Hello all, ive got a Aerothrem plus 5kW. Had cooling set up for a while and pretty happy with it! The only issue im having is a lot of cycling… It normally runs at around 430-470W (input power), with a typical on cycle of around 30 mins, and around 30/40 mins off. See attached screenshot for yesterday.
Ive got UFH (or UFC?!) and MVHR with heating/cooling coil FYI.
Has anyone got any ideas of how i can reduce cycling?
by adding fancoil. Cold don’t emit well with only floor or rads…
I just finished to install one 6 kW fancoil on my VWL 55 5k system, test ongoing…
It was emitting poorly luckily without cycling ( 5 rads & 160 sqm floor )
I can’t go to low because of the DEW.
Thanks to the fancoil, it’s possible. I’ve place it right on top of the system before the Rads & Floor, his T output is monitored to be kept at DEW +1 so the input can be much lower
more than twice the output during a day !
Does anyone use cooling with normal rads with retrofitted fans?
I won’t be installing fancoils, but can use @Andre_K ‘s excellent fan controller to give the rads a boost in cooling mode. Is this a waste of time?
They’d be working against natural convection - unless you flipped them over and moved them to the top. 
It works nicely - even against the natural convection. Definitely shaves a few degrees off for me. Here, I turned coolingnin around noon and the temperature in my bedroom stops rising and stabilizes at around 23.5°C for an outdoor temperature >30°C. One issue is the circulation direction in the radiator - the whole rad doesn’t get cold, only a part because it’s optimized for distibuting hot water inside itself. Condensation can become an issue where very old rads can become rusty.
Thanks, very helpful!
Do the standard Vaillant controls have a built-in ‘above dew point’ feature? If so, how does this need to be activated?
Here is how I flipped the flow to the rads, it’s manual twice a year
Winter mode
Summer mode
Dew point survey you activate in the controller, installation menu
Thats interesting and a little surprising.
HeatGeek did some experiments with fans on radiators for cooling, and the effect was negligible because the cold all stayed at the bottom. However I suspect that plumbing practice here in the UK (where its most common both flow and return to be connected to the bottom ports, one at either end of the radiator) may differ to that where you are. Does it differ or are both your rad connections also also at the bottom ?
All connections are at the bottom and yes, most rads are cold mostly at the bottom. My radiators are severely oversized though and that might have to do with it. I’m running with 35°C flow temperature in winter at -10°C outdoor temperature, so I have a lot of radiator surface area.
Thanks.
Thats still interesting. Add on fans for the few days of summer when its needed seems like an attractive option to me. I do have one fancoil and should have got more. If I could squeeze a bit more cooling out it would actually be useful. The radiator in the main bedroom, which is a particular problem, is well oversized in my case (and a type 33 so 120mm fins fit nicely). I feel some more experiments coming on!
Same situation for me. Oversized type 33 with six 140 mm fans in the bedroom, and having 24 instead of 28°C at night is a big difference.
How does the ‘dew point survey’ work? Does it effect a hard minimum flow temp limit, preventing it from ever creeping below the calculated dew point?
