Gravity fed CH system - Pump question

Hughmungus · 19 Oct 2009

Hi, been on here as a guest never as a poster.

I have an ex council house gravity fed CH system which worked well apart from the odd cold radiator but was always fixed with a bleed. I have now discovered tonight the delights of balancing (and i thought they where just so you could remove the rad!) which I will get round to once I have an answer to this question.

Not sure if this is right and I can't remember if it did this before or not but should the pump run all the time whilst the CH is on, mine only runs whilst the boiler is fired and shuts down when it stops, this only started to do this in the last week I think. When it does shut you can hear the 2 port valve wind back. When the boiler fires up again the pump runs. I'm sure it should run all the time the CH is on?.

Consequently the downstairs rads don't get warm and I assume this is because it is only pumping when the boiler is fired plus of course the balancing issue?.

If it should run all the time could it be the overrun stat (wherever that is) or something else?

Thanks for your time

bengasman · 19 Oct 2009

Pump should run constantly when there is a call for heat i.e. BOTH timer AND thermostat on.

petit_pablo · 19 Oct 2009

1st question, what boiler? It should run all the time unless its been incorectly wired

Hughmungus · 19 Oct 2009

Blimey that was quick ... thanks.

It's a Wickes Heat 60 which I had fitted when I had an extension about 4 years ago

You have to have the HW going if you want CH.

Timer set to on both HW and CH but pump switches off when boiler reaches temp and the 2 port valve winds back which I get it should do.

Not been an issue up until this last week when I removed a radiator upstairs to decorate. May be a just coincidence though.

Thanks

petit_pablo · 19 Oct 2009

It shouldnt be shutting off the zone valve and pump every time burner goes out. The water needs to continue to circulate to dissipate the heat. The valve closing is probably why the pump is stopping. Depends if its 3 or 5 wire valve.

Do you have access to a multimeter?

Need to know if the valve is getting correct voltages

Hughmungus · 19 Oct 2009

Hi yes I do have a multimeter. The valve I put in last year as the previous one was stuck open. It came in a kit form from Scewfix which I'm sure is a Horstmann F322 2 port valve and according to the Screwfix site is 5 wires.

The pump shuts off, then you can hear the valve wind afterwards.

Can't look now a it's getting late (the boss is in bed

) but will after work tomorrow

Thanks

bengasman · 19 Oct 2009

Sounds like it's wired up wrong

Hughmungus · 19 Oct 2009

Has been working ok I'm sure up until the w/e.

I just copied the wiring exactly, this was summer 08, have had one winter out of it and no problems?

petit_pablo · 19 Oct 2009

Ok well if its a 5 wre then you need to check these voltages when CH on and thermostat turned up.

Brown 240V
Orange 240V
Grey 240V
Blue & green/yellow 0V

What happens when the burner goes off?

I imagine that you will lose 240V to brown and orange.

If so there is a wiring fault. In which case you will need to trace the voltage from CH on at the timer to thermostat then from thermostat to valve

Hughmungus · 19 Oct 2009

Thanks, will try that and post the reuslts tomorrow night.

Hughmungus · 20 Oct 2009

Hi, checked voltage and as you suggest I lose voltage at the orange and brown. The cable from the tank stat looks damaged so will strip that back first and look.

Will report back

Hughmungus · 20 Oct 2009

Looks damaged but its ok. Just got the heating on. Turned down the the tank stat so that doesn't interfere. Put a new timer on that I had and testing now.

Hughmungus · 20 Oct 2009

Ok that didn't work. The only way it will stay on is to push the valve motor to manual, does the mean it's the valve?

Thanks

Hughmungus · 21 Oct 2009

Any views on this yet please?. As I have said I have fixed the arm in manual mode and all is ok apart from it pumping hot water round the tank as well as the heating.

Do you think it needs a new motor, If so I will go to SF tonight.

Thanks

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Gravity fed CH system - Pump question

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