Grant Vortex 26-36-s Pro Utility Lock Out

26 Nov 2019
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United Kingdom
I have a Grant Vortex 26-36-s Pro Utility oil fired boiler which keeps going into lock out.

It will fire up, run for 30 minutes or so and then go into lockout, I'm assuming because it's overheating. It seems to be intermittent as it will eventually get going again but then lockout again.

I press the overheat reset button, but it then seems to take hours to come back to life, and the problem is getting progressively worse.

I've checked a number of things like water in the oil tank, blockages in the pump but they seem to be fine.

I've read some threads about the automatic air vents but not sure how to check these or replace them.

Any ideas on what else I can check or what the issue may be?

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Which reset button are you pressing? You refer to the high limit, but lockout usually refers to the burner control. If the burner lockout, your problem could be with the oil pump solenoid; certainly the place to start. If the high limit, then this is associated with circulation or boiler thermostat problems.
Perhaps the place to start is with an experienced oil technician.
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The OP also stated it “takes hours to come back to life”, so that does sound like the boiler is overheating and once high limit button is reset it would take a while before boiler starts up again if system hot.
The thermostats on Grant boilers have been known to go faulty recently

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