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Old 09-13-2020, 06:57 PM   #1
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Mount the MiniSplit in the Engine Compartment?

I have an International RE3000.

There is a lot of room in the engine compartment.
I think this would be a good spot for the mini-split we are planning to purchase.
My plan would be to mount the intake flush to the drivers side wall, and add a screen to allow intake air flow.
output airflow would be blown into the engine compartment.

The other location we could consider would be under the bus, within the chassis.
I would face the intake down and the exhaust up at the ceiling.

Thoughts?
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Old 09-13-2020, 07:57 PM   #2
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you need to evaluate how the air flows in the engine compartment. so that you arent blocking any engine airflow.. rear engine busses need all of the air they can get to stay cool..


you cannot turn a minisplit unit on its side, the comporessor needs to be upright, however people have succesfully moiunted them on RE busses inside the frame rails vertically hanging down. sideways. and they seem to work fine this way even driving.
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Old 09-13-2020, 08:09 PM   #3
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Thank you very much!
I'll think on it.
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Old 09-13-2020, 08:54 PM   #4
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I wouldn't do it. Refrigeration operates solely on the principle of transferring heat from where it is not desired to be exhausted elsewhere. If the system is exhausting condenser heat into an already hot engine bay, it will likely overheat, which will cause overpressurization of the system, forcing it to shut down on high pressure and will eventually damage the system permanently. Not to mention it could also tempt the fates with an engine cooling configuration that already has its own unique set of challenges, being a rear-engine.

I had very similar and nearly disastrous results from a simple electric condenser fan turning the wrong direction because it was wired reverse polarity. I was fortunate in that it only cost me a new compressor (after the $2200 system rebuild - over a $50 fan that worked just enough to trick everybody into thinking it was good).

I predict you will likely have issues with both the engine cooling (condenser heat will kick your engine bay temps up at least 20-30 degrees), and the condenser has to be able to get rid of heat quickly, which it cannot do when inside a cabinet with a 600 degree exhaust manifold, 600-800 degree turbocharger and a 195-220 degree radiator and engine block.

Possibly these problems can be solved with a custom dual electric fan setup mounted on the inside of the engine bay door, but I wouldn't bet on it. Just make sure they're wired to push air outside through the door's grilles / vents or you are guaranteed to fail. Mounting your condenser here will likely hinder engine cooling, already an issue with this engine configuration.
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Old 09-13-2020, 09:13 PM   #5
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Very valuable experience info.
Thank you very much!
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Old 09-13-2020, 09:18 PM   #6
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Oh, and if you have contact info for Transcendence, please have them contact me for a possible future build.
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Old 09-13-2020, 09:32 PM   #7
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Oh, and if you have contact info for Transcendence, please have them contact me for a possible future build.
I'll mount my Pioneer 12K mini-split's condenser unit between the frame rails directly above the front axle - there's just enough vertical room for it to fit and still keep enough space between the axle and its casing (I hope!). It will get plenty of cool air from under the bus when parked, and it should also work well if I need it on when driving. The indoor unit will be next to the stairs, just a short distance from the condenser. I think the biggest challenge will be cutting a big hole in the floor that I'll lower the condenser down through, but I've done much harder things than that so far with my bus!

Definitely keep your mini-split well away from your engine and anything else that's hot.

John
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Old 09-14-2020, 07:02 AM   #8
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how do you plan to service your minisplit if you have to shoe-horn it in so tight that you cut a hole in the floor and drop it down? something as simple as blowing a fuse on the outdoor board requires taking the top off of the unit which in a normal install is a 5 minute job..


I would want something where the unit is installed from outdoors so iut can be pulled down to service or replace if needbe..



the longevity of minisplits on the road is still yet to be determined..


the chinese units in my house are 11 years old now and many dont last that long even in a residential or light commercial situation..



