Hot water only with Central Heating

[Brian L]

Hi all, I feel this may be a long question but the solution is probably in the detail

Boiler Worchester Bosch 28i RSF (fitted circ 2002)

For some time the PRV has been leaking, I have eventually resolved this by installing a new expansion vessel (in the return, not replacing the original in the boiler). In my madness I thought the system would work better, it is quite a long way to the furthest radiator, to keep the system at around 2 bar. It worked well, most of the time we used DHW the CH was on and everything was fine. However it turned out that if the CH was not on the DHW didn't work. I turned down the pressure on the CH to 1 bar and this resolved the problem, however this now turns out not to be 100% reliable and the DHW doesn't always work when the CH has been off overnight and the CH had not yet fired in. The boiler operates using a water flow turbine and an air pressure switch, I do think it is one of these parts but don't know which one to try first. My question - any thoughts?

Thanks for your help
Brian

 

[aggis]

Heating wouldn't work if it is your air p swt, need to do voltage tests on water f turbine.

 

[Brian L]

Cheers Aggis, will do
Brian

 

[Johnnyd]

Hi Brian,
My 28i is having the same problem, did you ever get to the cause as im thinking the flow turbine or thermister/sensor as the pcb was replaced less than 12 months ago.

Cheers
John

 

[Brian L]

Hi John
Yes I did get to the bottom of it. The bearing in the flue extractor fan was worn and it was taking a while to get up to speed thus not causing a vacuum. I sprayed it with WD 40 and it has worked ever since.
Hope this helps