Vaillant System Gremlins

I fully expect that my lack of knowledge of plumbing and heating systems is the problem here, but I hope someone can help find the issue.

My heating system is simple single zone open vent setup in a Y-plan configuration consisting of a Vaillant Ecotec Plus 424 with a VR66 wiring centre (setup in monozone/VR65 mode), Vaillant NTC and a single 3 port valve. It originally had the VSmart controller but that was recently replaced by a VRC 700f, by me, as I want to add the Ambisense TRVs (not looking for an opinion on those!).

The VR66 is wired up in line with the diagrams in the VR66 wiring installation guide (see attached) but I have an issue with the heating. If the room is already above the temperature set in the VRC700 the boiler still fires up and the radiators get warm.

If I set heating to OFF on the control and let the rads cool down and then set the heating back to AUTO at a time when it is programmed to be on, but with the room temp already above the required temp, the boiler goes through the following sequence:

1. S.04 Burner on (at the lowest modulation level)
2. Flow temp rises to 38C
3. S.07 Heating mode: Pump overrun (5 mins)
4. S.08 Heating mode: Anti-cycling time (20 mins)
5. S.00 Heating mode: No heat demanded
6. Flow temp drops to 32C
7. S.46 Comfort protection: min load, loss of flame + S.04 Burner on (min modulation)
8. Flow temp rises to 43C
9. Go back to number 3 and loop round again and again ....

The rooms get very warm eventually and I have to set the heating to OFF on the controller to stop the boiler firing up.

The only thing that I needed to set in the new controller was the system diagram. It indicated an error if I selected anything other than number 1. None of the diagrams seems to correspond to my configuration as they all seem to include VR70/71 wiring centres. The controls brochure states that the controller is compatible with the VR66 in a Y plan config.

I asked Vaillant which diagram I should select and they just sent me a copy of the Basic Diagram Book that I already had.

Sorry for the long-winded post but any help for a amateur would be much appreciated.

There are some fundamental settings that really require the knowledge of the system in front of you. However, as a starting point the following settings are important.

You can't just plug a VRC700 in and it will work! BTW Ambisence will only work with a VR70 (not a VR66) and an additional VR920 gateway.

A 700 'should' work with a VR66 with a 424, but depending on your version of VRC700 (1 2 3 or 4) you may need a VR70.

Set the rotary sector on the VR66 to show 1 in the dial window. Make sure it shows 1 not 0!

Factory reset the VRC 700 and power down the boiler and VR66 by turning the spur off. Leave off for a minute, power on, then set up the installer menu on the 700. After you have gone through the installation set up, go to the installer menu, password 000.

In installer settings go to system configuration. Scroll down through the list and change the following settings using the wheel and OK button.

Adaptive curve to Yes.
Configure heat circ to Zone 1
System diagram to 2.
Type of circuit to Heating
Set the curve to 2.3.
Min temp 25C
Max temp 80C
Auto off mode Eco
Room temp modulation to Thermostat.
Zone 1 assignment to VRC700.
Cylinder to active.
HW temp to 60C.
Parallel charging to Off.
Max cylinder charging time to 45mins
Ch pump over run time to 3mins

Desired temperatures are a personal thing, but 21C and 15C are good starting points.

See how you get on.

Thanks for your extremely helpful information. The problem was caused by the Room Temp Modulation being set to none. Pretty dumb mistake I guess!

It isn't happy with anything but a System Diagram of 1 though. It generates a fault if I select 2, which seems like it should be the correct one, particularly as 1 seems to relate to having a combi boiler.

In any case, it appears to be working OK now, so thanks again.

If/when I get around to investing in the Ambisense TRVs, is it a straightforward swap over from a VR66 to a VR70 or is that definitely a job that should be left to a pro?

