RV schematic w/240v subpanel - is this close?

[missadventure]

I'm going to punt this one to the RV and mobile pro's on here since they know better than I which type of plugs to use but definitely something weatherproof and murphy-proof. My guess, since you're going to be using a 3p array, would be to either get a 2nd SCC that goes from the exterior plug to the batteries and bypass the AIO, OR if you can get a 4th panel on the roof to do a 2s2p on the roof and a 2s$p ground mount that plugs to the AIO. Either way the goal is to get more panels working for you without mixing & matching voltages.

Cool, I'll look into that...

I just had a thought about your AirCon unit, are you sure you're not looking at a European 220v unit? They run 220v as their base which is different than the 240v split-phase that we run. Same numbers, COMPLETELY different wiring.

Nope, it's a North American Blueridge mini split.

Yeah, I have one in my camp (it started life as a 1972 Kit Companion travel trailer) and I absolutely HATE IT WITH A FIERY PASSION!! That thing will constantly short cycle and burn through 2 of the 40Lb propane tanks in a week without making a noticeable temperature change. I've gone to the Chinese diesel heaters that burn less fuel, less electricity, and more heat for way cheaper. Probably not the first option unless you were willing to deal with another type of fuel, but it's worth noodling. When I'm shoreside (I'm a merchant sailor) and get to be at camp it's usually winter so 10F outside. I currently have 2 of the diesel heaters installed and about 400sq ft of cabin and those things will keep the place between 68-73 all week long for about 6 gallons of diesel each. There are many, many videos on U-Tube-University about installing those in travel trailers.

Mine is a Kit Companion too (1984)! I'll check into these options.

If you do get a little propane heater, make double sure it's rated for indoor use and have a Co detector! Not all of them are and you don't want to wake up dead one cold morning. If you have the ability to pipe in a propane port from your main system to feed it that would be bonus points and you wouldn't have to have a propane tank sitting on the floor. Make sure you can feed the heater from a regular BBQ 5Lb tank too, those Coleman 1Lb bottles suck!

Great thoughts--will do!

 

[Rednecktek]

Nope, it's a North American Blueridge mini split.

??!!?? 9k BTU on 220v American split phase? Are they crazy? Link please? I gotta see this!

Mine is a Kit Companion too (1984)! I'll check into these options.

The heater cabinet should be more than large enough to house the heater, and it'll already have the wiring in place. Drilling the intake & exhaust holes through the floor (mine has a steel base under everything, ugh!) and figuring out where to stick the annoyingly loud pump and the fuel tank are the hardest parts.

 

[missadventure]

Should only use the top 90% of that.

Yep, that's about what I've calculated. My audit has me at 4486/day. I am planning to expand the battery bank to get at least an extra day stored.

Please post a picture of the legacy ac/dc distribution panel so we can see what you are working with.
We need to see the fuses and breakers and also the maps for each.

I'll get this, but I'm curious why this is important?

q: Are the legacy batteries 12 volts?

q: Why are you keeping them?

q: How will you charge them?

-Yes they are 12v.
-I'm keeping them because they're already in place and it saves me from rewiring most of the trailer and having to figure out things like trailer lighting, water pump, etc. Also, they mostly just power the lights; worst case scenario, they'll last me a number of days should everything else have some catastrophe.
-I was planning to continue charging them as they are currently charged: from the tow vehicle when running or from shore power (solar will replace and act as shore power in this system). An alternate idea that I'll need to look into is using a 24v-12v stepdown from the new lithium batteries, but I'm not wholly sure how the charging works (like, will it stop charging when they're full or keep draining my lithium bank?)

Heating with electricity is basically a non-starter.

For space heaters, I wholeheartedly agree; however, this is a heat pump, part of my mini split and should run around 400w (flooring will be the same, but will only be on for an hour or so in the morning). I know that's not nothing, but it doesn't sound terrible to me. Am I missing something?

 

[missadventure]

So the more I noodle on that AirCon unit, the more it bugs my inner electrician. Can you post a link to what you're looking at? It sounds like it's either a EU 220v system and/or your auto-transformer is WAY oversized.

