Oil boiler shutting off before room temp reached

Joined
17 Jan 2017
Messages
6
Reaction score
0
Country
United Kingdom
Hi

I'm hoping for some advice on what to do next with a boiler problem we have been experiencing for the last month. We had a leak off one of the central heating pipes and had to shut off the CH to have it fixed. When it was switched back on the boiler wouldn't fire. The engineer diagnosed a faulty boiler thermostat. It's been replaced and the boiler will fire, but shuts down after the boiler thermostat temp is reached, but before our set room temperature is reached. The override light doesn't come on at all. I've never had to adjust the boiler thermostat before but if I turn it up now the boiler will run until the new temp is reached. The radiators have to become almost cold before it will fire again.

Since moving into the house 18 months ago we have had the boiler serviced twice and the zone valve replaced (I think that's what it's called!).

The two engineers who have looked at it recently have not been able to offer a solution. They have just noted that:

- the room thermostat definitely works and calls to the boiler.
- the zone valve is opening and closing as it should be.
- the pump is running, albeit continuously, which it apparently shouldn't.

We have a Grandee G7 boiler and plenty of oil in the tank.

Should I now call an engineer to check the pump?

Thanks

Jen
 
Sponsored Links
Thanks, as far as I can tell there is no air lock, all of the radiatotrs in the system get hot, as to the pipes leading to and from the water cylinder.

It's been suggested to me that the PCB could be at fault, does that sound right?
 
Only my opinion but I'd imagine there is a small but not complete airlock in the top of the boiler which is interfering with a thermostat......I think this one has an automatic air vent on the top RH side with a plastic cap on.
Can you undo the cap to see if there's any air present?
We assume all was well before the system was worked on.....did this involve a drain down, do you know?
John :)
 
Sponsored Links
Thanks John, I'll take a look for an air vent when I get home from work. The system was drained when the leak was fixed so an air lock is feasible. We've not had this problem with the boiler prior to the leak.
 
The pump will run for as long as you have a heating demand. If the boiler stat is cutting out, it suggests that there is an easy path back to the boiler for water, rather than around the rest of the system. This could be because of an airlock in part of the system or just a case of rebalancing. I would be getting impatient with my engineer.
 
Thanks, I can't see an air vent on the boiler, but there is what looks like a drain valve on the bottom left.

Last night I noticed that the pipes taking hot water to our tank had started rattling, not violently, but enough for me to hear from the room upstairs. There is what appears to be a small pressure gauge/ valve on the end of one of the pipes and when I adjusted it slightly the rattling stopped? One of the engineers noted that he had adjusted it, but I dont know why.

The radiator in the living room, which is possibly furthest away from the boiler and pump, also only heats at the top now so now seems to be full of sludge.

I've asked for one of the engineers to come and take another look. Fingers crossed this time.
 
I'm not sure, how would I tell? My knowledge of the system is limited I'm afraid.

There is a valve that allows me to add pressure to the system, the gauge notes that the pressure is about 1.5.
 
The pressure seems fine - presuming the gauge is working!
Have you the boiler cover off? The auto air valve is under that, on the top, right hand side I'm pretty sure.
John :)
 
I'm definitely looking under the cover, I can't see an air vent on the boiler itself. There is a square nut on the top left and what looks like a drain valve on the bottom left. It's a pretty old boiler.

There is a small air vent off one of the pipes leading from the water tank. I loosened the nozzle slightly and some air escaped, but not much.

Jen
 
I think you'll find there is an air lock and I think you'll also find your pump although spinning is goosed so you'll have to replace it,I had one just like it some months ago,but I don't like grandee boilers.Bob
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Back
Top