Potterton Combi 28i - no hot water - advice please

[Dan Vittori]

Hi All

I thought it would be a good quick end to the story but maybe not yet. Although the CH and DHW are working fine, boiler pressure is now rising to the maximum 4 bar on the gauge.

My first thought was that I had overfilled it when I operated the filling loop 3-4 times during low supply pressure by Thames Water. So bled the radiator to bring it under 1 bar. But now it has happened two more times. I have taken out around half-litre water every time but it is slowly going back to maximum again after a few hours. Have noticed some damp below the overflow pipe outside today as well.

I have checked the filling loop valve and it appears tightly closed. Not sure what else could be causing this issue. Any advice would be very helpful. Thanks in advance.

 

[CBW]

Hi Dan, If it’s rising that high with the heating on, then you have an expansion issue, which will need the services of a gas safe registered engineer. If it’s doing it on its own, then you have a passing filling loop, or a pin-holed plate heat exchanger.

 

[Dan Vittori]

Thanks for a quick response.

I have now physically disconnected the filling loop at the non-return valve end. It doesn't appear to be the issue. Will keep an eye on the pressure to see if it increases during heating only or on its own. Although a bit difficult to check as pressure normally drops when the boiler is not operating.

Haven't cancelled BG visit yet so will wait and may need to use their service in the end. At least the boiler is working and the family is happy. Now need to train them on reading pressure gauges and radiator bleeding.

 

[oldbutnotdead]

Hmm. See what BG can do- with luck it's the expansion vessel.....bet they try and sell you a new boiler

 

[Dan Vittori]

Hi All

Hopefully last update on this topic. I was wrong in my assumption that filling loop was ok. Once I disconnected the loop, the pressure problem went away. Have noticed that the loop is leaking very slowly (3-4 drops a minute). Couldn't see it first and also it was difficult to imagine that a small leak could increase boiler pressure to maximum. Good lesson learnt.

I still need to fix/replace the filling loop but did cancel BG in the end as not looking for a new boiler as such.

Thanks again for all your contributions.

 

[HERTS P&D]

It's good to see that within 1 page the boiler is working with help from gas engineers on this site, if the diyers know-it-alls would have been involved then this thread would be 8 pages of complete nonsense from them.

Andy