AC while towing

[casrad]

I tow a 27 foot Globetrotter with an F250.
Can I run the AC in the trailer while towing it?

[DKB_SATX]

Originally Posted by casrad

I tow a 27 foot Globetrotter with an F250.
Can I run the AC in the trailer while towing it?

Not without some effort. *IF* you have a 30A trailer with a front electrical inlet, you could run a generator in the pickup bed and (with a suitably secured shore-power cord) supply power to the AC that way. Alternately, you could convert to a giant lithium battery bank with a a big inverter and a roof full of solar panels and get several hours of AC off the batteries.

[moosetags]

It can be done, but it ain't easy. We carry a Honda 3000 in the back left corner of our pick-up bed. Our generator has an exhaust extension that goes outside the topper. We also have an exhaust fan in the ceiling of the topper. We have tried running the generator while underway and have plugged in the Airstream in order to run the air conditioning in the trailer. It works, but I can not get comfortable with the generator running in the back of the truck while moving down the road.

I think that the answer to this problem is just about here. I have been researching the new on-board power generators on the new Ford F-150 trucks. they offer a 7200 watt generator system built into the truck. This would be more than sufficient to handle the air conditioner on the trailer while underway. This would also be a great generator while boondocking or spending an evening in a WalMart parking lot.

Hopefully, these onboard generators will soon become available on 3/4 ton trucks in all of the brands.

Brian

[uncle_bob]

Hi

The A/C units really are not designed for operation while in motion. If you do this you will be a "beta tester" for this application. Maybe it works, maybe the A/C dies for some obscure reason. That's why they have beta testers

As noted above, you will need a *lot* of power to run the A/C. That's got to come from somewhere. Either you set up a generator in the TV or:

1) Put a second alternator on the TV. Something in the 400 to 500A range should do the trick.

2) Run wiring back to the trailer that is adequate for > 300A at around a 1/2 V drop in each leg. ( so 1V total ). That sounds like a lot of drop, it's already a giant piece of wire. (4/0 likely isn't big enough ...).

3) Put in an inverter that will do 3KW full time. You will not *run* 3KW all the time, but that's the category you need to shop for. The beast will be running a lot of power for a very long time.

More or less:

Figure the A/C pulls 16A at 120V running, that's right at 2KW. If the inverter is around 80% you are up to 2.4 KW running. Cable drop likely gets you to 2.6 or 2.7 KW.

2.7 KW at 11V will be close to 250A. Starting surge will be higher than that, likely by 1.5 X even with a soft start. Alternator will see nearly 400A at times.

That all sounds pretty easy ... but ... what happens when you pull up to a stop light. Truck goes down to idle. Alternator max output is now < 250A (probably much less).

How long are you at idle? Are you stuck in traffic? Could be a while.

So now you need batteries that will put out a couple hundred amps without complaining. Figure four 100AH lithiums. (Yes, you might get by with three).

I would suggest that the generator sounds like a more practical solution ....

Bob

[Belegedhel]

Originally Posted by casrad

I tow a 27 foot Globetrotter with an F250.
Can I run the AC in the trailer while towing it?

So, why would one want to run the AC in the trailer while underway?

[uncle_bob]

Originally Posted by Belegedhel

So, why would one want to run the AC in the trailer while underway?

Hi

Because it's 104 out and we want it cool back there when we get to the campground .... ( at least that would be my guess ).

Bob

[az-streamer]

Knowing what we do about Airstream construction and the quality of various components (ie: air conditioner), what might be the results of operating the a/c while traveling at 65-75 mph?

Does the Airstream/vendor warranty cover use at highway speeds?

Is it even legal to have a truck:bed generator in use while driving?

BTW:
I can't even get my pillows to stay put on the road.

[ITSNO60]

A lot of motorhomes run the roof air off the on board genny while traveling, and they use the same AC units as many trailers use including Airstream. I can't see a problem, if anything the extra airflow over the condenser might make them more efficient. In fact I recall some posts here a while back of people doing it. If anyone can think of a good reason not to do it, I'd sure like to know. It's no fun arriving at camp and having the temp inside 90 or 100 degrees which is not uncommon in the South and deserts, and it takes hours to recover. BTDT.

