Vailliant sustain 418 heat only problem

Johntheo5 · 2026-08-11T23:43:52+0100

That's the way I see it so its not wired like shown in post #24 where the 3 way valve is connected to SL in the boiler and PL is connected to the pump and this is what the Vaillant engineer is stating?.

diycooper · 2026-08-11T23:52:19+0100

Johntheo5 said:
That's the way I see it so its not wired like shown in post #24 where the 3 way valve is connected to SL in the boiler and PL is connected to the pump and this is what the Vaillant engineer is stating?.

Yes, exactly. That’s what I believe the Vaillant engineer is saying. At the moment it isn’t wired like your diagram in post #24, and it needs to be, with the 3-port valve/Y-plan switched live going to SL at the boiler and PL from the boiler going to the pump.

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Vailliant sustain 418 heat only problem

Johntheo5

diycooper

DIYnot Local

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