Replace 1997 Mountain Aire A/C Units

[97MntAir3760]

I recently purchased a 1997 Newmar Mountain Aire 3760. I am upgrading/customizing the entire unit.
My next project is replacing the roof air. The current unit is a pair of Dometic Duo-Therm Penguins (Original). Is it possible to replace these with a pair of Dometic Duo-Therm Brisk II Air Conditioners (13500) (w/Heat Pump).
I am aware that there may be some issues with ducting? But I can fabricate most anything. I am a DIYer, R&D engineer with access to shop equipment and 3D printing.
Has anyone made this work and is it worth it? Is there a much easier path?
Most info I have found is 4 years or older.

Jerry

[hclarkx]

Originally Posted by 97MntAir3760

I recently purchased a 1997 Newmar Mountain Aire 3760. I am upgrading/customizing the entire unit.
My next project is replacing the roof air. The current unit is a pair of Dometic Duo-Therm Penguins (Original). Is it possible to replace these with a pair of Dometic Duo-Therm Brisk II Air Conditioners (13500) (w/Heat Pump).
I am aware that there may be some issues with ducting? But I can fabricate most anything. I am a DIYer, R&D engineer with access to shop equipment and 3D printing.
Has anyone made this work and is it worth it? Is there a much easier path?
Most info I have found is 4 years or older.

Jerry

Jerry, you sound like a candidate for a switch to a mini-split. They are a DIY project for sure! If you are not a dry-camper/boondocker, their huge efficiency advantage isn't worth much. But they are quiet. You would need to find a place for the outdoor unit and upper wall space for the indoor units. Lot's of RVers have pulled this off and all rave about it.

Just a shot in the dark from another DIYer.

["007"]

Welcome to the forum, Jerry
In the QT's links 1 & 2 and #3 you will find info for older coach's and in this one upgrades for what you also want to do.
The two remaining in my signature have info for older coach's also.
You may find interest in this thread also.
Good luck with your upgrades, enjoy the forum and safe travels when you do.

[Dutch Star Don]

Jerry....it's hard to remember how my A/C's worked 25 years ago. I think my Class C adjusted right at the unit, no wall thermostat. Depending on how yours work and how you want them to work may be different.

If you buy something that adjusts at the unit, probably pretty easy. If you want them to talk to each other and adjust at a thermostat, that may require running a phone line to each. You'll definitely need a new style thermostat that works with the new units. I've found in the past that PPL Motors Parts is pretty good about matching A/C units to thermostats.

[Luv2go]

Originally Posted by hclarkx

Jerry, you sound like a candidate for a switch to a mini-split. They are a DIY project for sure! If you are not a dry-camper/boondocker, their huge efficiency advantage isn't worth much. But they are quiet. You would need to find a place for the outdoor unit and upper wall space for the indoor units. Lot's of RVers have pulled this off and all rave about it.

Just a shot in the dark from another DIYer.

x2!

[97MntAir3760]

hclarkx,

Thanks for the suggestion on the splits. I wasn't aware that people were hooking these up in RVs. I definitely see the advantages. And I enjoyed reading up on them and looking at some of the builds. But I would be concerned about the outside unit as we are planning quite a bit of travel. Alaska is one of our destinations. (10,000 mi round trip, I made that trip 3x back in the 70's before I met my wife, 28' Champion) Concerned about the bouncing around and then coming up with an appropriate mounting location. Also I have existing ceiling ducting throughout configured for 2-zones. Not sure I want to give that up. My concerns are more around mounting issues and gasket design if I try installing a pair of brand new Dometic 13500 Duo-Therm Brisk II w/ Heat pump. I have the opportunity to get two of these locally for a very reasonable price. (Purchased for a customer then cancelled, still in the box) They both come with individual digital thermostats. I'm thinking I might replace my old 4 button 2-zone thermostat with the 2 separate thermostats.

[Luv2go]

With the mini-split's you'd definitely lose the ducting, though you can get a dual zone mini-split, just not sure you can get a 120VAC one.

The way the 4 button is wired you may or may not have enough wires going to each unit for single zone thermostats. You'll have a 4 conductor telephone cable from the 4 button thermostat to the front unit, then a 4 wire cable from the front to the rear unit. From the rear unit there will be a cable to the small sensor in the bedroom, that may only be two wires.

When I look at the doc for the Brisk Air I only see the CCC2 thermostat and the roof mounted manual controls, they don't have the single zone manuals available so I can't determine how many wires the single zone t'stat will need.

There is a thread on this forum where someone replaced their Penguins with Brisk II Airs, IIRC they had to do some kind of adapter which was fairly easily done in sheet metal. Newmar has some documentation on how to convert the older plenum which your 1997 may have to the newer style needed for Penguin 2, I believe this applies to Brisk II Air also. 007 will have most or all of this in his QT links posted above.

