# Break even month for solar/minisplit



## peakbagger (May 4, 2016)

I got my monthly electric bill and looks like April was the month when my solar generation matches my total electric usage including heating load with my minisplit. Despite running the mini split hard as primary heat up until mid December last year, I still managed to carry forward a 830 KWhr surplus over the winter, similar to the previous winter. From now on barring a cold cloudy May, I start building up surplus for next winter. A second mini split is being considered for my office which should actually reduce my power usage as I currently have to overheat the main floor to get heat to the office.

I love it when a plan comes together.


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## DBoon (May 4, 2016)

I also have a Fujitsu mini-split that I run constantly over the winter to keep a soon to be renovated house at 55 to 60 degrees all winter.  It is backed up by a oil furnace that consumes ~50 gallons or so a year.  The previous winter, I was about even with 5.8 MWh of production and 5.5 MWh of usage.  This year, about the same production and probably about 4.3 MWh of usage when the heating season ends.


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## CaptSpiff (May 31, 2016)

DBoon said:


> I also have a Fujitsu mini-split that I run constantly over the winter to keep a soon to be renovated house at 55 to 60 degrees all winter.



Does the Fujitsu mini-split allow a thermostat heating setting of 55 degF?
I stopped my search when a HVAC guy said the lowest heat setting was 65 degF.
I was planning to install it at a vacation home usually set for 50-55 when unused.


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## peakbagger (May 31, 2016)

I am not sure on my minisplit, worse case is that my Mitsubishi restores to the prior setting after a power outage. Therefore a volt line voltage T stat could be installed on the incoming circuit and use that to cycle the unit for low temps. I have considered using that method as a poor mans setback rather than going to expense and hassle of figuring out what I need to hook it up to the Mitsubishi communications port.   

I know of someone that heats his seasonal place in the white mountains of NH with a minisplit during the winter.  He hasn't had any issues but both he and I agreed that it takes forever to bring the heat back up after the house has been sitting cold for week of so. There is no substitute for lots of BTU's to warm a place up quick and during cold weather (anything under 20 deg F) the unit starts to lose capacity under nameplate. If I was to do it I would put in couple of  strips of electric heat set at 45 deg F as backup.


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## CaptSpiff (May 31, 2016)

peakbagger said:


> I am not sure on my minisplit, worse case is that my Mitsubishi restores to the prior setting after a power outage. Therefore a volt line voltage T stat could be installed on the incoming circuit and use that to cycle the unit for low temps. I have considered using that method as a poor mans setback rather than going to expense and hassle of figuring out what I need to hook it up to the Mitsubishi communications port.



That's some good "out of the box" thinking. I've rigged line voltage stats like that before, but hadn't considered it in this case. I'd probably throw in a time delayed restart also to make sure it didn't cycle too often. The whole house is electric baseboard, so that could be set for lower, say 50 degF.

Thanks.


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## DBoon (Jun 4, 2016)

CaptSpiff said:


> Does the Fujitsu mini-split allow a thermostat heating setting of 55 degF?


The Fujitsu I have allows setting for heat down to 60 degrees F.  I too was a little disappointed when I learned that I couldn't set it lower but realistically for me, it is not bad.  The unit is slightly undersized for what I am asking it to do, so having it maintain 60 degrees on a warmer day (when it is more efficient) doesn't seem to cost much more.  And when it gets really cold, the temperature will drop below 60 degrees anyways while the unit just runs constantly to keep up with the heating load.


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## begreen (Jun 4, 2016)

It looks like the Daikin LV series heat setting range is 50-86ºF.


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## georgepds (Jun 13, 2016)

CaptSpiff said:


> Does the Fujitsu mini-split allow a thermostat heating setting of 55 degF?
> I stopped my search when a HVAC guy said the lowest heat setting was 65 degF.
> I was planning to install it at a vacation home usually set for 50-55 when unused.




My Fujitsu  RLS12H mini split (12 k BTU/hr)  has a 50 degree mode.. the lowest setting on the normal heat mode is 60 deg F.


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## DBoon (Jun 14, 2016)

georgepds said:


> My Fujitsu RLS12H mini split (12 k BTU/hr) has a 50 degree mode.. the lowest setting on the normal heat mode is 60 deg F.


Yes, that's correct.  I don't use the 50 degree F setting because if I do, the oil-fired furnace will kick on well before the mini-split turns on.  I simply forgot it was even there...


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## georgepds (Jun 20, 2016)

No oil furnace in my house.. just a wall propane heater with a dial thermostat. Like you I don't use the 50 deg  mode much because the wall heater will kick on ( the thermostat does not go low enough, it is an Empire wall heater). When I'm away I set the split duct at 60, and the wall heater at 50 ( it's lowest setting) 

I'm thinking of getting a commercial 40 degree thermostat, so that the wall heater will kick in when the split duct cannot keep up with losses., thus allowing the split duct 50 degree mode to be useful

If anyone can recommend a good thermostat that goes this low... I'm open

--G


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## begreen (Jun 20, 2016)

If the wall heater takes a standard millivolt thermostat, this one goes down to 45ºF. 
http://luxproducts.com/DMH110.html


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