Installing a 2nd Air Conditioner

[scottkeen]

I have a 2011 Montana Mountaineer 347THT. It came with only one 15,0000 BTU Coleman-Mach air-conditioner in the main (center) area. This actually does a great job of cooling the entire coach.

But I'd like to add a 2nd air-conditioner, in the hole in the roof of the bedroom. There's a circuit breaker labeled "AC2" so I assume it's pre-wired for a 2nd AC (Yes, there's also a circuit breaker labeled "AC" for the main AC).

I'm happy with the Coleman-Mach and I'd like the 2nd AC to also be a Coleman-Mach.

1. Should I get a 13,500 or 15,000 BTU AC for the bedroom? My reasoning for a 2nd AC is in case the main AC konks out. I'm only 1-year old with RVing and I'm learning that things break on RVs. I don't want to be somewhere without cooling if the main AC konks out.

2. Is this easy to install? I'm handy. I can install a toilet. I can change disc brakes. I can hang drywall. I can't replace a transmission. Is this just a matter of removing the vent in the bedroom and there will be the AC2 circuit wiring there ready to plug into? Then I just mount the rooftop unit with some sealant and secure it with the bolts through a ceiling AC cover plate on the inside?

3. For the Coleman-Mach, what parts or install kit do I need? Is it worth also getting the heater strip?

Thanks

Picture: This is a cover plate on the ceiling near the bedroom ceiling vent.

[prndl]

I installed a second A/C in the bedroom just like yours. 13K is more than enough for the bedroom but 15K will work with fans to blow into the lower area.

Unless you want to go thru the aggravation of connecting to the ducting I would just block off all four sides of the hole between the roof and ceiling and install an A/C that blows just into the bedroom, either down or to the side or both.

I installed an additional thermostat for the new A/C by the other one but it really is not necessary. Just get an A/C with the controls on the cover and that is good for the bedroom.

Wiring is simple from the access plate you show. Follow the instructions for the roof seal and bolt tightening. setting the A/C in place is not hard since you can see the hole from the ceiling and get the unit and seal in position.

I rented a pallet lift at the local equipment yard to raise the A/C up to roof level. You could also slide it up a ladder leaning against the trailer. And you could also have it slide off the ladder or drop it

I have only used it twice since installing it but it's always better to have it when needed than not having it and needing it. Bit additional fans the upper unit cools as well or better than the ducted lower unit.

p.s. I don't know how to remove the emoji on the header!!!

To remove the icon: Edit the post, select Advanced, and then just below the text is a box labled "Post Icons" Click on the "No Icon" button and poof, the previous icon is gone.
P.S. I did it for you as too much time has elapsed for you to edit the post
Carl n Susan

[BB_TX]

I had a 13.5k A/C installed in ours. About the only time I ever use it is after a long travel day in hot weather to cool the trailer more quickly before nighttime. Once cool, we turn off the 2nd unit and the main 15k keeps it cool, even if the next day is still very hot.

[scottkeen]

Thanks! Sounds like 13.5K is the way to go and that it's pretty much going to be DIY.

I don't need it, but I really want it if the main 15K unit konks out.

Sounds like the hardest part is going to be getting it to the roof. It's around 80 lbs. I live in a condo and my Montana is kept in storage at a campground, so I'll have to do the install at the campground. Maybe I can get a campsite neighbor to give me a hand getting it up the ladder onto the roof.

I didn't know there would be duct work connections in the 4 sides between the roof and ceiling in the 14x14 hole. I was planning to just blow the air directly down into the bedroom, but I'll tie into the duct work if it's already there.

Question 1: Was everything you needed in the box? Was there a roof gasket and do I need one? One of the online retailers sells a universal roof gasket seal, wasn't sure if I need it or not. https://www.adventurerv.net/coleman-...al-p-4566.html

Question 2: Which Coleman-Mach unit did you guys get? I'm leaning to getting the Mach 3 PS (Power Saver) which is $100 more than the Mach 3 Plus. I figured if I'm ever going to install a bank of 100Ah Lithium Iron Phosphate batteries and solar and attempt to run AC off batts (it can be done!), then I'm going to wish I spent the $100 for the Power Saver model.