The autotransformer is absolutely oversized, but I really struggled finding one. I may have better luck going to an electric supply store.

From the sounds of it they're DIY's, she mentions they're Lithiums and 105Ah suggests LFP.

New batteries are 12v lithiums. Old ones are 12v deep cycle or agm or something--I haven't even looked tbh, but they're not lithiums.

??!!?? 9k BTU on 220v American split phase? Are they crazy? Link please? I gotta see this! \

Haha--most of the 240v mini splits are suuuper high efficiencies, like up to 38 SEER with the wall unit. However, I'm going for personal preference, which means sacrificing some of that efficiency. Like I said though, this is the ONLY WAY to get a flush mount ceiling cassette on a mini split, which is important to me.
Mitsubishi, Pioneer, Senville, Cooper & Hunter, etc etc all make them, but they're mostly available on larger BTU units. I just need a little guy. Here's a link to the one I'm currently considering:

Blueridge BMHH09Y25CC 9,000 BTU (0.75 Ton) 25 SEER - S4 SERIES - 208/230V Single Zone Ceiling Cassette Ductless Mini Split System - WiFi Capable

www.alpinehomeair.com

 

[Rednecktek]

Am I missing something?

Yes, but it's not what you think. I just did the math and my cheap Wal-Mart not-high-efficiency-piece-of-junk-window-aircon unit gives me 8000BTU at 960w of draw. The unit you're looking at, according to what I can google and find on the product page, gives you 9000BTU for 2160w (9a @ 240v)! I can't wrap my head around how they can claim "efficiency" with that.

Also be aware that the condenser unit (the big part with the fan) is very much a This-Side-Up item so you can't lay it down and it's 22" tall and 88lb!

The cassette in the ceiling makes perfect sense though.

You're right though, all the systems I'm finding with that type of cassette are 220v units, so it looks like you might be stuck with the autotransformer mess.

 

[John Frum]

I'll get this, but I'm curious why this is important?

1. to identify the ampacity rating of your legacy ac2dc converter.
2. get a sense of how much legacy 12 volts loads you have.
3. get a sense of the ac loads and see which ones we might want to disable.
In particular to see if you have an RV style fridge and determine how best to handle that.

-Yes they are 12v.
-I'm keeping them because they're already in place and it saves me from rewiring most of the trailer and having to figure out things like trailer lighting, water pump, etc. Also, they mostly just power the lights; worst case scenario, they'll last me a number of days should everything else have some catastrophe.
-I was planning to continue charging them as they are currently charged: from the tow vehicle when running or from shore power (solar will replace and act as shore power in this system).

If the legacy 12 volt stuff is only running/charging from the ac2dc converter/charger that is only power by shore power and tow cable that is fine.
If the legacy 12 volt stuff was running/charging from a dc2dc converter that would be another story.
If the legacy 12 volt stuff is running/charging from the ac2dc converter/charger that is powered by the all_in_one that is brutally inefficient.

An alternate idea that I'll need to look into is using a 24v-12v stepdown from the new lithium batteries, but I'm not wholly sure how the charging works (like, will it stop charging when they're full or keep draining my lithium bank?)

Its a bit complicated but I have dealt with it more than a few times.

For space heaters, I wholeheartedly agree; however, this is a heat pump, part of my mini split and should run around 400w (flooring will be the same, but will only be on for an hour or so in the morning). I know that's not nothing, but it doesn't sound terrible to me. Am I missing something?

I was thinking resistive heat.
Sounds like you have done the math and have it under control.

 

[missadventure]

Yes, but it's not what you think. I just did the math and my cheap Wal-Mart not-high-efficiency-piece-of-junk-window-aircon unit gives me 8000BTU at 960w of draw. The unit you're looking at, according to what I can google and find on the product page, gives you 9000BTU for 2160w (9a @ 240v)! I can't wrap my head around how they can claim "efficiency" with that.

Also be aware that the condenser unit (the big part with the fan) is very much a This-Side-Up item so you can't lay it down and it's 22" tall and 88lb!

The cassette in the ceiling makes perfect sense though.

