Mitsubishi mini splits off-grid?

[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!

 

[zanydroid]

That's a bold general thing for the HVAC person to say... how would they know the kind of inverter a customer might install?

I do have a Mitsubishi 36K but I have yet to set up an off-grid system. From measuring the surge (low, but I didn't use the highest sampling rate approach) and power level range (1kW - 3.3kW) I think it is pretty doable.

If someone mails me an autotransformer to achieve the step-up I can test it with my 120V inverter generator...

 

[RCinFLA]

Mitsubishi is one of the few mini-splits that has true electronic power factor correction which is important when running from a battery powered inverter. Their AC current profile is near perfect sinewave with greater than 0.98 power factor.

Good luck on finding another mini-split manufacturer that even specs power factor.

Most cheap mini-splits have just a simple rectifier-filter capacitor which has a terrible high peak current crest factor and a power factor of 0.5 to 0.65. Larger units usually have a filter choke between rectifier and filter capacitor which reduces current peak crest factor approximately in half with a power factor of about 0.8. They only put the choke in to prevent circuit breaker from popping from high current crest factor with the larger btu units.

 

[drps10]

following. I don't have a solar setup, but I have a 42k hyper heat outdoor unit. I don't see it being an issue. These don't have a high surge draw with their variable compressors. I've been monitoring my usage for almost a year. A/C would be no issue, but heat could be a potential problem just from the high load.

 

[zanydroid]

Mitsubishi is one of the few mini-splits that has true electronic power factor correction which is important when running from a battery powered inverter. Their AC current profile is near perfect sinewave with greater than 0.98 power factor.

Most cheap mini-splits have just a simple rectifier-filter capacitor which has a terrible high peak current crest factor and a power factor of 0.5 to 0.65. Larger units usually have a filter choke between rectifier and filter capacitor which reduces current peak crest factor approximately in half with a power factor of about 0.8. They only put the choke in to prevent circuit breaker from popping from high current crest factor with the larger btu units.

Hmm I see some search results that imply 120VAC (North America) units are notoriously bad but 240VAC units have a chance to be better because they're already engineered for a lot of jurisdictions that require PFC.

 

[new2solar2]

following. I don't have a solar setup, but I have a 42k hyper heat outdoor unit. I don't see it being an issue. These don't have a high surge draw with their variable compressors. I've been monitoring my usage for almost a year. A/C would be no issue, but heat could be a potential problem just from the high load.

Thanks for your reply.
How many sqft are you conditioning with your 42k unit?

 

[new2solar2]

Mitsubishi is one of the few mini-splits that has true electronic power factor correction which is important when running from a battery powered inverter. Their AC current profile is near perfect sinewave with greater than 0.98 power factor.
View attachment 171810
Good luck on finding another mini-split manufacturer that even specs power factor.

Most cheap mini-splits have just a simple rectifier-filter capacitor which has a terrible high peak current crest factor and a power factor of 0.5 to 0.65. Larger units usually have a filter choke between rectifier and filter capacitor which reduces current peak crest factor approximately in half with a power factor of about 0.8. They only put the choke in to prevent circuit breaker from popping from high current crest factor with the larger btu units.

Thanks for your reply.
What about Fujitsu?

 

[Lt.Dan]

I remember reading somewhere about the hyper heat models having a very high (200w) idle draw, even when off? I wonder if that's what he means?

 

[pvgirl]

I made a quick check of mistu's tech notes, and warranty and did not see anything obvious warnings about off grid or inverter use.

 

[drps10]

I remember reading somewhere about the hyper heat models having a very high (200w) idle draw, even when off? I wonder if that's what he means?

It's 70*f in the house (set temp) and 50*f outside. My outdoor unit is off completely because nothing is calling for heat. My Emporia is saying 0w are being pulled. It's been like that for the last 3 hours (we cooked dinner in the oven so the house is still warm).

 

[drps10]

Thanks for your reply.
How many sqft are you conditioning with your 42k unit?

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

 

[new2solar2]

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

I'm considering a 9k concealed duct for a 270sqft 2nd story loft, 12k for 600sqft living room, and 12k concealed duct for downstairs bathroom, utility room and bedroom. I'll prob do the install myself too, but have the hvac company charge the lines.

