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Tim Cooke
Tim Cooke,
Category: Plumbing
Satisfied Customers: 41
Experience:  Owner at Self-employed
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I've no heating from my combi boiler

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Hi, I've no heating from my combi boiler
Customer: replied 8 days ago.
Hot water circuit is fine. On the central heating circuit, hot water is being produced and leaving via the flow (pipe is v hot) but only seems to be reaching the radiator in the bathroom (above the boiler). The Boiler then shuts off after a couple of minutes, cools down and then starts it's cycle again. Pump body gets v hot after some time but it seems to be working as it is rotating (visible when removing cover to inspect) and the flow pipe is getting v hot

Hello, there's more than one possible cause of this. For example, although the pump spindle is rotating there could be a blocked or loose impeller. There could be a blockage elsewhere in the system.

How old is your boiler and the rest of the system?

Customer: replied 8 days ago.
Boiler approx 12 years, new system when it was installed. All on microbore. I've had the pump off an impeller seems okay, resistance tested okay......
Customer: replied 8 days ago.
Main 30he, soft water

Did you dismantle the pump, i.e. remove the head from the body so that you could see the impeller?

Customer: replied 8 days ago.
Yes the impeller looked okay, didn't seem loose or stuck or missing any fins etc...
Does the system have an unblemished history in terms of corrosion protection? If not, I think you’ll need to locate the microbore manifold and check it for blockages.

Or, if you have a spare pump head, for that and you might be surprised to find a pump that “looks” ok often isn’t.
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Customer: replied 8 days ago.
Not really got any history that I know about. I did drain it a few times trying to diagnose etc and seemed pretty clean. Just a slight orange tint on the fins of the impeller. I actually ordered a pump yesterday. I had asked this question last week but didn't get an answer. Thanks for your answers, I hope the pump arrives tomorrow and I'll cross my fingers. Otherwise I think it may be time to lift the floorboards....

If you're feeling adventurous, you could uncouple the CH flow pipe from the boiler, assuming that the filling loop is connected to the CH return, close down the bypass valve, close the valve on the return into the boiler, couple up a temporary pipe from the CH flow into a bucket, and open the filling loop. See what comes out under the "encouragement" of mains cold water. Be careful not to overpressurise the system though or you could encourage leaks.

Customer: replied 8 days ago.
Thanks, will give that a try if all else fails. How do I close the bypass valve?
You’ll have to set it to maximum and have faith that it works!