Oil boiler problem - tripping out when windy

[robgraham]

I've now realised that every time recently that it is windy, the oil CH boiler has a tendency to trip out with an apparant overheat problem.

This has been going on for about 8 weeks (maybe more, I can't remember), and became a major nuisance during all the recent gales.

The boiler is an external version of the Boulter Camray and has hung and worked perfectly happily for approaching 20 years on the back wall of the house.

I'm not totally blaming the wind yet but the boiler has worked without a failure for the last 48 hours and I've done nothing to it after the last reset, and had been resetting it several times a day during the gales.

I was blaming this problem on the control thermostat so replaced that just before Xmas and have checked it is working (at 70C). The overheat trips at 95C according to the handbook.

Anybody got any ideas what could be happening ? The trip that is going is the boiler overheat, not the flame out detection in the Riello burner.

Rob

[harryagain]

[harryagain]

Well either it's overheating or it isn't and the overheat thermostat is faulty. As you've replaced the control thermostat, obviously it isn't actually overheating. So it might be the overheat thermostat or associated wiring Check out all electrical connections for tightness and being corrosion free.

You could experiment by turning the control thermostat down & see what happens.

[Michael Chare]

You may well be able to remove the limit thermostat from the boiler and test it in a pan of water. You could compare it to the thermostat which you have already removed or, if you have a suitable thermometer, measure the temperature at which it fires.

[JimK]

/You may well be able to remove the limit thermostat from the boiler and test it in a pan of water. You could compare it to the thermostat which you have already removed or, if you have a suitable thermometer, measure the temperature at which it fires. /q

Worth a look, but how does the 'only when it's windy' fit in with the 'stat' suggestions?

Jim K

[Roger Mills]

Very odd. How does the overheat stat work? The one on my gas boiler has a bulb which fits into a pocket on the flow side of the boiler - so as to sense outlet water temperature - and is connected to the electrical bit (presumably a pressure switch) by a capillary tube. Is yours the same? If so, the effect of wind is very difficult to explain!

My boiler has been known to go out in gusty conditions - despite having a balanced flue - if the wind blows the pilot away from the flame detection sensor, but not to trip under those circumstances.

[Michael Chare]

Boiler working harder, therefore getting hotter, because the wind is cooling the house more.

If the warning light comes on then the thermostat circuit is 'open circuit' either because the thermostat switch has opened or there is a bad contact.

I would say check the wiring with a meter at the time of the fault, but the wiring is probably in some box which you don't want to fiddle with whilst the boiler is switched on.

[JimK]

/Boiler working harder, therefore getting hotter,/q

? I verymuch doubt this age of oil boiler will modulate at all, it will be on or off. If its cold it will be on longer not hotter....

Jim K

[Tim+]

Failing pump maybe? In cold weather the pump may be running almost continuously whereas in finer weather it'll be running more intermittently. Falling flow rate through the boiler could then cause it to overheat.

Tim

[Martin Brown]

Look for signs of corrosion or leakage on the exhaust from the boiler or inspection plate. Hot gasses getting into the wrong place might trigger an overheat fault. Mine tends to fail by sooting up its magic eye flame detector if the gales are strong and in the wrong direction.

[Michael Chare]

It may have got a bit hotter as a result of being on longer is what I was suggesting. If the temperature warning light comes on then there has to be a problem with that circuit if you can prove that the normal thermostat is working correctly.

[JimK]

/temperature warning light /q

Eh? Where's that?

Jim K

[johnjessop46]

Possibly hot gases being forced out of a poorly sealed inspection door by w ind pressure impinging onto the overheat capillary? It may be worth checki ng if there should be a pump run-on period. Some boilers use the boiler sat isfied connection of the thermostat so it's important your replacement ther mostat is a true match.

[robgraham]

wind pressure impinging onto the overheat capillary? It may be worth chec king if there should be a pump run-on period. Some boilers use the boiler s atisfied connection of the thermostat so it's important your replacement th ermostat is a true match.

Thanks guys for your input to the discussion.

There might be some mileage in the flu gas leakage theory as I did discover that part of the flu coupling to the outside world had fallen off - 20 yr old boiler!. But this has been fixed and a bit of refractory panel silicon ed over the capillary tube that is near the flu. This could well have been the cause one would think but there are three bulbs in the boiler and this one is the frost protection bulb - I've checked that twice but am still wo ndering if I'm right on that, but having put protection over it while the w inds were still blowing I think I have taken that capillary pipe out of the equation. Actually what I have found is that I never wired in a 'keep-ali ve' supply that this sensor would have used.

Since Friday there's been no wind and no trips - the temperature is far low er so the boiler has been running longer.

Yes, this is an old device and is a bang/bang type - and no there is no pum p run on as it was never specified in the manual and this problem has only appeared in the last few months.

I can only wait now for the next round of windy days to see if I can find a cause. I've wired in a repeater light to the house so I can get an idea w hen a drop-out occurs and also attend to it before everything gets cold.

Again thanks Rob

[Michael Chare]

On my internal Camray 50/70 boiler there is a warning light that comes on if the overhead thermostat opens.

[JimK]

/On my internal Camray 50/70 boiler there is a warning light that comes on if the overhead thermostat opens./q

Wonder if the op has such, its not been mentioned iirc.....

My old external wall mounter camray just had a red illuminated 'lock out' button...

Jim K