Mitsubishi mini splits off-grid?

[Cardude]

@Cardude That looks good but the video is over 2 years old. I have never done a vehicle mounted system, you will get much better input than I can give you by starting a new post in the Vehicle Mounted Systems section.

Understand. Thanks.

 

[Zwy]

I’m looking to power a 12k btu 120v Pioneer mini split and looking for some sizing ideas (from someone who has done that) for a van build.

What size Growatt do I need for the van. Everything else will be DC powered except maybe for an AC fridge (if I go that way), TV, occasional coffee pot, and other small appliances.

How much battery capacity do you think I need?

It could use up to 1200W when going full tilt, after initial cooldown/heat it will ramp down. It doesn't take long for most of these to slow down to idle. There isn't a surge at startup, the motor and compressor speeds are slowly ramped up.

I have a 12K Pioneer and if I turn up the heat in the morning it will use around 1000W after ramping up speed. I'm currently in the process of installing a 9K Senville in my truck camper and will be running it off a 24V Growatt 3000W inverter.

 

[Cardude]

It could use up to 1200W when going full tilt, after initial cooldown/heat it will ramp down. It doesn't take long for most of these to slow down to idle. There isn't a surge at startup, the motor and compressor speeds are slowly ramped up.

I have a 12K Pioneer and if I turn up the heat in the morning it will use around 1000W after ramping up speed. I'm currently in the process of installing a 9K Senville in my truck camper and will be running it off a 24V Growatt 3000W inverter.

What batteries will you use in your truck camper, and how much capacity?

The more I think about it, I’m not sure the 5kw 100ah 48v rack battery mentioned in that video will be able to run that 12btu 120v mini split all day when he’s gone to keep the pet cool and also have enough left in the battery to power it a few hours at night.

I think that Pioneer 12k btu uses 900w per hour, so it needs 8x900w= 7200w while he is at work to run the AC? How much solar will he need during that time to keep the battery fully charged so when he gets back he still has some juice and an alive pet?

He might need to find a way to plug in while gone if he has the pet inside on a hot day. Or maybe we will keep the pet for him during the hot months. Not worth the risk of failure.

 

[Zwy]

What batteries will you use in your truck camper, and how much capacity?

24V system, 280Ah cells.

I've run the roof air with some sun for over 4 hours at 68F and battery still had 45% capacity left. The idea is to install the mini split, run off solar during the day and possibly charge up batteries some. Roof air draws 1200W.

The more I think about it, I’m not sure the 5kw 100ah 48v rack battery mentioned in that video will be able to run that 12btu 120v mini split all day when he’s gone to keep the pet cool and also have enough left in the battery to power it a few hours at night.

It will run longer than you think.

I think that Pioneer 12k btu uses 900w per hour, so it needs 8x900w= 7200w while he is at work to run the AC?

My 12K Pioneer in my house uses 300 to 400W after initial cooldown and it idles along to maintain temp. 900W would be initial cooldown or intial heating. After that, it idles along and doesn't draw much. I'm very impressed.

How much solar will he need during that time to keep the battery fully charged so when he gets back he still has some juice and an alive pet?

More than 400W is all. That is why I think PV powered mini splits are a waste of PV.

He might need to find a way to plug in while gone if he has the pet inside on a hot day. Or maybe we will keep the pet for him during the hot months. Not worth the risk of failure.

I think you need to check out real use cases of what a mini split actually has for a load.

 

[Cardude]

24V system, 280Ah cells.

I've run the roof air with some sun for over 4 hours at 68F and battery still had 45% capacity left. The idea is to install the mini split, run off solar during the day and possibly charge up batteries some. Roof air draws 1200W.



It will run longer than you think.



My 12K Pioneer in my house uses 300 to 400W after initial cooldown and it idles along to maintain temp. 900W would be initial cooldown or intial heating. After that, it idles along and doesn't draw much. I'm very impressed.




More than 400W is all. That is why I think PV powered mini splits are a waste of PV.


I think you need to check out real use cases of what a mini split actually has for a load.

Thanks for that real world info. That really helps me out since I was just shooting from the hip on my mini split numbers obviously.

 

[42OhmsPA]

My 12K Pioneer in my house uses 300 to 400W after initial cooldown and it idles along to maintain temp. 900W would be initial cooldown or intial heating. After that, it idles along and doesn't draw much. I'm very impressed.

I love my Pioneer 12k.
I got home from work (around where the mouse pointer is) and it was a little chilly inside so I cranked the heat to 82 and put the fan on turbo (it's in the bedroom but covers the upstairs pretty darn good) then made something to eat heated up leftovers and went to work in the garage / spent a lot of time on the forum ?. I'm ready to unwind after coming back upstairs and it's to hot so I'll flip it to cool and sleep like a hibernating bear.
I also love free energy and pulling from the battery bank, that was charged with panels I didn't dedicate to hvac, with the mini split overnight.

 

[Cardude]

This is the forward interior view of box truck he’s thinking about converting. One good thing about it is it has this very powerful engine driven AC system that can be used to cool the box down pretty quickly when he comes in if it’s it’s super hot. Then the mini split can take over and not have to work so hard.

