More C/H issues

[Roscoff]

Hi guys, from reading the forums seems like lots of people having C/H problems this Xmas - here's mine:

During summer had a number of problems with the boiler had it serviced, 3 port valve and pump changed and everything seemed fine. However problems have started to resurface, the main one is that the boiler will not get up to operating temperature when just the central heating is on. Boiler thermostat will get to around 58 degrees then it will switch off the burners. With water on, either on it's own, or at the same time as CH, boiler will operate correctly. The HW circuit is much shorter than the central heating circuit so obviously a lot less resistance but still don't really understand why it's doing what it's doing, all radiators start to warm up but they are not getting hot enough!!

Boiler is also refusing to ignite on random occasions but not sure if that's related to this fault!

Thanks for reading any suggestions will be much appreciated.

 

[Terry lambert]

Is the boiler thermostat turned up? Are the rad valves all fully open. Check pins on TRVs are not stuck down.

What speed is the pump on?

Bleed the rads

 

[Roscoff]

Thanks for the reply, boiler thermostat is set to 80 degrees which is the temp which the boiler will run to when it's heating the hot water circuit. We do have some rad valves on TRV's but there are plenty that are non TRV and open. All radiators have been bled and all radiators warm evenly. Pump is on 2 - was previously on 1 (after boiler service etc) and worked fine. increased speed doesn't seem to make any difference. Cannot use 3rd speed setting as pump keeps cutting out (faulty switch?)

 

[MrTherm]

Hi Roscoff,

I would check your 3 port valve outlets orientation and correct any wiring to suit if required.

Your valve outlets are somehow reversed. Your DHW outlet is feeding the rads (58 degrees) then go off, which will be via the cyl' stat? (no higher than 50c/120f is standard) Obviously when the valve is in mid position everything will get hot, even though reversed because all outlets are open when on full demand.

The boiler randomly refusing to ignite will be directly associated (cool down time) and could well resolve itself when the valve outlet flow direction is corrected. When all is put right you might be able to set the pump back at the 1 position.

Good luck.

 

[Roscoff]

Thanks or the reply, 3port valve is definitely not reversed. Just had both DHW and CH on calling for heat - boiler running beautifully. If i switch off the DHW demand the boiler switches off as soon as the 3port does it's stuff and whilst on this occasion the boiler did relight some minutes later the boiler green light will switch off at around 58 degrees even though the boiler thermostat is set at 80.