Radiators downstairs cold, upstairs hot?!?!?

[mattway]

Hi
I hope someone can help!!!

I have a Potterton Nettaheat Profile boiler, controlled with a digital timer and thermostat in hallway.

In the airing cupboard the cylinder is using a multihead II pump and a Potterton PMV3 spring return diverter valve

OK, my problem.....

I have the theromostat set to 20deg. the hotwater is currently switch off, the diverter valve is operating (all be it very noisy) and supplying the central heating flow and the pump is very hot and seems to be working. The radiators upstairs are red hot and working fine however downstairs the rads are ice cold. I have tried resetting the thermostat and resetting the boiler but to no avail. The boiler is currently set on '5'. It comes on periodically for about 30secs to 1 minute then shuts off again

Can someone help in identfiying what part of my central heating is knackered? I'm guessing the boiler but though it maybe the thermostat?

thanks in advance
Matt

 

[chrishutt]

Can someone help in identifying what part of my central heating is knackered

My first guess would be the pump. Something is causing the circulation to slow down. If the pump has a screw cover at the end open this and check if the spindle is rotating. I expect it's not and you're just getting gravity circulation.

 

[mattway]

Hi Chris
Thanks for your quick response, sorry if this sounds pedantic but there isn't a screw on the front of the pump just a hex bolt head is this what you mean? is about 25mm across flats


Thanks
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[chrishutt]

Is it a Myson pump? I think hex head will unscrew and can be pulled forward when it should engage with spinning spindle, making a noise. If it engages to a stuck spindle, twist it back and forth to free spindle. Some water will leak out while you do this so have a rag handy.

 

[mattway]

It is a Myson pump.

Should I shut down the heating system before removing the hex bolt?

 

[mattway]

oddly enough the boiler downstairs has just fired up and remained on for about 15 minutes where the rads began to get hot, now its switched off again.... this is really annoying!!!

 

[ollski]

It is a Myson pump.

Should I shut down the heating system before removing the hex bolt?

No you want to see if it's spinning or not which it won't be with no power, plus it will leak more if its not spinning.

 

[mattway]

OK just undid the hex bolt as I pulled it towards me I could here it and feel it spinning against the spindle didn't remove it completly but the spindle is definatley turning. By the way its on setting 2, which I beleive is the mid power setting?

 

[JPC]

try turning the upstairs rads off, turn the pump to three and see if they warm up.

could be balancing u need ?

if it works try it at spped 2 again....if it still works try openig the upstairs rads all a little and see if u cant balance it...

water flows the easiest route, what u are trying to do is force it round the bits it does not want to travel to by restricting the easy route

 

[mattway]

thanks JPC for the tips

Just carried out the sequence you told me, closed all upstairs rads, switched pump to setting 3 and let it run for an hour, no change unfortanely still stone cold downstairs....

Think I better call out a plumber tomorrow.....

thanks anyway
Matt

 

[mattway]

just to close out this thread, had a plumber come around, apparantly the spring return valve is on its way out. After 3 days of no rads he told me that they may come on but it would be sporadic as the valve was sticking now and then.

Low and behold that night the rads come on.... new actuator on the way but at least I have my trust renewed in the honest tradesman!

Thanks for all your help.... thread closed