Oil burner hot start problem

18 Dec 2018
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United Kingdom
My oil boiler will happily start from cold but not from hot. I believe the boiler stat stops the burner then a short period later restarts it. It's the restart that fails, press the lockout button and it won't start. Leave it to cool off a bit, press the burner lockout button and it fires up again.

It's an rdb 2.2 burner. Following the reillo fault chart I've checked the solenoid, 50v feed, and replaced the photocell. Next on the list is the control box. When it does start you hear a click before ignition. I don't hear this click when it doesn't start. Before getting a box is there an easy way to check for spark? (Remove photocell and look through the hole?!)

Ideally I'd get someone in but work and Xmas are in the way.

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The click is the solenoid opening the valve to let oil through to the nozzle if it's not clicking try a new coil what burner have you got.Bob
Ah, apologies I should of mentioned I changed the solenoid already. There is a sound after purge occurs which I assumed to be the solenoid being activated. There is a separate click when the burner successfully ignites which I don't hear on a hot restart failure.
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Change the photocell

Yep, already tried that one. Following the rdb fault chart it indicates control box next. Just looking best way to test / ignition is working, other than pull it out when hot to see if it's sparking but not sure I fancy that if there's a better way.
Without the click, the solenoid valve will not be opening. RDB cells are notorious for holding burner in purge. If you have changed the cell, along with all the other components listed, you've only got the control box left.

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