Supporting two air conditioners

[JoleneAS]

Hello. My millionth question here it seems, but not finding the answers through searching. 27’ Overlander currently gutted with an old duotherm AC. I am in the process of removing this and am hoping to install two separate Dometic Penguin II AC units (13,500 btu with heat strips). I’m noticing that the current AC install site is placed between two ribs that are spaced closer together than most of the other ribs. I’m not sure if this is to help support the air conditioner, or unrelated. Also, the configuration on the roof is two vents up front, AC in the middle, and a vent in the rear. I plan to use a Maxxair Maxxfan in the frontmost and rearmost vent holes, and place the ACs in between. I can put an AC in the middle vent hole, but this will not give enough clearance for the other AC if place in the existing AC hole (if that makes sense). Thus, the way I see it, I will need to place a sheet of aluminum over the existing hole (or 14” skylight) and cut a new hole for the rear AC.

Are there any guides to cutting in the second AC as far as where exactly to place the hole and how to properly support both of these 100 lbs units?

I can post a diagram if I’m not explaining this well. Thanks!

[OTRA15]

Originally Posted by JoleneAS

. . .
Are there any guides to cutting in the second AC as far as where exactly to place the hole and how to properly support both of these 100 lbs units?
. . .

This would require the expertise and judgment of a very skilled Airstream mechanic, with the necessary tools and shop to do the work right. [IMO] The work required [cost] may outweigh the benefit? With your gutted interior, however, adding new ribs and ceiling frames can at least be done without much further demo.

What did the old AC weigh? The addition of extra weight may be more than your trailer's roof can bear IMO. Keep in mind that, when bouncing down a bumpy road at highway speeds, the forces generated by extra weight in the center of the roof are geometric or exponentially greater than the extra weight.

Good luck,

Peter

[JoleneAS]

I see, thank you for the helpful reply! So when people have these threads about 1 vs 2 air conditioners, it’s orimarily for Airstreams that are designed with two air conditioners in mind from factory, or those that have been outfit with extra ribs? That’s a bummer but makes sense.

[JoleneAS]

It’s funny, I see post after post of people recommending two ACs on vintage Airstreams, “two is the only way to go!” Yet I am hard pressed to finding anything discussing the logistics of this or even so much as a photo of two AC units on a vintage trailer. I might not be searching properly.

[OTRA15]

Older Airstreams were usually not designed for 2 AC, and do not have the proper roof structure to add 1 AC IMO. You are probably searching well, but the "2 AC" well is empty!

[JoleneAS]

I’m wondering something. On my frontmost vent there was wood that was underneath the skin, apparently to support the tv antenna maybe? Anyways, looking at this, it made me wonder if the weight of an air conditioner could be supported if I ran a couple pieces of aluminum bar across, sort of like how that thin piece of wood spans the two long rails that extend down the center of the ceiling. Would that be enough to support a 100lbs air conditioner, or does that seem like it’s just too much weight without adding an extra rib?

I don’t think I’d be up to the fees associated with adding a rib, but if I could just get away with some cross members to support it, I might be cookin.

Oh and as for the weight of my current AC, it’s still attached so not sure just yet. Per the shroud it’s a Duotherm Quick Cool, but there’s no info about this unit online.

[gklott]

Two 13,500 BTU AC units should mean 240/120V 50A shore power service. Is this also in your renovation design?

73/gus

[harryk]

You are somewhat near Colin Hyde Airstream Restoration...I would consult him and you could take it to him for just the reinforcement.

[JoleneAS]

Originally Posted by gklott

Two 13,500 BTU AC units should mean 240/120V 50A shore power service. Is this also in your renovation design?

73/gus

Yes, definitely have 50A service in mind.

[JoleneAS]

Originally Posted by harryk

You are somewhat near Colin Hyde Airstream Restoration...I would consult him and you could take it to him for just the reinforcement.

Isn't Colin Hyde in New York? I'm in Oregon.

[T2Airstream]

I solved the issue of adding a second and third AC to my 31' Excella 500 by purchasing two 14,000 BTU Black/Decker portable heat pumps for under $500 each. Located one in the rear and the other in the front. Secured to floor with tie down straps, and ran separate 115 VAC 20A power cables behind the cabinets. We camp in central Texas and now have complete control over the interior environment of our AS.

