No its not necessary (or so far as I am aware possible) to buy directly from Vaillant. However Midsummer wholesale, the go-to for keen pricing, sell at this price, I haven’t found anyone who sells the ‘official’ part number at any radically different price and its well known in the UK that the part is a rip off!
Im looking at mainland european sites but haven’t so far found one that will ship outside the EU 
However if it is the same as the gas coding plug that is anyway simpler!
If you don’t find an answer (can’t help with that, unfortunately), I’d be happy to buy one here and ship it to you at no extra charge.
Thanks. Im hoping someone here will confirm that 0020266328 works. If not it looks like https://www.eibabo.nl/ will ship to UK.
I’ve set a 4K 1€ resistance on a Molex 2 pins connector and it works perfect
Hi James, short answer is no, I didn’t get it working. I was due a visit from my installer, so removed the chip before they arrived, just in case. I’ve since found further information on the group, and some settings I should have added, as I was missing a cooling option in one.
Over the next couple of weeks I’ll install the chip again, once I’ve found the articles on the other settings I needed to make and let you know the outcome.
Russ
Thanks, thats very helpful. I have found the ‘correct’ one online for about EUR40 from Holland, but will await your test to see if the one you have works
That is the plug we are using for cooling, specifically from this retailer:
I have the 0020266328 which cost around £5, and yes, it works
Hi,
I have just found my Vaillant 0020266328 code plug.
I have managed to get the cooler working, after looking through various posts!
How well does the dew-point control work? Any issues with automatically keeping the flow temp above dew point?
Still playing currently, I have now set both zones to 16c. No condensation on any pipe work, had also notice the house temperature was still rising.
I have setup a schedule for cooling from 03:30-20:00, hopefully it will help get the temperature down by early morning.
I had to close and reopen the app to see the cooling option, which I think I’ll need to do with the VRC702’s I have as they don’t have any detail of cooling.
My 5kw is using around 380-390 watts, about the same when heating our house.
Update: Dew point when I started playing I’m sure was 14c, is now 10.5-11c.
How low should I go with the cooling tempreture anyone?
Hi James, took me a while to find the plug, but works and can see the Vaillant units cooling options now.
In case this helps anyone, I bought the cheaper of the parts (… 328) and can confirm it is just the 4k resistor.
I also had the issue where it would go to cooling for a minute and then just show standby. I followed all the advice I could find but nothing helped. What finally worked for me was going on to the actual controlling unit (not the wireless sensocomfort unit) and changed the ‘cooling technology’ from ‘no cooling’ to ‘active cooling’. I can’t remember where exactly it was but I think it was under the installer configuration.
I Tried cooling for real today with the plug available for GBP5 in the UK, which clearly is the same hardware as the official one available for >GBP400. It worked but… an hour later the unit threw an F70 error - device-specific number (DSN) is invalid or missing.
According to the online manual this error does not exist for Vaillant Heat pumps, but clearly it does! If you read the description of F70 for boilers it basically says that the unique ID doesnt match the PCB and other components and is a fatal error (ie it disables everything).
I did check that mine will still heat hot water, but this makes me wonder if Vaillant do a hash of the components at install time, and periodically compare the configuration with the hash. However this would not distinguish between an ‘official’ plug and the same plug but with a different part number, so would equally affect people in countries where you could buy the plug for eg EUR40, unless of course its installed by a Vaillant installer who presumably knows how to regen the hash… unless of course they are terribly clever and factor in the country of initial sale 9in which case they should declare this in the sale agreement!).
Has anyone else got the F70 in any circumstance or alternatively has anyone else installed a cooling plug themselves (whether its one with the right part number or not) and NOT got the F70 (after cooling has been running for a while)
I installed the “original” 40€ plug myself and the heat pump has been working flawlessly for a year. This is in Germany with an aroTherm plus VWL 105/6 A S2.
Thanks thats useful.
It cant possibly tell which 4.1k resistor has been inserted so it cannot possibly, so far as I can see, be that the plug was sold under a different part number. It could be the fact its in the UK, or of course the error could be entirely unrelated (but if so its worrying and a bit much of a coincidence).
Its encouraging yours also has the S2 suffix which, according to the manual, signifies ‘sold originally without cooling’
I will try again today and see what happens.
If the error doesn’t happen immediately but with a delay, it might be that the resistor is barely within spec to begin with and experiences some thermal drift as the heatpump warms up. I have no clue what tolerance the heatpump expects for the resistor to be appropriately detected, but I have seen similar issues in devices using resistive coding before.
Now thats an interesting, and possibly encouraging, thought for which many thanks. I will watch behaviour carefully when Its next on.
Has anyone worked out the cycling logic for cooling? I presume its controlled by
Compressor start cool from (degree min -default +60)
Compressor hysterisis cool (degree - default 15)
Is this correct?
Yes, same logic as in heating with inverted sign for the integral. Also if you have it enabled somewhere, some dew point influence might be there (I don’t have that).
