Adding AC

[Crisfole]

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?

[Native]

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.

[JDOnTheGo]

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.

Originally Posted by Crisfole

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.

[alpine44]

'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.

[alpine44]

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.

[Crisfole]

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.

[alpine44]

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.

[Native]

Should you need to go the 240V route, Aimes and Magnum make 240V split-phase inverters.

[cadillackid]

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

[Crisfole]

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.

[alpine44]

Originally Posted by Crisfole

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.

1. Less than what alternative?
2. Each additional indoor unit (evaporator) will increase the electrical power consumption of the outdoor unit. Obviously, the max BTU/hr rating of the outdoor unit must be at least as large as the sum of the indoor units.
3. That is correct with the caveat that several right-sized systems are more efficient than one over-sized unit.
4. The 'inverter' in mini splits is a variable frequency drive (VFD) that allows adjustment of the compressor rpm and thereby the compressor displacement per time unit. Once the set temperature has been reached, the compressor rpm will be reduced to maintain an equilibrium between heat removed via A/C from the room vs heat added to the room through the walls and internal heat sources. If the room temperature still drops at the lowest compressor rpm, the unit will start cycling on/off.
The best way to reduce your A/C power needs is good insulation and keeping the sun out of the space you want to keep cool.
5. The difficulty here is to facilitate the transfer from generator to battery/inverter power. You cannot just parallel the generator output and the inverter output due to the phase difference. You either need a switch or build the generator for DC output and run everything through your inverter.

When you run the A/C with your battery bank it is kind of silly to go through an inverter to obtain 120/240V and then have another 'inverter' (VFD) in the mini split to regulate the compressor displacement. That can be achieved more efficiently with a brushless DC motor/controller driving a conventional compressor or a simple DC electric motor driving a variable displacement compressor.

I am currently building a system like this mainly because the mini split outdoor units do not lend themselves to underbody mounting like vehicle A/C condensers. An residential outdoor unit hanging somewhere on the body of a box van looks 'ghetto' IMO and would defeat the stealth goal of my build. I also read several reports that mini-splits are not intended to be subjected to the shock loads and water/salt spray typically associated with vehicles. The cheaper unit will not even survive a coastal residential environment for a satisfactory length of time.

[Crisfole]

OK, that all really helps, thanks! The reason I'm asking is that there's so little space under the bus that I will likely need to mount the outdoor unit on the back of the bus. I don't think I'll have space for two units _and_ a generator.

I'm not being stubborn for fun...a generator would be a ton easier and cheaper...but it's a 31' low floor bus. The photos look like there's not a ton of space. Happily I know everything will change after literally every step...even have a replanning step scheduled between every step of the process...

[alpine44]

On your doubledecker I would install a 2nd floor deck where you could put the outdoor unit(s). That would not increase your parking space needs for most locations.

There will also be some space somewhere on the bus for vehicle-type condenser units.

[TheHubbardBus]

Originally Posted by alpine44

5. The difficulty here is to facilitate the transfer from generator to battery/inverter power. You cannot just parallel the generator output and the inverter output due to the phase difference.

One potential solution, Crisfole, would be to use an inverter/charger with AC pass-through capability. Your generator/shore power would feed into the inverter, and, when energized, be the power source for your home. When not energized, the inverter would switch back to your battery source. The potential downfall to this approach, however, is that your inverter (and generator, of course) would have to be sized to supply your total power needs, which means that at times when you're not running near max, you'll be burning a lot of juice just keeping that big inverter alive. And if you run w/o incoming AC, which may be a big temptation at times, you might draw your batteries down real far, real fast.

Another possible solution would be to split your incoming generator/shore input into two circuits... one for your inverter/charger input (into a smaller ac pass-through inverter), and another for your 'heavy' load(s) (like AC). On battery power alone your A/C would not be available, but everything else would. On generator/shore you'd be running everything, with any extra juice going to charge your bank.

[Crisfole]

Originally Posted by TheHubbardBus

One potential solution, Crisfole, would be to use an inverter/charger with AC pass-through capability. Your generator/shore power would feed into the inverter, and, when energized, be the power source for your home. When not energized, the inverter would switch back to your battery source. The potential downfall to this approach, however, is that your inverter (and generator, of course) would have to be sized to supply your total power needs, which means that at times when you're not running near max, you'll be burning a lot of juice just keeping that big inverter alive....