[rbs]

the correct answer is no

[pteck]

Originally Posted by ITSNO60

A lot of motorhomes run the roof air off the on board genny while traveling, and they use the same AC units as many trailers use including Airstream. I can't see a problem, if anything the extra airflow over the condenser might make them more efficient. In fact I recall some posts here a while back of people doing it. If anyone can think of a good reason not to do it, I'd sure like to know. It's no fun arriving at camp and having the temp inside 90 or 100 degrees which is not uncommon in the South and deserts, and it takes hours to recover. BTDT.

Agreed. The very same rooftop A/C units and thermostats are run enroute all the time on Class A, B, and C RVs.

No reason it can't be done on an Airstream if a proper power supply is routed.

[uncle_bob]

Originally Posted by pteck

Agreed. The very same rooftop A/C units and thermostats are run enroute all the time on Class A, B, and C RVs.

No reason it can't be done on an Airstream if a proper power supply is routed.

Hi

While MH suspensions are *not* super duper, they are *way* ahead of the suspension in your trailer. The level of knocking around the A/C will "see" going down the highway will be worse in a trailer. Is that significant? Who knows ....

Bob

[n2916s]

I suspect the folks that are prototyping the installation of a propane fueled generator in the spare tire space will have the answer for us soon.

[Foiled Again]

Again, with newer remote control fantastic fans, pull in to your camping space, open the trailer door, start both fans at highest speed, and step out leaving only the screen door closed. You can plug in the power cord, level up, and go into a trailer that has already reached ambient temperature. The A/C will bring down the heat the rest of the way by the time you have finished setting up your campsite.

[Bcc75]

I'm like others in saying that I just I just don't feel comfortable with something like the A/C with its moving parts(fan/compressor) etc, running while traveling.
With a motorhome, you can set a glass of water on the counter while traveling and it won't spill. Try that in an Airstream.

We just got back from a trip to Disney/Ft Wilderness in Orlando FL. On our arrival day at the campground, at 1:00 in the afternoon it was 93 degrees and high humidity. I have a 25' with one 15k A/C. As soon as we arrived I ran the fantastic fans to suck some of the hot air out and turned on the A/C.
I also bought one of those cooling towers from Amazon for $79.


Turned it on high, in oscillating mode to help circulate the air. Within 2 hours the inside temp was down to 75 degrees. At night we had to turn the A/C off because it was freezing. The cooling tower was the single best purchase that we have made for the Airstream for hot weather camping.
The key that most people don't realize is that it's the circulation of the cold air within the trailer that cools it down.
I was nervous about my decision to only go with one A/C , but now I am convinced that it will suit our needs just fine.

[LilPeanut]

I did it on Monday. I have. Victron multiplus that provides enough converted power from 600ah of batteries. It was hot and I was headed to Tampa from Savannah so cooling things down before I stopped was the reason.

Even with all that and 1000 watts of solar, I only do it for an hour or two or until my battery bank gets to 50%, then I stop and hope that was enough to cool things down to the low 80s. The ACs seem to be ok, I figured they were the same as class A, B or Cs. But it might wear out my squirrel cage sooner if it bumps or scrapes. I also have a 40A Dc to DC charger but when the sun is out, the solar really pull in the watts.

Remember to close your shower vent and the cooling down works better. Don’t know why I mention that, just sayin.

[LilPeanut]

Only my front AC is ‘inverted’. My rear AC is passed through and requires shore power.

[DKB_SATX]

Originally Posted by Bcc75

I'm like others in saying that I just I just don't feel comfortable with something like the A/C with its moving parts(fan/compressor) etc, running while traveling.
With a motorhome, you can set a glass of water on the counter while traveling and it won't spill. Try that in an Airstream.

We just got back from a trip to Disney/Ft Wilderness in Orlando FL. On our arrival day at the campground, at 1:00 in the afternoon it was 93 degrees and high humidity. I have a 25' with one 15k A/C. As soon as we arrived I ran the fantastic fans to suck some of the hot air out and turned on the A/C.
I also bought one of those cooling towers from Amazon for $79.


