Beast Method to Heat and Cool a Cargo Trailer?

Most economical way is to do nothing.

What conditions do you want to maintain? Or better yet, what conditions are you trying to avoid?

I would guess a small window or ceiling fan from an RV dealer would work fine.

Your title had "Beast Method . . ." so I was going to offer my ex-wife.

park in the shade.

Bottom vents, with a small blower, air in one side, air out the other. A small fan will do.

cheap.

You mean you want to cool it when it's hot and heat it when it's cool...hmm?

Bury it underground, deep enough & the temperature will remain stable year-round.

There are combination heating / cooling units available for boats, you could put one of these into the trailer somewhere. You're going to have to do something for the heat exchanger as the boat types use water. Other than that you would have to get a rooftop unit for a typical RV. There are aftermarket types available but I don't know if they heat and cool.

It's going to be freaking expensive to maintain any kind of temperature without insulation though. Maybe it would be better to build an insulated pole barn to put the trailer in? Just remember to put hot water heat in the concrete slab so your feet don't freeze in the winter!

Go to an RV store and they should have a system available. I always used a portable oil filled radiator ($40) in the winter, but did not use anything other than fans to cool.

Is the R-5 a foam insulation or other? this also makes a difference in how much heat or cool load is on the trailer.

You could also look at old reefer boxes, if you want to get a cooler that you could hang meat in. You're not a traveling serial killer, are you?

the best and most economical way to "heat and cool" this unit?

REPLY: "best" and "economical" are mutually exclusive terms. <grin> However if you are not trying to maintain living room comfort at one fixed temp level I suggest your first line of defense is a shade awning about a foot or so above the trailer.

When this is done on boats we find the cooling load on the air conditioning is reduced by some 20% . To reduce any accumulated humidity have lots of ventilation. Solar panels to charge a battery and power a 12V fan like the Maxi vent sold for RV use is fairly efficient. Remember to keep the solar panels out in the sun and not under the shade. < grin>

If the trailer is aluminum can you polish it like the old Airstream trailers. That would help reflect a lot of the sun's heat away from the trailer interior. A local trailer builder paints his trailers gloss black. These get brutally hot in the summer. Not recommended.

For air conditioners, look at mermaid brand marine air conditioners. The company is in Ft Meyers FL. This company has done research into energy savings specifically to run their product on inverter and one or two 8D truck batteries overnight.

My clients who use them are happy. They are water cooled so you will need 25 times as much heat exchanger area to cope with dumping the accumulated waste heat using air flow only.

Reverse cycle heating stops working below 45F. Colder than that requires some form of resistive heater strip. So a reverse cycle unit is pointless.

I don't know why you need to heat and cool a "cargo trailer" if you are not using it for a temporary living environment, so it is hard to recommend "how much" heating/cooling you need.

It seems that for travelling you are not (legally) allowed to have any humans in the trailer anyway, so a simple ventilation system should keep summertime heat to a minimum. Take advantage of the air stream while travelling. Install simple screened (to keep the bugs out) vents or even a home rooftop style unpowered turbine ventilator on top taking advantage of natural convection. Any powered equipment while travelling is sure to put a serious dent in your fuel economy and who wants that these days! If you REALLY need on the road A/C then the RV units are probably your best better, engineered for best efficiency when operating on DC. Unless it is freezing and you have precious cargo that cannot drop below 32°F (0°C) I would fore-go heating on the road. Lots of 12VDC "Car Heaters" are available if you really need it.

For parked use, take advantage of the AC power. Sam's Club (www.samsclub.com) has a nice selection of portable A/C units, some with built-in dehumidifiers (which utilize condensed water for extra cooling efficiency, exhausting the vapor with the hot air) or with built-in heat pumps (more efficient than resistive heaters). These are usually on rollers, so you will have to lash them down and mount the exhaust tubing to a hole in the side or bottom of the trailer.

One of these A/C dehumidifiers, the Amcor ALD12000M indicated that its A/C cooling power consumption was 950 watts / 9A @ 110 VAC for 12,000 BTU of cooling. So you could run it off your inverter. Of course, these units are intended for inside usage, such as a computer room, so "your mileage may vary". Speaking of which, if you run these mobile, you will probably need to stop for fuel more frequently!

Since you mentioned that 115 AC was available, I am assuming that this is for maintaining a reasonable temperature when it is parked and stuffed with household overflow. The awning idea is a great start. Using a silver tarp over the top is cheap and useful. Temperature drop will be minimal at best and it will not address humidity (don't forget mold). So much for the easy way.

Pick an area on the floor that will be as out-of-the-way as possible. If you can, choose a spot just behind a frame member to prevent road water from splashing in. Drill a number of 1/2" holes in a 3" dia.You can then install a plate from the frame member to the underside of the floor to shield the holes. Don't forget the mesh screening to prevent spiders etc. Mount a muffin fan, flow rate and voltage of your choosing, on top of the holes. Box in the fan with a perforated heavy duty enclosure. If the fan is at one end of the trailer, install a small shielded vent somewhere on the wall at the opposite end. Try to get a cross-flow going. DON'T cut into the roof for a vent unless you are going to install air conditioning. Even though good roof vents are available, there will come a time that the vent is left open and is struck by a tree or a blowing rainstorm. Been there, done that! Besides the size of your trailer doesn't warrant it.

For heating, I would go with the previous suggestion of a cheap oil filled portable radiator. Even if something like a blanket fell on it, it won't be a problem, assuming you only need enough heat to keep only a bit above freezing. A 100W light bulb might be enough in an enclosed space, believe it or not, as long as it won't overheat anything near it. I have put a 100W bulb under my car hood about 1' from the battery on 0 F nights. Makes a big difference. Don't forget to plug up the top vent.

Thanks to all for the " interesting " input.

And thanks for the thoughtfull responses, Help is always appreciated

One of these days I will learn that I must proofread and not simply rely

on spellcheck. That way the "Beasts" are kept at bay.

One of these days I will learn that I must proofread and not simply rely

on spellcheck. That way the "Beasts" are kept at bay.

I find it amazing that CR4 had such restraint on your typo that only one poster made reference to it, and that was only in a humorous , non-critical way. Typically, some people would be all over such a flub, particularly in the title of the thread!

Probably since we'll be next. Spell check has it's problems. What gets me is when even spell check isn't used.