Potterton turns off within 60secs...

[G40_Dave]

Hi,
I'm having problems with my central heating and was hoping for a bit of advice.
Firstly the setup; It's a Potterton Suprima 30 which is approx 10 years old. Its a vented system with a 3 port diverted valve and is in a 2 bed house with 5 average size rads.
The system was off this morning when I woke up and the house was cold and no hot water. Having had to go to work I haven't been able to play for too long, but I can't get it to run for more than 60 seconds for CH or HW. If I start by switching everything off at the mains for a minute then on again the boiler appears to go through the correct sequence for starting up. The boiler recieves the call for heat and fires up, and I can hear the pump running. In under a minute the boiler switches off leaving the red led on and the green flashing slowly. As of yet it has not fired up again of its own accord despite there being no hot water and the thermostat being 'clicked' on (left for almost an hour before i started fiddling again).

Things that may or may not be relevant:
The system was drained and flushed a week back due to Kettling and gurgling.
The pump is running and i have checked that the shaft is actually spinning.
The pump also gets very hot and might be noisier than before (I might just be trying to make things fit though).
The flow pipe from the boiler is very hot but the return is stone cold.
When the pump stops a few times there has been a big rush of gurgling/bubbling.
All the rads are fully bled and i have rechecked them several times.

I'm aware of the dodgy PCBs in these boilers but this doesn't appear to be the usual fault. I have several thoughts as to the problem, but would appreciate some pointers of what to look at.

Thanks,
Dave

 

[JohnD]

sounds like water is not circulating through it

pump might be faulty or a valve might be closed. How hot is the pump? Is the heat cinducted down the pipes each side to any distance? does any water drip out when you remove the screw?

might be TRV stuck

might be an air lock

check you have bled everything and that when you bleed the highest rad, water squirts out forcefully

check that if you draw a bucketful of water out of the drain cock at the bottom, exactly the same amount of water is fed in through the F&E (if not, you have a blockage)

Did you use a chemical cleaner, or just drain it? Was it blocked before, or just dirty? What colour was the sediment? How dirty is the F&E?

A recalcitrant airlock can often be removed by draining, by filling from the bottom using a hose pipe on the drain cock.

 

[Agile]

You seem to have forgotten that not will not work without water in the system.

The feed pipe is probably blocked from the F&E tank.

As a temporary solution you can probably back fill it from the vent pipe.

The permanent solution will involve replacement of the blocked pipe. This is usually where the feed enters the Ch pipework.

Tony

 

[G40_Dave]

Wow, thanks for thew quick replies.
Pump is too hot to touch for more than a second or two. The heat from it only spreads about 10cm either side. I cant get the screw out all the way for some reason, I can get it mostly out though so it is very loose and can move side to side but no drips come out.
There are no TRV's in the system (although I was thinking about fitting them)

I have just gone round again now and bled the system and yet more air came out the top rads although I only visualize the water being down a cm in each of them.
I'm not sure I could say the water came out forcefully - more than a dribble, but possibly not much more than when the pump is not running.

check that if you draw a bucketful of water out of the drain cock at the bottom, exactly the same amount of water is fed in through the F&E (if not, you have a blockage)

I'll give that a go tonight.

I flushed the system with fernox ds-40 (I think) and the water didn't come out to badly to be honest. No sludge and a opaque brown colour. There was no blockage, but I was hoping to stop/reduce the kettling and generally just give the system a bit of a clean and some protection as I have no idea what was done before I moved in 3 years back.

The F&E is brown, but not dark and fairly clear.

A recalcitrant airlock can often be removed by draining, by filling from the bottom using a hose pipe on the drain cock.

Again, something I can try although not so easy with the location of the hose and drain point.

Cheers for the help,

Dave

 

[gas4you]

Drain some water from a system drain point. If f&e tank level drops, or you hear it filling as you drain then there is no blockage. If it remains the same and quiet follow Agiles advice.

Also check there is 230V to pump terminals.

 

[bathjobby]

Definitely sounds like an air lock preventing circulation. Check to see if you have a bleed cap above the pump, if so bleed there too.