Vaillant VR65 + VR392 + standard cylinder thermostat help

20 Oct 2013
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United Kingdom

After quite some research I decided to upgrade from my ancient switchmaster 805 programmer after having a new Vaillant ecotech plus 415 boiler installed a couple of years ago. So I've gone down the Vaillant route with the following:

VR65 Control Center
VR392 Room Programmer
I've kept my switchmaster cylinder thermostat and connected up these items as per the 3 port valve installation guide that came with the VR65. I've used just the brown and blue cable of the old thermostat in the VR65 CYL electrical ports. Everything powers up fine the programmer works great and the central heating settings seem to work as they should, but the hot water isnt running right. So i want to check that i've not got something wrong?

The VR392 programmer instructions state to remove the red jumper link in ports 3&4 of the boiler if external 230v controls are to be fitted? I understood this to mean any additional third party programmer controls, but does this mean the old cylinder thermostat control? So by removing this jumper i'm assuming the VR65 would then supply power to the CYL electrical ports and the thermostat would start working correctly?

At first I thought I may have had the polarity on the cylinder thermostat around the wrong way as it seemed that when I turned the thermostat down to 20degrees celsius the boiler turned on, and when i turned it up to 70degrees celsius the boiler went off? Changing the polarity over made no difference.

The only way I can seem to get the water working is by turning up the water temperature on the boiler from 15 to the next value up 40. But then the cylinder thermostat clicks at near on 80 degrees and the water is squalding when it comes out of the taps.

What do other people have their water flow temperature set to on the programmers too? Although I'm pretty sure this is unmeasured unless I connected up the VR10 sensor that came with the VR65. If I was to connect this up along with the exisitng cylinder thermostat, how would I wire these two up in the VR65?

Any help ad advice is much appreciated :)
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it's either the vr 10 (recommended) or the on off thermostat on the cylinder, not both.

Either of them go back to the vr65, if the cylinder sensor is not 2/3 of the way down the cylinder or higher the hot water will get very hot.

It sounds like its the position of the thermostat that is the issue.
Thanks for your reply Alec, but it never got this hot before? but then I used to have the water temperature set to 15degress on the boiler with the old programmer and I guess the cylinder thermostat did the work last time?...did use to take a while to heat though. the only new thing is the programmer? Its the fact that the next water temp setting from 15 is 40!? even then the water temp is getting on 80degrees Same boiler and thermostat in the same place as before on the old cylinder? So am I right to leave the red jumper in then?

Have you got any recommended temperatures for the boiler/programmer/flow temps etc? It is a very old thermostat, do you think that the new programmer vr392 with the VR65 have just highlighted this? Does the boiler have a high temp cut-off point? Am I connecting it up right, using the brown and blue wires in the CYL ports on the VR65?

Thanks :)
Okay, having just seen a post regarding my actual thermostat, I'm thinking I may have chosen the wrong 2 wires to connect to the Vr65..can anyone confirm?


I have this very same existing thermostat that i'm trying to wire up to my new Vaillant VR65 Control Center. (To enable me to use the eBus system on my exisitng EcoTech plus 415 boiler) The control center only has 2 ports for the CYL thermostat control...on and off. I think I may have connected the wrong ones having looked at your colour guides...

So I'm assuming I should connect it like the following?

wire 2 - red (demand)/on?
wire 3 - blue (satisfied)/off?
and the wire 1 - common becomes redundant?
the thermostat states it must have an earth, so i've connected up the earth to the earth on the VR65 unit

Any assistance would be much appreciated.


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with either the vr10 or an on-off thermostat the boiler will always go to high temperature and heat output when there is a call for heat of hot water. Thats 80c (unless adjusted in d codes)

If the cylinder thermostat is too far down the cylinder then the boiler will spend too long at high power so the hot water will get too hot, as high as 80c.

Before the new controls were installed the hot water cylinder heated the cylinder at the same temperature as the radiators as determined by one of the knobs, I forget which!

so even if the thermostat was calling along time for hot water it would only ever get to the maximum temperature of the knob setting.

Indeed you would probably not notice with the old system as it probably had flow sharing as a meaning it would do both heating and hot water at the same time.

You now have hot water priority meaning it does either or...

move the thermostat position and all will be well

One of the good things about these controls is that its impossible to get wrong...

where is the cylinder stat in the cylinder...and how old is the cylinder?
Thanks Alec, Ok, so that makes sense why the change of temperature...I think I'd like to reduce that 80c temperature with the d codes then, any ideas any Vaillant boffs out there? I must have the thermostat wired wrong though as I even set it to as low as 40c so as to kick the system into turning the hot water off, but nope it still kept heating it...

Just for peace of mind, can you or anyone else confirm exactly what 2 wires from my thermostat as described, i should connect to the vr65 please? I'm still not convinced I have the right ones connected?

To answer your question the thermostat is about 3 quarters down the tank. The tank is about 3-4 years old now.

Just want to make sure there's no possibility of the hot water going over temperature should I have something wrong on my thermostat wiring etc. But it makes sense that the boiler would have a maximum water temperature cut out too.

This was one of the attractions to the Vaillant controls, the ease of install, just want to make sure i'm doing it right.

So my thermostat as described just to get straight although previously connected to a 230v, will still work using the correct 2 wires plugged into the VR65? Can anyone confirm the correct port 3-4 jumper. I still have the jumper in which is correct if I have no other controllers using 230v.

Assuming this means the VR65 will supply the CYL ports with 230v becasue of this? Please someone clear this point for me, i'm going barmy.

Thanks for your help Alec, really appreciate it.
there are two terminals one saying NTC for the VR 10 and the other saying something else, its all on the wiring diagram on the cover.

If you lower the temperature of the reheat you will spend longer heating hot water...and less time heating.

the d code is in the book.. you just have to look I am afraid...
Yeah the other 2 are marked as CYL...but they dont illude to exactly what 2 cables from the cylinder thermostat are required?
its either or.. i am afraid.. not both...either the vr10 or its the on-off cylinder stat
yeah sure I get that thanks, i'm going to use just the cylinder thermostat, but what 2 wires from the cylinder thermostat do i connect to the Vr65 CYL ports?
so long as the boiler has the water temp cut off at 80c as a fail safe then this is ok to use? Only I was concerned if the VR10 sensor came away from the cylinder then there was no failsafe?

Any recommendations on where on the cylinder to place this?

Guessing the VR10 is connected to the CYL ports NOT the NTC one...?
NTC is for the VR10, where it says CYL is for the cylinder thermostat.
Okay thanks

If I was to connect up my old switchmaster cylinder stat though, can you guide me through the connections to the VR56 and or any other connections required?
I am not really that familiar with cylinder stats..some have three wires some have want the ones that make on a temperature drop...

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