noisey central heating pump

[ashleyk]

Hi, new to the forum and a bit of a novice when comes to plumbing and I have a question about my central heating pump, its constaintly running and im wondering if this normal? and is noisey!

Any help would be great, Ash

 

[WHPES]

The pump will run whenever your controller is calling for heating or hot water, so it will be on most of the time when the water and heating system is on.

If it sounds like trapped air, unscrew the bleed screw on the front slightly to let out trapped air.

If it's rumbling or rattling, the bearings will be worn and its time for replacement.

 

[ashleyk]

Thanks for that WHPES, the pump seems to run even when the boiler isnt on could it have something to do with the motorised valve? and the pump is not even 2 years old yet.

I will try bleeding it a see if it quietens any

Cheers, Ash

 

[LIFES A GAS]

Could be a fault with the pump over-run, often this is incorperated on the boiler's main PCB but on older boilers it was often a simple button stat attached to the flow pipe work.
Martin

 

[ashleyk]

so its nothing I could fix my self then? I will mention to the plumber when he comes to service it and see if he can identify the problem.

Cheers

 

[dontknowitall]

Just expanding on WHPES post to clear confusion (hopefully!)

Most systems are wired so the pump is constantly turning when the programmer is on, whether or not the boiler is running or not.

When all the TRVs and room stat are satisfied the boiler will stop because the thermostat in the boiler senses the hot water as being hot enough. As the house cools the boiler won't know to start again unless colder water passes through it.

If the pump isn't running then it would take an eternity for the cold water in the radiator(s) to reach it but with the pump running the water comes back much sooner and so less heat is lost in the house and the boiler will keep the house at a more constant temperature.

So if your pump is running all the time, presumably the programmer is set to 24 hour running. If the programmer was set to run twice a day for say, an hour in the morning and five hours in the evening, then the pump would only be running for six hours each day.

The noise could be because the pump is on its last legs. If it's a cheap pump then it might only last a couple of years or it could be on the wrong setting or the wrong size.

In a "Y-Plan" the single motorised valve allows water to pass either to the hot water, or the heating or both. In an "S-Plan" you'll have two motorised valves, one for the heating and one for the hot water which basically operate independently and either allow water to pass or stop water passing through.

Hope all this helps.

 

[LIFES A GAS]

Just to clear up a few points made, modern boilers have a much smaller water capacity than older boilers with cast iron heat exchangers, the water content of some boilers is less than a pint at any given time therefore if the pump were to stop when the controls (programmer, room or cylinder thermostat) turned the burner off the residual heat from the heat exchanger could cause the boiler to overheat, (like turning the electric ring off under the boiling milk, it could still boil over). A pump over run prevents this by keeping the water circulating for a while controlled either by a timer chip on the PCB or a separate thermostat clamped onto the pipe work in the boiler. If your pump continues to run for more than 5 min or so after your controls have turned the boiler off then you have a problem. You could have a wiring error or the overrun stat is faulty.
P.S. If your programmer is on constant but your room & cylinder stats are satisfied the pump should still stop after a short time.
Hope this helps, Martin

 

[ashleyk]

Thanks for the help guys, it has helped me understand about how the pump works, I have got british gas coming to service it soon so hopefully they will be able to advice me if theres owt wrong!

Thanks for all the help, Ash

 

[LIFES A GAS]

.I have got british gas coming to service it soon so hopefully they will be able to advice me if theres owt wrong!

Thanks for all the help, Ash

They will probably try and sell you a new boiler, their cure for everything LOL
Martin