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Old 09-08-2019, 06:51 PM   #1
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Adding AC

I'm converting a 1985 Leyland Olympian, it arrives next Saturday. (Photos from inspection available in my only Album on this site). It's a double decker (31' long, 8'2" wide, and 13'6" tall. 1985 was the first year Olympians had AC, but this unit did not. I think only the ones that wound up in Hong Kong got the AC units.

Since there is no built-in AC, I'll need a system I can run on the road (three little boys won't do great stuck in a carseat without AC). I also would love to be able to use it off grid, minimizing generator usage. To that end, it seems like a good idea to zone it so we only cool/heat the areas in use. With a double decker I can think of four main zones, aft and fore on the upper and lower decks.

We are not terribly excited about running a generator non-stop; our boys make more than enough noise by themselves without having a mechanical partner in crime. Ideally we'd not have one at all (ideally, but not realistically).

Thoughts on what I need, should do? Folks here seem resistant to adding 220 appliances to be run off-grid, there's probably a good reason for that, just haven't found the posts that explain why.

Relevant question: Are there any inverters that have both 110 and 220 outputs that can run at the same time?
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Old 09-09-2019, 01:24 AM   #2
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Yes, there are inverters that produce two legs of 110V AC. The GoPower products such as GP-ISW-3000 & GP-ISW-2000 provide two 110V/50A outputs.
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Old 09-09-2019, 07:41 AM   #3
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Given what was said, I think you are asking about air conditioning which is abbreviated "A/C" as opposed to "AC" which is alternating current.

Running anything (A/C, appliances, etc...) without a generator requires a battery bank and inverter. That is very common. What is difficult/expensive is a massive battery bank sufficient to run A/C and/or power hungry appliances. You will need to understand your electrical needs and goals to sufficiently size your system. This is done with an energy audit. Once you have that completed, you will begin to see the challenge you face with storing huge amounts of energy. At that point, most people begin focusing on 120VAC appliances (or DC appliances) and begin accepting that running A/C from battery for any length of time is not easily achieved (not to say it is impossible).

220VAC appliances are an additional challenge as a 220VAC is a huge energy drain for a battery bank. Also note that a 120VAC inverter with two outputs is not the same as a 220VAC inverter.

Quote:
Originally Posted by Crisfole View Post
Relevant question: Are there any inverters that have both 110 and 220 outputs that can run at the same time?
I've never seen one but haven't been looking.
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Old 09-09-2019, 07:55 AM   #4
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'Split phase' is the key word to search for inverters that deliver both 100VAC and 220VAC like a common household hookup.

The typical use for 220VAC here in the USA is when the current of a 110VAC circuit would exceed 30 A like on a stove, clothes dryer, or big A/C unit.

I Europe, 220VAC (50Hz) is the standard and even low power appliances like radios are run on that.

It is not the voltage that determines the power consumed. It is not the current (Amps) either. Power is the product of Volts times Amps and is measured in Watts. Perform an energy audit like JD suggested and do it in Watts.

Then you can decide whatever voltage you need to keep the current (Amps) at a reasonable level. Keep in mind that losses increase with the square of the current but power is a linear function of current. The reason for high voltage transmission lines it to transmit the same power at a higher voltage, which drops the current and therefore significantly decreases the line losses.
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Old 09-09-2019, 08:13 AM   #5
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Please post pictures of the engine bay when you get the bus so we can see how an engine-driven A/C compressor could be retrofitted.
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Old 09-09-2019, 11:16 AM   #6
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Huh...could have sworn posts could be edited retroactively...I must have been wrong.

@JD:

Thanks for the heads up on the AC A/C abbreviations! I'll be more careful in the future. I was actually hoping you'd respond. I've read every page of your build thread and all the electrical pages I could find on your blog (you should display tags and allow searching by them). I had been (perhaps incorrectly) assuming that since the wattage on a 4 zone LG mini split was only 2310 Watts, and since mini splits use less power once temps are stable, and since a zoned system uses even less power if some zones are off, that it might be doable. I'm willing to spend on a battery bank, and I'm also willing to run generators a few hours a day if necessary...just preferably not all the time. I've already done an energy audit, lost the sheet of paper I did it on, unfortunately. I've since consolidated to a notebook and a gist on Github...Anyway, the pieces of the rig we want to run offgrid are basically fridge/freezer, A/C as sparingly as possible while still sleeping comfortably, window fans upstairs to reduce need for A/C, the electric part (thermostat basically?) of a propane tankless water heater, a range hood, model/router, device chargers (I work remotely as a software engineer too, so this is about 24 hours a week, I have arranged a pretty unique schedule), LED lights, 3 sound machines during naps and bedtime, and the water pump.

I figured the multi-zone would be really helpful for a few reasons: 1. once it's at temp it reduces its draw (and we could just run the generator to get down to temp to begin with) 2. We can use minimal number of zones. I assume that if I have 3 7k BTU zones and 1 9k BTU zone, but I only use two of them that I basically draw the same wattage as somoene running a single 14k-16k BTU zone. Is that assumption off?

@Alpine, check out the photo album, there are a handful of good shots of the engine. Thanks for the 'split phase' phrase. My job is literally being great at Google (software engineer), but if I don't have the words to search my skills are useless.
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Old 09-09-2019, 11:54 AM   #7
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The ability to edit a post on this forum expires after a certain time. Maybe somebody knows what that time is.

I'll check your photos this evening and hopefully respond with some ideas.
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Old 09-10-2019, 02:17 AM   #8
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Should you need to go the 240V route, Aimes and Magnum make 240V split-phase inverters.
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Old 09-10-2019, 07:51 AM   #9
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were those the old cumminds L10 versions?



this is listed for a Digger but could get you a single Sanden compressor assuming the cleanrances are there in the bus..



its a start.. AP air is still in business.. as is red dot who makes a lot of specialty A/C pieces..



a single Sanden enhanced compressor can be spun up to 4000 compressor RPM and can get you in the 60,000 btu range.. (im running mine with 70k total btu of evaporators ands im still able to pull the suction down so you may be able to get more than its rated 60k.


you could at least cool a decent portion of your lower floor while on the road im thinking..



dont mess with imposters.. use a genuine sanden Enhanced SD7H15 compressor.. (yes its different than the regular SD7H15). mate it to an ACT CS-3 condensor and 2 30-40k btu evaporators of your choice and your lower floor is likely liveable on the highway..


https://www.apairinc.com/shopping/pr...=146421&c=4608


-Christopher
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Old 09-10-2019, 08:02 AM   #10
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Rated Cap: 17500, probably kg
So can someone check my assumptions up there?

1. Does a mini-split actually use less power once the indoor units find equilibrium?
2. Does using fewer zones reduce the whole system's power usage? (Each indoor unit is rated for a certain number of BTUs, so I sort of assumed they were 'energy independent').
3. It's wattage times time that matters, right? Using a bigger system doesn't necessarily mean it's going to consume more electricity if it's managed well?
4. I had read somewhere that mini splits are at their most efficient when running at less that 100% power...because they are inverting systems does that mean they just run at lower wattage once each space is cooled or heated to the desired temperature?
5. Can I supplement with a generator while the system is using full power to get down or up to temperature, then turn off the generator once it comes to equilibrium? (Will that be enough to keep my battery needs down?)

I'm re-working my energy audit at this time...not sure how to calculate without the big appliances which consume the vast majority of my budget.
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