Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×
 

Go Back   Montana Owners Club - Keystone Montana 5th Wheel Forum > MOC Technical Forums > Additions & Improvements
Click Here to Login

Reply
 
Thread Tools Search this Thread Display Modes
 
Old 04-03-2019, 06:49 PM   #1
mtlakejim
Montana Master
 
mtlakejim's Avatar
 
Join Date: Oct 2017
Location: Bee Branch
Posts: 2,620
M.O.C. #20693
Adding a third A/C

I am going to add a third A/C to our HC381TH:
  • Install in kitchen where current power vent is located.
  • Non ducted "dump" style discharge.
  • Run power separately from the 110volt on pedestal.
  • Already have two Dometic Brand units so plan on getting matching third unit.
With the above, can anyone tell me:
  • Can I run the larger 15amp unit on the typical 110volt outlet?
  • What is the difference between "heat strips" and heat pump?
  • Has anyone installed a third A/C on a 381TH or similar? I don't think it is prewired for third A/C.
  • Can I buy a unit with the Thermostat built into the ceiling fixture or do I need a remote thermostat?
  • Do I need a separate interior "install" kit or will the unit come complete with everything to install?
 
__________________
James & Irene Wilson
Bee Branch, AR.
2017 Ram 1 ton diesel duallyCrew Cab/Long Bed
2018 Montana High Country 381TH Garage Full of Toys
mtlakejim is offline   Reply With Quote
Old 04-07-2019, 03:31 PM   #2
mtlakejim
Montana Master
 
mtlakejim's Avatar
 
Join Date: Oct 2017
Location: Bee Branch
Posts: 2,620
M.O.C. #20693
Not sure why this didn't get any responses previously. We have a very serious issue and would appreciate the feedback:
We are forced to live in the middle of the New Mexico desert with zero shade due to work at present. Summer is coming up quick with a 90F day predicted this week! We have to leave our Chihuahuas in the camper during the day as we work. I don't want to come home to dead from heat stroke pups.
As such I need advice on the previous post that for some reason did not get any responses??
__________________
James & Irene Wilson
Bee Branch, AR.
2017 Ram 1 ton diesel duallyCrew Cab/Long Bed
2018 Montana High Country 381TH Garage Full of Toys
mtlakejim is offline   Reply With Quote
Old 04-07-2019, 04:05 PM   #3
Ram Montana High Country
Montana Master
 
Ram Montana High Country's Avatar
 
Join Date: Jun 2017
Location: POINTBLANK
Posts: 1,873
M.O.C. #19944
You need a good ac guy to answer. I’d be tempted to make a new door for one side of garage and install a big window unit with wireless remote. Or a stand alone and duct in thru windows for supply and return.
__________________
RAM 22' DRW 3500 Crew LB 40 gal reserve tank / RETRAX Bed Cover / 2020 373RD HC / IS / MOPEKA Tank Monitor / Furrion Side&Rear Cameras
Slide Toppers / EMS-HW50C / Sailun 85's
3rd AC / Dometic 320
Ram Montana High Country is offline   Reply With Quote
Old 04-07-2019, 04:15 PM   #4
mtlakejim
Montana Master
 
mtlakejim's Avatar
 
Join Date: Oct 2017
Location: Bee Branch
Posts: 2,620
M.O.C. #20693
I know a few folks that have actually done the 3rd A/C. DQ Dick for sure (he was next door to us until recently). Putting a third one on the roof is a lot "cleaner" looking install. I know it can be done just needing to hash out the details. IE: do my research first. Roof A/Cs are not the cheapest things and I want to make sure we get the right one for this application......
__________________
James & Irene Wilson
Bee Branch, AR.
2017 Ram 1 ton diesel duallyCrew Cab/Long Bed
2018 Montana High Country 381TH Garage Full of Toys
mtlakejim is offline   Reply With Quote
Old 04-07-2019, 04:19 PM   #5
Ram Montana High Country
Montana Master
 
