Sanden water heater, split CO2 heat pump
It looks like this is the way to go for Domestic Hot Water (DHW)! There are a couple of places to buy these over the internet with the contractor support gambit of no warranty but the published pricing should, hopefully, reduce contractor greed. The 43 gallon system @ $3900 or the 83 gallon for $3950
Why would anyone choose the 43 gallon? The installation only involves water pipes so NO refrigeration skills are needed, just plumbing and electrical. Only needs 15 amp 240V circuit. There is NO resistance heater! Plumbing MUST include a “tempering” valve on the output side as the system can produce up to 175 deg f. hot water. There is an online test report of the Australian version which is a good bit different (149 deg fixed water temp & 84 gallon tank) but the tank heat loss should be close & was reported as 4 BTU/Hr deg f and COP @ 17f out door temp was 2.1 while it delivered 4KW of heat. The US versions permit adjustable peak temperature settings from 130f to 175f and some time of day cycle time options. Obviously the most efficient operation will be at the lowest temperature setting at which the owner “doesn’t run out of hot water” With 130 f tank temperature and 70 f ambient it’ll take 2.87 hours to lose 1 deg f. I couldn’t find answers to my question about set point, hysteresis and minimum heat output, it is a variable speed (inverter) system. The only partial answer to the operational details, that I found, was the compressor starts when there is 40 gallons remaining at the selected temperature. I’d sure like to know much more about operational details to avoid “short cyclic” operation. Now all I’ve got to do is build the house for it.
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