Wiring bus for 50amp 240 for mini split

[Jcparmley]

I am in the process of building my MCI 102c3.  I haven't gotten to the wiring stage.  I have done a bunc of reading on mini split system.  What is hard to find is a conversation specifically about wiring a 220v mini split.  I would like to know your thoughts specifically about how to wire bus to handle a mini split ac for 220v.  I have a 12.5kw generator, Zantrex SW3012 inverter.  The inverter is only 120 volt capable. 

[sledhead]

I was going to use one of these with a 240 v split but ended up using a 120 v split so I could use it off the bus alternator when driving

https://www.wholesalesolar.com/2500182/outback-power/inverter-accessories/outback-power-fw-x240-auto-transformer

big and heavy

dave

[Geoff]

It doesn't seem to change anyone's thinking, and it doesn't seem to matter to them, that THERE IS NO 220 VOLT IN 60 HERTZ in America!  It is 120v or double that to two legs and a ground, or 240 volts. Once you get modern, it helps to understand voltage in our USA buses so novices can figure things out. 

[Jcparmley]

Wow!  My Grandma used to say "if you don't have anything nice to say, don't say it at all."  No need to comment if you don't want to be helpful.  How about giving some advice to us novices rather than being critical.  We are all just trying to figure things out.  I thought that's what this board is all about.  Buswarrior was right when he said in another thread that this forum is going the way of social media.  To quick to poke fun and act superior.  I guess I know what he meant now.

It doesn't seem to change anyone's thinking, and it doesn't seem to matter to them, that THERE IS NO 220 VOLT IN 60 HERTZ in America!  It is 120v or double that to two legs and a ground, or 240 volts. Once you get modern, it helps to understand voltage in our USA buses so novices can figure things out.

[Jcparmley]

Sledhead

I was going to have a three zone ac.  Your 120 must only be one zone, correct?  How do you cool the rest of the bus? 

I was going to use one of these with a 240 v split but ended up using a 120 v split so I could use it off the bus alternator when driving

https://www.wholesalesolar.com/2500182/outback-power/inverter-accessories/outback-power-fw-x240-auto-transformer

big and heavy

dave

[oldmansax]

This is over simplification but, assuming the source 50A service is wired correctly, you will have 240V available. If you wire your main electrical panel just like a standard house panel, you will have 240V available from the panel. You then need to wire your mini split to a double breaker and you will be in business. The problems with all of this is first, not all 50A sources are wired correctly. Some older campgrounds cheat and wire BOTH sides of the 50A receptacle to the same leg of power meaning you will only have 120V no matter what you do. Another problem would be you need a 240V inverter if you run everything through it, and that brings a whole 'nother set of problems.

This simple basic wiring scheme worked for me:

12K, 240V generator and 50A shore power wired to the LINE side (L1,L2, L3) of 2, separate, 3 pole, 100A contactors used as a transfer switch. They are controlled by a double pole double throw switch (ON-OFF-ON, labeled SHORE-OFF-GEN)
Both LOAD sides (T1, T2, T3) of the contactors are wired to your main panel. All heavy loads (ACs, electric heaters, electric ovens, AC feed to refrigerator, whatever you don't want to run off your inverter) are run off this main panel. Try to split the loads as evenly as possible between the 2 feeds.
The 120V IN to the inverter is run from the main panel.
The 120V OUT from the inverter is run to a secondary panel.
All of the small 120V loads (TVs, computers, receptacles to charge phones, any 120V load that you want to run while on battery power only) are run from the secondary panel.

This setup will give you 120V where you need it and 240V IF it is available from what ever source your are plugged into or when the generator is running.

YRMV

TOM

[buswarrior]

There's good reason to use 110 and 220 in busnut conversations, and especially when labeling stuff in the coach because of typos or partial label losses.

You aren't owning that coach forever... Someone else will have to deal with faded labels...

We have 12/24 volts..
Too easy for labeling trouble if you use 120/240.

12/24... 11/22... 10/20...

These are the things that in history sink ships, or otherwise cause grief.

As for the question, using a transformer to make your 240 gives you more freedom in accessing campground power, so long as your mini-split doesn't suck back more juice than is available...

Maybe $100 IIRC? I have one lined up in the bookmarks on the other computing device...

Dead simple, step-up transformer. 120 to 240

Happy coaching!
Buswarrior

[buswarrior]

And there seems to be lots more failures of generators wired for 120/240 and then tried to balance, than wiring them for straight 120.

Pretty hard to get them to balance in a conversion, too big percentages, too small load, etc etc.

Anecdotal from all those peeps that piled onto the mobile command unit bandwagon, post 9/11, and kept on having trouble over and over...

I don't have government ca$h to keep mine going...

Happy coaching!
Buswarrior

[oldmansax]

I would used 3 mini splits if I were doing things that way. I like redundancy. I have 3 roof tops now and that means if one quits, I'm still cool. Also, I have camped in places that only had 20A service. I could still run one AC.

TOM

[oldmansax]

I can't complain about mine. It failed after 33 years and 1251 hours. I just put a new head on it & I'm back in business.

TOM

[Jcparmley]

That is the way I originally had thought about it, using 3 separate 120 systems.  My problem is where to put the three outdoor units.

I would used 3 mini splits if I were doing things that way. I like redundancy. I have 3 roof tops now and that means if one quits, I'm still cool. Also, I have camped in places that only had 20A service. I could still run one AC.

TOM

[Jcparmley]

So rather than using my generator or shore power to bring in 240 I should use a transformer?  That would solve the problem of shore power wiring that can't support 240.   I would hate to have 50 amps at the campground and still have to use the generator for the ac. 

There's good reason to use 110 and 220 in busnut conversations, and especially when labeling stuff in the coach because of typos or partial label losses.

You aren't owning that coach forever... Someone else will have to deal with faded labels...

We have 12/24 volts..
Too easy for labeling trouble if you use 120/240.

12/24... 11/22... 10/20...

These are the things that in history sink ships, or otherwise cause grief.

As for the question, using a transformer to make your 240 gives you more freedom in accessing campground power, so long as your mini-split doesn't suck back more juice than is available...

Maybe $100 IIRC? I have one lined up in the bookmarks on the other computing device...

Dead simple, step-up transformer. 120 to 240

Happy coaching!
Buswarrior

[luvrbus]

On my ex bus the stove was 220v a lot of parks the stove never worked unless I ran the generator.Finding a location for the condenser where it can have good air circulation without giving up to much space is challenging,then I read where people can hang meat with1- 9,000 btu split unit in a 40 ft bus   

[oldmansax]

Finding a location for the condenser where it can have good air circulation without giving up to much space is challenging,then I read where people can hang meat with1- 9,000 btu split unit in a 40 ft bus

Hey Clifford, I read somebody was getting 13MPG in an old MC7 too....... LOL!

TOM

[Jcparmley]

Is it possible to mount the outdoor unit inside the rear cap or even on the outside like this guy?