Danfoss ATC wiring

[AJSmif]

(system is vaillant 428 boiler + 3 port valve, cylinder stat, room stat & grundfoss pump, plus Danfoss FP715 programmer)

I had some suspicions about the operation of my Danfoss ATC cylinder stat and was thinking of replacing it ... (turning the stat up or down seemed to have little difference on the temp of the water)…

Anyway I took the cover off just to see how it was wired … and how easy it would be to replace…

It has 3 wires coming in to it … blue, brown & green/yellow

• The green yellow earth wire is connected to terminal 1 (co)
• The blue wire is connected to terminal 2 (nc)
• The brown wire is connected to terminal 3 (no)

I was somewhat surprised that nothing (including the green yellow wire) was connected to earth…

Does this sound ok … or not?

BTW: Should the stat be directly controlling the 3 port valve ie should the motor be opening closing the valve immediately the stat clicks on/off … or does the stat feed into something else which decides when to operate the 3 port valve?

Thanks for any help

 

[twgas]

Most cyl stat are bouble insulated so do not needto be earthed (not sure, from memory, about the ATC)
3 wired connections is correct for a 3 port valve, common from prog, NC to grey, NO to orange.

 

[AJSmif]

thanks

3 wired connections is correct for a 3 port valve, common from prog, NC to grey, NO to orange.

interesting ...
on mine NC seems to go to 3-pv orange
and NO seems to go to 3-pv grey

is this the wrong way round? What effect would it have?
How would I test it?

Thanks again


(Ps Danfoss wiring is a bit confusing as the dafoss atc label conections nc & no while the danfoss HSA3 diag use HWS call & HWS sat)

 

[D_Hailsham]

It has 3 wires coming in to it … blue, brown & green/yellow

• The green yellow earth wire is connected to terminal 1 (co)
• The blue wire is connected to terminal 2 (nc)
• The brown wire is connected to terminal 3 (no)

I was somewhat surprised that nothing (including the green yellow wire) was connected to earth

Whoever installed the stat was lazy as he should have used a 3-core plus earth cable; but he didn't have any, so he used a standard 2-core plus earth.

The connections are correct:

T1 is common
T2 to valve orange (and boiler switched live)
T3 to valve grey

If you have a multimeter you can easily check if the stat is working OK.

Disconnect wires grey from 'Grey terminal' and orange from 'Orange terminal'
Set timer to HW ON
Set stat to max
Measure voltage on 'Orange Terminal' (should be 240Vac)
Measure voltage on 'Grey Terminal' (should be 0Vac)
Set stat to min
Measure voltages: 'Orange' should be 0Vac; 'Grey' should be 240Vac

If the voltages are OK the fault is elsewhere.


PS If the stat has an earth connection it should be earthed, so you should really be using a 3-core plus earth cable.

 

[AJSmif]

It has 3 wires coming in to it … blue, brown & green/yellow

• The green yellow earth wire is connected to terminal 1 (co)
• The blue wire is connected to terminal 2 (nc)
• The brown wire is connected to terminal 3 (no)

I was somewhat surprised that nothing (including the green yellow wire) was connected to earth

Whoever installed the stat was lazy as he should have used a 3-core plus earth cable; but he didn't have any, so he used a standard 2-core plus earth.

The connections are correct:

T1 is common
T2 to valve orange (and boiler switched live)
T3 to valve grey

If you have a multimeter you can easily check if the stat is working OK.

Disconnect wires grey from 'Grey terminal' and orange from 'Orange terminal'
Set timer to HW ON
Set stat to max
Measure voltage on 'Orange Terminal' (should be 240Vac)
Measure voltage on 'Grey Terminal' (should be 0Vac)
Set stat to min
Measure voltages: 'Orange' should be 0Vac; 'Grey' should be 240Vac

If the voltages are OK the fault is elsewhere.


PS If the stat has an earth connection it should be earthed, so you should really be using a 3-core plus earth cable.

Thanks - sorry for late reply - family problems again...
yes voltages seem ok


I also not that the posyting from Mick above has t2/nc & t3/no opposite way to you & yours seem to match mine
though annoying my botched wiring colours make it a little confusing...

thanks again - I've had some further thoughts on my problem - but I start a new post to avoid confusion.