Vokera Compact 25HE DPS (Air Pressure Switch) Bouncing....

[Squares]

Hi

I have a Vokera Compact 25HE with DPS bouncing. Basically with any demand the fan runs, pump runs, all sensors ok and relevant switches closed, DPS closes, boiler fires. After about 20secs flame goes off, when I check the DPS it's open circuit, wait about 45s-1min, DPS closes and boiler fires. This is a continuous cycle and as you can imaging the rads take ages to get hot due to the cycling and hot water is intermittent due to this. New DPS was fitted but same problem. I read a few threads about the Venturi being blocked so we have checked them and the silicone tubes and they are not blocked or broken. Any ideas? it's defo the DPS bouncing causing the flame to go off/on..... just can't figure out why. We disconnected the shorter tube from it's venturi as we discovered the longer tube was the one activating the switch then fired up the boiler and it ran fine, no switch off so the conclusion is some sort of difference in pressure (being a DPS!) between these two ports is causing the 2nd port (shorter tube) to pull the DPS off... but what? Flue looks ok and no obstructions. Been running fine for 3.5yrs......

Any help appreciated

Thanks

 

[Terrywookfit]

Have you visually checked venturi or just blown down them?

 

[Squares]

Hi Terrywookfit

Took the pipes off the venturi, un-screwed them from the fan and looked at them close up, they were not blocked for what I could see. Poked something through them while in my hand too...

 

[Squares]

Although I am thinking of getting a set of new venturi and pipes (I think they are around £15+vat for a kit) as I read somewhere even the smallest amount of crud could make the DPS play up.

Also I read if the main heat exchanger plates are dirty this could cause reduced air flow and maybe the same problem ?

 

[Agile]

Quite apart from any work on the combustion/safety devices needing to be done by a gas registered person you have now partially disabled a safety device.

In accordance with the forum rules I cannot give you any advice on gas/combustion related matters.

The obvious advice would be to call a competent engineer.

Tony

 

[Squares]

Quite apart from any work on the combustion/safety devices needing to be done by a gas registered person you have now partially disabled a safety device.

In accordance with the forum rules I cannot give you any advice on gas/combustion related matters.

The obvious advice would be to call a competent engineer.

Tony

That's ok.

BTW how do you know I'm not gas registered?

Having a card/cert to say your certified doesn't mean you are competent, my experience from dealing with heating engineers....

 

[Agile]

Because you dont post in the Combustion Chamber part of this site and because you ask questions which would be simple for many RGIs.

I suggested a "competent" RGI because some are registered but dont do boiler repairs.

Tony

 

[Squares]

Because you dont post in the Combustion Chamber part of this site and because you ask questions which would be simple for many RGIs.

I suggested a "competent" RGI because some are registered but dont do boiler repairs.

Tony

Yes Boss!