My heating pump keeps running even when the heating goes off, why?

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I have a sealed central heating system with 1 pump. When the heating comes on the pump starts but the pump continues even when the heating is off.
I expect a little overrun, I understand this is to keep circulating the water until it cools down?… but on my system the pump goes on and on… all through the night. It is driving me crazy to the point I switch the heating off at the mains every night just so I can sleep!!!
This never used to be the case… in the past the pump would run for a short while after the heating goes off then stop running. What is happening, why does the pump keep running?

2 answers

Dominick Staff December 13, 2013

Well it’s suppose to keep running even when your boiler is off. All night ? well if you need heat, then yes. Try turning the thermostat down low and see if it still runs. 
However these pumps don’t make much noise at all. Even if you’re standing right next to it they can be hard to tell if they are even working. You could have lots of air and thats what you’re hearing. 
Do you hear water running through your heaters / pipes ? 
also know what type of pump you have would be helpful. Can you take a picture and email to me. dom@askmediy.com 

#1
  1. Water stat is set very low and the heating stat is on a timer so it switches off at night. Even when I turn down the room stat so the heating switches off, the noise continues.
    I do think I have a problem with air in the system as I can hear water running through the boiler when I first switch the system back on. Also when I use hot water, I hear a loud trumpet type noise for a few seconds. I have tried bleeding all of the rads with the system off (whilst cool) but after a couple of attempts over a few days, no more air comes out of any rad.
    Pump is a Grundfos 15-60 domestic pump.
    Thanks for the quick reply!
Dominick Staff December 13, 2013

Make sure the fresh water supply to the boiler is always on. And yes of course you have air in the system. Air get at very loud on some system. 
Lucky for you I’m home today working on the website. And painting lol. 

#2
  1. Cheers Dom!

    Think I'll just drain the whole system down and start from scratch. I've given up bleeding the rads.

    Good luck with the painting!

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