Vaillant heating and cooling zone

Absolutely no problem, a lot of the info is relevant. Can you attach a drawing of your actual install? It sounds very similar to mine except I have split the fan coils and radiators into separate zones so I can have different time periods, set temperatures and overnight roll back temps etc. for the two zones. Cooling was only planned for the fan coil zone and this is where it all went wrong with the Vaillant install drawings and info. Looks like you have got where you wanted to be regarding your control. Basically for one zone you do not need any VR (also called FM) modules but 2 zones and above you need one (or more) modules depending on number of zones. However I don’t think the various modules/controllers are what you would call fully programmable but rather designed to work with a number of equipment/install scenarios envisaged by Vaillant. So if you were trying to do something that Vaillant had not previously envisaged/done on a single zone it might not be possible, or need changes (updates) from Vaillant to enable it.
Don’t get too hung up on scheme numbers (like Daniel said) all the number does is allow access to different control options within the controller. The same scheme number can be entered into the controller for what seem like physically different installs.

I don’t have a proper Vaillant drawing, our installer asked them about the cooling and they came back with something crazy - So we designed that part ourselves. I’ve create a diagram here:

There’s only a single zone - There’s no room influence at all as we’re using pure weather compensation with a setback overnight.

Vailliant’s whole ecosystem is very rigid, it’s a shame because their setup could do a lot more than they allow.

What’s the PHE for? Do you have a Mixergy or another specific UVC that uses this?

OK, similar for me. Vaillant supplied my installer with 2 drawings. One would work fine for two zone heating, the other fine for zone 1 heating and zone 2 cooling but impossible to combine their drawings to allow zone 2 to heat and cool.
Looks like you have tried to create a copy of the basic system 8 schematic. As mentioned previously these schematics are more for control options rather than install but at the end of the day if it works that is the main thing, secondary question is could efficiency be better?
Do I understand that the heatpump supplies the flow for the house heating circuit and there is no additional pump circulating water to the house circuits?
Not sure why you would have a separating heat exchanger for your DHW circuit. Any exchanger reduces efficiency, the outlet side temp heating your DHW will be lower than the inlet from the heatpump meaning lower heatpump COP to get same DHW temp compared to no heat exchanger.
Also 110L tank seems small, ours is 200L for only two in the house, no kids etc.
Currently our control is the same as yours, pure weather comp, but objective is to have room influence. Reason is rooms lose heat to air only (upstairs) and air and ground (downstairs). Heat loss to ground is not directly related to air temp. Depends on what you have for floor insulation but in our house as air temp goes up (weather comp reduces flow temp) room temp goes down. Reason is loss to floor does not immediately reduce because air temp has gone up. Also if you have trickle vents or windows cracked open then depending on wind direction and strength you lose more or less heat.

Let me say my mother was German so none of the following has any xenophobia element. Many (most?) Germans have a mind set which is “we know what you should do with our equipment and we do not understand why you would want to do anything different”. In this case why would you want cooling in the UK, our standard supply is no cooling. This is where it goes wrong, I don’t think UK ‘technical’ support has much, if any, experience/knowledge of integrating the cooling option. Separate FYI to enable cooling on the heatpump you have to install the cooling resistor option. Supposedly Vaillant UK (or any other UK supplier for this part) want £300 to £500. However you can order it for about 50 euro from abroad and the true value of the component is about £2 and any UK electrician could could make you one. However guess Vaillant would dodge any warranty issue if it was not their direct supply.
Also looks like Vaillant have a full ventillation system that can be integrated with the heatpumps but my installer didn’t want to talk about it as he had zero knowledge.

No, it’s a standard Vaillant Unistor cylinder. (Sorry it’s 150L, not 110L) It only has a coil surface area of 1m^2, so our plumber wanted to run an experiment to investigate how the surface area affected efficiency. (The experiment is ongoing, the next step is to change the restriction on the charging pump loop to see how the flow rate affects it)

The standard coil has also been plumbed in but has been shut off with some valves.