[twindman]

I have a 13 Mountaineer. I also added a BR A/C unit. A point about fans blowing into the main living area - Our thermostat is in the hall and if you are running both A/Cs the cold air from BR will turn off the living room unit unless you set it WAY down. And like you said, I don't think our older units had duct work in the bedrooms to feed the living room.

As for the main A/C, it won't keep the unit cool if outside temp is much over 80 - perhaps 85. Of course DW likes it around 73 or 74, so that makes a difference!!!

[scottkeen]

Originally Posted by twindman

I have a 13 Mountaineer. I also added a BR A/C unit...<snip>

That's a very interesting point about the cold air blowing from the BR AC onto the thermostat in the hall (mine is right above the stairs), causing it to shutoff the main AC, unless you set the desired temp very low. Seems like they put the thermostat in the wrong spot!

I guess I'm glad that there isn't duct work in the BR AC hole to have to mess with. It would have been nice though, to have both ACs feeding into the same duct work.

Which AC unit did you buy for your BR in your Mountaineer? Any issues, tips, tricks, gotchas?

One concern I have was with choosing a standard height AC. I think it raises the overall height clearance for the RV. I think the height slopes down from fore to aft. So adding the AC to the BR would become the new high spot. For that reason, I was thinking I should get a low or ultra-low profile AC for the BR. What did you do?

[prndl]

There is ducting in the bedroom from the rear A/C unit. The OP's unit may or may not be connected to the opening, just a heads up.

OP make sure you are ordering a low profile A/C unit or you may not fit under the benchmark Zion Tunnel.

[scottkeen]

Originally Posted by prndl

<snip>
OP make sure you are ordering a low profile A/C unit or you may not fit under the benchmark Zion Tunnel.

I just posted ^above about that. Yeah, so when I'm looking at the various ACs and heights for Coleman-Mach, this is what I've found for height:

Mach 3 Power Saver = 13.8"
Mach 3 Plus = 13.8"
Mach 10 (low-profile) = 11.8"
Mach 8 Plus (ultra low-profile) = 8.25"

Only a 2" difference from the standard height to low-profile, but a much greater 5" difference to the ultra low-profile.

Are you serious about needing to try and save the 2" or 5"? The sacrifice, besides money, is that the Mach 3 Power Saver uses 3.1 amps and 400 watts LESS than the ultra low-profile Mach 8 Plus.

[prndl]

We posted at the same time.
You could always measure your rig while hooked up to see how much height you can add safely.

I installed a low profile Mach on my former 5th wheel and when it was running it sounded like a Cesna was on the roof. It was a newer model with the "fan fix" already on it. It bothered me under the awning so I know it bothered my neighbors. It was as annoying as the sound of the motorhome A/C underfloor unit I was camped next to.

[twindman]

I forgot to comment on height. I got a 13.5 low profile. It is whatever camping world sells. I am a little front high to start with, and when measured at the rally, I think it was 13'4 or 5". So yes, you need a low profile and maybe the 'Ultra'.
Good luck.

[scottkeen]

I would have preferred to get the standard height 13.8" Mach Power Saver model as it would be better to use for dry camping with Lithium batteries and solar, but if height is really an issue then the Mach 8 Plus is 8.25"

Coleman-Mach says: "The Mach8 has the lowest profile in the industry measuring in at 8 inches tall."

My rig is currently 12'9" tall to the top of the main A/C. But the roof under the main A/C is lower than the roof over the bedroom.

[scottkeen]

With you guys talking about tunnels and low-profile, maybe I really don't want to add to my RV height at all.

Maybe it just makes more sense to get a portable indoor A/C that I can roll out of the closet and use if needed. A portable 14,000 BTU A/C uses 1,370 watts and 12 amps and costs $400 bucks. If I can trace the AC2 circuit wiring in the ceiling for the BR AC unit, I can install an outlet on the wall so it uses the AC2 circuit instead.