You're right though, all the systems I'm finding with that type of cassette are 220v units, so it looks like you might be stuck with the autotransformer mess.

True, I've done that math too, and I don't understand how they rate those, but I've seen it on too many mini splits to count--their amp/voltage = watts is really high, but real life is ultra low. My thought is that the online info shows max possible usage--such as trying to go from a 120 deg RV down to 65. However, I'll put the detailed info below. The btu range is from 3600-10300 for cooling and similar for heating, using 728-925watts. I'm basing my estimate of 400-600 on other users who have shown their real life consumption for similar units.


Also, here's a thread talking about actual mini split power usage on this forum: https://diysolarforum.com/threads/how-many-watts-does-your-ductless-mini-split-ac-use.6953/

The condenser unit goes outside. I'll attach some pics of other people's setups:

 

[missadventure]

1. to identify the ampacity rating of your legacy ac2dc converter.
2. get a sense of how much legacy 12 volts loads you have.
3. get a sense of the ac loads and see which ones we might want to disable.
In particular to see if you have an RV style fridge and determine how best to handle that.

Ok! All i have on there is a few LED lights and the range hood. The fridge is a small residential on an 110 outlet which I plan to do dedicated, along with a dedicated for the espresso machine. Why separate circuits? Idk, it sounded like a good idea but may not be necessary. I have 2 circuits on the legacy panel that I might use for these dedicated outlets, then wire the rest of the outlets from the Growatt. Again, why? I don't remember if I had a reason, but it might be attributed to a certain amount of laziness re: wiring....?

If the legacy 12 volt stuff is only running/charging from the ac2dc converter/charger that is only power by shore power and tow cable that is fine.
If the legacy 12 volt stuff was running/charging from a dc2dc converter that would be another story.
If the legacy 12 volt stuff is running/charging from the ac2dc converter/charger that is powered by the all_in_one that is brutally inefficient.

Ok, this is where I'm unsure. Are you saying:
24v-->AIO 120v -->rv panel (as pseudo "shore power")-->legacy converter/charger--> legacy 12v = brutally inefficient?
Would it be better to go 24v -->24/12 battery charger--> straight to the legacy 12v -->rv panel for 12v lights?
Or...??

Thanks!

 

[John Frum]

Ok! All i have on there is a few LED lights and the range hood.

This is a wfco power center.

Amazon.ca

It is a combined ac/dc distribution center usually with an ac2dc converter.
Do you have something like this in your trailer?

Why separate circuits?

Not understanding your question.

Idk, it sounded like a good idea but may not be necessary.

I think I am missing some context.

I have 2 circuits on the legacy panel that I might use for these dedicated outlets, then wire the rest of the outlets from the Growatt. Again, why?

Lost the plot.

I don't remember if I had a reason, but it might be attributed to a certain amount of laziness re: wiring....?

Still lost.

Ok, this is where I'm unsure. Are you saying:
24v-->AIO 120v -->rv panel (as pseudo "shore power")-->legacy converter/charger--> legacy 12v = brutally inefficient?

Yes.
The all in one charger is ~80% efficient.
The all in one inverter is ~85% efficient.
The legacy ac2dc converter/charger is ~70% efficient.
When the efficiencies are compounded its gets brutal.

Would it be better to go 24v -->24/12 battery charger--> straight to the legacy 12v -->rv panel for 12v lights?
Or...??

A decent dc2dc converter/charger is >90% efficient.
How best to address the situation depends on how much load there really is.
Do you have slides or jacks or similar?

 

[missadventure]

Do you have something like this in your trailer?

Pics attached... they're blurry. Do you need breaker amps/etc?

Not understanding your question.
I think I am missing some context.
Lost the plot.
Still lost.

Hahaha! Sorry, those were all rhetorical questions posed to myself. Basically, I don't remember if I have a reason for wanting to put those on separate circuits.

A decent dc2dc converter/charger is >90% efficient.
How best to address the situation depends on how much load there really is.
Do you have slides or jacks or similar?