-Christopher
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Old 09-14-2020, 07:13 AM   #9
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Forget the engine compartment. Too much heat. Reminds me of when we had VW bugs, there was a gasket around the engine , between the engine sheet metal and the body, to keep the hot air from coming back into the engine compartment. Also the coils for the AC will be warm and need to be cooled, so keep away from existing heat, like the bus engine.
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Old 09-14-2020, 09:12 AM   #10
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Isn't the plan to use it when parked, not when running?
If that is the case, your concern is having it obstruct the airflow for the engine when its running.
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Old 09-14-2020, 11:19 AM   #11
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Cheese Wagon
I conveyed your message to Wess.
You can find him on the "School Bus Conversion" Facebook group page and message him there directly if you like.
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Old 09-14-2020, 11:25 AM   #12
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BeNimble, yep the plan is to use this when we are not driving and the engine is cold.
My only concern is how hot does it get in the engine compartment?
It's a big space.
So if it gets up to 100 deg F, in there, it shouldn't bother the mini split and the mini split shouldn't have any effect on air flow, given where we might locate it.
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Old 09-14-2020, 11:35 AM   #13
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Quote:
Originally Posted by Michael_Grumbach View Post
BeNimble, yep the plan is to use this when we are not driving and the engine is cold.
My only concern is how hot does it get in the engine compartment?
It's a big space.
So if it gets up to 100 deg F, in there, it shouldn't bother the mini split and the mini split shouldn't have any effect on air flow, given where we might locate it.
Depending on which way you have that unit moving air, you might be able to run the fan separate from the cooling capability of the unit and use it to better cool the engine compartment while running down the road. The cooler the engine is, the happier it stays.
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Old 09-14-2020, 11:42 AM   #14
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the minisplit is a compujter controlled unit, its fan cannot be used without the unit cooling.. the nig issue isnt running it while driving, although if you dont have road A/C you can do that for at least a little relief.



but the issue is making sure the engine compartment has enough air to cool the engine properly..



and after you park while the engine is hot radiating heat everywhere.. keeping the minisplit cool is a concern till the engine cools off.
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Old 09-14-2020, 12:12 PM   #15
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Quote:
Originally Posted by cadillackid View Post
how do you plan to service your minisplit if you have to shoe-horn it in so tight that you cut a hole in the floor and drop it down? something as simple as blowing a fuse on the outdoor board requires taking the top off of the unit which in a normal install is a 5 minute job..

I would want something where the unit is installed from outdoors so iut can be pulled down to service or replace if needbe..

-Christopher
It's not going to be shoe-horned in - there will be plenty of space around it on all four sides. The reason for a floor hatch is simply because it's too damn heavy to maneuver into place above the front axle if I'm lying on my back under the bus: it would get banged up and damaged, and it would need to be tipped over to get it over the axle, than temporarily located in place while the support struts underneath it are attached to the frame rails. I simply cannot do this by myself. It was difficult enough getting my little 40-lb electric air compressor into that location previously, so there's no way I can get a 75-lb much larger thing in there the same way. There's already a floor hatch for accessing the fuel tank that's directly behind where the condenser will go, so all I'm doing is making a second floor hatch. In the big scheme of things, and considering all that I've done so far to the bus, this A/C installation will not be the hardest job by a long shot. And if I need to change a fuse or do anything, then all I need is to remove the floor hatch, take the condenser's cover off, and it's all right there. Easy!

And to answer your question why I'm putting it there in the first place, it's simply because I have no other space anywhere for it. All, and I mean all, empty space under the floor is now used. Real estate under my bus's floor is becoming as valuable as in Manhattan! To put the minisplit's condenser in a luggage bay would be an inefficient use of space.

John
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Old 09-14-2020, 12:45 PM   #16
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Quote:
Originally Posted by Michael_Grumbach View Post
BeNimble, yep the plan is to use this when we are not driving and the engine is cold.
My only concern is how hot does it get in the engine compartment?
It's a big space.
So if it gets up to 100 deg F, in there, it shouldn't bother the mini split and the mini split shouldn't have any effect on air flow, given where we might locate it.
My engine room gets well over 100F. I wish mine would only get to 100F! And even after I turn off the engine there's still heat there for over half a day - it takes a lot of time to dissipate 200F heat from 2100 lbs of cast iron and steel.

An engine bay is NOT where an A/C condenser should be located.

