No central heating in combi mode

[Arran2711]

Hi,

I've recently moved into a rental property with a Remeha C28. We have had hot water without issues but as it's got colder we went to turn the central heating on but it doesn't work in combi mode. It does also drop pressures so I have needed to refill the loop every 1-2 weeks. Troubleshooting steps taken:

Displaying code 8 - control stop and will appear if the measured flow temperature (t1) is higher than the flow temperature set (Tset flow). The boiler will start working again automatically once the flow temperature falls below the flow temperature set.

Every 5-10 minutes the boiler cycles through 2 to 4 on screen but returns to 8 within seconds.

t1 is reading in the 60s. Tset flow is set to 75 which is factory default. t2 (return temp) is the same as t1. t3 (boiler temp) is not reading anything.

When boiler switched to DHW off and CH on, the central heating then works. I am currently manual switching between boiler modes manually to use the heating and hot water.

I was suspecting an issue with the diverter valve but it seems to work when changed manually. Could it be a sensor issue as the control stop is being triggered despite the temp readings being within normal ranges?

 

[Murdochcat]

If it’s a rental you need to address this to the LA or LL

 

[Arran2711]

My landlord is someone I know and is giving me a good deal. He is more than happy to get someone out, I'm just trying to save him some money by figuring out the issue first.

I have found that the code 8 only comes on when DHW is on and when it attempts to reset the code 2->4->8 would suggest it is calling for hot water even when all taps are off. When I take the hall effect flow sensor off the pipe but keep it plugged in, the central heating then works but obvious the hot water does not. I'm going to order new sensor but could it also be a hot water circuit leak? I am losing pressure frequently

 

[cross thread]

Isolating the cold supply to the boiler if it then works it’s a leak on hot water feed