The conversion info is all really helpful. The load is ultra small. No slides, manual jacks. I legitimately mean that I have a handful (7-9ish right now) of LED lights, the range hood, and I am adding 3x 12v USB outlets. Can't even think of anything else I might power with 12v. Maybe a fan to the new battery/inverter compartment. Open to suggestions!

Throwing in a pic of the legacy batteries for fun.

 

[John Frum]

I made a mistake earlier.
You can do 3p and 3s for panel configurations.
Subject to voltage restrictions of the solar charge controller in the all in one.

 

[John Frum]

Wow never seen a panel like that.
Looks like the handiwork of Travis W. Redfish

This is what I was thinking before I saw that panel

3000 ac watts / .85 conversion factor / 24 volts low cutoff = 147.058823529 inverter amps
147.058823529 inverter amps / .8 fuse headroom = 183.823529412 inverter fault amps.

30 pure dc serivce amps / .8 fault amps = 37.5 pure dc fault amps
183.823529412 inverter fault amps + 37.5 pure dc fault amps = 221.323529412 total fault amps

ac_domain {
    // 120VAC RV panel
    // hopefully there is a spare breaker in the panel
    |<-30A_master_breaker<-growatt<-surge_protector<-shore_power
    |->?A_branch_breaker->auto_transformer->mini_split
    |->branch_breaker->ac2dc_converter(disabled)
    |->branch_breaker->branch_load
    |...
}
dc_domain_legend {
    // { comment }
    {} { functional block }
    nnn|NNN| { fused busbar position where nnn is wire size in awg and NNN is the fuse rating in amps }
    nnn|UUU| { un-fused busbar position where nnn is wire size in awg }
    <-> { bi-directional current flow }
    -> { uni-directional current flow }
    <- { uni-directional current flow }
    dpst { double pole single through switch }
    @ { back reference }
    & { not connected }
}
dc_domain { 24 volt floating system
    busbars {
        positive {
            1/0|UUU|<->disconnect_switch<->250A_fuse<->battery_subassembly
            002|200|<->growatt.out
            006|100|->battery_protect->dc2dc_converter->dc_distribution
        }
        negative {
            1/0|UUU|<->shunt<->battery_subassembly
            002|UUU|<->growatt.out
            006|UUU|<-dc2dc_converter->dc_distribution
            016|UUU|<-battery_protect.ground
        }
    }
    growatt {
        in {
            positive<-dpst<-panels_in_series
            negative->dpst->panels_in_series
        }
        out {
            positive@
            negative@
        }
    }
}

 

[missadventure]

ac_domain {
    // 120VAC RV panel
    // hopefully there is a spare breaker in the panel
    |<-30A_master_breaker<-growatt<-surge_protector<-shore_power
    |->?A_branch_breaker->auto_transformer->mini_split
    |->branch_breaker->ac2dc_converter(disabled)
    |->branch_breaker->branch_load
    |...
}
dc_domain_legend {
    // { comment }
    {} { functional block }
    nnn|NNN| { fused busbar position where nnn is wire size in awg and NNN is the fuse rating in amps }
    nnn|UUU| { un-fused busbar position where nnn is wire size in awg }
    <-> { bi-directional current flow }
    -> { uni-directional current flow }
    <- { uni-directional current flow }
    dpst { double pole single through switch }
    @ { back reference }
    & { not connected }
}
dc_domain { 24 volt floating system
    busbars {
        positive {
            1/0|UUU|<->disconnect_switch<->250A_fuse<->battery_subassembly
            002|200|<->growatt.out
            006|100|->battery_protect->dc2dc_converter->dc_distribution
        }
        negative {
            1/0|UUU|<->shunt<->battery_subassembly
            002|UUU|<->growatt.out
            006|UUU|<-dc2dc_converter->dc_distribution
            016|UUU|<-battery_protect.ground
        }
    }
    growatt {
        in {
            positive<-dpst<-panels_in_series
            negative->dpst->panels_in_series
        }
        out {
            positive@
            negative@
        }
    }
}

Thanks! But what does this mean? the code part...