John
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Old 09-14-2020, 12:54 PM   #17
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I didn’t realize the floor hatch was staying. I was thinking it would be like a lot of conversions here where people cover up any and every access point with their pretty carpets and floor coverings only to need to service somethjng later. It makes sense to put it there esp since the hatch stays.
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Old 09-14-2020, 01:35 PM   #18
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I’ve mounted 2 under my bus.
The rear one is sorta’ in the engine compartment. I’m also gonna’ mount the generator in there.😎
They work great.
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Old 09-14-2020, 08:51 PM   #19
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Quote:
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I’ve mounted 2 under my bus.
The rear one is sorta’ in the engine compartment. I’m also gonna’ mount the generator in there.😎
They work great.
That is a friggin' beautiful installation! I am planning on the same exact spots on mine.
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Old 09-15-2020, 03:13 AM   #20
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Quote:
Originally Posted by Iceni John View Post
An engine bay is NOT where an A/C condenser should be located.
Clarification... for rear-engine, I agree. But that IS how they are typically installed in most conventional front-engine configurations, which do not have the cooling challenges of a rear-engine configuration. I think that is why OP is considering this -- NOT a good idea with a rear-engine setup.

Quote:
Originally Posted by Michael_Grumbach View Post
Cheese Wagon
I conveyed your message to Wess.
You can find him on the "School Bus Conversion" Facebook group page and message him there directly if you like.
Thanks, it's appreciated.

Quote:
Originally Posted by Michael_Grumbach View Post
BeNimble, yep the plan is to use this when we are not driving and the engine is cold.
My only concern is how hot does it get in the engine compartment?
It's a big space.
So if it gets up to 100 deg F, in there, it shouldn't bother the mini split and the mini split shouldn't have any effect on air flow, given where we might locate it.
WAY more than 100 degrees after the engine has been running.

Quote:
Originally Posted by cadillackid View Post
The minisplit is a compujter controlled unit, its fan cannot be used without the unit cooling.. the big issue isnt running it while driving, although if you dont have road A/C you can do that for at least a little relief.

But the issue is making sure the engine compartment has enough air to cool the engine properly..

And after you park while the engine is hot radiating heat everywhere.. keeping the minisplit cool is a concern till the engine cools off.

CK is right on the money. I couldn't have said it better myself. You need to think about the need to use this equipment immediately after shutdown of the main engine after driving. That is when the compartment will be hottest, and adding condenser heat will only prolong cooldown time.

I can't run an RV rooftop A/C with a tarp covering the leaky roof for exactly this reason. The condenser has to blow off heat, and it cannot do that underneath a tarp, much less in a compartment that is already at 300-600 degrees after engine shutdown.

I don't advise doing this at all with a rear-engune configuration, and it's likely not the best idea with front-engine either. But if you do, I would set up a seriously overkill cooling solution for use immediately following engine shutdown, including...

1) Coolant-temperature-controlled exhaust fans to blow heat out of the engine bay, perhaps even a pull-in - push-out arrangement, which would create a vortex for more efficient cooling.

2) Supplement said fans with an auxiliary electric coolant pump to keep the coolant flowing through the engine block, cylinder head and radiator until coolant temperature matches ambient outside temperature. NOT to substitute for the engine-driven unit while driving, mind you.

3) Condenser would best do its job mounted on the inside of the engine bay door with high-pressure rubber hoses to and from, providing that door gives sufficient ventilation -- and with its own fans pushing air through the door and out the back.

The electrical part of this would need to be on relays triggered by the mini-split's operation and coolant temperature controlled to minimize power consumption and unecessary wear on the cooling solution. Otherwise, you are guaranteed to have problems. And I can't guarantee you won't have problems anyway. Reason being that the only thing that will safely cool your 600-degree exhaust and turbocharger is time. Creating a vortex with electric fans will help, but only so much. Cast iron takes awhile to cool from such temperatures.

Quote:
Originally Posted by Iceni John View Post
And to answer your question why I'm putting it there in the first place, it's simply because I have no other space anywhere for it. All, and I mean all, empty space under the floor is now used. Real estate under my bus's floor is becoming as valuable as in Manhattan! To put the minisplit's condenser in a luggage bay would be an inefficient use of space.
A lot of newer buses with factory auxiliary A/C have larger rooftop units. You say you have little to no room underneath, why not mount the compressor / condenser(s) on the roof?

You might also consider converting one of the rear windows to a dedicated compartment for the minisplit, setting it up to exhaust that way, but you would need some soundproofing and insulation for heat and noise mitigation. (I recommend DynaMat).

Oh, and Shay...


You don't HAVE to mount your mini-split under your bus...
But it HELPS... It DOES help...

Sorry, couldn't help myself...

But seriously, if your bus is rear-engine and especially if your generator is air-cooled, not a good idea either, for the same reasons.
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