Vaillant heating and cooling zone

Sorry maybe in the wrong place as i thought this was a vaillant specific site. My question is does anybody have experience of vaillant arotherm plus heat pump with 2 zone control, one which is cooling and heating. Vaillant seem to be unable to supply a workable installation drawing and how to control the cooling/heating zone

Welcome, Hugh, to the OEM forum.

We’re Energy Monitoring in the broadest terms, so expect to see all sorts of energy being monitored (specifically) and in general controlled and discussed, and our information and designs are all open source - hence the name. I’m afraid I can’t advise you on your specific problem, but I’m reasonably certain someone will be along soon who can.

Yes, I have three mixed circuits, three zones and cooling enabled.

I’m unclear what your specific question is though? Do you want one zone cooling and another zone heating concurrently? Or what’s the specific query/issue? The installation is no different for cooling than it is for heating.

Hi thanks for the response.
Zone1 is house (heating only), zone2 is conservatory (heating and cooling) concurrently are not required. Vaillant are saying for cooling the heat pump only must supply the flow, by passing the buffer tank, and the main circulation pump used in heating must not run so very different to the heating set up. I’d like to see your install drawings. Happy to send you mine but they cannot work for a combined heating and cooling zone. Also Vaillant have not answered my instsaller how the control on zone2 would be set up (ideally with a VR92f)

My cooling uses same buffer and pumps. Can’t understand why you would need to bypass the buffer or do anything different TBH. Did they give you a reason? Is this Vaillant or an installer?

I’m not sure how you plan to setup the zones, but if you are using mixed circuits (where each zone can have it’s own weather compensation curve and flow temperature) then you don’t need a circulation pump, instead each circuit has it’s own pump after the mixing valve.

Our second zone has a VR92f. You need a cooling resistor too, but make sure you don’t pay £400 for it!

Can’t see a drawing if attached but new to this.
All information about installation is suppsedly from Vaillant. Installer has been working with Mitsubishi and Nibe for years but is new to Vaillant and i am (i think) 2nd install with cooling option on a zone both of which he is ‘discussing’ with Vaillant.
No mixing cicuits in my set up, one pump supplies both zones. With SensoComfort control for zone1 and VR92 for zone 2 i assume heating conditions demand for zone 1 overrides zone 2 but if only zone2 has demand then system would run on zone 2 settings, correct?
Is the cooling resistor in the heat pump, if so it is supposedly already installed but don’t know if i paid extravor it.

I didn’t no. See page 45 here, I am using 1 UFH zone and one fancoil zone, but it’s the same.

Not sure exactly how it works without mixed circuits, but what I assume is that both zones run with the same temperature and whichever zone has highest heat curve (if there are two configured and both zones enabled) wins. I assume each zone will have a zone valve and therefore if cooling is enabled for one zone, and not the other zone, cold water will only flow to one zone, right?

@dfeist You should be able to attach images to your posts, @HJG I’ve promoted you so you should be able to do the same now. (Just drag and drop into the post.)

Unless there might be copyright issues, we prefer you to post drawings/diagrams etc here rather than on 3rd party sites – there’s a much better chance they’ll remain available for reference in the future.

OK looking at p45 in the link you attached you have a hydraulic station which I understand to be only an electrical back up heater so with that removed you appear to have more or less exactly what Vaillant gave my installer for a two zone heating install. See following drawing:
31170-1012-B.pdf (490.3 KB) Ignore the indicated control, it will be SensoComfort for zone1 and VR92 for Zone2. This is absolutely fine for heating. But Vaillant gave my installer the following drawing for cooling on zone2.
31170-1012-A.pdf (385.7 KB) A 3 way valve has appeared to divert the cooling flow around the buffer tank directly to the zone2 2-port valve in front of the fancoil and there is no longer a heating water supply to the fancoil! Also the 2-port valve opening must not start the main circulation pump (but it must for heating)! So obviously with these drawings zone 2 is not capable of heating and cooling depending on actual zone temperature.
Do I understand correctly that with your heatpump on cooling the rest of the system runs exactly the same as heating it is just cool water circulating? If so do the notice any operational issues?
If anybody has a logical explanation for why Vaillant would want to bypass the buffer tank I would love to hear it.
Current position is I have an operational 2 zone heating system, my installer was on a Vaillant course earlier this week which he described as a total waste of time as he got no answers to his questions and is still trying to get workable drawings from Vaillant. So any help/information would be much appreciated.

