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Mini Split

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lighthunter:
Hi all! During summer months, any extra solar panel power goes to the 100gal hot water heater. Works great as it can carry a couple cloudy days and good sized dump load in two stages. During winter i dont need it as the outdoor wood boiler heats the water. Air source heat pumps boast a 3 to 1 gain over electrical resistance heating in watts per btu out. I think thats a pretty optimistic figure strictly for above freezing outdoor temps.

So i finally bit the bullet and installed this a week before it turned cold.
R410A, 12000btu 1 ton, 5.3Amps at 240VAC cost $750.

It does what it says do so im happy. Id say it works darn well just above freezing. 5 deg below freezing and its busy with defrost cycles a lot. Right now its 25 deg, and solar panels have plenty so its busy heating.

I guess if thats your need its real nice, i think it would take a few years to pay for itself. They are immensely complicated so i cant think this will be running 20 years from now the way old fridges do. Its got a 3phase inverter for variable speed refrigerant pump and the same for the indoor air handler and outdoor fan. Not to mention electric refrigerant reversing valve maybe even variable plus pressure transducers and temp sensors etc all over. 

Not complicated to install, refrigerant came inside. The liquid and vapor lines are different sizes but dont expect traditional pressures if your used to older refrigeration systems. The larger vapor line is indeed 125-150 psi in cooling mode but in heat mode the same line becomes 400psi. Once you install you can move it if you have to without loosing refrigerant. There are two valves one on each line and in coolling mode you can shut the liquid valve and leave pump on to evacuate the vapor side. Then shut the vapor valve and turn it off, esentially putting the jack back in the box. Of course a vacuum pump is needed same as the install to remove contaminants from lineset. They do sell canned nitrogen to puff them out if preferred.

All in all, im happy with it but it wont be a great idea for everybody. I can see more and more new homes with these covering the entire heating and cooling as a cheaper install and cheaper to run than traditional systems until the temp drops to -25 (-32C) then people will freeze to death.

Pete:
Hi LH, it sounds like a good system.
How realistic are the power draw figures on the unit?
I have been wondering about fitting a heat pump type unit to our place as it would be better environmentally than burning wood.
Sounds like the unit you have is rated at around 1200 watts, that would be fine for us, depending on how long it runs for each day.
Our temperatures are much milder than yours, we never get below about -3 degrees C at night. Winter days are around 1 to 3 degrees at a minimum, so the unit should not freeze up.
It sounds like they don't like very cold temperatures, not so good if you prefer to stay defrosted.
Let us know how it goes, and what sort of power consumption it has.
Pete

lighthunter:
Hi Pete!

The 5.3 Amps @ 240V is a measured value on max heat at 34 F (1C),  they list the max power current as 6.1A and rated 4.9A.

This thing really pushes heat above freeze point. The real question is, at what temperature does the coefficient of performance drop to 1. This is where youd be better off switching on a resistance heater. The sales flyer says it will heat down to -13F, ok maybe it will. I have only seen it working at 25 so far and it does ok minus the frequent 5 minute defrost cycles. Realistically i cant see it as a heater if outdoor temp hits 0F (-18).  They dont like to print the COP vs temp graph. 

So it works, just less so as you go below freezing which makes sense as your really trying to get heat from an ice cube at that point. I would hate to try to run it on battery to heat a home though. I suppose anything is possible but my bank couldnt do it.

It is interesting to note that a 9x7 foot garage door framed with thick clear vinyl will produce a comparable amount of heat with considerably less up front cost but a window that size may not always be an option.

Pete:
Thanks for that info LH.
We never run heating at night, our house if tiny, so once it is heated up it stays warm enough for a long time.
We open doors when the house gets to 22 degrees C, that is too hot for us.
So I would only use a heater in the mornings and sometimes in the middle of the day in winter.
Cheers
Pete

lighthunter:
Yeah, sounds like your weather would work real well with one of these.  Today i took this photo at 12:30 PM 38°F (3.3 C) . I mustve caught it just before a defrost cycle.
This is side view, the back is the large surface area of radiator, it had same ice pattern.
I think defrost is triggered by outdoor air temp, coil temp and a timer and software.
As expected, the heat output varies a lot based on the outdoor temp and ice packing the coil. They mitigate the effects of this by ramping the fan up and down on the indoor HX, this gives a pretty constant discharge air temp but at varying flow.

With the mild temps weve had this year so far I'm very happy with it.

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