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Roof mounted A/c on a hard top?

m109guy

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Nothing new if you are looking to do it.

MLVW's (Canadian M35's) have had them installed.
 
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clinto

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Blythewoodjoe

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I didn't get a picture of my rig, but in 2004, I drove the deuce to Aberdeen with a window unit mounted in the front rack of the cargo bed and run it from a generator I had in the M105 trailer. I just stuck it up to the rear window in the canvas cab cover. If I had used a bigger unit it would have worked much better. If I had thrown a mat in the floor to keep some of the heat out it would have been nice too. I have a diesel powered refrigeration unit that is mounted to the front of an old truck bed I have thought about rigging up to set in the back of a large M-series truck and pipe the AC to the cab. I could cut the truck off and run the unit while relaxing in the cab eating lunch. But then again, I have a dodge now and you can keep your 6 x 6 oven :twisted:
 

m16ty

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With 20 amps of 120 vac available, it would work.
That would be to down side to a RV unit.

I've seen roof mounted units mounted on old big rigs that was completly self contained. It used water and you had to add more water every day. Don't know how well it worked. I think it was made by Kaiser ( different company than the Kaiser that made MVs).
 

OPCOM

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I've been looking at this for 4-5 years now.. ever since the first time I drove the deuce from Dallas to Austin in July. These are my opinions on ths 'problem'.

First, I'd like to comment about the ice chest and fan combo. The amount of cooling needed for a space is expressed in BTU per hour. 12,000 BTU/Hr is called a "ton". This means it is equivalent to the amount of heat absorbed by melting a ton of ice to water. So, we can see that 50 LBs of ice in a cooler with a fan is going to make 300 BTU. Not per hour, that is total, then the ice is gone and you are just humidifying with water.

Next, the kind you have to add water to. This is a "swamp cooler" or water-evaporator and won't work well when the humidity is high because it adds humidity to the cooled space.

The unmodified deuce cab, by my calcs, takes about 3 tons to get it to 65 degrees in 100 degree weather at 55MPH (engine heat blast) assuming every hole is sealed. Adding 3/4" rubber foam insulation (Nomaco K-flex) on the floor and firewall, hardtop ceiling, and rear of the cab, as well as on the doors (inside them is possible?) could reduce this enough to hit 70 with 1.5-2 tons. Memphis equipment uses this material for insulation inside the cab. Major air leaks difficult to seal would be at the roill-down windows where they 'seal' to the top frame and the doors. Memphis could be considered somewhat of an expert at M35 cab cooling, because they do it for money. (they farm it out to a local custom A/C shop actually)

One must also be very diligent when looking at BTU claims not just for a self contained A/C unit, but for the pieces one might install to make a system. Thisis because there are standards and not all makers adhere to them. Sort of like the old hi-fi stereo ratings of "RMS power" and "music power".

I took this from Kysor's pages, but niether Kysor nor Red Dot seem to offer an all-electric A/C unit, meaning a compressor has to be mounted on the engne. DCAirCo does, but it is only 9000 BTU.


"Kysor’s published BTU ratings are based upon IMACA Standard 200. This standard was established to provide uniform methods, instrumentation, facilities, test procedures, and methods of calculations for conducting tests on vehicle air conditioners to determine their capacity and related performance. Kysor adheres to the purpose of IMACA 200. However, some competitors choose to list their ratings based upon other criteria. One such measure is 80°F wet bulb and a 36°F refrigerant. Based upon that method we have restated our performance ratings by unit in the right hand column below. Always attempt to determine how a competitive system is being rated prior to making any comparison. The IMACA rating should be used for condenser and compressor sizing."

I was considering using two self contained roof mounted units side by side to stay cool in Texas. Most take a full 25A. That leaves me with 10A reserve on a 60A alternator. This is why I have asked about more amps from an alternator in other threads. The units are pretty wide. How wide is the M35 hardtop? How much weight can it safely support without bending/cratering?

I found one model of totally self contained unit of the 24VDC 25A type. It is 9000BTU, so two would be needed in hot climates. They are 30" wide and have side vents, so side by side mounting could cause issues. This is the above mentioned DCAirCo DC9000 dc powered air conditioner.

I found a larger capacity one in the past, 13500BTU. - link is lost or gone..

There are separate DC-operated components available like a condensing unit which has to be mounted somewhere. One is the "Renegade Auto Cool".

From work of Devilman we also know that an A/C condenser cannot be put in front of the M35's radiator because it will dump too much heat there and overheat the truck. Devilman built up a custom truck with A/C - that would be a good thread to see.

Some rooftop units that include a condensing unit dump the heat out the back. If you have an M109 or an M35 with a shelter, there is alot of wind pressure behind the cab that could oppose the fan-forced airflow.

Some roof top units are designed to pressurize the cab to avoid sucking in dust, but any time you do that you are also blowing hard-earned cold air out any crack or hole.

