Stanley Super Star 60k Oil range - overheating problem

'morning all
Would appreciate advice on overheating problem with one of these beasts, which apparently has been a problem since owner moved in 18 months ago.
Basically, with baffles set to oven, the oven is prevented from reaching temperature because the thermal cutout button activates and the hot water is very hot with knocking in the pipework. Up till now, owner has lived with this by drawing-off the hot water until the reset button can be used. Was less of a problem in winter when CH was on, presumably because the rads provided a heatsink. Now, however, it happens even if the CH is on and the latest twist is that steam is being emitted from the bottle air vent situated next to the range.
I was thinking one or both two-port valves could be sticking but retired colleague said something about checking the "interstat" - which I must confess I've never heard of. Can't find much service info online, so would be very grateful for advice from someone familiar with these oil-fired ranges.
Cheers!

 

Thank you, heatyman.
Any tips on how to check/replace the interstat? I've emailed Waterford Stanley requesting installation/commission instructions, wiring diagram, etc. but no response so far. There is no easy access to the pump - new kitchen units will have to be removed to give access - so I don't want to cause disruption until I have all the info to hand. Meanwhile I'll replace the two-ports as they are noisy and so suspect in any event, in the hope that will help. Or do you think they are a separate issue? Really appreciate your help with this! If you are near Dorset/Hants/Wilts I'd ask you to do the job .

 

Hi Peter, thanks for your suggestion but the flueways are clear.

 

Hi heatyman and thanks for your continued support.
It is S plan system, with one 2 port for the indirect HW cylinder and another for CH. One bathroom towel rail is uncontrolled heat sink. I'm guessing the by-pass is gate valve not auto. I haven't checked the wiring at the junction box (still waiting for response from Waterford Stanley) and I don't know if any pipe stats were installed or are working. I have no idea where the "interstat" is located or how it is supposed to be wired. Maybe I'll just suggest she moves house ....

 

Thanks for that.
This is (supposed to be) a favour for an elderly relative, although oil ranges are not my field - as you probably have gathered. Just spoke to her on phone and it seems she mostly cooks on electric and uses the immersion for hot water - the Stanley is only really required for CH. However, when she switched it on last week the limit stat popped out (as usual) and steam was emitted from the automatic air vent - this latter frightened her so she has stopped using the range.

 

Hello heatyman
Yes, I can check those when I pop over next week. Latest report is that with programmer set to constant DHW & CH, the baffles set to oven, the boiler stat on idle and the oven stat set to 150 she had heating all night without limit stat popping out or any steam from the auto air vent. So my guess is the boiler stat is faulty. Still, if she can get heating with those settings, with luck we'll avoid an 88 years old hypothermia victim ....

 

Thanks, heatyman.
Well, I've replaced the two 2-ports and the auto vent and initial results are encouraging. With boiler stat on idle, oven stat on 200C and room stat 21C the CH rads (and house) are up to temp, the DHW is hot but not scalding and the oven is up to temp without the limit stat popping. I'll ask her to try controlling the DHW and CH with the boiler stat today - i.e. with oven stat on idle. BTW no sign of an "interstat" behind the panel, so perhaps it was only fitted to later models.