I chased vailant, they told me it would be £500 (+vat presumably) to replace the board and went to lengths to point out the issue is not covered by warranty and wouldnt even guarantee the replacement would have the newer rom… my current heating installers think im some sort of OCD freak if i mention it
I would say mine starts cycling at around 5’c too, right now with both zones in Active mode it is cycling every 30 minutes at 7’c.
To compensate for warmer weather cycling ive been increasing the heat curve for higher flow temps. This always gives back better efficiency above 5’c. but i have to drop it when it’s colder. Obviously this strategy only works in expanded mode too.
Anyway, i assume there’s no way I can configure Vaillant’s controls to tie the two zones? I need to ask my installers to bind them together?
Cant you you just do something like set both so that any external call for heat is constantly on, then simply set them both to the same FT on the Vaillant controller. Without more detail and c control/system diagram its difficult to give a recipe but essentially you are trying to disable some controls and the best way to do this is usually to set the thermostat (or whatever sensor) that is the controlling element well above the desired value so its constantly ‘on’.
Cheers - I guess setting both zones to Active room mod is effectively this.. the problem is the cycling when its warmer outside (doing this now and it’s cycling at 2x hr @ 5c..). When its cycling my HP has a major dip in COP 5-10m into each cycle which takes another 10m to recover from. Since each cycle is so short most of the heating period is impacted.
So I’ve been using Expanded mode with higher FTs and letting it turn off the heating when it overshoots, using it as a method to extend the cycle period. It’s harder to setup as a combined’ zone if I wanted to maintain Extended mode setup.
Does anyone know by what quantity it can adjust the heating curve up or down? And if it’s better to go slightly higher on the set curve, logic in my mind says yes.
I’ve had a few occasions where the machine has cycled off but interior temp was 0.5 below desired when it did, and thus by the time it cycled on it had dropped 1C below target - so I’m going to move to active in the hope to reduce this happened. Also unfortunately yesterday it cycled off 20 mins before DHW run and thus when DHW was done had dropped 1.2C below target.
This seems to happen worst around 7-10C as we are oversized and cycling at these temps. Consequently when it’s decently cold we are always warm, but when it’s not properly cold, the house can be colder than when cold! Ironic. Oversizing for you.
Odly before my PCB was replaced I had sensible COP and temps read the same. Now return is reading above flow. This was on idle pump between cycles. Also my COP is impossibly low for the power used / property heat loss.
I’m not sure if return temp is used for anything (don’t think so) but will ask them to look at it all the same.
The controller subtracts the current room temperature from the set point temperature and adds the result to the set point temperature, then looks up a flow temperature off the heat curve using that value.
I would pick a heat curve 0.1 below what you think you need and turn on expanded mode and adaptive heat curve. When it’s proper cold outside (around freezing) it will adapt as necessary. Expanded mode is a prerequisite.
On Samsung units, return temp also appears to be used for minimising the target compressor discharge pressure (the refrigerant/oil mixture saturation pressure at RWT with a small margin applied, to ensure its complete condensation with minimal subcool). May be similar with Vaillants?
Credit due to my vaillant today. I woke up and only realised it was -5 outside when I went outside. It just works to keep the house warm with no input now. I’m also glad my unit is oversized a bit, we don’t get many defrosts and after a power cut the other day it had no issue re heating the house. I know everyone bangs on about not oversizing, but I’d rather have some cycling (we cycle over 6C) and less efficiency at mild temps for peace of mind at cold temps.
Compressor was at 70rps this morning at -5. Design temp is -7 and we can see lower.
If you have a home battery can better to have lower COP in mild weather if it results in higher COP in very old weather as electricity is cheap until run out of battery capacity.
Due to cycling, the house is under heated at mild temperatures ~11C when no solar gain is present. I wish there was an option that changed the algorithm to stop it turning off due to energy integral if internal temperature < desired temperature. We are only talking .3 C under desired but it makes a difference to feel in the house. I did bump up desires temp the other day and that helped a bit but not perfect. I’m runnin active weather comp.
This is not due to cycling but an improperly set weather compensation curve. Try increasing the minimum flow temperature by a degree. This will not impact anything when the weather is colder but just operation when the flow temperature would be below the min temperature.
My min flow temp is 28C already. I guess I can take it up a bit and see. I can see how it would put a bit more heat into the house as it’ll heat more when on, and come back on faster.
It’s a shame you can adjust the curve with a bit more refined detail.
Hm OK, so at 10°C out you’re already at 34°C flow, so this might now help without affecting the general heating performance of the system. You’d only see a difference now if min was set above 34°C which seems excessive.
I’m afraid you’ll have to manually up the desired room temp in those situations. It’s not a perfect system, unfortunately.
Yes, not perfect. The ironic thing is the machine would have no issue giving the heat needed, but the computer algorithm is preventing it doing so. It seems to me that adding a check like i described above would be a simple rectification for this issue. I’d guess the people deciding and writing the algorithms might not be living with heatpumps… as is often the case. This is definently a hole in the way it works.
Maybe this is where something like Havenwise might work, if they can tell the machine what to do. But it’s a Vaillant software issue, which they should consider, and I don’t desire to pay Havenwise money…
This also raises the point that it’s not quick to swap between active, inactive and expanded. You should be able to do it in the app. Then I could make use off expanded to push the temp back up to desired and then return to active. I’d write to Vaillant but I doubt they care.
Hi, has anyone had any issues with the air inlet temperature sensor? Mine is reporting 40C, when it’s actually 2C outside in the Midlands in the UK right now.
Consequently my Arotherm isn’t getting close to desired temperature of 41C, flow temp is around 33.
I’ve reported it to the installer who is normally very good at responding to any issues.
André, I’d like to share with you a text that I’ve written recently about Vaillant heat curves. The title of my note is “Kühne’s formula and a physical interpretation of Vaillant heating curves”
Could you send me your email address to *********@gmail.com, and I’ll forward the document to you? I’d love to have your feedback before I circulate it more widely.