How much do those 9000 BTU 24V A/C's cost? I did not see prices, which could mean they are high. It could be cheaper to use a big RV one and a sinewave inverter over-rated for motor starting. A 120V 10 Amp coleman 13500BTU model is about $650 1200W - that is right at 50 amps at 24V assuming a perfect inverter. That is alot of continuous amps from a 60A alternator.

In the end analysis, the most practical way to get lots on BTUs out of the cab is probably to:
1.) Mount the biggest compressor (displacement) you can find on the engine. This is important because the M35 engine turns slow unlike a 3000RPM cruising speed car engine, so a small compressor won't give as much cooling, especially while running 2000RPM and the like. Having the smallest available compressor pulley could help this.

2.) Mount a condenser under the truck or bed or somewhere like the passenger fender so that it will get lots of airflow.

3.) Use a roof top evaporator/cooling unit only if necessary. If you remove the passenger seat and install another driver seat, a large evap unit could fit between the seats leaving the roof clear (for RADARs, gun mount rings, etc..)

4.) Buy large, like 25,000 to 36,000 BTU and use an evap. with 400+ CFM. You can always turn down the A/C if it gets too cold, but you can't increase its mechanical capacity if it is not cold enough, especially when sitting idling at 800RPM in traffic in August.


Sorry to ramble on, this is just my opinion having had alot of hands-on with air conditioners in general including building two 120V units from piece-parts and having worked at the theory and engineering end of this M35 cab cooling problem for a few years. The fact that I have not yet installed an A/C in the cab means I'm still not satisfied with available DC powered solutions. But I'm pretty tired of waiting. It's a shame the military always seems to focus on putting heaters everywhere, but seldom considers air conditioning! Ask any soldier who's been to Iraq about that one.
 

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wreckerman893

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What about one of those units that go on front of the big van trailers. I scrapped three off the one I have.
One could be secured in the bed of the truck (deuce or 5 ton) and be powered off the stock alternator or an additional one if needed.
The cool air could be ducted to the cab.
As mentioned above the cab needs to be as sealed as possible.
Devilman did a frame off build. He was able to work the insulation issue from all angles while he had the cab suspended.
He used that foil backed insulation/noise deadner that the hot rod guys use that sticks onto the metal.
There are also aftermarket companies that make AC setups for hot rods/custom vehicles.
If there is enough interest one of them might decide to market a kit to the MV crowd.
In fact the heating and cooling unit could prob be made into one unit that would fit under the dash like the heaters that are in there now.
Just my rambling thoughts.
 

NDT

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Has anyone done the Red Dot installation on their truck, like the one that was discussed in the HMMWV thread? I called the local dealer and he said bring the truck in for a quote. I would like to have an idea how many $$$$ it will take so I won't have sticker shock too bad.
 

OPCOM

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This would be a great thread to post all pics and details of sir conditioning the cabs of these trucks. Devilman - can you take pics of where your condenser is?
 

Mark3395

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Here's an AC unit for your amusement... but would need to go into an old M35 gasser.

I was at a gun show years ago and a fellow had an old box with an auto air conditioner in it. A gasoline air conditioner.

What you did was tap off the gas line to the carburator.... run it into a box on the transmission hump where it entered an enlarged area and flashed to vapor in the box... and cooled the box. A fan blew through the box, as I recall, and the vapor , still hopefully contained, was drawn out a larger tube and into the carburator for consumption. I don't know how many BTUs it pushed, but I sure wasn't impressed with the possibilities of that box in an accident.

Still, I almost bought it for a few bucks just to watch friends shudder at it.

I'd sure like to put a nice discrete AC unit onto a deuce. Something easily removable and that wouldn't look like a swamp cooler. For that matter, it would be nice for somebody just to sell a decent set of insulating floor mats to restrain some of the heat coming through it.
 

tprthom

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You are here: Home -> Evaporator Units -> Roof & Floor Mount Evaporator Units -> UD-520 Big Truck Floor Mount Evaporator Unit
UD-520 Big Truck Floor Mount Evaporator Unit

Large Capacity Evaporator Unit! Steel Case!


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Price: $499.99
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Floor Mount A/C only evaporator with four round vents surrounded by Steel case for durability. Designed to sit between the seats, or the floor in the rear of a vehicle. The evaporator has four round louvers that can be pointed in all directions or closed off completely. The controls are located on the center of the unit. The evaporator has a three speed blower motor with a dual fan setup. The evaporator has approximately 310 CFM and 18000 BTU. The evaporator unit is compatible with R-134a and R-12 refrigerants.
The evaporator unit includes:
  • Three speed blower motor
  • Adjustable temperature thermostat
  • Evaporator unit mounting hardware
  • Expansion valve
  • Drain tube
  • Orings
  • Two rubber grommets
  • Available in 12 or 24 Volt
The evaporator unit measures: 13" wide x 9" deep x 19" tall
If you would like to add this unit to a complete kit please go to the complete kits page and select the make of your vehicle. In that selection we offer complete kits with "select an evaporator" option. Add this evaporator to your shopping cart, and select the kit for your make, add it to the cart and follow the directions for checkout.
This evaporator unit is manufactured in the U.S.A.




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