Cost of constantly running heating pump??

simonhgreen

Hi guys

I've identified a dodgy motorised valve on my heating system that means it works fine but just doesn't turn the pump off when it's up to temp.

I have put a manual timer on the plug to the programmer so I can leave the programmer on constant heat and time the power to it.

Oddly, if I leave the power off for a few hours & turn the power on the pump doesn't come on, which is somewhat mystifying.

Anyway, my question is - will it be very expensive to keep the pump running constantly when the heating is on, or does that happen anyway?

Any advice/ideas much appreciated.

moneysavingplumber

Pumps are now energy rated in much the same way other appliances are , which would suggest it makes a difference. Without pump over-run the pump should switch off when the room thermostat and cylinder stat are satisfied, along with the boiler. Even with over-run it would only run on for 8 minutes usually.

The reason turning the power off resets it is because it maually springs back to its resting position, which would reset the microswitch.

simonhgreen

Hi msp

The oddity is that if I turn the power off for even an hour it doesn't reset it, but after a few hours it does.

The valve is definitely closing when temp is reached (I took it off & checked it), so am I right in thinking its the signal the valve should be sending to the pump when it closes that seems to be at fault?

You mentioned that the pump switches off (or should do) when the room & cylinder stats & are satisfied. How can I check there's not a fault in this realtionship?

caveat_emptor

simonhgreen wrote:

Hi guys
Anyway, my question is - will it be very expensive to keep the pump running constantly when the heating is on, or does that happen anyway?
Any advice/ideas much appreciated.

Pump will take about 150w so over 10 hours would cost about 15p. Heating systems vary but on my old boiler the pump stops as soon as the t/stat switches.

simonhgreen

Thanks for the advice.

The pump is meant to stop but doesn't, hence the question.

If it's only 15p for 10 hours I won't panic about it too much, I just can't work out why it's working sometimes and sometimes not.

Thanks

Thanks anyway.

moneysavingplumber

simonhgreen wrote:

You mentioned that the pump switches off (or should do) when the room & cylinder stats & are satisfied. How can I check there's not a fault in this realtionship?

I'm assuming the pump is running cold and the stats are successfully providing the boiler interlock, which would suggest they are working fine.

In this case I tend to agree with plumb1 from your original post that it is almost certainly the MV.

espresso

It sounds to me as if the actuator return spring is not quite breaking the contacts.

If you go to the DIYdoctor you should find some wiring diagrams.

You may be able to either lubricate the actuator mechanism or adjust the contacts slightly to rectify this problem.

simonhgreen

Thanks, I'll give it a go, but if you're right why does it make a difference turning the power off for several hours, after which the pump isn't running when I turn the power back on??
Thanks to all, any other suggestions greatly received.

espresso

Not sure, could it be the effect of cooling down over a period of time?

I have sucessfully adjusted the contacts on a Honeywell valve.

Best of luck with it.

wizzer

i have had a similar problem. When my system is set to CH/HW on then the pump turns off after a couple of minutes over-run.

However, when on HW only it runs constantly.

This is a replacement system and we can't seem to get to the bottom of it although I seem to think (i'm not a plumber but I've just read up) is that it may be something to do with the temperature difference on the flow and return.

djohn2002uk

wizzer wrote:

i have had a similar problem. When my system is set to CH/HW on then the pump turns off after a couple of minutes over-run.

However, when on HW only it runs constantly.

This is a replacement system and we can't seem to get to the bottom of it although I seem to think (i'm not a plumber but I've just read up) is that it may be something to do with the temperature difference on the flow and return.

Some systems are designed for the pump to run continuously on "Hot Water Only" I think it's called Y Plan system.

Sorry, Ignore that. It's the other way round.