That smakes sense. Two zone non-mixed setup, where both zones will use the same temperatue. If both zones need roughly the same heating flow temprature then this will be cheaper than setting up mixed circuits as you won’t need an additional pump, and 2 lots of mixer valve + actuators.

What emitters do you have in house and conservatory? Conservatory isn’t a fancoil is it, as fancoil would typically need higher temps than UFH or probably radiators too.

I strongly recommened going for the wireless version of these, it means you can adjust position of them to get the best result. And the 4xAA batteries last min 2yrs, which suprised me.

Agree, this could work if zone 2 was a “cooling only” zone potentially, but you don’t want that. The only advantage of bypassing the buffer IMO is that it will be quicker to switch between heating and cooling (but you aren’t typically going to want to do that). The buffer ensure sufficient volume for defrost which is not required for cooling, but the buffer also adds volume to the system which can help reduce cycling, especially if you zone2 volume is only the conservatory and not that much. Reducing cycling is a good thing for efficiency and for longevity of the compressor, so personally I’d keep the buffer in play for cooling.

Yes, once configured it will automatically switch from heating to cooling mode based on the outdoor temperature. Then, cooling demand will be based on target/actual room temperature. The one difference vs. heating from what I’ve seen is that it doesn’t use any type of weather compensation I don’t think. (it will adjust flow temp based on a specified minumum as well as the humidity to avoid condensation).

I mentioned one reason (if a zone is cooling only and/or you want to switch from heating/cooling faster without cooling/heating the whole buffer when you switch), but I think there are also reasons to use a buffer (increased volume).

Install if as if it was only going to do heating only and don’t worry :slight_smile:

Thankyou for the info, it really helps. Final control will be sensocomfort and VR92 both wireless as you recommend. Do you have the background configuration settings for your controllers that automatically switch the heatpump to cooling etc? As mentioned earlier my installer is new to Vaillant and struggling to get reliable information from them.

These settings (all via sensocomfort controller) as far as I can remember:

  • Enable “automatic cooling” in installation configuration → installation.
  • Configure “cooling at outside temp” in installation configuration → installation.
  • Enable “cooling allowed” in circuit(s) installation configuration → circuitN…
  • Configure “min cooling temp” and “dew protection offset” if/as required in circuit(s) installation configuration → circuitN…
  • Set manual/schedule configuration for cooling (as you would for heating)

If the first two config options are not available then cooling resister is missing.

I mentioned one reason (if a zone is cooling only and/or you want to switch from heating/cooling faster without cooling/heating the whole buffer when you switch), but I think there are also reasons to use a buffer (increased volume).
I think (But don’t hold me to this) that the additional volume is only used when defrosting, which in turn only makes sense when heating. (You’re controlling the indoor humidity when cooling with a fan coil unit, so I don’t think it will need to defrost - And even if it did, the outdoor temperature will be high so it will be easy for it to bring in the required heat)

We also have a cooling setup, one single zone with a mid-position diverter to switch between heating (radiators + fan coils) and cooling (fan coils) - Only we’re trying to do it without the additional VR 71. (The heat pump interface has an output X5 / MA1 which in schematic 8 (Which we are using) can be a zone valve or cooling signal - But we have no idea what controls that mode so I need to get in touch with Vaillant technical support on that. The annoying thing is that cooling won’t operate until it’s more than 10C outside so we can’t test it yet!

It’s interesting to see how they have used the heat pump interface input MI / ME to control the cooling demand, the manual doesn’t specify how to use the input but it looks like you just short it out. It’s worth noting that if you don’t use this input for cooling, there is a setting to change it to act as a PV input - That means you can have an external PV diverter trigger the DHW boost mode. (I have not tried the PV diverter either, so YMMV)

When cooling demand is on then cooling MO will go live. First you need cooling resister, then you need to enable cooling for the installation and also for the circuit in question. Then you need to set a schedule or “manual” if using vaillant controls.