Ram Montana High Country's Avatar
 
Join Date: Jun 2017
Location: POINTBLANK
Posts: 1,873
M.O.C. #19944
We were at a boat show and a SOB had three units and the units were low profile , more btu each and the unit was still operating on 50a total plug. Thinking it was Coleman RV8, maybe
__________________
RAM 22' DRW 3500 Crew LB 40 gal reserve tank / RETRAX Bed Cover / 2020 373RD HC / IS / MOPEKA Tank Monitor / Furrion Side&Rear Cameras
Slide Toppers / EMS-HW50C / Sailun 85's
3rd AC / Dometic 320
Ram Montana High Country is offline   Reply With Quote
Old 04-07-2019, 08:02 PM   #6
MidMOTraveler
Montana Fan
 
MidMOTraveler's Avatar
 
Join Date: Oct 2017
Location: Fulton
Posts: 456
M.O.C. #20688
Jim I believe the Dometic Duo therm II can be ordered either ducted or with the interior kit. Which has the controls and adjustable vents on the bottom and is basically a straight dump.
Only thing that might be odd would be how tall the ceiling is where you plan to install. Reaching the control panel might be the issue.
It will be the standard 14” hole in the roof, around 12 amp load at 115V.
Getting the power to the unit might be a challenge.
Strip heat is just electric heat like glowing wires.
Heat pump will have the AC compressor running,
Good luck and send pictures of your progress.
I remember the heat in Carlsbad it gets bad but you won’t have the humidity like Arkansas.
__________________
Wayne & Malinda
2018 Montana 3731FL
MORryde IS/DiscBrakes
2017 F450 DRW KR 4x4
MidMOTraveler is offline   Reply With Quote
Old 04-07-2019, 08:06 PM   #7
mtlakejim
Montana Master
 
mtlakejim's Avatar
 
Join Date: Oct 2017
Location: Bee Branch
Posts: 2,620
M.O.C. #20693
Thanks folks. Really worried here about the extended high temps in this area
__________________
James & Irene Wilson
Bee Branch, AR.
2017 Ram 1 ton diesel duallyCrew Cab/Long Bed
2018 Montana High Country 381TH Garage Full of Toys
mtlakejim is offline   Reply With Quote
Old 04-08-2019, 11:20 AM   #8
jeffba
Montana Master
 
Join Date: Oct 2017
Location: Bastrop
Posts: 2,892
M.O.C. #20753
Can I run the larger 15amp unit on the typical 110volt outlet?

Depends on the current draw of the AC unit. Don't be surprised if 15AMP is not enough.

What is the difference between "heat strips" and heat pump?

Heat strip is just a big ole resistor that gets hot, like in a space heater.
Heat pump basically runs the AC backwards. For a 3rd AC I would not bother with either.

the rest are beats me
__________________
Mocha, one-eyed toothless, hurricane survivor, Pirate dog
2019 20th Anniversary Edition 3701LK
B&W 20K for Ford OEM Puck
2018 Ford F-350 Lariat CCLB PSD DRW KJ5CQH
jeffba is offline   Reply With Quote
Old 04-08-2019, 11:45 AM   #9
jetskier
Montana Fan
 
jetskier's Avatar
 
Join Date: Aug 2018
Location: Minden - NV
Posts: 499
M.O.C. #22360
When I installed my 3rd AC, it was pre-wired for the thermostat and power (12ga romex). There was a single gang junction box in the ceiling that had the power wire terminated. If you don't have the junction box, you probably aren't pre-wired. You would have to fish it through the ceiling and down the interior wall. It's not hard, but you have to be patient and creative. You may be able to get it to run on a 15A breaker, but it would likely trip depending on the wattage and startup surge. I just added another 20A breaker to the main box and run it off the 50A connection. If you're out of breakers, you can add a second panel. I added a second breaker panel to separate power from my inverter. You can search out that thread for more details, but it did open up the main panel as mine was full with the basic circuits. The main panel uses Square D Home Line breakers from Home Depot or Lowe's.



