Boiler firing up then cutting out after a couple of minutes...!

[andyf3050]

Hi y'all,
I have my hot water set to heat up twice a day and I've noticed that my boiler (not a combi) fires up, heats the water as it should but cuts out after only a minute or so. Is this a sign that the internal thermostat is knackered or could it be something to do with the stat on the tank? The stat control on the boiler has settings 1 to 5 (warm to very hot) and I currently have it between 3 & 4. IIRC it also used to do this when the central heating was on which leads me to believe it is thermostat related. I hope this makes sense and if you need me to post some pictures up to clarify things just let me know.

Thanks, Andy...:hammer:

 

[ecowarm]

Check the water in the system, the f&e tank may be dry

 

[diamondgas]

Boiler make and model Andy? Really would like to know system design also to be honest. Fully pumped or gravity? Any ideas

 

[andyf3050]

Its a Glow Worm Fuel saver F. The system is gravity fed with a main water tank and additional header tank for the CH system. I've just changed the control unit (thanks diamondgas... you're help was spot on...) so my hot water is easier to programme and I've set the 3 way so the hot water only heats up. Need to sort the motorised valve out soon as well. I'm just concerned about this cutting out. I've posted a picture up of the circuit diagram inside the cover and it does actually mention an overheat cutoff device... at the bottom of the diagram... could it be something to do with this...?

Thanks...Andy

 

[diamondgas]

If you've got a 3 way valve then the system is fully pumped Andy, not gravity. That means the pump should be on when the hot water or heating is calling! What did you mean by "...set the 3 way so hot water only heats" ? They're usually spring return to hot water only! From what you've said so far I'm not thinking there's anything wrong with the boiler, sounds more like the heat isn't getting away from it!

 

[andyf3050]

I've probably confused you so far... it is a pumped system as it has an inline grundfos above what I think is a 2-way valve... one feed in to a control valve and two outlets, one to the hot water tank the other to the CH side (I'm assuming)... heres a pic

I think the motorised valve is burnt out and I have got another one to replace it. I have the problem of the CH getting hot when only the HW is heating up. I have turned off all the rads and I suspect that this two-way valve isn't functioning right. The little lever in the next pic can be moved upwards against the motor but when I let go it drops back to the bottom... does this make sense?

I'm at a bit of a loss as to what could be causing the boiler to fire up as it should only to cut out after a minute or two. If that motor needs replacing first then I will do it at the weekend and let you know. If not, I'm all ears for suggestions.

 

[RoryD]

with the system running undo the silver screw on ur pump and check it's spinning. If it is put ur screwdriver in it to see if it's possible to stop it with little force. I think it may be the pump or even the dreaded sludge. As you'll appreciate it's hard to tell.

 

[andyf3050]

with the system running undo the silver screw on ur pump and check it's spinning. If it is put ur screwdriver in it to see if it's possible to stop it with little force. I think it may be the pump or even the dreaded sludge. As you'll appreciate it's hard to tell.

The pump should be fine as it was unnecessarily replaced by some Eon numpties in December last year...! Plus, the hot water is heating up fine and the CH gets hot too. If it is sludge, how would it affect the boiler? I'm all ears... thanks so far guys... appreciate it...!

Andy

 

[diamondgas]

Star off your pump is in a horible position pointind downward *yuck*! Bye-the-bye though. Lets go back to the original concern regards it going on and off within a minute or so! When you say cutting out do you mean it is cycling on and off? Not over heating? A good sign that the boiler thermostat is on it's way out/becoming over sensitive! It's at times like this when you really need to be feeling pipes flow and return and listening to boiler and pump etc. If you're getting plenty hot water and the rads are heating up okay I wouldn't be too concerned Andy!

 

[stevetheplumber]

replace the three way valve mate your not getting full flow thru it and boiler is going of on temp rise hooking the lever open is more for venting the system it doesnt put it in either mode

 

[andyf3050]

Star off your pump is in a horible position pointind downward *yuck*! Bye-the-bye though. Lets go back to the original concern regards it going on and off within a minute or so! When you say cutting out do you mean it is cycling on and off? Not over heating? A good sign that the boiler thermostat is on it's way out/becoming over sensitive! It's at times like this when you really need to be feeling pipes flow and return and listening to boiler and pump etc. If you're getting plenty hot water and the rads are heating up okay I wouldn't be too concerned Andy!

I know what you mean... that pump is fitted in a pretty crap position... I think Krusty the Clown did all the work on this house... you should see the kitchen wiring...!
It seems to be cycling on and off and doesn't appear to be overheating although the pipes above and below the pump get really hot to the touch but I'm guessing that's normal?
I'm getting plenty of hot water and the heating has always worked fine... I suppose it's one of those 'if it aint broke' scenarios....! Many thanks yet again for all your help mate... I may be picking your brains over the winter at some point if the reliability of our system is aything to go by... touch wood we don't encounter any major problems like last year...!

Andy

 

[RoryD]

can you test this out on the central heating mate, lets see if it's sytemic or in the boiler. Have you removed the anti gravity valve (non return valve) on the pipework???