Qick plumbing question

[locksmith]

Central heating pump, does it keep running when the thermostat clicks the heating off or should it stop and come back on when the thermostat clicks on again?

[erix2]

Pump goes on and off with the clock or override switch.....thermo just turns the boiler on and off....i.e. pump runs all the time.
 
 
Eric 

[locksmith]

Cheers mate

[evesdad]

depends what system you've got.

[slappy]

some pumps fire up at intervals set by the manufacturers to make sure they don`t seize.

[rustyrider]

On other systems the pump switches on and off controlled by a room stat.

[Chillum]

Even a system that shuts the pump down after the heating is switched off will carry on running for a while until the water has cooled down

[pete786.u]

The one on my system stops running when the bolier shuts down but mine only runs 5 Radiators.

[pitternator]

generally if you have  a gravity fed system, the pump circulates water to your rads, and is switched on and off by the room stat.( or by switching the boiler off at the mains)
 
more sophisticated systems have motorized valves and hot water may be pumped. Its hard to make generalizations.

[locksmith]

As always theres more than one way to skin a cat

It's a gravity system with a conventional boilerand two motorised valves.
Reason I asked is that I've noticed a bit of banging every now and then.
The other night I'm laying in the bath and heard the boiler stopping, and a  valve whirring. Then I heard some banging and the sound of water "wooshing" (for want of a better word). It lasted for a few seconds. The pump kept running and sounded a bit more vibey than it had.

The boiler is under two years old and the full system is covered and I shall be calling them out but I wanted an idea of whats going on so they can't baffle me with bullshit.

[Chillum]

Sounds a bit like an air-lock. Have you bled it?

[Fazerider]

If the banging noises are coming from the boiler itself then it could be getting overheated, either because it's silted up (unlikely with such a new system, assuming the water includes inhibitor) or the internal thermostat has failed. Despite the name, the boiler shouldn't make the water boil.
If it's just general noise from the circulation (especially the pump) then you've simply got some gas in the pipework. If the header tank hasn't run dry, all you'll need to do is bleed the system. Depending on how lazy/stupid the original plumber was, this can be easy or a PITA.

[evesdad]

if you have got two motorised valves its a fully pumped system. Each valve actuator has an end switch which provides power for the pump and boiler (usually the orange wire). These switches sometimes stick, so when the valve body springs closed (the whirring noise you heard) the pump and boiler still run but there water has nowhere to circulate. The boiler actually boils which is the resulting banging noise you hear!

[chris.biker]

You should have been left the manufactures manuals its a legal requirement. read through that it tells you all you should need to know. If you search the boiler make and model in google it will if your lucky find the manuals.

[locksmith]

Quick update.
The engineer visited and (fingers crossed) has fixed it.
The system has what he described as a bypass loop so that when the valves shut the water has somewhere to run round instead of nowhere. There is an adjustable spring tensioned valve that the water pushes open. It was a little too strong for the water to push open cleanly - hence the banging. So he loosened the spring tension and hey presto no more banging so far).