You can confgure this, but yes. There is a simple workaround if you have a wireless outdoor thermostat; bring it indoors!

The circuit demand is via S6/S7. It seems they are showing the MI being used for switching to cooling.
I’m pretty sure I never had this option in installation configuration before, and it’s not in the manual I have. However I just checked and I this option is now avaialable! (maybe this came as part of my firmware upgrade?). I also found a newer version of the manual online that explains how it works (see below).

That said, I don’t think this is really required if you are using Vaillant controller(s) as they will automatically switch to heating based on outside temp and well as the cooling configuration setup. I can see this being useful for external controls though, as in the schematic you are referencing.

I don’t think you need to use MI either, just configure MA1 for cooling signal and then connect it to diverter valve.

Ah that’s perfect, thank you for confirming this behaviour. Vaillant technical support are very quick at responding, but they keep telling me what it does for system diagram 10 (For a post-buffer pump) even though I keep asking about system diagram 8.

In that case, I think that’s the easiest setup if you have a heating / cooling mid-position valve without the extra VR 71.

Sadly ours is hardwired, so I think we’ll just have to wait. I might be able to enable cooling via the test mode on the heat pump interface though, will have to give that a go.

I didn’t realise it could even do firmware updates, not that ours has the internet gateway - But even so I thought that was just for the app. Good to know!

Yes in our case, we’ll just control it through the Vaillant controls - Either manually or, ideally, automatically. We don’t have any room influence configured so it will be interesting to see how cooling works with that, there doesn’t seem to be a separate heat curve for cooling mode which is a shame. We’ll probably get frozen into an ice cube! I also noticed that there are some references to dehumidification in the manual, I have no idea how that is setup though.

I haven’t seen that version before, the version I’ve been using has a cooling heading and then no content! Please could you link to that version as it sounds like it’s much later than most of them?

As we don’t have a buffer, I do wonder if we could use the buffer cylinder offset setting to allow the PV mode to boost the cylinder temperature much higher than it’s normally configured for - That would be good for a PV diverter!

8 and 10 are almost identical. One powers circulation pump and the other one doesn’t, that’s all I beleive.

Sorry, why do you need a heating/cooling diverter valve or VR71. It’ll just work as is, no special setup is required for cooling if you don’t have external controls or don’t want to skip a buffer (which I think is questionable anyway).

Yeah, cooling doesn’t seem to use any kind of curve of weather compensation. The first summer I was turning it on and off manually, this last summer I’ve been using external control (via) ebus to enable/disable cooling based on slab temperature (after waiting to see if Vaillant would finally release the modbus inerface that marketed or not). This coming summer I’m going to see if I can implement a cooling curve externally :slight_smile: The problem I have is that the UFH pipes are in a 200mm concrete slab so reaction time is very vey slow, for other situations the Vaillant cooling controls probably work just about OK, albeit without a curve, but not for me.

Are you referring to the dew-point monitoring that limits flow temperature based on humidiy. The aroTherm won’t dehumidify, but if you have a fancoil (and dew monitoring is turned off for that circuiit) this will provide some dehumidification.

Does your controller have this option? This manual version also seems to have more information about cooling in general.

A signal on “Photovoltaics” MI will boost UVC yes, but I’m not sure there is a way to set an increased temperature for this, it will just heat tank. Note though that this is fundamentally different to a PV diverter that uses variable/excess current from PV, once ASHP fires up i will then continue to consume a couple of kW unless UVC is at target temperature regardless of if there is excess PV or not.

sensocomfort-vrc720(3)-operating-and-installation-instructions.pdf (1.9 MB)

Sorry Hugh, I appear to have completely hijacked this thread! Hopefully the information is still helpful to your project though as it’s all cooling-related.

I think it’s more about the use of a buffer. In scheme 10, MA1 is dedicated to the “intermediate heat exchanger pump” while in scheme 8 it could be either a zone valve or a cooling signal, unless that’s what you meant by the circulation pump?