 

[Brett V]

I have a 24k btu Pioneer on 240 and a 9k btu Senville on 120 and both work perfectly on the Growatt.

 

[RCinFLA]

I am referring to mini-split sold into U.S. market. E.U. has power factor regulations that require mini-splits to have good power factor. Manufacturers save a few bucks in material cost when selling into unregulated U.S. markets by leaving out the power factor correcting circuit.

My expensive Samsung variable speed refrigerator has a power factor of 0.5 to 0.65 depending on running speed. Running 130 watts with a 280 VA. Multiply the numbers up for a mini-split power consumption. Worse than the VA is the 3-6 times peak crest factor current over the measured rms current drawn. The short 120 Hz high peak current pulses can drive a battery power inverter crazy.

The mini-split will run, just don't complain when your lights start flickering because inverter cannot control its AC output voltage regulation.

 

[new2solar2]

I am referring to mini-split sold into U.S. market. E.U. has power factor regulations that require mini-splits to have good power factor. Manufacturers save a few bucks in material cost when selling into unregulated U.S. markets by leaving out the power factor correcting circuit.

My expensive Samsung variable speed refrigerator has a power factor of 0.5 to 0.65 depending on running speed. Running 130 watts with a 280 VA. Multiply the numbers up for a mini-split power consumption. Worse than the VA is the 3-6 times peak crest factor current over the measured rms current drawn. The short 120 Hz high peak current pulses can drive a battery power inverter crazy.

The mini-split will run, just don't complain when your lights start flickering because inverter cannot control it AC output voltage regulation.

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.

 

[zanydroid]

I've read that most "inverter compressor" mini-splits ramp up slowly to prevent what you're describing.

Your mental model is wrong. Power factor is different from surge. The ramp is somewhat orthogonal to power factor.

Power factor is the relationship between current and voltage. Ideally these would be in sync (PF = 1.0) to maximize the capacity of the inverter. As you deviate from PF = 1.0 the inverter has to work harder. Eventually the inverter may even turn off / not be able to satisfy the shape of the current waveform.

 

[Brett V]

Considering my experience with “cheap” mini splits, I can’t think of any good reason to spend 4 times the price for one of the aforementioned units. Mine ramp up slowly over maybe 30-45 seconds when the come on. There is no surge. I’ve observed this both with a clamp on at the AC input and from watching the inverter load on Solar Assistant.

 

[zanydroid]

I am referring to mini-split sold into U.S. market. E.U. has power factor regulations that require mini-splits to have good power factor. Manufacturers save a few bucks in material cost when selling into unregulated U.S. markets by leaving out the power factor correcting circuit.

My expensive Samsung variable speed refrigerator has a power factor of 0.5 to 0.65 depending on running speed. Running 130 watts with a 280 VA. Multiply the numbers up for a mini-split power consumption. Worse than the VA is the 3-6 times peak crest factor current over the measured rms current drawn. The short 120 Hz high peak current pulses can drive a battery power inverter crazy.

The mini-split will run, just don't complain when your lights start flickering because inverter cannot control its AC output voltage regulation.

How much does the inverter need to be oversized to compensate for this?

There are couple ways to get PFC in the US, right? Certain states, and levels of Energy Star

I actually see it on the spec sheet of the entry level Gree in the US (Livo 120VAC), they say that it is power factor corrected but does not give the power factor.

 

[new2solar2]

Considering my experience with “cheap” mini splits, I can’t think of any good reason to spend 4 times the price for one of the aforementioned units. Mine ramp up slowly over maybe 30-45 seconds when the come on. There is no surge. I’ve observed this both with a clamp on at the AC input and from watching the inverter load on Solar Assistant.

What mini split do you have and for how long have you had it?...Nevermind...just saw your earlier post.

 

[zanydroid]

Considering my experience with “cheap” mini splits, I can’t think of any good reason to spend 4 times the price for one of the aforementioned units. Mine ramp up slowly over maybe 30-45 seconds when the come on. There is no surge. I’ve observed this both with a clamp on at the AC input and from watching the inverter load on Solar Assistant.

Depending on what the answer is on oversizing the inverter to compensate, it might be better to put money into the inverter than the mini-split.

That said, it's possible that the PF could be so bad that another load with a lot of active power needs to be added to push it back within the range spec'd on the inverter.