240vac split phase solution for mini split AC

[Houseboat100]

Hi, newbie to this group so please be patient if this topic has been covered in other threads. As the title infers, I have a houseboat that is an off grid system. 1000W 24v solar, BlueSky 50A charger, Xantrex 3000W inverter/charger, 5x150Ahr LiFeP04 batteries, Honda EU3000is generator. Our friends and family are more sensitive to the 100+ degree days in central CA. That has started the design of a significantly expanded system to take on more refrigeration, ice maker, mini split AC (240VAC split phase) which complicates the system. What I am planning on is:

-double solar (2000W total) 24vdc
-100A solar charger
-double battery capacity and set up for 24vdc (24 to 12vdc converter for local 12vdc loads)
-after reading some threads, maybe get a second 3000W inverter instead of getting a single, larger one. Depends on the answer on 240vac split phase generator or Victron transformer decision
-So big decision is whether to bite the bullet for a 7kva 240vac split phase RV generator and a new power panel, (2) 3000w inverters, and split the 120vac loads, OR a 5500W 120vac RV generator and use a Victron split phase transformer for the mini split. I’d have to use 3 120vac mini splits to do the job, so one 240vac mini split is much preferred.

Questions and suggestions appreciated.

 

[Supervstech]

Keep in mind, unless the inverters are DESIGNED to be linked up for split phase, they cannot be.

 

[Supervstech]

Wait...
Your houseboat needs THREE 120V minisplits to cool it? How freaking big is this houseboat?

 

[Houseboat100]

Keep in mind, unless the inverters are DESIGNED to be linked up for split phase, they cannot be.

Hi,
The Xantrex are, but for the same price as a second Xantrex unit

Wait...
Your houseboat needs THREE 120V minisplits to cool it? How freaking big is this houseboat?

Hi,

The issue is I want a 3 zone system, which even for a 6KBTU unit per room, is 240VAC for a 1.5T system. It's small, 340 sq ft interior space, but it has 3 separate rooms to cool, 2 bedrooms and the living area. There is no one place to put a single unit to reasonably cool the whole houseboat so I wanted 3 zones. They won't work hard to cool the areas, so either (1) 3 zone 1.5T 240VAC mini split or (3) 0.5T single zone 120VAC mini splits to get to an equivalent solution. So the 3 zone solution is the best, but requires 240VAC split phase to accomplish, so either the 240VAC split phase generator and a new panel to wire it appropriately of a 120VAC generator and Vicron or equivalent step up split phase transformer of sufficient size.

 

[zanydroid]

Are you ever on shore power? Using an autotransformer with shore power requires some care to disconnect its center tap as appropriate.

 

[Supervstech]

Hi,
The Xantrex are, but for the same price as a second Xantrex unit

Hi,

The issue is I want a 3 zone system, which even for a 6KBTU unit per room, is 240VAC for a 1.5T system. It's small, 340 sq ft interior space, but it has 3 separate rooms to cool, 2 bedrooms and the living area. There is no one place to put a single unit to reasonably cool the whole houseboat so I wanted 3 zones. They won't work hard to cool the areas, so either (1) 3 zone 1.5T 240VAC mini split or (3) 0.5T single zone 120VAC mini splits to get to an equivalent solution. So the 3 zone solution is the best, but requires 240VAC split phase to accomplish, so either the 240VAC split phase generator and a new panel to wire it appropriately of a 120VAC generator and Vicron or equivalent step up split phase transformer of sufficient size.

Ahh, that makes sense. I would forgo the three units, and install a ducted unit if possible.

 

[zanydroid]

A single head ducted might well be more efficient than a multisplit or three single heads. For the former because single head is generally more efficient than multisplit and for the latter because of the high chance of short cycling with one head per small room thus being rarely hitting the steady state optimal efficiency.

 

[Houseboat100]

The problem with ducting is where to run the ducts. Ceiling is only 88", roof is 2x6 construction so can't bury them there. Roof top is all usable area so maybe I could build and enclose runs there. Underneath is all pontoons and steel and only 18" above the water so it would have to be waterproof and structural to survive waves and storms. I have an existing propane forced air heating system and had to change out the original flex under the boat with 4" ABS because they got wet and fell apart. I don't want to give up the propane FA heater because I don't have to run the generator to use it as I would for a heat pump. I will put more thought into a single unit heat pump with forced air delivery. I was concerned with short unit cycling too.

My question was mostly about anyone's experience with using a 120VAC system and a Victron or similar step up split phase transformer to run something like a mini-split 240VAC unit. If that is a viable solution I would bypass the Xantrex inverter and wire directly from the generator to the transformer to the mini-split.
Otherwise it is a 240VAC split phase generator and wire the VAC panel appropriately, and consider how to split the loads on each phase and to the inverter (or 2).

