Hacking DC supply into DC inverter mini split.

[hwy17]

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

Conclusion of this thread is that mini splits really can draw a .1 power factor in standby.

 

[Supervstech]

Do they have working compressors and EEV? Or you are keeping the good parts.

They are pulls that I replaced with new units.
System leakers, acid buildup from poorly installed systems. That kind of thing.
Scrap value only.
Happy to demolish them for a cause.

 

[AntronX]

They are pulls that I replaced with new units.
System leakers, acid buildup from poorly installed systems. That kind of thing.
Scrap value only.
Happy to demolish them for a cause.

Hmm, could you spin one up (without refrigerant) to test injecting DC into post rectifier HV DC bus? But it sounds like a lot of work for not much reward.
What do you think of Everwell and Daizuki brand mini splits? They sell them here in South FL for $600 for 12k BTU 20 seer. They have variable speed compressors but use capillary tubes. I want the one with EEV but the cheapest Pioneer EEV unit is $1000.

 

[hwy17]

Hmm, could you spin one up (without refrigerant) to test injecting DC into post rectifier HV DC bus?

That's what I've been testing. It works.

 

[AntronX]

That's what I've been testing. It works.

Without grid, fully on DC ? That's great!

 

[hwy17]

Without grid, fully on DC ? That's great!

Ah, no. It works for assist.

I don't know if my array is just inadequate but I do believe the indoor units don't run off the DC bus and therefore don't run without the AC supply.

 

[Plum Crazy Rob]

Maybe they are not regulating. Looking at the manual I don't see MPPT mentioned anywhere. DC input range is 90-380V which could mean that PV is directly tied to DC bus and regulation could be done via compressor inverter speed control acting as backwards MPPT.

Fyi, Your first assumption was 100% correct WRT to Deye and MPPT Booster:

 

[Hedges]

Ah, no. It works for assist.

I don't know if my array is just inadequate but I do believe the indoor units don't run off the DC bus and therefore don't run without the AC supply.

Makes sense. Controls may have transformer, may have switch mode supply. If switch-mode, could also be powered by DC (either direct to DC bus as you did for compressor, or through its AC leads.) If through transformer you'd need to substituted switch-mode supply

Existing fans likely AC motors, substitutes could also be powered by DC/DC but wouldn't fit nicely.

If you determine that 100% of the device is powered by SMPS and switch-mode supply, all having rectifier/capacitor front end (no AC motors), in that case the entire unit could be powered by DC.

To feed from both AC and DC, you could get a bank of 6 diodes (3-phase rectifier), and wire as single-phase full wave rectifier (for AC input) plus pair of blocking diodes (for PV DC input).

We have fed SMPS from DC. Even though they were power-factor corrected, they worked with straight DC.

 

[copec]

Most of my electricity gets used for AC and/or heating. I've wanted to work out something where I tap the HV DC bus inside the inverter and use it directly in a programmable variable frequency drive for a refrigeration loop compressor - to generate both hot and chilled water for HVAC and DHW. It would cut out a couple power conversion stages. There are a few ways I could coordinate it.

There have been and now more mini-splits that match (or use) the VFD at MPPT. I want a small system that will make as much hot water and cold water to respective temperature limits as an energy storage mechanism. I think there would be a market for that too.

Solar Air Conditioner Manufacturer & Supplier | Deye

Deye is famous Solar Air Conditioner manufacturer and supplier. We wholesale Solar power air conditioners for sale worldwide. Type: battery powered or no battery.

www.deyeinverter.com

 

[hwy17]

I left the 10 panel array (450 VOC) plugged in overnight by accident and in the early morning when the compressor was cycling on and completely off, maybe 50 degrees outside, I started getting IPM voltage errors.

This I think finally concluded my experiment and confirms that it is tricky to balance the voltage range of the raw panel output to align with above 340v and under 450v.