Glowworm fuelsaver- RGI has given up

[Slugbabydotcom]

Seems like a circulation problem to me as well.
Check your float valve in the loft isn't stuck in the 'up' position.
When you bleed a rad does it take ages and ages? Could be you have a blocked feed pipe.
And finally YES I have come across the spinning pump without the impeller attached a few times before. I usually find it more common on old grundfoss pumps.
They also tend to suck in air which causes a similar issue so if if your pump is old then a new one might just sort it. When you take the head off the pump; if the inlet [in the middle] is black and the outlet is red you know the pump is sucking in air itself.
If the pump inlet and outlet are rusty the you know there is another source. Quite often a blocked feed pipe or air separator causing air to be sucked in through the vent.

 

[halton1957]

Sounds like the boiler has just enough water flow to allow a little circulation allowing the boiler to heat up quickly cool down quickly.

I would drain the system down. Check operation of pump perhaps flush the system out with the mains cold. Then try it again.

Very little to go wrong in the boiler.

Many thanks for your input.

Tried it first thing this am after it had been completely off overnight. It ran for 1m 45sec then cut out for 3mins. I let it cycle a few times and it returned to it's 30 sec runs then 3-4 mins resting, so decided to take the advice to check the pump.

Drained down, took off pump motor assembly, impeller very clean, pump body & ports v clean. Ran pump on 240v, it spun freely and impeller firmly on shaft. Able to stop it with my thumb, but it's only a baby motor so I guess that's normal.

Opened heat exchanger drain point and found tubes clear as far as you can tell with a bit of stiff wire.
Everything reassembled and bled, boiler symptoms unchanged.

Fitted new sealing foam tape to be sure casing sealed correctly- no change.
Observed sequence closely and now 99% sure that the fan stops and causes the shutdown. Contrary to what RGI said before there is not 240v at fan after shutdown.
None of the pipework to or from, nor the heat exch pipes and fins are hot a few seconds after shutdown, so it seems to me that the pump is shifting hot water v quickly.

Many thanks to anyone who has read this far. I am now stuck. There is a glimmer of light though- I have bought a pcb on ebay today, it's not guaranteed but is thought to be OK. For £7.60 +p&p it's worth a try.

 

[TCCHeating]

I was happy to advise you until you went into the combustion chamber. Thats not somewhere you should have been mate. I'm sure you realise that yourself. Sorry

 

[halton1957]

Seems like a circulation problem to me as well.
Check your float valve in the loft isn't stuck in the 'up' position.
When you bleed a rad does it take ages and ages? Could be you have a blocked feed pipe.
And finally YES I have come across the spinning pump without the impeller attached a few times before. I usually find it more common on old grundfoss pumps.
They also tend to suck in air which causes a similar issue so if if your pump is old then a new one might just sort it. When you take the head off the pump; if the inlet [in the middle] is black and the outlet is red you know the pump is sucking in air itself.
If the pump inlet and outlet are rusty the you know there is another source. Quite often a blocked feed pipe or air separator causing air to be sucked in through the vent.

Hi Slugbaby, Thanks! I didn't see your post till too late. Header tank and float OK. Drain down seems fine, but I opened bleed valves on the rads.
It is a grundfoss pump, prob 114 yrs old and I took no notice of the colours, just surprised it seemed OK. My thoughts are that as none of the pipework is hot the pump is OK but I'm willing to try anything, prob drain down again tomorrow and have a look at the pump ports.
Do you mean a blocked feed pipe from boiler to pump? I guess a Myson aerject is the separator you refer to?

 

[halton1957]

I was happy to advise you until you went into the combustion chamber. Thats not somewhere you should have been mate. I'm sure you realise that yourself. Sorry

Sorry, Didn't realise that. I thought if I left gas pipework alone I was OK. Didn't go into where the burners are just into the boiler casing. My reference to the heat exch fins was to indicate the place, I didn't see or feel them, just the s shaped pipework that is on each side.
Won't do it again. No wish to break any regulations, too long working on aircraft to take chances like that. Thanks for your previous help

 

[halton1957]

Hello Slugbaby, Missed your question about bleeding a rad, Yes there is a lot of air and it takes a few minutes to let it out, but I only open the bleed screw about 1 turn.

 

[gas112]

Pretty certain these dont have a fan over run on them so if the boiler stat is being satisfied it should drop voltage out of pcb to fan but your still getting voltage out which makes me think the boiler stat is not actually satisfied and fault lies between the board the fan or with it being a new air pressure switch possibly the tubes to it.

 

[halton1957]

Pretty certain these dont have a fan over run on them so if the boiler stat is being satisfied it should drop voltage out of pcb to fan but your still getting voltage out which makes me think the boiler stat is not actually satisfied and fault lies between the board the fan or with it being a new air pressure switch possibly the tubes to it.

Thanks 112, My normal reaction to check this out would be to run a temporary cable from the pcb output direct to the fan as a test. But I'm not sure now what I can do as not gas safe. Can I open the boiler casing and check out circuits?

 

[TCCHeating]

Some fuelsavers are positive flue. You described replacing the foam seal. If your boiler is a positive flue which i suspect. You should have your seal checked for leaks by an rgi. V important on positive flued boilers. Unlike most negative flued boilers the outer casing is the seal.

 

[halton1957]

Some fuelsavers are positive flue. You described replacing the foam seal. If your boiler is a positive flue which i suspect. You should have your seal checked for leaks by an rgi. V important on positive flued boilers. Unlike most negative flued boilers the outer casing is the seal.

Thanks for that clarification, yes the boiler casing is sealed and many notes in the servicing booklet about it. I have worked on the foam, and straightened a few dents in the casing edge. Now I'm unsure whether I should have taken off the casing. I can access most components without removing it, just not the fan connection chocolate block. As I posted earlier, I won't do anything else that puts me outside the regulations, so an opinion on taking off the casing would appreciated.

 

[Agile]

Very simply you should not have removed the casing as a DIYer!

Usually we just stop advising someone who does safety critical work like that.

Did you not think of measuring the voltage to the fan from the PCB end ???

Tony

 

[TCCHeating]

Im pretty certain the boiler is positive flue from what you have described. No it shouldnt have been opened by a non rgi, but now you have, my best advice would be to have it checked.

Dont mean to sound like a jobsworth or anything but that seal is very important on those boilers

 

[halton1957]

Thanks both, Now I am aware I will not take the casing off again.

 

[halton1957]

.

Did you not think of measuring the voltage to the fan from the PCB end ???

Tony

Yes, but the RGI already did that, but I couldn't figure out why the fan stopped if there was a supply to it, hence checking at the fan end.

Things have been made plain to me now, I will not be doing anything inside the sealed boiler casing. The RGI will come back if I can get a diagnosis of the problem. The only major component that hasn't been changed or checked out now is the pcb.
People seem to be advising that the problem lies in the plumbing rather than the boiler, so I'll carry on checking that out as far as I can without interfering with gas components etc.

 

[Slugbabydotcom]

Do you mean a blocked feed pipe from boiler to pump?

No I mean the usually 15mm pipe feeding water from the F&E tank into the >>>>

I guess a Myson aerjec is the separator you refer to?

Yes that one!

If a magnet sticks to where this feed enters it you know it will be chocka with crud.