The interior trim kits are separate from the exterior AC units. You can order with or without the controls depending on the model. I bought a separate thermostat and placed it in the wall next to the rear AC control as that's where the pre-wired was located.


My trailer came with the heat pump model in the rear and an AC only unit in the bedroom. I bought another heat pump model and put it in the bedroom and the AC only unit in the kitchen. The heat pump units run in the ducted system which is nice for spring and fall camping when it's above 35°F. I bought it off rvpartscountry.com after failing to find it anywhere else. If they don't list it on the website, they can usually get it if you message them. They had excellent prices and drop ship.
__________________
2013 F350 Lariat Ultimate CC LB
2019 3790RD
jetskier is offline   Reply With Quote
Old 04-08-2019, 01:47 PM   #10
AZ Traveler
Site Team
 
AZ Traveler's Avatar
 
Join Date: Sep 2017
Location: Oro Valley
Posts: 3,891
M.O.C. #20477
Jim,

Are you sure your current a/c is working properly? Ninety degrees here in our low humidity should not be a problem if everything is working right. We can handle 110 and our inside temp will not get over 80.

I would shop around and get a couple of estimates and ask a lot of questions if you add a third unit.
__________________
Zack and Donna plus Millie and Ranger
2018 3160RL

"Life is too short to stay indoors, enjoy the ride!"
AZ Traveler is offline   Reply With Quote
Old 04-08-2019, 03:14 PM   #11
DQDick
Site Team
 
DQDick's Avatar
 
Join Date: Jun 2011
Location: Wilsey
Posts: 18,799
M.O.C. #11455
Jim, The one thing I forgot to show you was the single 20am breaker box I have installed in my basement that the AC feeds off of.
__________________
Dick, Joyce, Diego, Picatso and Gustav
2017 3720 RL, and 2013 HC 343RL
Pullrite Hitch, IS, Disk Brakes, 3rd AC, Winegard Traveler, Bathroom door mod, Dometic 320, couch for desk swap, replaced chairs, sun screens, added awnings, etc.
DQDick is offline   Reply With Quote
Old 04-08-2019, 06:44 PM   #12
Mikendebbie
Montana Master
 
Mikendebbie's Avatar
 
Join Date: Jan 2018
Location: Austin
Posts: 2,381
M.O.C. #21044
3rd A/C

I see big motor homes with more than 2 ac units. How do they run off of a single 50 amp source?
__________________
MikenDebbie Aggie ‘77 in the sticks near Austin TX
2019 Chevy 3500 High Country DRW
2018 Montana 3921FB
Aussie Gus + Texas Heeler Jimmy
Mikendebbie is offline   Reply With Quote
Old 04-08-2019, 07:27 PM   #13
jetskier
Montana Fan
 
jetskier's Avatar
 
Join Date: Aug 2018
Location: Minden - NV
Posts: 499
M.O.C. #22360
Quote:
Originally Posted by Mikendebbie View Post
I see big motor homes with more than 2 ac units. How do they run off of a single 50 amp source?
Each 15KBTU AC is about 13-14A. A 50A service is 2 legs of 50A or 100A @ 120V (12000W). So three ACs would be about 40A leave 60A for the other circuits. This is a simplified explanation. You wouldn't put all three on the same leg of the 50A service. You have to load balance when you set up an electrical panel so each leg has the similar amount of current. For comparison, a 30A service is only 3600W (120*30)
jetskier is offline   Reply With Quote
Old 04-09-2019, 08:57 PM   #14
mtlakejim
Montana Master
 