I had no idea that the inverter used a lot of power without draw...I (apparently incorrectly) assumed the wattage was just a max, and that it would only produce what was needed to run whatever was being consumed. Am I misunderstanding you?

[alpine44]

Originally Posted by Crisfole

I had no idea that the inverter used a lot of power without draw...I (apparently incorrectly) assumed the wattage was just a max, and that it would only produce what was needed to run whatever was being consumed. Am I misunderstanding you?

Inverters have an 'idle' draw to provide the voltage for turning AC consumers on. Once the consumers draw current, the inverter ramps up its current delivery to the AC circuit and its current draw on the battery. That's part of the voltage regulation circuitry of the inverter.

Generally speaking, the bigger the inverter, the bigger the idle draw.

[Crisfole]

Originally Posted by alpine44

On your doubledecker I would install a 2nd floor deck where you could put the outdoor unit(s). That would not increase your parking space needs for most locations.

There will also be some space somewhere on the bus for vehicle-type condenser units.

Right, this was my plan already, but since I'm currently assuming almost 0 space under the bus, this would also be the location of a generator. Two condensers basically fills the width of the deck.

I'm very much hoping I'm wrong about under the bus, fwiw...

My other option is if I can get my engine running the A/C while we're driving I could have a portable generator that I can leave chained to something and plug it into my shore outlet? Not really sure about any of this just yet.

[Crisfole]

Originally Posted by cadillackid

were those the old cumminds L10 versions?

One and the same, I think. The product you linked is exactly the same as the vehicle id plate shows: E06-CLTA-10-2.

Originally Posted by cadillackid

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

Sorry, I'm definitely in slightly over my head here. "Digger" is a brand? Or literally heavy digging equipment? Any chance there's a 101 thread here or any other resource for fully getting caught up on engine driven A/C...I'll be needing some catching up...

[alpine44]

Originally Posted by Crisfole

One and the same, I think. The product you linked is exactly the same as the vehicle id plate shows: E06-CLTA-10-2.



Sorry, I'm definitely in slightly over my head here. "Digger" is a brand? Or literally heavy digging equipment? Any chance there's a 101 thread here or any other resource for fully getting caught up on engine driven A/C...I'll be needing some catching up...

Click the link towards the end of Christopher's post for a compressor bracket that fits the L10 engine. The bracket linked is for a Komatsu excavator (aka digger or track hoe) but the same company has other brackets for the L10 engine.

AFAIK we do not have an A/C wiki or tutorial on this forum.

So here is the vehicle A/C 101 version:

There is a refrigerant compressor mounted on the engine that gets powered by the engine when the compressor clutch is energized with vehicle voltage (12 or 24 Volt).

The compressor raises both the pressure and the temperature of the refrigerant vapor (e.g. R134a) flowing through it. The hot, high-pressure refrigerant vapor then flows into the condenser, a heat exchanger where the vapor is cooled by ambient air and condenses to a liquid. The phase transition from vapor to liquid releases a large amount of thermal energy that is being removed from the system via the condenser.

From the condenser, the liquid refrigerant flows into a receiver/drier which acts as a reservoir and removes any residual moisture from the refrigerant loop. Exit side of the compressor, condenser, receiver/drier and associated piping is called the 'high (pressure) side' of the system.

After leaving the receiver/drier, the liquid refrigerant is expanded through a small orifice into the evaporator, a heat exchanger inside of the vehicle. The orifice can be either static orifice tube or a thermostatically controlled valve (TXV). Everything past the orifice to the compressor is called the 'low-side' of the system.

The drop in pressure from high-side to low-side causes the liquid refrigerant to evaporate and the same amount of heat that was released during the phase transition from vapor to liquid is now 'sucked' out of the evaporator core, which will then cool the air of the vehicle cabin. (It is important to understand that phase transitions do the work in a refrigeration cycle. Google 'latent heat' if rusty in Physics)

The refrigerant vapor goes back to the compressor suction port from the evaporator outlet and the cycle repeats itself.

Pressure switches in the system control the compressor clutch to deliver enough liquid refrigerant to the expansion device at the evaporator inlet. If there is too much liquid produced for a given flow through the expansion device, the high side pressure will rise and the clutch will disengage the compressor. Once the pressure drops to a certain level, the compressor clutch will re-engage.

Newer cars have a 'clutchless' variable displacement compressor and a more sophisticated and efficient control but that is not 101 territory anymore.

[Crisfole]

Awesome. That's super helpful. So doing this would require a completely A/C separate system for running from the engine (including ductwork, etc?)