There’s no additional pump. It’s an annexe (Approx 60sqm upstairs and 60sqm downstairs) with the standard radiators - There’s even some microbore pipework in there as we intend to switch to underfloor heating throughout once some building work has been completed. The current all-time COP for heating is 3.9 (And 3.3 for the DHW), that’s since about November. The flow rate is an “acceptable” 850l/h, but that will improve once the underfloor heating goes in. Without the fan coils, we were using a heat curve of 0.55, but now with the fan coils (With a fan speed of half), we are using a heat curve of only 0.3 which is an amazing improvement!

As above, it’s an experiment regarding surface area - The same reason why Mixergy cylinders use a plate heat exchanger instead of using the built-in coil. Sorry I mistyped the capacity, it is 150L - My parents live in the annexe so but it’s enough for their use even though it’s only heated to 42C. In the main house, we have a much larger cylinder (250L) but that’s because we have thermal solar panels - We probably only use about half of that between the two of us.

It will be interesting to see what your experiences are once you have tried it with room influence. We don’t really find a difference between the upstairs and downstairs even in our main house, although that might be due to the poor wall insulation. My only experiences are:

  • Main house, 1800’s with solid walls oil boiler, radiators are either roasting hot or cold - Not great, but we are waiting on some major renovations before addressing this
  • The annexe, is newer with cavity walls but I believe the floor is uninsulated, steady state and the temperature is extremely stable

I’ve been so impressed with the weather compensation in the annexe that I’m thinking of adding a buffer to the main house and DIY steady-state weather compensation for it - I’d be curious to find out how it will behave as it is a very different beast to the annexe.

It’s incredibly frustrating, they have so many great options throughout Europe and in the Nordic regions but most are either not available or are prohibitively expensive over here. They even have drying cabinets in the Nordics - Why don’t we have them over here? Do they not realise that we only ever see rain??

Ah yes thank you, I’d already seen the other thread on that. We ended up with the boiler coding plug: Vaillant Part No: 0020266328 | Plug, coding (blue) | 24 Hour Delivery | Heating Spare Parts. Do you have any links to the ventilation options? I hadn’t been able to find any information.

I’ve just found a copy of the original schematic they produced:
30713-1002-A.pdf (348.4 KB)

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The Vaillant ventillation is called recoVAIR I think. If you search the Vaillant site it admits to its existence but gives zero technical detail. Looks like some UK companies can supply but I have not looked to see if they give any technical info.

So far I have not seen a Vaillant schematic that shows a combined cooling and heating zone. They all seem to show zones as heating or cooling only, never combined.

Thank you Hugh, looks like they are very expensive MVHR systems and have been discontinued. I found two models:
Vaillant Recovair Var 275 0020064652 : Vaillant (Discontinued 21/10/2020)
Vaillant Recovair Var 350 0020064653 : Vaillant (Discontinued 08/11/2017)

They do have a PDF on that site:

It would have been interesting to see how they integrated with the controls, but it’s a moot point if they aren’t really available anymore.

Hi all, recently installed the cooling resistor in my Aerotherm Plus and trying to get my system ready for cooling this summer. Ive found this thread really helpful so far, so thanks!

Just to add to the above, you also need to set the heat pump interface to cooling:

Installer - config - cooling technology - cooling possible (although please note this option only shows up when you have the cooling resistor installed)

Im still tinkering with my system and trying to figure out the best controls so will keep and eye on this link going forwards.

So can I assume that when I see the cooling option I do have the resistor installed? That’s what I get in the SensoComfort installer menu:

No, that is always there. If resistor is installed you have additional options in “installation configuration”. These are “automatic cooling” and “cooling when OT temperature”. Cooling also becomes an option in heat pump controller (not sensoConformt) installation config, this is what @SimonCD was referring to.