mtlakejim's Avatar
 
Join Date: Oct 2017
Location: Bee Branch
Posts: 2,620
M.O.C. #20693
In my case, I want the third A/C to be completely independent as it is the fail safe to protect our puppies should the 50amp that feeds the trailer should trip while we are both at work. That being the purpose, I will run an independent power line even if the hole where I install the unit is pre wired. Yes that is a LOT more work but only way to assure total independence. That is of course if the 15 or 20 amp 110 breakers are independent of the 50amp wiring at the pedestal. We have electricians coming out to check the pedestal and I plan to get with them to verify exactly what we have. I worked in industrial electronics so I know just enough to be dangerous LOL or maybe smart enough to know what I don't know..... One upside, there is a 1' wide trim piece above the center cabinet about 3' from the hole and it runs down the wall. So if I can fish wire from the hole to the ceiling trim with my fiberglass fish poles I am in business fairly easily. The extra tall kitchen ceiling is a bit of an issue for the wife but I have seen some units with remotes and I can always add a thermostat on the side wall of the trim.....


I also plan to get a texting thermal alarm to alert us if there are power or excessive heat issues. And of course we need to add a really good auto reset surge protector.
__________________
James & Irene Wilson
Bee Branch, AR.
2017 Ram 1 ton diesel duallyCrew Cab/Long Bed
2018 Montana High Country 381TH Garage Full of Toys
mtlakejim is offline   Reply With Quote
Old 04-10-2019, 06:23 AM   #15
rollingdownthehighway
Montana Fan
 
Join Date: Jul 2017
Location: Where ever we park
Posts: 201
M.O.C. #20273
You may be wired for a 3rd AC already, so it may just be a "plug and play". When we bought our 3700LK, our dealer said "most of the new models are wired for a 3rd AC, all they have to do is remove the 3 vent and replace it with the AC unit". We have a sticker next to our LR vent that says "wired for AC" (or something like that I forget the actual wording). I'd check first before you do anything you don't need to do
__________________
Mike
2016 Chevy CC DRW Duramax
2019 Montana 3700LK
rollingdownthehighway is offline   Reply With Quote
Old 04-10-2019, 08:30 AM   #16
DQDick
Site Team
 
DQDick's Avatar
 
Join Date: Jun 2011
Location: Wilsey
Posts: 18,799
M.O.C. #11455
That's true, but they are wired to a controling device that will only let two of them run at the same time which is why we wired ours separately. Also, that won't solve Jim's concern.
__________________
Dick, Joyce, Diego, Picatso and Gustav
2017 3720 RL, and 2013 HC 343RL
Pullrite Hitch, IS, Disk Brakes, 3rd AC, Winegard Traveler, Bathroom door mod, Dometic 320, couch for desk swap, replaced chairs, sun screens, added awnings, etc.
DQDick is offline   Reply With Quote
Old 04-10-2019, 08:33 AM   #17
rollingdownthehighway
Montana Fan
 
Join Date: Jul 2017
Location: Where ever we park
Posts: 201
M.O.C. #20273
Quote:
Originally Posted by DQDick View Post
That's true, but they are wired to a controling device that will only let two of them run at the same time which is why we wired ours separately. Also, that won't solve Jim's concern.
It may, I agree, not all 3 will run at the same time, (none do), but it may be cheaper and cost effective in the long run instead of doing like he's talking about and for a resale, trade in (if he ever does) doing it has he's explaining may really hurt the value there
__________________
Mike
2016 Chevy CC DRW Duramax
2019 Montana 3700LK
rollingdownthehighway is offline   Reply With Quote
Old 04-10-2019, 10:49 AM   #18
jetskier
Montana Fan
 
jetskier's Avatar
 
Join Date: Aug 2018
Location: Minden - NV
Posts: 499
M.O.C. #22360
Quote:
Originally Posted by DQDick View Post
That's true, but they are wired to a controlling device that will only let two of them run at the same time which is why we wired ours separately. Also, that won't solve Jim's concern.

You can take out this "device" out and just add a separate breaker if you have room for another circuit in the main panel. I had two devices before I removed them. One was for the front and 3rd AC and the other was for the microwave and vacuum. I'm certain it's only purpose is because the main panel only has room for twelve circuits and this would make it fourteen.


