Short Cycling Boiler Problem

[Fred56]

Hi,
No doubt a problem others have had. We live in a rented house, the landlord won't do anything that is not mandatory. Heating is gas fired by a Myson WM40/50 balanced flue boiler. It's mounted at first floor in a cupboard in the bathroom. The cylinder is at the other side of the first floor but lower than the boiler. The pipework runs up, 8m across the loft and back down to the cylinder.
I'm looking carefully at energy costs. Last year we used 22500 kWh of gas in small 3 bed semi and we burned 1.2tonne of solid fuel on the fires.

The biggest problem I can see is the boiler short cycling. When the central heating is running and up to heat the boiler runs for 15 to 20 seconds and then shuts off for approx 10 seconds and then re-fires. It does this constantly. If heating hot water only it kettles really badly.
At the last annual test I raised this with the engineer. He said it should not do that but as he was instructed to test only he could not do anything. He did not report it on the test sheet although he did witness the kettling.

This boiler is listed on SEDBUK as only 65% efficient which bad enough without the short cycling.

Does any forum member any suggestions to cure this problem?

 

[gas4you]

You could check if the pump is set to maximum speed?

Other than that it sounds like the whole thing needs a good descale, but to be honest this would be a waste of time and money.

New boiler is what is needed if it is that bad.

I always note things like kettling/noises etc on the CP12.

 

[Fred56]

Hi,
I've bought a bottle of descaler and plan to put it in sometime soon. I have tried the pump at all speeds. The system is very noisy at high speed but it sometimes needed to get water through some of the ground floor radiators. The ground floor is suspended timber and the pipes go into the void beneath. Experience have shown me that that type of layout always leads to silting in the bottom of the pipe run. The landlord's plumber was supposed to have descaled the system last year but he never turned up, probably a set-up with the landlord.

Do the boiler controls not have an affect on the cylcing?

 

[Agile]

The flow rate through the boiler will be too low hence the cycling.

The normal solution is power flushing.

You could try adding Sentinex X800 for a day with the system on heating to circulate it well and then draining the system and see if that improves it much. But without considerable skill in using it you might not get optimal results.

If you must use X200 descaler then turn off the rads and use it on HW only for a few days so that it is concentrated in the boiler.

Tony

 

[Fred56]

Thanks

I can't recall what type of descaler it is but I'll read its instructions carefully.

I must learn to spell cycling.