All the shelving and other items will be removed. It’s a 18’x7.5’ box.

 

[SilverbackMP]

Just saw this thread today and found this on another forum:

"I am a controls engineer at Mitsubishi. The answer is that your energy meter doesn't take into account the power factor, and is therefore giving you incorrect readings. In reality you are only drawing 3-15 watts when the unit is off; unless the compressor heater or pan heater is active, in which case you'd be drawing between 70-120 watts. All of these numbers are perfectly acceptable for any modern appliance, and especially for an HVAC system.

Please let me know if you have any questions."

From here:

Phantom Electrical Loads With Mitsubishi Minisplit - GreenBuildingAdvisor

Hello everyone, I recently finished building a pretty good house using a few single zone mitsubishi hyper heat minisplits. The 18K unit I mostly use will draw around 200 watts […]

www.greenbuildingadvisor.com

 

[Warpspeed]

Unless the compressor heater or pan heater is active, in which case you'd be drawing between 70-120 watts.

Yup.
Its the compressor sump heater that may be the problem, as I suggested back in post #55

 

[SilverbackMP]

Yup.
Its the compressor sump heater that may be the problem, as I suggested back in post #55

Yeah, from the same thread and poster:

“In the chart on page 2 of the following link, you can see that the base pan heater for MXZ-3C24NA models only draws 80 watts, and that it is only energized when the outdoor temperature is 39°F or less. http://meus1.mylinkdrive.com/viewPd...c.com.s3.amazonaws.com/DAMRoot/Original/10006\M_SUBMITTAL_MXZ-3C24NAHZ2_en.pdf

In section 11-1 on page 81 of the following link, you can see that the compressor heater (labeled Pre-heat) only draws 50 watts, and although it isn't listed in this manual, it is only energized when the internal compressor temperature is 68°F or less. http://meus1.mylinkdrive.com/viewPd...c.com.s3.amazonaws.com/DAMRoot/Original/10006\MXZ-5C42NA_MXZ-2C20-3C24-3C30NAHZ(2)_SERVICE_OBH702H_11-20.pdf

As you can see, the system is only capable of drawing a maximum of 130 watts when the units are not operating, and that's only when the outdoor temperature is 39°F or less. In other words, the 230/260 watt reading is due to your energy meter not taking into account the power factor.”

 

[SilverbackMP]

One of the major Japanese manufacturers (I forget which for sure, but I think Daikin) doesn’t equip theirs from the factory with pan heaters. It’s an additional item that requires installation. I’d rather have it and not need it than need it and not have it. Then again, I plan on only using the heating function in the shoulder months. Might just flick the breakers off for the winter.

 

[RCinFLA]

I've got 4 5.12kw 100A eg4 48V batteries and a sol-ark 15k. I've read that most "inverter compressor" mini-splits ramp up slowly to prevent what you're describing.

Startup ramp up of the unit compressor with variable speed compressor has nothing to do with running power factor and peak current crest factor. Ramp up reduces initial startup surge current to spin up compressor.

Issue is how the AC supply input to high voltage DC supply rectification is done in power supply for the three-phase, variable frequency AC inverter to drive the variable speed compressor. The AC to DC rectification process can creates high peak AC current pulses as the high voltage DC filter capacitor is being recharged on each half cycle of the full wave rectification. All the required input AC power to run the unit is supplied only during the short current pulses.

For a PWM AC sinewave inverter with output L-C filter, the short load current pulses are like plucking the string of a guitar. It causes the inverter output filter to oscillate at filter's cutoff frequency which is in the 2-4 kHz range. The 2-4 kHz ringing causes interference with the sinewave inverter 60 Hz AC output voltage regulation.

The high current pulses can also saturate the core of the sinewave inverter toroid filter inductor which causes the filtering to drop out and put high surge current into the sinewave inverter's output power transistors.

 

[G00SE]

It's a bit misleading, but about 2,200sq ft. The 2 bedrooms are 6k units (smallest they make) and they are oversized, but I knew that going into it. No other option. 12k in the basement and 18k upstairs does most of the work! We only turn on my sons room when it starts getting cold (constantly 32*F outside). Our bedroom stays on 24/7 but doesn't run that much because we like it cold and leave it set at 67*. I have the wall unit fans set to NOT constantly run in the winter. I wish I would have went 2 outdoor units and not this big unit, but to late. Did the install myself

Hey this is the closest I’ve seen to what I was spitballing.
I too noticed that 6k or 7k was the smallest one could readily find. What kind of negative impact if any has these had in the two bedrooms?
Does this also contribute to your comment on desires of 2 outdoor units?
I previously intended to run 1 outdoor with 4 indoors but was now considering 2 outdoor units with 3-6k and 1-12 or 18k for the great room.

 

[Bob in Tucson]

Hey this is the closest I’ve seen to what I was spitballing.
I too noticed that 6k or 7k was the smallest one could readily find. What kind of negative impact if any has these had in the two bedrooms?
Does this also contribute to your comment on desires of 2 outdoor units?
I previously intended to run 1 outdoor with 4 indoors but was now considering 2 outdoor units with 3-6k and 1-12 or 18k for the great room.

