vaillant 637- no hot water

16 Sep 2008
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United Kingdom
Just installed a new boiler system:

Vaillant 637:
Ariston Primo ITI 300:
2x 2 port valves(grey & orange wires isolated):
VR 65:

The CH seems to be working fine but im getting no joy with the DHW. I've swaped the 2 port valves over and still getting the same problem. the d.70 is set to 0. i get the DHW symbol on the boiler so i assume the VRT 360 is working. i've checked the voltage on the vr 65 and only get 240v on the DHW 3 port valve terminal and no voltage on the DHW 2 port valve terminal on the vr 65.

can anyone help?

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Where have you connected the cyl stat to, or have you used a VR10?
instructions say NTC is only for vaillant unistor cly so only the ariston third party cyl stat is connected to the cly terminal on vr65.
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I take it the VR65 is plugged in, working with the green neon lit?

What voltage are you getting on the DHW zone valve brown wire terminal?
Well either you have connected the wires incorrectly, which I will assume is incorrect, or the VR65 is faulty.

I have had these dead out of the box before.

Either get your installer to replace it or call Vaillant under warranty, but tell them it is a VR65 problem, otherwise they will turn up without one ;)
Thanks Gas4you.

Had a closer look at the third party cyl stat wiring diagram (Not very clear to understand) and swaped the number 2 wire from the stat terminal to thermal cut-off terminal and got the vr65 working with the DHW 2 port valve.
It sounds as if he has now corrected his mistake!

Pity he never answered if he was a CORGI registered installer or a DIYer !
Since when has being corgi reg had anything to do with wiring a VR65 :rolleyes:

It does not!

But since he installed the boiler himself he needs to be reminded to read up about notifying Building Control otherwise when he sells the property he might find problems.


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