[OTRA15]

Originally Posted by T2Airstream

I solved the issue of adding a second and third AC to my 31' Excella 500 by purchasing two 14,000 BTU Black/Decker portable heat pumps for under $500 each. Located one in the rear and the other in the front. Secured to floor with tie down straps, and ran separate 115 VAC 20A power cables behind the cabinets. We camp in central Texas and now have complete control over the interior environment of our AS.

How do you remove the hot discharge air from inside the AS? Air conditioners are on the roof mainly for that reason.

Thanks,

Peter

[T2Airstream]

Originally Posted by OTRA15

How do you remove the hot discharge air from inside the AS? Air conditioners are on the roof mainly for that reason.

Thanks,

Peter

Peter,

The exhaust was vented through the floor to the underside of the trailer. I purchased a through the wall/rain proof vent from Amazon to supply fresh air to the condenser. Send me an email address and I'll send pictures of the installation.

Tom

[T2Airstream]

Originally Posted by JoleneAS

Yes, definitely have 50A service in mind.

Renovation of the electrical system was part of the project. I installed a 4-prong weather-proof electrical receptacle on the outside of the trailer and mated it with a new electrical panel inside. Since the trailer doesn't have any 230V appliances, the panel was laid out as two 120V 50A feeds with the first unit being connected to the first 120V leg, and the second connected to the second 120V leg. At the end of the day the trailer actually has 100 Amps of 120V service, more than ample for the two ACs, electric stove, electric hot water heater, charging system, simulated electric fire place, sound system, video system and internet system, with plenty of current left over. Going totally electric eliminated the need for bottled gas and it's cost and potential for accidents.

Tom

[JoleneAS]

Thanks for the info, T2Airstream! Can I bug you for some photos of your setup too?

[Starstream]

Hi, JoleneAS

What made you decide on the Penguin II to replace your old AC & to possibly add one as a second unit? There are different brands/models with some variances in physical dimensions, weights & footprints. Dometic alone has a “few” different models. Another model might allow you to add a second AC without too many adjustments to structure, if it weighs less & its weight is properly spread over the immediate area. Though you’re probably better served just getting 1 AC & maxing out the BTUs. Is your project going to continue being a “travel” trailer? Then there is a bigger picture which you really shouldn’t lose sight of, whether you’re replacing old/worn out or making significant modifications. You do have to keep the overall weight of your finished trailer in mind, to stay within the limits of your tow vehicle. Sure, your vehicle can pull something. But it’s more important to stop that something safely, especially in less than ideal situations. And there are plenty of less-than-ideal situations to be encountered when you’re on the road.

The whole environmental comfort issue should ultimately be addressed by more than one system/product you will use in your rebuild. Types of insulation and the “real” effectiveness of potential roof cooling products being two of the biggest. Both in amount of real estate they cover, and number of threads discussing them. If you haven’t looked at any of those yet, consume them in small doses. Otherwise, it’s enough to make your head spin, to the point where you might find yourself feeling queasy. Don’t forget using your surrounding environment to your advantage either. One of many examples - even in a sticks & bricks house benefits from a shade tree or 2 to help manage the electricity bill.

One other thing to look at…

There is a beef I’ve found on the forum concerning the Dometic air distribution box, which you may want to be aware of before deciding on any AC. Some people are happy with the performance of the ACs themselves, but complained the air isn’t being properly distributed between the front & back of their trailers. One or two of them got creative & made their own modifications.

[Starstream]

This not to pick on T2Airstream, please don't construe it that way.

When we got our trailer, my husband suggested making it all electricity. I nixed it, since the experience of living in an all electric house after Hurricane Ike (2008) was still fresh in my memory. We had no power for three weeks, therefore no appliances. There wasn't power here for a few days after Harvey either. We were in the Black Hills with our trailer & missed out on that one. Did get to experience an area power outage in the Hills last year though. No AC for a while, but I could still cook dinner (& bake) with our pretty little propane Dometic CU-434 range. How big a generator will you need to run an all electric trailer during a power outage?

Neither electricity or gas are benign energy sources. Both require common sense & understanding of their safe use to prevent accidents. Never take either for granted. Even when on the road you still have use 12V electricity to operate your signal lights & breakaway switch. If there is a damaged wire in the system you're unaware of, you have a fire hazard. The propane should be turned off at the tanks while your trailer is moving. A hefty aluminum propane cylinder is also harder to damage than steel.