This is what I was thinking before I saw that panel

3000 ac watts / .85 conversion factor / 24 volts low cutoff = 147.058823529 inverter amps
147.058823529 inverter amps / .8 fuse headroom = 183.823529412 inverter fault amps.

30 pure dc serivce amps / .8 fault amps = 37.5 pure dc fault amps
183.823529412 inverter fault amps + 37.5 pure dc fault amps = 221.323529412 total fault amps

Are you recommending a setting or a breaker/fuse size, or just telling me something (that I'm not quite catching)?

Wow never seen a panel like that.
Looks like the handiwork of Travis W. Redfish

Haha! This is what 1984 looked like

 

[John Frum]

Thanks! But what does this mean? the code part...

Its not code, its a textual representation of the system.
It shows what connects to what.
The dc part of the systems we make are all connected between the main busbars.
The system is a ladder where the busbars are the risers and the circuits are the rungs.

Are you recommending a setting or a breaker/fuse size, or just telling me something (that I'm not quite catching)?

I'm showing how to determine wire size and over-current protection size.

 

[John Frum]

Hopefully the ac_domain should be self explanatory and the dc_domain includes a legend(primer).

 

[missadventure]

Its not code, its a textual representation of the system.
It shows what connects to what.
The dc part of the systems we make are all connected between the main busbars.
The system is a ladder where the busbars are the risers and the circuits are the rungs.

I'm showing how to determine wire size and over-current protection size.

ahhh thank you!

 

[missadventure]

@smoothJoey


?

 

[Rednecktek]

OK all, I'm back and ready for more!

Those batteries are FLA, so even in best condition (which those are very much NOT) you're looking at 50% depth of discharge. A new battery box that you can stick a couple larger batteries in will buy you a LOT of stress relief. Even something like the Harbor Freight Tongue Box will buy you a lot more room for batteries/fuses/wire. Good thing you've already planned to get different batteries, but it may well be a moot point.

Yeah @smoothJoey , Kit (the manufacturer) didn't really keep up with the times, they shaved their sideburns off somewhere around the mid 90's.

That transformer isn't going to accomplish jack if it only puts out 12v of DC, your batteries are going to need 13.8v to charge your 12v batteries at the very least, more for LFP batteries and/or the bulk/absorption cycles that make acid batteries happy. I think that entire power system is going to be a complete loss save maybe the wiring for the 12v appliances.

For the 12v stuff, the best option is getting a beefy 24v-12v buck converter and going 24v Battery -> Buck -> Fuse Block -> 12v Stuff. As Joey points out going back and forth from one voltage to the next and again and again is going to seriously nerf your efficiency..

So, in short:
Dump the old power panel and use the space for new DC fuse block, battery monitor, autotransformer, breaker box, etc.
Take the old batteries out of the loop completely and just use a buck transformer to get your 12v supply.
Find a way to get a 4th panel involved and stick with 2s2p strings, that's going to max out the PVInput on that Growatt (145v)
External jack that you can add in a ground mount array of 2s2p or 2s4p will help big time.
Get the most LFP battery you can afford/physically stick in the space involved.

OK, here's a revamped doodle of what we're all looking at so far by the sounds of things, my changes in orange:

 

[Rednecktek]

Just one more thought, but my camp was a 23ft trailer and I can't imagine where I'd stick 4 batteries in there, where are you planning on sticking yours? If the layout is anything like mine the bed covers the fresh water tank, the hot water tank is under the stove, and the furnace cabinet would only hold 2 maybe if I built a shelf.

If you throw them in a tongue box that's going to add quite a bit of heavy wire run. When calculating the wire size remember that it's measured in round trip, so AIO to batteries to AIO.

 

[Rednecktek]

The autotransformer is absolutely oversized, but I really struggled finding one. I may have better luck going to an electric supply store.

Absolutely. That's not the kind of thing you find in stores unless you go to specialty shops like electric suppliers. You're going to need to pick their brains to find a "Single Phase 120v to 240v split phase with neutral in the 2.5-3KVA range"

Another option to research would be getting an inverter that does 24v to split-phase 240v and running that from the batteries as a second circuit. Not sure on the cost but might be easier to source.

They'll know what that means.