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Old 03-12-2018, 06:05 AM   #41
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Originally Posted by Jdawgsfanasty View Post
I thought that would work...probably wouldn't need more than 4hp...

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A/C takes a surprising amount of horsepower.. Joe did the math and ive played with it in the past too.. the compressor manufacturers also Specify the horsepower required for the amount of BTU you wnat to get out of your system.

its then Very important to control the amount of air you push over your evaporator... in Joe;'s case because his is insulating his bus, we assume he wont need near the A/C capacity that it did was a bus... as a bus its running in city traffic full of people, door open and close every 2 minutes... as his use it wont need near the original BTU.. so he will spin the compressor slower.. pullied down from his pony engine..

the coils are of course sized for the large system.. if you try to blow lots of air across the inside coil it will not do a very good job of controlling humidity or will end up with high suction pressure and just not cool well.. so the way to reduce the capacity is to lower the fan speeds and blow less air over the inside coil... the expansion valve will control the freon flow on its own to make sure it doesntr freeze up..

what he is doing is to me a solid solution to having A/C for the road and A/C for being parked.. technically he could lower the fan speeds inside even more when parked and even lower the RPM of his pony engine.. and get almost mini-split style variable control over the A/C system. use of a variable speed fan controller on the outside coils would keep from loading the condensor too heavy..
-Christopher
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Old 03-12-2018, 07:57 PM   #42
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Originally Posted by cadillackid View Post
A/C takes a surprising amount of horsepower.. Joe did the math and ive played with it in the past too.. the compressor manufacturers also Specify the horsepower required for the amount of BTU you wnat to get out of your system.

its then Very important to control the amount of air you push over your evaporator... in Joe;'s case because his is insulating his bus, we assume he wont need near the A/C capacity that it did was a bus... as a bus its running in city traffic full of people, door open and close every 2 minutes... as his use it wont need near the original BTU.. so he will spin the compressor slower.. pullied down from his pony engine..

the coils are of course sized for the large system.. if you try to blow lots of air across the inside coil it will not do a very good job of controlling humidity or will end up with high suction pressure and just not cool well.. so the way to reduce the capacity is to lower the fan speeds and blow less air over the inside coil... the expansion valve will control the freon flow on its own to make sure it doesntr freeze up..

what he is doing is to me a solid solution to having A/C for the road and A/C for being parked.. technically he could lower the fan speeds inside even more when parked and even lower the RPM of his pony engine.. and get almost mini-split style variable control over the A/C system. use of a variable speed fan controller on the outside coils would keep from loading the condensor too heavy..
-Christopher
Cool, I only know what a mechanic told me...and it seems logical to me that most folks ain't gonna want to give a lot of hp to a a/c system...it's my understanding that the RPMs is the most important factor, which is in the pulleys since 3600rpm is fairly common in small engines...
Condenser fans and evaporater fans wouldn't be affected by the compressor drive unit...they would still be DC voltage...that's my guess

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Old 03-13-2018, 06:39 AM   #43
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Originally Posted by Jdawgsfanasty View Post
Cool, I only know what a mechanic told me...and it seems logical to me that most folks ain't gonna want to give a lot of hp to a a/c system...it's my understanding that the RPMs is the most important factor, which is in the pulleys since 3600rpm is fairly common in small engines...
Condenser fans and evaporater fans wouldn't be affected by the compressor drive unit...they would still be DC voltage...that's my guess

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I cant remember what Joe said the RPM of his pony engine is.. its a diesel so likely lower.. but i think he is pl;anning to run his compressor between 600 and 900 RPM.. A/C on a bus takes much more horsepower than a car... 4-5 HP for a car system is correct.. a standard school bus. full length will be running somewhere above 100,000 BTU of A/C.. ive worked on a few ThermoKing systems that had dual compressors and are 120,000 BTU in an 11 row school bus.. thats close to 10 tons of A/C.. if you were talking about a building, thats one of those fairly large rooftop units..

https://cdn.shopify.com/s/files/1/15...g?v=1501334892

a regular car on average is 9000 - 12000 BTU.. Vans and suburbans have double that.

my 6 row Bluebird has a TransAir 45,000 BTU system in it.. decent insulation, white roof, tinted windows.. and on hot days in the summer south im definitely not roasting but im not lookinfg for a sweater..

once you insulate a bus, take out some windows, get rid of the passive ventilation, etc, the A/C requirements go way down. bit the road produces alot of heat.. you are still blowing a 70 MPH wind at your bus along a hot freeway with vehicles producing heat... front engine you have to overcome the fact all of the heat your own bus is producing is essentially being driven directly into.. RE at least your big heat producer is in the back.

