to have worked.
How do I balance the system now?

A ver grateful Londoner! :roll:
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Postby becky » Sat Mar 22, 2008 10:56 am


We had same problem with cold radiators and followed Roger's advice of only having two radiators on at once which has worked perfectly. Just wanted to say thanks Roger, you've saved us from a chilly Easter and an expensive plumbers bill!!

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