Camray 5 Limit Stat issue

[Vetinry]

Good morning
I have been struggling with an issue with my Camray 5 65/95 oil boiler.
The limit stat has been kicking in intermittently for quite a long time.
A couple of weeks ago, my burner blew up and we changed it for a new Riello burner. That is now working great but unfortunately the issue with the limit stat continues.
Everything appears to run fine for a while but then (usually overnight), the limit stat comes on. If I reset, the boiler fires fine and then runs ok for a while before the same thing happens again.
Inside the boiler I can see some sort of thermostat. One long copper tail runs out of the boiler housing and around the water return pipe just as it enters the boiler. There is also another shorter tail which is just sitting loose in front of the boiler water tank cladding.
I'm assuming that if the limit stat is firing then it must mean that the main thermostat isn't switching off the boiler when it gets too hot. Therefore, if I replace this, will it fix things?
What I'm not sure about is exactly where the ends of the main thermostat and limit stat should go
Any help and advice would be gratefully received
Thanks
Steve

 

[Vetinry]

A quick update. I've been looking at spare parts and think that what I can see is the main thermostat phial rather than the limit stat. What I don't know is where it should be fitted. Presumably the one end around the CH return pipe is correct. Does the other end need to go somewhere? If so, where? I've looked at as many diagrams as I can find but can't see how to fit the thermostat and limit stats
Thanks
Steve

 

[Best]

That is a fairly major safety fault!
I don't know about that boiler, but most oil boilers have a pocket on top area of boiler (hottest area) for the stat sensor to fit into and some have a locking device to prevent accidentally pulling it out.
Somebody is clearly not checking your boiler properly. Get an oil service person out

 

[Best]

Not sure if this is your exact boiler, but page 26 shows a view of the top of boiler, -
https://www.buderus.co.uk/files/Camray_5_4065_6590_95135_Nov_01_Iss_4_Inst_Serv_.pdf

 

[Vetinry]

Thanks for the replies. I have seen that diagram before but hadn't got the orientation right. Tomorrow I shall have a look at the top of the boiler (not the front) and see what I can see
What I thought was a thermostat is actually a copper wire that runs out through the boiler room wall with the oil pipe. Not the same at all.
For the sake of about £20, I'm thinking it might be just worth replacing the main thermostat to see if that improves things. As far as I can tell, all 3 motorised valves are working fine and also the main circulation pump.
Cheers
Steve

 

[Best]

Yes, it is easy to mistake the orientation of the diagram. That is the plan view, in other words, the top of boiler.
The probe you found with a copper “wire” to outside is most likely a remote fire valve. The “wire” is actually a small pipe, all very similar to a thermostats.
If your boiler keeps going onto the limit stat, then the control stat (if fitted into pocket okay), must be faulty.

 

[Vetinry]

Thanks very much
Didn't have a chance to look today but will check tomorrow and if everything looks in the right place, I'll order a new control stat. Is there an easy way to test if the current one is working or not?
Thanks
Steve

 

[Best]

If your control stat is turned to a low or medium setting and the rads get extremely hot, plus limit stat cuts out, then control stat faulty.

 

[fixitflav]

Thanks very much
Didn't have a chance to look today but will check tomorrow and if everything looks in the right place, I'll order a new control stat. Is there an easy way to test if the current one is working or not?
Thanks
Steve

Yes, remove the stat and put the phial in a saucepan of water on the hob. As the water heats, by turning the knob back and forward you should hear and feel it click at different positions. If you can remove the outside cover so you can see the contacts, better still. If in doubt connect a multimeter across the terminals. If the water is close to boiling and the contacts don't open at any position, or only at very low settings, then something's wrong. It's possible for the bellows in the stat to leak, causing a failure.

 

[Vetinry]

Thanks for the replies - I've just checked the boiler and it looks as if both the control stat and limit stat are correctly positioned in their pockets - I'm just trying to fire up the heating with the stat on low to see how hot the radiators get - if not, I should have time at the weekend to test in the pan of water.
Really appreciate your help
Steve

 

[Best]

Some stats go out of setting and will allow the system to go to a higher temperature than indicates, but will still be operating if you keep them lower.

 

[Vetinry]

Quick update. I turned the control stat all the way anticlockwise (off?) and switched the heating on - when I moved it clockwise, there was a click, which I presume is the stat switching on. But even leaving it at about 8 O'clock (only just on), the radiators are red hot - so I'm thinking that it probably isn't working properly?
Steve

 

[Best]

Correct

 

[fixitflav]

Quick update. I turned the control stat all the way anticlockwise (off?) and switched the heating on - when I moved it clockwise, there was a click, which I presume is the stat switching on. But even leaving it at about 8 O'clock (only just on), the radiators are red hot - so I'm thinking that it probably isn't working properly?
Steve

I think that pretty much settles it, without doing the saucepan test. For £20, I'd order the stat!

 

[Vetinry]

Stat ordered. I'll let you know how I get on
Thanks again for the help
Steve

 

[MikeJhn]

Well how did you get on?

 

[rpm]

Well how did you get on?

What, from Feb last year!

 

[MikeJhn]

Yes why not, most of the people who posted are still here why not the OP.