One last question on wiring for wet underfloor heating!

[HappyHippyDad]

I've pretty much sussed out the wiring for the radiators and underfloor heating, thanks to help from the forum. I do have one more question though. I feel the answer is obvious but i just wanted to double check.

In the diagram below there is a terminal block labelled manifold pump or valve.

Could I confirm that I attach the brown wire from the pump to the orange wire from the valve?
Also, that both the grey and brown wires from the valve go into the same terminal block (i.e. L)?

It just seems strange that the valve has 2 of its cores going into the same terminal. Usually in a valve, grey is PL and brown becomes live when the thermostat calls for heat (and this in turn closes the micro switch).

 

[ferg]

Either would work as the live input to the microswitch is only required at the same time as the switched live to the valve motor.

 

[davesparks]

It just seems strange that the valve has 2 of its cores going into the same terminal.

It is an unusual configuration yes, but you are right that in this case the two are joined together (it would work equally well with the grey in a permanent live too)

Normally you have 2 or more valves connected to the S/L of one boiler so need to microswitch to be fed separate from the valve motor to prevent a backfeed latching it open. In this case there is only one valve operating a pump so there isn't a second valve to backfeed into.

 

[brianmoooore]

Only downside of wiring the valve grey as shown, instead of to PL is if you should want to turn the valve and pump on using the manual lever on the valve for some diagnostic or testing purpose.

 

[davesparks]

Only downside of wiring the valve grey as shown, instead of to PL is if you should want to turn the valve and pump on using the manual lever on the valve for some diagnostic or testing purpose.

It won't affect that at all, the lever will still operate and the manually latches position stops just short of the microswitch so doesn't operate it.

 

[brianmoooore]

It won't affect that at all, the lever will still operate and the manually latches position stops just short of the microswitch so doesn't operate it.

Can't say for all makes, but the Danfoss valves I've used for decades most definitely do switch the microswitch 'on' when the valve is opened by the manual lever. I've just opened the airing cupboard and confirmed it.

 

[HappyHippyDad]

Update...

I wired up my first heating system today!
Thanks to all the help in this thread, (and the initial thread) I was completely prepared.

Turned up and the plumber had had to change the heatmiser unit for a different one with a different wiring diagram! Ahhhh.

Luckily, all the time I'd spent reading about it on line (John ward and also the forum) meant it wasn't too difficult to work out. Plus the plumber is friendly and helpful too.

Job completed