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If your heat pump is UK supply/install then standard supply is no cooling resistor unless specifically requested. You need to look in the heat pump interface module to see if you have a “cooling technology” option (think thats what its called but on holiday so can’t look at mine to check), if there you should be able to chose no cooling or active cooling as settings. Heat pump interface can be a separate control box, or integrated into something else like a hydraulic unit (depends on what you have in your installation), but it is the “main” controller for the heat pump with many more settings than accessible through the sensocomfort unit. If active cooling is set then you should have the options Daniel mentions under the “installation configuration” in the sensocomfort unit.

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Thanks! Looks like I’ll need to score a cheap resistor then.

Hi Daniel,

Would like to confirm something with you. You have Vaillant controllers and if outside temp goes above “cooling at outside temp” setting the heat pump switches to cooling mode and if zone controller then calls for cooling heat pump starts as cooler. My installer should be switching me to wireless Vaillant controllers hopefully next week and I thought we were sorted until he mentioned a relay to switch the heat pump to cooling which rang alarm bells. I assume you don’t have a separate relay?

No, no relay. This never even existed in the manual before, and seems to be something new. We’re not using it though, and I don’t see why it’s required unless maybe you are doing something like in the Vaillant schematic vs. just standard heating/cooling circuits.

I can’t remember what you were doing now, but if you have a diverter valve for cooling/heating before your buffer, then you might need something. I don’t as heating/cooling is all plumbed the same.

@HJG . Relay or switch? My understanding is that an external switch allows manual control of cooling: when the signal is on (closed) and MI set to “external cooling mode” then cooling will follow the settings in the Cooling setup for the Zone. Otherwise, you have to use “automatic cooling on” (which is constrained by 24hr average temperature setting, so does not flip immediately) or the “cooling for several days” option.

So, don’t expect cooling for the Zone to work manually without this switch, regardless that the vr720 GUI for cooling a zone is identical in apparent logic to that for the heating of a zone! It’s taken me two years to work that out, and even the Vaillant service engineer had no idea why “the cooling wasn’t working” whe

I only learned this today from email discussions with a very experienced designer who was trying to get some sense out of Vaillant. The updated vr720 manuals and his contribution led me to the above conclusion. Alan, if you are on OEM, I can credit you better!

Andy, waiting for diagram from installer to see exactly what he means, a picture paints a thousand words as they say. If I understand you correctly the Vaillant controls will switch the heatpump to cooling but under their logic which may not match when you want the cooling. An external relay/switch allows you to force the heatpump to cooling mode?

Just so. If I walk into the house and think cooling is needed, the only option I have is to use “cooling for several days”, regardless of the fact that the Zone cooling setting is “On” in manual mode with a target temperature well below the room temperature. I do not have “automatic cooling” enabled, as the need for cooling is very rare. I am now going to investigate the hard switch option which could, so I understand, be a further thermostat device or, for my use case, a simple direct circuit switch.

I have just discovered some of these nuances today as well having tried to turn cooling on in one room with no success. I had “Automatic cooling” turned on but the “cooling at outdoor temp.” was set to 21C. Today the avg. 24hr temp is reported at 17.5C by the controller so it doesn’t consider it “cooling mode” yet. I changed the “cooling at outdoor temp.” to 15C but this still wouldn’t allow cooling and I suspect this config change isn’t processed immediately and it will work tomorrow.

Eventually I set “cooling for several days” to run until 1/1/2025 and now the cooling is working but this is not an ideal solution.

As suspected “Automatic Cooling” at some point after my last post started working and I no longer needed to use “cooling for several days” to get cooling to turn on. It has now, a day later, got colder again and the system switched back to heating mode and the cooling stopped working without using “Cooling for several days”. I can’t see a way to tell if the system thinks it’s in heating or cooling mode.

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It would be very nice if Vaillant would document somewhere exactly how this is intended to work, wouldn’t it? !!