Boiler not firing after power cut

[perrancott]

X-No-Archive:I have just got home to find that there has been a power cut at some time today. My boiler, an ideal standard isar was off and showing the code L F. The user manual told me to press the reset button and the boiler fired immediately. Other notes under the same code suggested that the gas supply might be off. Clearly it was not when the boiler relit and I have never known the gas supply to fail in the twenty odd years I have lived here. Apparently the boiler tries to fire three times and then gives up.

Power cuts are fairly common occurrences where I live so I am worried that this will happen everytime. Is this a known problem or was it a one-off set of circumstances? Why does the boiler not try again when the power comes on?

[Psst]

Well its just how the software in the boiler control unit is programmed. The manufacturers are just being ultra safe.

[Tony Bryer]

That would be really helpful if there was a power cut in the middle of your winter holiday, leaving you with a flooded house.

[Roger Mills]

I don't know what 'LF' means, or whether the following applies to you - but power cuts can sometimes cause the problem described below.

If the boiler controls the pump in order to provide pump over-run, and if there is a power failure when the boiler is in full flight, the boiler may overheat and trip the over-heat cutout - because, with no power, the pump can't continue to run in order to carry away the residual heat. This would require a manual reset before the boiler would fire again. Short of providing a UPS for the heating system electrics, there ain't a lot you can do about it.

[John Stumbles]

X-No-Answer:if you don't want others down the line to benefit from what you may learn here then I'm not acting as your exclusive personal helpline!

[Psst]

Yes indeed,of course it depends o the boiler make and model,,some will just keep cycling,others will just try maybe 3 times then lockout.