Turned it on high, in oscillating mode to help circulate the air. Within 2 hours the inside temp was down to 75 degrees. At night we had to turn the A/C off because it was freezing. The cooling tower was the single best purchase that we have made for the Airstream for hot weather camping.
The key that most people don't realize is that it's the circulation of the cold air within the trailer that cools it down.
I was nervous about my decision to only go with one A/C , but now I am convinced that it will suit our needs just fine.

You had to turn the AC off because it got too cold? Does your thermostat not work properly?

[pteck]

Originally Posted by uncle_bob

Hi

While MH suspensions are *not* super duper, they are *way* ahead of the suspension in your trailer. The level of knocking around the A/C will "see" going down the highway will be worse in a trailer. Is that significant? Who knows ....

Bob

The A/C equipment won't care. These very same units are used in so many more applications and vibration prone environments than our Airstreams. They are designed to be used underway, against vibration and environmental factors.

Again, get the power part of the equation figured out, and it'll work just dandy.

[Bcc75]

Originally Posted by DKB_SATX

You had to turn the AC off because it got too cold? Does your thermostat not work properly?

The thermostat is about 4 degrees off(high)The remote sensor is in that notorious spot right beside the fridge compartment that holds a lot of heat. I insulated it enough to get it to within 4 degrees. Before I did that it was 20 degrees off. By turning off I meant setting the thermostat high enough that the A/C wouldn’t come on unless it warmed up in the trailer a lot. The Oscillating cooling fan was more than enough at night once the trailer cooled off.

[uncle_bob]

Originally Posted by Bcc75

...

We just got back from a trip to Disney/Ft Wilderness in Orlando FL. On our arrival day at the campground, at 1:00 in the afternoon it was 93 degrees and high humidity. I have a 25' with one 15k A/C. As soon as we arrived I ran the fantastic fans to suck some of the hot air out and turned on the A/C.
I also bought one of those cooling towers from Amazon for $79.


Turned it on high, in oscillating mode to help circulate the air. Within 2 hours the inside temp was down to 75 degrees. At night we had to turn the A/C off because it was freezing. The cooling tower was the single best purchase that we have made for the Airstream for hot weather camping.
The key that most people don't realize is that it's the circulation of the cold air within the trailer that cools it down.
I was nervous about my decision to only go with one A/C , but now I am convinced that it will suit our needs just fine.

Hi

Even with one A/C running, in most situations we can cool the trailer pretty fast. If it really *is* over 100F inside and out, then the dual A/C comes in very handy. I don't ever remember any situation that it took more than 2 hours to cool down the trailer.

Indeed there are a few "details" associated with that claim:

1) We put out the awnings. They make a *big* difference if you are in direct sun and there's no breeze at all.

2) We pull down the shades to help things. Even with the awnings out, this helps the cooling.

3) We use a couple of small 120V AC fans in the trailer. They also get used when the AC is not running (if we have shore power).

4) For us "comfortable" is as much about humidity as temperature. 80 and dry is way nicer than 75 and 90% RH.

If we run the A/C at night, it's never both units. We run the unit that is the furthest from the sleeping area and let the ducts do their thing. That works very well for us. Probably *not* the most efficient approach. We also run at least one of the little fans to move air at night.

Heading back to somewhere near on topic:

One could argue that most of our usage is a single 15K BTU unit. That's true most, but not all the time while running A/C. Most of the time we don't run A/C at all, so most of the time while running A/C is a pretty good percentage. The gotcha is that 5, 10 or 20% of the time that it *is* so ghastly hot out that you need them both. Then we're up around 28K BTU.

Efficiency does not help in the case of "need 28K BTU". It simply means you get things done while pulling less power off the pole. Is the magic number 28 or 25? We could debate that for a lot of days. It's significantly more than 15K, I have data on that.

So, if you are Airstream, you need to put 2 mini splits into a trailer. You still need propane up front. You still need this and that here and there. It's going to take a pretty significant redesign of the inside of the trailer ....

Bob