 

[Houseboat100]

The only time I would use shore power is when the houseboat is out of the water to do maintenance, which is every 8-10 years. There I only get 120VAC and would wire it in appropriately. I expect to be out for maintenance this fall/winter which is when this work would get done. So with the exception of out of water maintenance, we are 100% off grid.

 

[zanydroid]

There is plenty of discussion on this forum about using auto transformers to go from 230V foreign spec inverters to 120/240

120 step up is simpler to analyze if you only have 240V loads.

Note that a lot of the ATs from solar vendors seem to be on the smaller side for their VAs, I surmise they can do that because they use active cooling.

 

[Houseboat100]

Thanks, I will look for other threads to get more information on ATs. The dual mode of 120VAC primary for most electrical (microwave, toaster, coffee maker, refrigerator loads on that side and 240VAC split phase for the mini-split is the issue I'm wrestling with. SO far these discussion have been helpful in getting the concerns more clear. I'll keep asking until I have it straight in my own head.

 

[zanydroid]

One thing you can consider is bench testing it with some cheaper stuff than buying a minisplit. For instance I have a few 240V plug-in kitchen appliances (imports from China via Amazon, or from restaurant supply shops) that draw more power than my 3 ton minisplit (though it likely does not match in surge).

For $700 for one of those mini 5KVA-8kVA ATs designed for solar/ESS (some of these ATs are intended for use with getting emergency [grid down] 120/240 out of UL-listed 240V inverter systems, so are fairly widely used. grid down is a pretty important detail wrt the pitfalls of using an AT) and $300 for one of those test appliances you can see what performance you can get out of slapping an AT onto your existing inverter. Assuming it has enough juice to handle all the loads. If it does not then you might just add both the capacity and the 240V capability at the same time by adding a compatible stacking unit, or upgrading your inverter. That avoids the ways you can burn yourself with an AT (seems to be more popular these days on the forum to just use a native 120/240 inverter system rather than hacking around with stepping down a 230V foreign monstrosity or stepping up from 120V).

 

[Houseboat100]

Thanks for the feedback. I have 240VAC EU appliances in my home that are single phase, so familiar with the integration issues of that type. It sounds from your discussion that split phase ATs are a reasonable solution if sufficient power rating is available. The mini splits are US versions so require split phase. I wasn't trying to use/find a single phase 240VAC versions. When I piece it together I'll post my proposed solution for comment.

 

[zanydroid]

My mini split (mitsubishi central air handler type) is 240VAC only, does not require 120/240 circuit. Since most designs are from single phase markets I would be surprised if there are many require both.

You can power both 120/240 and 240 off an autotransformer.

 

[Houseboat100]

Hi,

That is a a great piece of info regarding single phase units. I will look closer for that. The ones I have seen (H&C and others) state split phase. Glad to have options and will post the final configuration when I get there.

 

[CoolWill]

I have never seen a mini split that requires split phase 120/240.

 

[Carrquik77]

Hi, newbie to this group so please be patient if this topic has been covered in other threads. As the title infers, I have a houseboat that is an off grid system. 1000W 24v solar, BlueSky 50A charger, Xantrex 3000W inverter/charger, 5x150Ahr LiFeP04 batteries, Honda EU3000is generator. Our friends and family are more sensitive to the 100+ degree days in central CA. That has started the design of a significantly expanded system to take on more refrigeration, ice maker, mini split AC (240VAC split phase) which complicates the system. What I am planning on is:

-double solar (2000W total) 24vdc
-100A solar charger
-double battery capacity and set up for 24vdc (24 to 12vdc converter for local 12vdc loads)
-after reading some threads, maybe get a second 3000W inverter instead of getting a single, larger one. Depends on the answer on 240vac split phase generator or Victron transformer decision
-So big decision is whether to bite the bullet for a 7kva 240vac split phase RV generator and a new power panel, (2) 3000w inverters, and split the 120vac loads, OR a 5500W 120vac RV generator and use a Victron split phase transformer for the mini split. I’d have to use 3 120vac mini splits to do the job, so one 240vac mini split is much preferred.

Questions and suggestions appreciated.

 

[Carrquik77]

With the size of the system you’re describing I’d consider getting close to an inverter(s) size of 8kw

 

[Houseboat100]

With the size of the system you’re describing I’d consider getting close to an inverter(s) size of 8kw

As stated before 1.5T, 3 zone solution. It's only 340 sqft total, but 3 separate rooms on a houseboat with no option for a single vent solution. Thinking harder about a mini split ducted system solution.

 

[johntaves]

Have you thought about getting 3 24VDC mini splits?