Over heating Myson Apollo 30/50

[Dave Morris]

Firstly thanks to Chris R for pointing me in the direction of my cold water feed blockage. The next problem may be what caused the water to be pushed into the expansion tank in the first place.
My Boiler is a Myson Apollo 30/50 with a High/Low thermostat switch on it. The boiler will now run smoothly with no kettling and all the radiators get nice and hot but the boiler will not shut down until the over temp stat in the thermocouple shuts it down and the pilot goes out. I have replaced both the High stat and the Low stat today with no difference. The pump appears to be working and runs on if I manually shut the boiler down by turning the thermostat switch to off. The boiler cuts in and out ok if i use the room stat or the tank stat. It just does not want to cut out using the high or low boiler stats. The radiators and hot water are getting a lot hotter than they used to so I don't think its the over temp stat operating to early.

HELP

Cheers

Dave

 

[ChrisR]

There's curious. Certainly sounds like it's the overheat stat being too keen. Remember it should be "set" to 90º or so which is jolly hot. Haven't dug the docs out , but I guess if you disconnect one of the other stats then switch to it, the boiler stops? Stats sometimes have to be in good thermal contact - was there any heat conductive goo under the old ones?
'Course I'd just check with a surface thermometer...

I guess it's possible that combustion gases are getting too near the overheat stat

Cannot condone touching anywhere near the gas/flue/fan/case seals on any boiler, but especially this one. It has killed about 40 people. Anything wrong with the case seal, & you're next.

 

[Dave Morris]

Thanks chris. I guess I'll leave it to the profesionalls then. It may be time for a new boiler cos I think its about 17 years old.

 

[ChrisR]

New boiler? Nasty complicated things. Yours is, or was, quite efficient. What would you replace it with, a B***** Suprima?!

New Limit Stat's £13.33 + vat rrp
If you really do want a new boiler , where are you?

 

[Dave Morris]

Im in Weymouth in Dorset Chris. I must admit things are pointing to the over temp stat, its just that the rads and the boiler seem to be so much hotter. On another note what is the normal life expectancy of a boiler now a days anyway?
I will try another over temp stat first but after that it doesn't leave a lot more to change in the boiler apart from the expensive parts. Hence would it be worth it on a boiler this old.

 

[ChrisR]

Some manufacturer I forget said combis last 5 years - then had to retract it! Many plain simple boilers go on for 30 years unless they get scaled up and it wont clear. Sometimes they start leaking, but generally they get changed because people want to move them somewhere else.

Sometimes the parts get very expensive or hard to get. Does yours have a fan? Check prices for your exact model here
On your boiler, bear in mind that even on "low" it has to get hotter than you'd want your water store to be by at least 10 degrees, otherwise it wouldn't heat it. Which means 70, which IS hot if it ever gets past a blocked pipe to a rad!

 

[Dave Morris]

Thanks Chris. It doesn't have a fan. It has a square balanced flue that comes out of the back of the boiler. I will go to hrpc poole outlet tommorrow and get a new limit stat. Thanks for your help and I'll post up how i get on.

thanks again

Happy new Year

Dave.

 

[Agile]

Thanks Chris. It doesn't have a fan. It has a square balanced flue that comes out of the back of the boiler. I will go to hrpc poole outlet tommorrow and get a new limit stat. Thanks for your help and I'll post up how i get on.

Dave.

I wonder how he got on and if that old boiler is still working!

 

[doitall]

Blimey Tony this thread was before you joined DIYnot.

You that bored you are digging out loads of old posts.

 

[Agile]

Just chanced across it when searching for info about finding case seals as no one had answered my CC question about them!

 

[mysteryman]

That's an interesting question. I always thought the Apollo 30/50B was the best little domestic boiler ever before condensing boilers came along. It would be good to know if it's still working.