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Old Yesterday, 06:01 PM   #41
GeologyTek
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Join Date: May 2018
Location: Foley
Posts: 17
M.O.C. #21745
Installed a 3rd A/C

Jim,

I have a 2018 3811-MS with the installed 3rd A/C. I have lived in my awesome Monty in Carlsbad, NM for over a year now. When I bought the unit in South Alabama I had Camping World (horrible experience) install a 13.5k BTU Dometic Penguin 2 A/C as my 3rd unit. The camper store just absolutely insisted that I was wasting my money because Montana's were just over the top insulated. They could not have been more wrong. Here is why:

For a year my 5th wheel was parked in a oilfield shop yard for 2 reasons. 1 There is no place to rent for campers in Carlsbad that is not full up. 2, my rent was free. When the weather started to heat up around April-May the afternoon sun would heat my unit up to 78-80 degrees with the front and rear units running. The 3rd unit could not run while the front air conditioner was on due to the power share relay. SO this leaves you with 28.5k but of combined cooling capacity. I could not sleep for my night shifts in 80 degree heat.

So, I added another circuit for the 3rd air conditioner. I can run all 3 at the same time for 42k BTU. My auxiliary circuit is a standard 30 amp twist lock style RV hook up like for a travel trailer. This is how it is set up:

The main 50amp circuit for the trailer powers the breaker panel. The rear heat pump has a dedicated breaker with no relay. The front a/c and the 3rd a/c share a 20 amp breaker through a relay.

I installed a double pole double throw transfer switch to select the power supply for the 3rd a/c from the relay on the 50 amp system or the 30 amp extra circuit I installed.

With this system I can run the 5th wheel in the standard 50 amp set up running the air conditioners through the relay. Or, I can switch it to 80 amp mode and run all three at the same time. It made a HUUUUUGE difference and was worth the money!

I also have pictures and I can draw a wiring diagram if needed. Stay safe in the patch!
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Old Yesterday, 06:09 PM   #42
mtlakejim
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Join Date: Oct 2017
Location: Bee Branch
Posts: 1,885
M.O.C. #20693
Quote:
Originally Posted by GeologyTek View Post
Jim,

I have a 2018 3811-MS with the installed 3rd A/C. I have lived in my awesome Monty in Carlsbad, NM for over a year now. When I bought the unit in South Alabama I had Camping World (horrible experience) install a 13.5k BTU Dometic Penguin 2 A/C as my 3rd unit. The camper store just absolutely insisted that I was wasting my money because Montana's were just over the top insulated. They could not have been more wrong. Here is why:

For a year my 5th wheel was parked in a oilfield shop yard for 2 reasons. 1 There is no place to rent for campers in Carlsbad that is not full up. 2, my rent was free. When the weather started to heat up around April-May the afternoon sun would heat my unit up to 78-80 degrees with the front and rear units running. The 3rd unit could not run while the front air conditioner was on due to the power share relay. SO this leaves you with 28.5k but of combined cooling capacity. I could not sleep for my night shifts in 80 degree heat.

So, I added another circuit for the 3rd air conditioner. I can run all 3 at the same time for 42k BTU. My auxiliary circuit is a standard 30 amp twist lock style RV hook up like for a travel trailer. This is how it is set up:

The main 50amp circuit for the trailer powers the breaker panel. The rear heat pump has a dedicated breaker with no relay. The front a/c and the 3rd a/c share a 20 amp breaker through a relay.

I installed a double pole double throw transfer switch to select the power supply for the 3rd a/c from the relay on the 50 amp system or the 30 amp extra circuit I installed.

With this system I can run the 5th wheel in the standard 50 amp set up running the air conditioners through the relay. Or, I can switch it to 80 amp mode and run all three at the same time. It made a HUUUUUGE difference and was worth the money!

I also have pictures and I can draw a wiring diagram if needed. Stay safe in the patch!
FYI,
We are at the SKP Ranch just past the KOA. It is a far better situation than any of the other campgrounds in town for sure. I work for XTO.
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James & Irene Wilson
Bee Branch, AR.
2017 Ram 1 ton diesel duallyCrew Cab/Long Bed
2018 Montana High Country 381TH Garage Full of Toys
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