Now I've had a fault with the boiler fixed with a new control board. I've spent a lot of time looking at the thing and timing the operation burner etc. when it was playing up.
When cold in the morning it takes about 16 min to reach flow temp initially.
Then, when up to flow temps yesterday, in -1C outside temps, it would fire burner for approximately 2min 30sec and then rest for virtually the same 2min 30 seconds and follow that cycle all the while, whilst getting the room up to temp.
That seems like a lot of burner cyclying, which I suppose is caused by over sizing, it is a 32kwh combi? Does that sound excessive, it seems it to me??
I looked at the gas meter and in the "burner on cycles" it was using 1.68m3 per hour gas rate.
The specs say minimum modulation of the gas valve is 1.64m3 so I guess there could be a small amount of adjustment if I get an engineer out but probably not enough to be worthwhile?
at 1.68m3 I calculate the Kwh at 18.7kwh at assumed 78% that is 14.6kwh if my logic is right.
My 9 rads would be no more that 9kwh. So I guess the over size and lack of further modulation causes the short cycles?
There is an adjustment potentiometer on the circuit board I could get an engineer to lower useful output but would this take it lower than the lowest modulation the gas valve is set for? It doesn't seem likely to me?
I suppose all this is leading to a more modern boiler with a higher modulation ratio so it is more aligned to heat demand on CH mode...
I have now had both the ignition and main PCBs replaced in the last 2 years and thinking the burner on / off cycles are playing a part...
Advice very much appreciated. Thanks
When cold in the morning it takes about 16 min to reach flow temp initially.
Then, when up to flow temps yesterday, in -1C outside temps, it would fire burner for approximately 2min 30sec and then rest for virtually the same 2min 30 seconds and follow that cycle all the while, whilst getting the room up to temp.
That seems like a lot of burner cyclying, which I suppose is caused by over sizing, it is a 32kwh combi? Does that sound excessive, it seems it to me??
I looked at the gas meter and in the "burner on cycles" it was using 1.68m3 per hour gas rate.
The specs say minimum modulation of the gas valve is 1.64m3 so I guess there could be a small amount of adjustment if I get an engineer out but probably not enough to be worthwhile?
at 1.68m3 I calculate the Kwh at 18.7kwh at assumed 78% that is 14.6kwh if my logic is right.
My 9 rads would be no more that 9kwh. So I guess the over size and lack of further modulation causes the short cycles?
There is an adjustment potentiometer on the circuit board I could get an engineer to lower useful output but would this take it lower than the lowest modulation the gas valve is set for? It doesn't seem likely to me?
I suppose all this is leading to a more modern boiler with a higher modulation ratio so it is more aligned to heat demand on CH mode...
I have now had both the ignition and main PCBs replaced in the last 2 years and thinking the burner on / off cycles are playing a part...
Advice very much appreciated. Thanks
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