Worcester 40CDi cutting in and out.

[Madrab]

What are the couple of things you think it could be and is the pump one of them?

As suggested Si, there are a few fundamental test that need to be performed but you need the correct kit and quals to be able to get into that part of the fault finding

After 10 minutes or so it cut out but that was at temps of 95° or more

The way you mention that it seems like that happened when the BG guy was there? If the boiler got up to 95deg with him there and he said there was nothing wrong then you need another engineer in.

it gets into a cycle of heating to 65 then cutting out

So that isn't an overheat point so it won't be the temp that is shutting the boiler down unless there is a faulty sensor

If you are seeing a gradient limitation error then it could be a circulation/pump issue but that would normally be associated with an overheat condition. TBH you really need an experienced engineer that knows his diagnostic procedures to go through it and check everything.

 

[Si 69]

Hi Gaz,
The BG man was happy with all his checks but he definitely didn't do a fan compression test. We will get someone else in...

 

[Si 69]

Thanks Madreb,
It did get up to 95deg with the BG man there and I think that's why he suggested a power flush as he was happy with the boiler but thought that there was a blockage in the system.
As suggested we will get someone else in. I'll let you know what happens.
Thanks again to everyone who has kindly replied.

 

[Johntheo5]

What mode & setting is the circ pump on, if not sure post a photo of the LEDs (if it has them) while running, is it Y or S plan and does it overheat if both DHW and heating are calling?, if the flow temp is rising 30C, from 35C to 65C and the burner is cutting out then looks like a circulation problem.

 

[Si 69]

Hi
The pump doesn't have any LEDs. It's a Grundfos UPS 25-55 180. I'm not at home now but I can send a photo of the switch later.
The boiler does the same cycle with hot water, heating or both on.

 

[Johntheo5]

Could obviously be the boiler Hx, especially if no magnetic filter installed but you can check out the pump easily enough yourself, even though the impeller is turning the capacitor could be gone weak, it can be checked by using a multimeter if its got the capacitor testing facility or you could simply just renew it. If you have gate type pump isolation valves then (after isolating the boiler/pump) you can shut them and remove the pump head and check the impeller and pump ports for blockage, if the pump isolation valves are the ball valve type then its more than likely that the O rings will leak on reopening which means drain down and isol valve renewal.

 

[Si 69]

Hi John,
Thanks. I think I've added a photo of the pump. I think it's from 2006 so might be worth changing anyway. There's a magna clean on the system but I appreciate what you say about the Hx. Someone is coming to take a look on Wednesday.
Thanks again
Simon