We use the extra diverter to prevent the radiators from being used during cooling. We have fully insulated pipework for the cooling, along with fan coil units with drain pans. The fan coil units are built for 7C water, so that’s what the heat pump has been configured for. Hopefully it should also allow it to pull a lot of the moisture out of the air.

We don’t have a VR 71, but I mentioned it because a lot of the setups I’ve seen seem to use one, but the heat pump interface itself appears to have just enough outputs as long as you’re not using a buffer.

Our volumiser is on the return and the fan coil return does go through it, I don’t think it’s needed but we told our plumber that the main priority was an efficient heating setup and that the cooling is a benefit - We have solar in the summer so the cooling setup doesn’t have to be perfect.

I’m very interested to see how this goes for you, I’d be interested in it for ours. We currently have ebusd for the collection of metrics, but it’s strictly one way - The Vaillant controls have absolute control right now. It’s a shame that they don’t have a curve for cooling, as it works really well for heating. I can see how manual control would be a pain for an underfloor setup - With fan coil units manual or basic automatic control may be fine but the curve is preferable as it works so well.

No I don’t mean that feature - But I don’t fully know what I mean. The various Vaillant manuals keep referencing dehumidification which I presume is an add-on configuration that they offer (They also support solar thermal and ventilation, for example) but I don’t fully know what they offer. Here’s an example on the MA2 output, it mentions dehumidifying unit as an option:

The manual you linked to also mentions a setting for “Humidity prevention”, but again gives no detail.

My thought was that given if knows the humidity of the room, with a heating and cooling setup it may be able to automatically use the cooling during the winter to control humidity as well. It’s just a guess though, their documentation is as amazing as ever.

Ours is quite new (Installed in November), but yes it has that option.

Sorry I misread the section of the manual you quoted, I didn’t see that the PV input first heats the DHW cylinder and then the buffer with the “Buffer cylinder offset” setting - I thought the “Buffer cylinder offset” setting applied to the DHW cylinder when I first read it. I also missed that it completes a full DHW boost cycle, I thought it would cut off if the signal was turned off - That’s a shame, it would work nicely with a PV battery setup though to use some energy once the battery was full.

Thank you for the updated manual!

In scheme 10 MA1 goes live when there is heating demand to drive post-buffer circulculation pump. In scheme 8 this isn’t required and doesn’t go live on demand (so yes, could be used for something else)

Right, but you could also simply use a zone valve. Unless this requires VR71 and using diverter doesn’t?

Agree. “Expanded” simply wouldn’t work with UFH in slab, but “active” works really well with no need for temp probe in slab, or external control or anything. Unfortunately cooling doesn’t work the same way.

Controller is used with ventialiation (and potentially MVHR) in europe i think, so could be this.

Turning HP on/off based on this signal when the sun behind the cloud obvisouly isn’t a good idea which is why it doesn’t do this and why it’s not comparable to a solar diverter. But yes, this works well with a battery as a buffer.

Or can alsoboost DHW via EEBus or ebus. Potentially also via the home assistant integration that uses the myVailant API too, that would be the easiest. (I’m still on old app, so haven’t tried this).

A 2 port valve could be used if you had a “heat” output from the controller - You could use MA2 with the “zone valve” configuration for that. The reason we used a diverter valve (Actually a mid-position valve) is so that we could select the functionality with a switch. (heating only / cooling only, or heating and cooling / cooling only) We did that because we didn’t know if the resistance of the fan coil units would be an issue but in practice, we shouldn’t have worried about it. Using the fan coil units for heating has been fantastic, our heat curve dropped from 0.55 to 0.3.

So yes, in short, we could have just used a 2 port valve to cut off the radiators.

I really wish they offered the full range over here. But that explains it if they have other products such as that.

I might have to try this, I haven’t used ebusd for any control yet but there’s more and more I want to do with it - It’s just getting the time to try it as with everything! Please keep us updated on your cooling curve project if you decide to go that way.

Just so you know, I’ve did finally get a response from Vaillant technical support on the cooling output, confirming that on scheme 8 MA1 is indeed used for cooling. They got there in the end!

1 Like