2 zone 2 port valve wiring

[davphi338]

Hi,

I have installed UFH in a new extension which meant I had to install 2 new programmable thermostats and 2 new 2 port valves. My boiler is a Vaillant combi.

I am planning to wire it as follows:

3 core cable to each Stat ( brown (live), Black (neutral), grey (switch live)

2 port valve fitted at UFH pump & 2 port valve fitted at boiler.

3 core cable between each 2 port valve. ( to feed live/neutral from FCU at boiler to UFH pump and to return the boiler fire signal (orange on 2 port valve at UFH pump)

2 port valve wiring at UFH pump (grey (perm Live), brown (switch live from stat), black (neutral), orange (to pin 4 on boiler).

2 port valve at boiler wired same as UFH 2 port valve.

Can anyone see any problems with this arrangement. My only slight concern at the moment is that the 2 orange wires from the 2 port valves will be commoned up at the boiler so when for example the UFH stat demands heat there will be 240v back fed to the orange wire on the 2 port valve for the normal CH 2 port valve. Will this cause any issues.

Thanks for any advice

 

[gas4you]

My only slight concern at the moment is that the 2 orange wires from the 2 port valves will be commoned up at the boiler so when for example the UFH stat demands heat there will be 240v back fed to the orange wire on the 2 port valve for the normal CH 2 port valve. Will this cause any issues.

This is a standard set up. When there is no demand from a stat the valve will be closed, so the microswitch in it will be open. The 240V backfeed as you call it will go no further than the orange wire on the open microswitch.

 

[simond]

Most German imported combis (Vaillant 8 series, Viessmann 200 series, Worcester CDi series) are designed to send out a live on one terminal, which when it is returned to another, turns the boiler on.

In the case of an ecoTEC, this is terminals 3 and 4 respectively, on the others they are labelled Ts and Tr.

For reasons I have mentioned before, I would suggest you use terminal 3 as the permanent live for your controls (eg: timer/thermostat feeds) and use 4 as the switched live to the boiler.

If you use a standard perm live you will find the the boiler PCB is still on even if you turn off the I/O switch, when the controls are calling for heat.