Nest/Boiler issues

[Mpw7826]

So I made ‘some’ progress. Disconnected the SL2 and the weather comp and turned It off at mains for 15mins. Restarted it and it came on for a short while and then turned off and went to 00. The issue I have now is the boiler is still faulting with FA intermittently, it will fault and then come back to a temp etc. At least the boiler now goes to 00 when not in demand now. Any ideas?

 

[shambolic]

Screw the bypass right out to 2

 

[Mpw7826]

Hey Shambolic, my knowledge is very limited so I have no idea what that means. We have HW and CH. Am I correct in saying this issue is unlikely due to the nest installation and was probably pre existing on boiler installation?

 

[shambolic]

Yes auto bypass between zone valves should be screwed right out to no 2 if white nob and no1 if red/black nob. Have found modulating pumps don’t open the valves if they are screwed in more.

 

[Mpw7826]

Thanks. Just to satisfy my curiosity. How come we have CE in both zones and HW if a valve isn’t open? Or is the issue that it’s not open enough?
My understanding is that the nest triggers the motorised actuators which open the valves and then send signal down SL1. Is this a different valve you speak of or related?

 

[shambolic]

If the trvs are shut on the rads you need a circuit for the boiler to get rid of heat.

 

[Mpw7826]

Thanks for all the help. I got the plumbers out who fit the boiler and they’d installed it incorrectly, the flow and return pipes were the wrong way round. So touch wood it’s running as expected now.

Does disconnecting the SL2 have any effect on the frost/pipe stats?