If you look at the body of the pump there is an arrow showing direction of flow, is it pointing up or down ?
I'm guessing with d40 higher than d41 the flow is going in the right direction.
If you look at the body of the pump there is an arrow showing direction of flow, is it pointing up or down ?
0.5 is too low. The water will never go round the rads.
Put it to 3.5 or 4 and follow the FAQ on balancing.
D.40 should gradually start to rise with the burner symbol displayed as the heating warms up.
D41 will start to rise later.
The brass cap under the red cap only goes in the following:
0.2 furthest out
0.3
0.4
0.5
0.6 fuly screwed in
What should I set to?
Apologies - I was thinking of that valves brother which is numbered 1 - 6.
Leave it on 0.4 for now.
S53 shows the boiler is not happy with the flow through the heat exchanger.
If you open the bypass too much the heating will never work. Open it too little and the boiler will drop out to an error.
Sounds like your system is a mess and needs a clean out.
THe only other thing I can think of right now is to drop D.0 to say 6 and see how it behaves then.
Only if the flow and return are the right way round![]()
The whole lot should be done. Might not be cheap... but the boiler should be salvageable unless it is making horrid noises.
With a lower D.0 setting the boiler should stay on s.4 for longer and D40 should reach the setting you choose on the lower knob - which should be 65 or 70 depending on your cylinder thermostat on the tank.
At this stage you are looking for hot rads. Maybe a bigger pump.
I could do it, but you are a long way from my operating area. If you like I can ask in our closed section of the forum.
The cost of a full clean could between £350 and £600 depending on time, severity and of course any remedial plumbing required.
Do not use any of the numpties you've had so far![]()
I could do it, but you are a long way from my operating area. If you like I can ask in our closed section of the forum.
The cost of a full clean could between £350 and £600 depending on time, severity and of course any remedial plumbing required.
Do not use any of the numpties you've had so far![]()
The problem is partly due to the time of year. Do you have thermostatic valves? If so they are likely to be closed down even when set to max. In which case you need to remove the heads.
From the sound of it; you haven't actually had a power flush yet- despite appearances.
Pump wise you should be okay. In theory. But a search of the forum and your S codes will show how fussy these boilers are with poor quality installation.
Ignore that until the other issues are addressed.

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