when parked your A/C requirements of course are much less.. most people find nice shady places away from the road to park, no road or engine heat, and the wind isnt likely 70 MPH..
-Christopher
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Old 03-13-2018, 01:39 PM   #44
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Originally Posted by cadillackid View Post
I cant remember what Joe said the RPM of his pony engine is.. its a diesel so likely lower.. but i think he is pl;anning to run his compressor between 600 and 900 RPM.. A/C on a bus takes much more horsepower than a car... 4-5 HP for a car system is correct.. a standard school bus. full length will be running somewhere above 100,000 BTU of A/C.. ive worked on a few ThermoKing systems that had dual compressors and are 120,000 BTU in an 11 row school bus.. thats close to 10 tons of A/C.. if you were talking about a building, thats one of those fairly large rooftop units..

https://cdn.shopify.com/s/files/1/15...g?v=1501334892

a regular car on average is 9000 - 12000 BTU.. Vans and suburbans have double that.

my 6 row Bluebird has a TransAir 45,000 BTU system in it.. decent insulation, white roof, tinted windows.. and on hot days in the summer south im definitely not roasting but im not lookinfg for a sweater..

once you insulate a bus, take out some windows, get rid of the passive ventilation, etc, the A/C requirements go way down. bit the road produces alot of heat.. you are still blowing a 70 MPH wind at your bus along a hot freeway with vehicles producing heat... front engine you have to overcome the fact all of the heat your own bus is producing is essentially being driven directly into.. RE at least your big heat producer is in the back.

when parked your A/C requirements of course are much less.. most people find nice shady places away from the road to park, no road or engine heat, and the wind isnt likely 70 MPH..
-Christopher
Isn't the 100,000btu divided by 2? It seems possible to leave one the engine and run the house unit on pony...Idk...I'm just a wanna be, but if I buy a bus with the a/c I'd hate to throw away pieces paid for...

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Old 03-13-2018, 02:11 PM   #45
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Originally Posted by Jdawgsfanasty View Post
Isn't the 100,000btu divided by 2? It seems possible to leave one the engine and run the house unit on pony...Idk...I'm just a wanna be, but if I buy a bus with the a/c I'd hate to throw away pieces paid for...

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most everytime on a school bus you'll see the A/C in 2 separate systems on a big bus.. in my opinion, take out the rear system and keep the front.. so you have driving A/C, but dont lose the space or have head-bangers out of the rear units..

on a transit bus or a coach bus the systems are often one large compressor and the A/C is integrated either into the sidewalls with vents below the windows or is over-head all along the ceiling of the bus.. those type you pretty much can either yank the whole system or keep it and find a way to use it for both your parked and your road A/C.

some people dont drive their bus much(they are parked 90% of the time), or are always chasing the "ideal" weather.. keeping the road A/C ends up getting in the way of their conversion so it gets yanked out..

I only wish wish when the systems were yanked that more care was taken.. I and others could use more A/C parts.. I have a couple friends that are looking for A/C parts for their busses and seems everyone we talk to has just torn out their system and destroyed it in the process...

-Christopher
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Old 03-13-2018, 03:22 PM   #46
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most everytime on a school bus you'll see the A/C in 2 separate systems on a big bus.. in my opinion, take out the rear system and keep the front.. so you have driving A/C, but dont lose the space or have head-bangers out of the rear units..

on a transit bus or a coach bus the systems are often one large compressor and the A/C is integrated either into the sidewalls with vents below the windows or is over-head all along the ceiling of the bus.. those type you pretty much can either yank the whole system or keep it and find a way to use it for both your parked and your road A/C.

some people dont drive their bus much(they are parked 90% of the time), or are always chasing the "ideal" weather.. keeping the road A/C ends up getting in the way of their conversion so it gets yanked out..

I only wish wish when the systems were yanked that more care was taken.. I and others could use more A/C parts.. I have a couple friends that are looking for A/C parts for their busses and seems everyone we talk to has just torn out their system and destroyed it in the process...

-Christopher
Yep...basically those folks have no concept of how much money they are wasting...

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Old 03-13-2018, 03:24 PM   #47
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The AC is worth the space it occupies, no question in my mind.

When you think about installing a pony motor to drive an AC compressor, consider how much that costs and how long it takes to have been less expensive than just running your main engine.

I figured it would never pay off for me.
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Old 03-13-2018, 04:19 PM   #48
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The AC is worth the space it occupies, no question in my mind.

When you think about installing a pony motor to drive an AC compressor, consider how much that costs and how long it takes to have been less expensive than just running your main engine.

I figured it would never pay off for me.
That's the thinking of most folks...but IF a 4hp motor would work...(I couldn't get Google to cooperate with me, so here's a UK version)

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Old 05-01-2018, 07:08 AM   #49
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same here.. i could use another one in my DEV bus..

-Christopher
Christopher, Ive got a Trans Air unit I need to remove from my bus that you can have if you help me remove it and program my cruise to work while running down the highway.
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Old 05-01-2018, 07:30 AM   #50
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Christopher, Ive got a Trans Air unit I need to remove from my bus that you can have if you help me remove it and program my cruise to work while running down the highway.
good deal!. are you pulling all of the AC out of the bus or keeping some of it? was it a dual AC system?

whats your timeframe for wanting to yank it out?
-Christopher
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