How to achieve 20 degrees C drop between flow and return?

[croydoncorgi]

Apart from the dodgy earth wire onto the base of the ignition electrode (now replaced with more robust version) I've never had a wiring problem as such. The tag-strip is (admittedly) foolishly low but hard to actually hit if the case goes on straight.

But I DO agree with you about the case design - really silly and can be absolute s*ds to get off.

It's silly, cheap mistakes that get to me - like today on a C36. DHW Return sensor fallen off because the cheap and nasty spring clip had completely rusted through!

 

[Onetap]

If you shoot from the hip, you miss - and then get nailed!

You appear to be referring to very old weather comps GENERALLY and very low function ones in particular................. In fact, you can even have the actual room temperature factored-in to the current Flow setpoint calculation! There's a night setback IN ADDITION to the compensated temperature (which might have been what confused you. )

I didn't shoot from the hip.

I asked the manufacturers because I didn't want to spend 2 or 3 hours trying to understand the manual for a product I might not want, without having the device to look at. I asked because I knew the reduced flow temperature was a problem with some weather compensated controls.

Maybe Vaillant were a bit confused by it.

I'll have to dig out my notes.

 

[gas4you]

Unfortunately it is widely accepted that the MI's for the VRC 400 are near on useless other than for the customers use. One of their tech bods is as we speak writing a full set that tells you what is happening when you change the settings and why, rather than do this and do that. I've been told I be first on the list for a copy. I hope so