I attached a pic of both the power share devices an the junction box on the ceiling before I installed the 3rd AC. The reason for the junction box is because you can't have 120V just capped off the attic space. It must be in an electrical box. If you don't see this box, you likely aren't pre-wired.
Attached Thumbnails
Click image for larger version

Name:	20180907_083138.jpg
Views:	113
Size:	207.4 KB
ID:	3455   Click image for larger version

Name:	20180907_073900.jpg
Views:	71
Size:	174.0 KB
ID:	3456  
__________________
2013 F350 Lariat Ultimate CC LB
2019 3790RD
jetskier is offline   Reply With Quote
Old 04-10-2019, 05:37 PM   #19
mtlakejim
Montana Master
 
mtlakejim's Avatar
 
Join Date: Oct 2017
Location: Bee Branch
Posts: 2,620
M.O.C. #20693
Quote:
Originally Posted by rollingdownthehighway View Post
It may, I agree, not all 3 will run at the same time, (none do), but it may be cheaper and cost effective in the long run instead of doing like he's talking about and for a resale, trade in (if he ever does) doing it has he's explaining may really hurt the value there
I am not interested in the least in the resale value at present. If you will read my posts, I am solely interested in not coming home to roasted Chihuahuas in this desert heat! To that end, if you will read my posts you will see that I want a TOTALLY INDEPENDENT THIRD A/C. By that I mean, on a completely independent wiring system from the trailer. As in NOT CONNECTED IN ANY WAY TO THE TRAILER WIRING.

The primary function of this third A/C is as a fail safe emergency back up to the other two factory units. If for any reason the other two units both fail (which they already have once) and particularly if they trip the 50 amp pedestal breaker in the process. I want the third A/C on a totally separate campground breaker. At my current lot we separate 50amp, 30amp and 20amp 110v.

In fact, I suspect that my method will actually enhance the value of the trailer as it will allow for 2 A/Cs to run when parked at a 30amp site since you could run one on the 30amp as normal and run the independent A/C on the 110v circuit that nearly all campgrounds have! You can't do that if you have all 3 A/Cs wired the way your recommending. So I think my way is better.

Finally I should mention that I have not seen any indication that our unit is in fact pre wired for the third A/C. That may be a function of it being a High Country but I can't swear to that. If it were prewired and I could jump off of the wiring to an independent plug and avoid a difficult wire pull I would of course consider doing that but it isn't a deal breaker to make the tough pull if it is necessary.
__________________
James & Irene Wilson
Bee Branch, AR.
2017 Ram 1 ton diesel duallyCrew Cab/Long Bed
2018 Montana High Country 381TH Garage Full of Toys
mtlakejim is offline   Reply With Quote
Old 04-10-2019, 05:51 PM   #20
mtlakejim
Montana Master
 
mtlakejim's Avatar
 
Join Date: Oct 2017
Location: Bee Branch
Posts: 2,620
M.O.C. #20693
Quote:
Originally Posted by AZ Traveler View Post
Jim,

Are you sure your current a/c is working properly? Ninety degrees here in our low humidity should not be a problem if everything is working right. We can handle 110 and our inside temp will not get over 80.

I would shop around and get a couple of estimates and ask a lot of questions if you add a third unit.
AZ, I don't think the High Country is as well insulated as the Montana. And my main concern is having a backup for our pups if the 50amp goes out for some reason (which it has a couple of times already).

Not worried about the cost or difficulty in running a totally independent circuit.

Thanks for the feedback though.
__________________
James & Irene Wilson
Bee Branch, AR.
2017 Ram 1 ton diesel duallyCrew Cab/Long Bed
2018 Montana High Country 381TH Garage Full of Toys
mtlakejim is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3
Disclaimer:

This website is not affiliated with or endorsed by Montana RV, Keystone RV Company or any of its affiliates. This is an independent, unofficial site.


All times are GMT -6. The time now is 12:56 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2024, vBulletin Solutions, Inc.