A big shout out to Simon Poskett at Heat Geek for the heads up here.
Posting this to make anyone else with dreams of high SCOP DHW and a Daikin ASHP aware that Daikin do not support the use of any of the heat geek tanks and it is against their third party tanks requirements.
The maximum coil size is 3.7m2, with heat geek tanks starting at 4.0m2 and most being 6.0m2. I have attached an extract from the installer reference guide regarding third party tanks to confirm (this is for the E(B/D)LA 04-08EV3 units but is the same for the big ones too.
This is apparently due to the units not liking running below 25°c. I do wonder if this is solely due to the use of booster heater below 25°c on the bigger units and posibally not an issue on the smaller ones (as no booster heater is used).
Not sure if there is any way to contact someone technical at Daikin and get some further clarification on this but thought I would add it here before someone spends the money on a Cylinder that they cannot “officially” use.
That’s very interesting, it’s quite surprising that Daikin have specified a maximum coil size. I’ve not seen any other manu specify and upper limit on the coil size.
If maximising SCOP is the goal, there are probably better choices than a Daikin heat pump.
Not liking running below 25C would also fit with the “no apparent benefit to running below 35C” observed by some thing to improve performance with weather compensation and less for temperatures.
Daikins perhaps optimised their performance envelopes for the “fit at fifty and fluff off” market.
You can run down as low as ~30 but you need to change radiators to UFH to be able to lower the DT . You also need some big radiators to be able to dissipate the heat at that low flow temperature.
I think the biggest issues with octopus installs are the radiator/ flow temperature design and the fact that the coverage is all over the place for most installs. Not wanting to change all the radiators is great but having one at 230% coverage and others at 98% leaves hot and cooler areas (yes this will disperse in an open house to some degree) and no one wants a bedroom at 25°c when they are trying to sleep or a lounge at barely 18 on a cold winters day.
Part of the Daikin spec is that the immersion (booster) heater element is above the coil.
It appears to be half way up on the HG tank (not sure how it gets “through” the coil into the tank though).
If the immersion heater was on while the HP was on the temp differential could be too high (parallel heating)? With the return potentially as high as the immersion temp setting?
Just a thought…
Thanks, that may be part of the reason but I see the line about the booster heater being located above the heat exchanger coil is listed as a separate item so this is likely not the only reason.
I am still looking through the technical data book and the installer reference guide to see if I can work out a way round the 25°c lower limit but it is not the most exciting read this year
Interestingly, the cylinder that Octopus installed for me does not meet the Daikin requirements either. The coil is in spec at 2m², but neither the immersion nor thermistor are above the coil. It does seem to work OK though, as far as I can tell.