Systems 1 and 2 are HW with a single heating zone. If 1 works fine, then that will be the slight incompatibility of the VR66. The VRC700 and VR70 launched together. The VR70 replaced the VR66. The VR66 has ‘previous’ logic, so is not 100% backward compatible. I’ve never fitted a VR66 with a VRC700 nor seen one in the field. Just got the info they don’t speak to each other very well lol!

Replacing the VR66 with a VR70 is straight forward. Only an extra ebus wire to run the 920 gateway for ambisense. It is physically bigger though.

Hi,

I have the same hardware and y-plan configuration. I can select CH and H/W individually but cannot get the VR66 (set to VR65 switch position 1) to demand the valve to mid-position when both selected.

Have you managed to demand CH and H/W together?

Thanks

Straiton70 said:

Hi,

I have the same hardware and y-plan configuration. I can select CH and H/W individually but cannot get the VR66 (set to VR65 switch position 1) to demand the valve to mid-position when both selected.

Have you managed to demand CH and H/W together?

Thanks

Click to expand...

Why would you when two completely different flow temperatures are required...?

I just thought it was something that could be done in a Y-Plan setup, but I understand what you are saying.

So its not a fault but as designed?

As been said, the reason there can be gremlins is that when they release a set of controls, the have specific wiring diagrams and settings for specific systems, if you install them to the correct tested systems the work brilliantly, but when folk start mixing new and old hardware there can be niggling issues that can be easy or impossible to correct.

You "shouldn't" be able to use a y plan in mid position with the VRC700, nor would you want to (or if you did then you've bought some expensive controls for nothing)

I've got the Ambisense system and I like it, depends on the house and system how well it will work and whether its of more benefit to run the heating as one large zone or "micro-climate" it, but I do like being able to alter the individual temps on the phone and with a digital sensor picking up the room temps rather than a wax or liquid capsule as normal TRVs have.

You'll need the VR920 Internet Gateway and a VR70, plus converting the mid position valve to 2x Two port valves as far as Im aware however.

Hi all

So I have a VRC700 that uses itself as the thermostat for heating zone 1, and a VR91 used as the thermostat for heating zone 2.

All wired via VR70 in the airing cupboard.

I have ordered an ambisense starter kit after realising this system is basically incompatible with the likes of tado/nest etc without a lot of work. Staying native even though it is more expensive!

So my questions to you if you don’t mind...

1) How do I wire the VR920 (or 921) that comes with the ambisense starter kit into my setup? Can I just connect the extra eBus wires into the eBus port in the VR70? I don’t know if “jumping”, if that’s the right term, works for eBus or not?

2) At first I’d like to not use the 3x ambisense TRVs and just have the system working with the current thermostat sensors on the VRC700 and VR91. Mostly cos the rooms containing those don’t have TRVs so will need to change the radiator valve connectors etc. Is this possible? I’ve read some stuff saying the VRC700 will not function as a thermostat with ambisense, but I don’t know if that’s only once you’re using the TRVs or not?

Anyway, I hope that all makes sense. Really appreciate any help you can give.

Matt

Yea, just wire the 920 ebus to the vr70. You can set up the app control and use it as is for as long as you want, once you've paired your first trv then the ambisense takes over thermostat control away from the controllers

That’s great thanks for the info

Apologies for lighting up this thread again but I’m having issues with the ambisense now that I’ve finally gotten round to installing the VR920…

So… without ambisense, all is well. In the app I have control of the DHW and the two heating zones (downstairs and upstairs).

The problem comes when I add ambisense to the app… it only applies them to zone 1 (downstairs) heating zone. There doesn’t seem to be any ability to assign them to zone 2 (upstairs). So if I install an ambisense TRV in a room upstairs, when it demands heat from the boiler it’s opening the wrong valve (opening zone 1, i.e downstairs).

Any help or suggestions massively appreciated.

Thanks

Did you ever solve your problems? I'm experiencing the same, although my TRVs upstairs (zone 2) can only command heat when zone 2 is in day mode, controlled by the vr91 upstairs.