Problem with boiler - High Limit stat cutting out

Its not the Hi limit stat thats tripping the boiler, if it was, you would have had to remove the little plastic cover (near "Firebird) on the stat box and press the reset button, it operates at ~ 110C/113C, its the control stat thats switching off the burner and then refiring the boiler, it looks to be set around 65C ish, so its cutting out at 65C and refiring at ~ 55C, IMO you have a circulation problem. Possibly the control stat not resetting but turning it up and down should give you a fair idea if its OK there should probably be a division or so difference between cut in/out.

Even if the hi limit stat operated it doesnt bring up the lockout on the burner.

Can you post or photo all the pump data, make/model/mode/setting, if it is a A rated pump with LEDs, post a photo of the LED status, (pump running).

As said likely to be no water in system or air lock. Did you turn any valves anywhere recently and could they still be off?

As you look at the upside down pump while running see which mode is highlighted or has the arrow pointing at, keep the mode button pressed until the bottom curve is selected which is constant curve or fixed speed then if required just press the mode button briefly to get just one LED, this is a 4M pump head setting which should be adequate. If it was set to full 3 LEDs then 7M will definitely cause air in a open vented system, keep venting the air regularly. If this settling is not heating all the rads change to (constant curve) 2 LEDs. How many rads? if you have pump instruction book try and post a photo of the pump curve settings from it.

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Id say your correct going by the white power substance on the casing. its a poor boiler install

that fire valve is really doing its job

The firevalve is fitted in the wrong position, it should be fitted before the tigerloop.Ideally it should be a remote acting firevalve.

Ideally the tigerloop should be an internal tigerloop if fitted inside the boiler casing.

Dirty/faulty photocell maybe, but several other possibilities.

You would be best to get a boiler guy out to sort it out, and resolve the other few bits while he is at it.

Interesting thread there, open to correction but should the pump be rotated to vertical or is it photo taken upside down?

I see the fire valve the old type, should that not be 1 metre from boiler?

That installation is technically correct even though it should be a remote one?

No - it would need to be fitted on the incoming oil supply line, not on the feed/return loop to the oil pump.

They are a very poor substitute for the remote acting valve which is now required by building regulations. They also leak!.

It’s incorrect as stated in installation manual supplied with that pump. Do you have a copy of that manual to verify what I’m saying?

I’d turn it up the right way, but having discussed it with DAB previously, I don’t think it’s a major issue.

They don’t like them mounted on their back, it gives rise to premature failure. As long as the shaft is horizontal it’s ok as far as I understand.

The pump is IP44 so I wouldn’t worry about a dribble from the bleed screw, it is designed to withstand that.

The manufactuter does say point it upright!

You should have a look at the dab installation manual. You are incorrect.