Sime with explosive ignition.

[DarkInferno]

I have a 5 Year old, Sime Family RX55CE IONO,

I've been told by Sime they don't make it, eventually got through to the technical of the actual manufacturers who said it was a gas valve fault (not ramping correctly), (I'd had already checked & cleaned the spark electrode, jets and leads) and advised swapping it out, which I've done.
However it is still giving the same symptoms,

Its a very simple boiler, Heat Exchanger, Gas Valve, Burner Bar, PCB, Stats and Electrodes, however it is only giving explocive ignition every few days, I've never actually witnessed it, so I'm going purely on what the customer is telling me.

the gas valve has only 2+E wires and both solinoids are connected in parallel.

What am I missing? PCB fault? Prolly somthing brain numbingly obvious but it has me staring at it blankly.

Help?

 

[kevplumb]

just a thought is it cross lighting all the burner bars

 

[DarkInferno]

All suggestions gratiously accepted,

It seemed to, but I'll give it another cleanout & check.

 

[felix]

I've seen this explosive ignition on two different boilers and the root cause was the same in each case. The gas was taking too long to ignite. In one boiler the burner bars nearest the pilot were dirty while in the other one the pilot was undersize.

 

[doitall]

Glowy micro had this problem a few weekends back.

Problem pilot flame size.

Not saying thay have a problem with the micron 80ff, but the glowy man went straight to the problem adjusted it and left without checking anything else.

 

[ollski]

Isn't the micron the one where glowworm have cut a 1" section out of the case seal to prevent the explosive ignition?

What is the gas inlet pressure on the sime?

 

[DarkInferno]

I honestly can't remember, but last time I was there I checked the pressures with the data plate (which is in italian) and all seemed fine.

No pilot, it ignites on the burner bar, (checked electrode gap, spark lead continuity)