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View the thread, titled "Combi Boiler CH system not working after system drain" which is posted in Boiler Advice Forum on UK Plumbers Forums.

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stuffedchsystem

Hello, hoping someone might be able to shed some light on our issue. I have a Combi Boiler - Worcester Highflow 400 electric - 2004 model.

We had a central heating leak, was losing 1.5 bar within 20mins. I located the leak under our solid oak wooden flooring, turned out to be a copper pipe with no lagging rubbing against a brick and had worn a hole.
I have replaced the pipework in this area by using 15mm couplers and re-soldering a section back into the two CH pipes which were laying across the brickwork.

Following the work, the system was re-pressurised and boiler power turned back on at the wall. I opened all of the valves on the radiators and bled the air out of each radiator whilst re-topping up the system pressure. The system is holding pressure (well has done in the past 5 hours) so I am assuming that the original issue is now fixed, but the CH system is not turning on when I start it?

If I turn the boiler off at the wall and then back on, both CH and Hot Water lights turn on red for about 3-5 seconds, then dissapear.
The hot water system is working ok, and the light comes on red when in use and boilder fires up. The CH system however, is showing no lights and the boiler does not even try to fire up when the CH system is turned on.

Is there a reset button you have to active after re-pressurising a system with this boiler?

One thing I notice is that the CH dial on the boiler (the temperature setting dial) spins around and around with no friction or end point, but the hot water one has an end point when you turn it anti-clockwise. Is this usual?

Thank you for any thoughts around this issue.
 
You guys rock! Thank you so much for helping with info, yes this was the problem. The dial spindle had snapped off the CH Boiler Control (not much to them, bad design really) and so I replaced with the hot water one and reset the CH system and now all working great.

This whole saga has been quite an ordeal, as we had this CH leak in a bungalow with no indication of where it was. With a new baby there have been a few nights where we would have had the heating on thanks to a summer that hasn't happened! I purchased a small inspection camera and drilled some 20mm holes through our solid Oak floorboards so I could try to locate the issue (as no indication of damp or water anywhere) When I cranked up the boiler pressure and heard some water noise down one of the holes I knew I was getting close.
Then removed a few T&G oak floorboards, cut through the ply and old pine flooring and saw this pipework issue. Soldered the new pipes in today and re-pressurised the system. Then my heart sank when the CH would not come back on.

But now, thanks to your help we have heat again. I appreciate your time to reply guys.

Now we have our house heating system working again, perhaps the weather will get better? (an im going to have to go and change my forum name!)

John.
 
Hi SafeGasInstall,
Located in Cheshire.

Are these replacement knobs easy to get hold of?

Would you mind me asking.... Now I have filled the system it is holding pressure again, but what is the best way I can drain it enough to add some inhibitor in?

Thank you again for the support.
 
Would you mind me asking.... Now I have filled the system it is holding pressure again, but what is the best way I can drain it enough to add inhibitor

Hi John easiest way is to inject inhibitor into a radiator, dependent upon type.

If air vent is on an end (rather than rear) you isolate rad, drain off sufficient water from valve nut, (retighten) open air vent and inject chemicals

Close air vent, open rad valves top up system and vent as necessary.

Run heating for a while to thoroughly mix/circulate inhibitor.
 
Drain some water out and oper air vent on tho highest radiator , that could be your tower rail , then after few minutes turn drain off fully and add inhibitor !
 

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Combi Boiler CH system not working after system drain
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