When units are oversized, the primary risk is short cycling; the consequences depend on local conditions. In humid environments, for example, not enough humidity will be removed because the unit won't run long enough. Modest short cycling can be slightly less of a concern with mini-splits because they don't operate at one rate like some traditional HVAC systems. A good quality 6k, for example, might operate between 1.5k and 9k depending on demand.

I run a 6k in a small bedroom from a multi-head outdoor unit and it does fine -- not ideal from an efficiency standpoint, but I've had no problems.

As an aside, it is best not to estimate based on square footage -- details of the wall, roof, and floor assemblies, windows, etc. make a considerable difference. Instead, use a calculator to do the load calculations (Manual J). Here's one that is free to run the basic calculations:

Cool Calc Manual J Software | Create a Free Account | Only $3/Report

Perform online ACCA Approved load calculations in minutes. Supports block load or room-by-room. 100% cloud based, can be accessed anywhere, anytime, from any device.

www.coolcalc.com

 

[RCinFLA]

You really want a mini-split to be a bit oversized. A mini-split running at full btu capability is usually less efficient than a conventional fixed speed split ducted air conditioner system running near full capacity. At full power, a mini-split has about 8-10% electrical power loss in the three-phase inverter. Mini-split efficiency is best in the 50-75% running capacity range.

Mini-split attributes:
+ the variable speed compressor/blower adjustable to variable demand.
- usually 'challenged' condenser and evaporator sizing resulting in higher compressor head pressure.
+ ability to run subcooling and superheating closer to zero degrees margin.
- poor indoor unit input/output air separation between return air and conditioned air resulting in direct air recirculation reducing efficiency.
+ electronic controlled EEV expansion valve.
- usually only a single EEV valve in outside unit resulting in poorer cooling efficiency due to heat absorption in low pressure (cold) line to inside evaporator.

 

[drps10]

Hey this is the closest I’ve seen to what I was spitballing.
I too noticed that 6k or 7k was the smallest one could readily find. What kind of negative impact if any has these had in the two bedrooms?
Does this also contribute to your comment on desires of 2 outdoor units?
I previously intended to run 1 outdoor with 4 indoors but was now considering 2 outdoor units with 3-6k and 1-12 or 18k for the great room.

no real negative impact really. The bedroom ones are more for comfort than anything. If we never ran them, we would notice the room many degrees off the main living room IDU. So it they are needed for sure to keep the rooms at the desired level. If I were to redesign, I would put 3 upstair units (18k,6k,6k) on one and the basement one on another. That way there would be no short cycling of the ODU because the 6k are oversized, but the 18k would be always running. As far as short cycling the IDU, i don't think there is a big ramification but I am no expert.

The desire to have 2 ODU, would be to be even more efficient than my current setup. It works great heating and cooling the house and I would not change a thing for the IDU. I just know from talking to other people that when it's 50*f outside and calling for heat in the house, I am not as efficient as a single ODU (by a long shot!) In the lowest engery consumtion possible, my ODU will pull 1.2kw, but a single ODU designed to match the IDU correctly could be as low as .3kw.

 

[AlaskanNoob]

Got our Mitsubishi 12K hyper heat installed a couple of days ago off grid. Temps have been warm outside with lows of about 34F and highs in the 40s, but it has heated the cabin very well and sipped power. Looking forward to seeing what it does in the cold weather later this year. I'll put some kind of clamp measuring system on it later and chart out its actual electrical usage along with temps, but even after a couple of days it's already obvious that it's a success. It will drastically cut our firewood usage down if not eliminate it completely.

 

[new2solar2]

I was wondering if anyone was using 24k or 36k Mitsubishi mini splits off-grid? I was told today by an HVAC guy it wouldn't work, but Daiken or Fujitsu would. I've read multiple other threads here, but didn't see anyone mention that they had Mits and were completely off-grid.

Thanks in advance!

I ended up going with a 36k Daikin, consisting of two 12k ceiling cassettes, and one 12k concealed duct unit. I couldn't be happier. It runs perfectly with my off-grid solar setup.

It pulls a lot of energy ~4k when I run all three to try to drastically change the temp, but keeping the system running full time seems to be the trick to maintain a constant temp. In that scenario it uses ~1k with occasional increases throughout the day, but it never takes my batteries below 40%.

I've had both hot and cold days ranging from 20s to 90s, but I'm still not done insulating my crawlspaces so I anticipate.it will only get better.

Why did I go Daikin? Apparently they are the world's largest mini split producer. The majority of reviews I read were positive, where as I read horrible reviews for Fujitsu(Not dissing anyone who has one and has had a good experience.). I passed on Mitsubishi because the 36k outdoor unit was significantly larger than the Daikin.

I put in an At&t access point to connect my inverter and Daikin thermostats, so I can remotely turn the unit on and off which is super cool.

I ended up installing everything myself but had an HVAC guy flare, connect and charge the lines I ran.

It was an incredibly tough decision, but so far so good.