Note that most of those threads from 4 years ago still apply, the Brisk II Air's were designed before 2014 (I found a YouTube video dated in January 2014 on installation of one).

[97MntAir3760]

Plenum and bolt pattern is my larger concern. I also suspect I will have to modify the plenum, plenum and possibly drill new bolt holes in the base of the new air conditioners. I came across one upgrade were that was necessary on a NewMar. So far I haven't found a definitive answer to the plenum situation on a 1997 Mountain Aire class A 3760. And what was actually needed. I would like to find out before I tear off the old AC units.
As far as the thermostat(s) which the deal includes two new digital thermostats. My first thought is remove the old 4 button/2 zone comfort control with a digital unit and hopefully have enough wires to control AC 1 then run a new independent line for AC 2 and install the second thermostat possibly next to the 1st or possibly a different location. (Note there is a separate temp sensor in the bedroom).
Does anyone see a problem with this or would it be worth my while to sell the 2 single zone controls and invest in a dual zone CCC and run the extra wiring I need?

[Luv2go]

Regarding bolt pattern, bruceisla's post here indicates he did need to drill new bolt holes for three of the four bolts. This may be the post you're referring to. If I understand his post correctly, he drilled new holes in the roof, not the unit.

If you're concerned about changing bolt patterns within the Penguin line, the bolt patterns have not changed over the years. Even when they went to Penguin II the patterns were close enough that I used the existing holes to replace a 13.5K Penguin to a "High Capacity" (almost 15K) Penguin II. Dometic has a very good reason to keep the patterns the same, so replacement units are "plug and play" when a service person replaces units. Of course when going from Penguin to Brisk II they don't care as you're just supposed to buy another Penguin!

Regarding plenum, there is no doubt you will have to modify your plenum. Here's a link to a document from Newmar regarding plenums for the older coaches. I'm pretty sure your '97 uses the non-universal type, however simply pulling one of your units will confirm. bruceisla's post here shows Newmar has come up with plenum conversion instructions, complete with a part you can buy from them. It's probably for the "universal" plenum but on second look you probably can use their kit for the non-universal plenum also since you're ripping everything out including the dogleg. You may have to piece in some duct but that's pretty easy.

If the single zone t'stats use the 4 wire straight thru cable you should be OK, at least for the front unit. It would really help if Dometic or someone else had the single zone instructions. It is possible that you may be able to use the CCC2 T'stat with the single zone control boards in the new Brisk II units.

If you can post the exact part number of the Brisk II units I can try to figure out how these single zone controls work and whether you could use a CCC2 in place of them. You probably could pay for your CCC2 by selling the single zone t'stats on eBay.

If you do decide to go with the CCC2 you won't have to run any more wires though you may have to remove any telephone-style couplers as bruceisla did.

As bruceisla said, it'll be easier to replace the units with Penguin II's, replacing with Brisk II's was "a LOT of work". However, I suspect you'll save a ton of money with your approach and it may be worth it to you.

Note that the Newmar Comnet links may not work correctly, 007 has detailed an alternate way to get to Comnet here. The A/C technical documents I linked to are in "Top Level > HELP & REFERENCE > TECHNICAL INFORMATION > AIR CONDITIONING & HEATING > Air Conditioning, Ducting – Roof" section.

[97MntAir3760]

Luv2go,

Great information.
And Yes, the savings is considerable and the extra work doesn't bother me. I just want like to have an educated plan before I start tearing things apart.

This is the info I received from the seller.
Dometic AC model number 541815AXX1J0
Control board part number 3312022.000
Thermostat part number 3314082.000
RJ -11 cable

[Luv2go]

Looks like the control boards and thermostats are actually CCC2's! You'll be able to sell one of the t'stats and put the other in the place of your existing 4 button CCC and use the existing wiring and zone 2 sensor.

[97MntAir3760]

Thanks for the confirmation.
If, the information I received is correct this is good news. I came to the same conclusions. I may actually be set with the wiring and a spare thermostat to boot. So it appears the only real work will be the plenum and the mounting. Oh lets not forget getting the old units down and the new units up on the roof.
But that's why I had kids.... I hadn't even got it home before one of them asked me if they could borrow it.
Thanks luv2go It looks like I have a plan and will be ready next weekend. (Still working full time, but getting ready to call it quits.)

[Luv2go]

There are many ways to get the units down, including kids

We happened to have a pole of the RV tent that I could maneuver the coach under. We used a winch and some pulleys but with a couple of people at the end for weight a rope and pulleys could be used. The units are around 100lb, so they aren't easy. I didn't want to bring it down the RV ladder, too much weight with me and the unit.

[97MntAir3760]

Luckily I have a son and two son-in-laws still local willing to help. Our initial plan includes an extension ladder as a ramp and three (ropes/straps). Two on top on either side and a guide at the bottom. And myself...