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PapaG 03-31-2015 05:31 PM

2nd Air conditioner addition
Hello Newbie to the boards here. I had a question. I am going to install a 13.5k 2nd air in the bedroom of my 30 foot TT, I have done my research but I have a question. I was told to use 12/2 to run the through to the circuit breaker box but I also read to run 10/3 on another site. The person that suggested using the 12/2 was a service rep at Johnny Walkers the person that suggested using the 10/3 was on a forum and stated they have done this many times before.

Basically I am going to run the romex through the roof panel and down a closet through to the basement and then into a breaker box and then install a marine 20 amp male plug with a door so I can hook up my shore power when the 2nd air is needed. Suggestions?

fonzie 03-31-2015 05:50 PM

Romex 12/2 copper is good for 20 amps. So normally you calculate at 80% loading which would give 16 amps continuous load. You 13.5K unit will draw app. 13 amps so technically you are OK. Since it is a short run, the voltage drop in the copper wire is not an issue. If you want to go with 10/2, then it is the extra cost that you will incur.

PapaG 03-31-2015 06:00 PM

So if I went 10/2 that would be even safer or going a little overboard?.
Also the short run is roughly 15 feet max from air unit to the box.

The extension cord I am going to have to run to the genny would be roughly 25-30 feet because the genny would be located on the back of the trailer on a storage rack. I may end up hard wiring from the box to another box closer to the genny but not sure how difficult this is going to be yet so will decide as I go.

Oaklevel 03-31-2015 06:09 PM

:) We have a similar set up but I have a second RV 30A service plug in & 30A RV cord. So I am using both the 30A and the 50A outlet on the pedestal (with adaptor) (I know it will not work everywhere.) It is a toyhauler & I have a small second panel box (and grounded to the trailer frame) & basically 3 outlets for the second AC the dorm refrigerator & the ice maker. :thumbsup:


fonzie 03-31-2015 06:11 PM

Going 10/2 will be safer as it is rated for 30 amps and at 80% loading, that would be 24 amps continuous....your call. As for the extension cord, if close to 30 feet and to limit voltage drop, then I would use a 10/3 cable. If you are going to wire as your last statement, then I would go romex 10/2 all the way.

codespy 03-31-2015 06:13 PM


Originally Posted by PapaG (Post 822256)
So if I went 10/2 that would be even safer or going a little overboard?.
Also the short run is roughly 15 feet max from air unit to the box.......

10/2 NMB is going a little overboard, plus the solid copper conductors are more difficult to bend, especially in the breaker cabinet.

12/2 is the way to go, even if it was 50 feet away.

PapaG 03-31-2015 06:15 PM

Lots of great input. These boards are great. Thanks to all...will update as I go.

PapaG 04-10-2015 12:19 PM

What do you think of running a 13.5k 2nd air with a 2k HondaEU2000 or should I go with the EU3000? I ran a house 10k air with the EU2000 all weekend a few years ago with another trailer but 13.5 coleman might take up way to much to run..Thoughts?

dustman_stx 04-10-2015 12:39 PM

If the factory had installed it there would be 12/2 going to it. And your primary A/C has 12 ga. going to it. No need for 10/2 at all. I ran 10/2 to one I added a few years ago, but only because I had some 10/2 laying around. If it makes you fell all warm and fuzzy inside, then go for it. Might as well go 8/2 and feel even warmer and fuzzier. Or 6 or 4 or …….

Edit: Just reread your post and realized you are doing the exact thing I did on the one I added. I had 30A service and didn't want it running off the camper service. Ran the 2nd A/C to an outdoor box mounted under the camper behind one of the steel frame braces. I ran a 12ga. power cord to the pedestal for power.

dustman_stx 04-10-2015 12:50 PM

2 Attachment(s)
Thought I had some pics of the outlet box I made, but couldn't find them. Basically took an outdoor outlet and mounted a male plug inside it to hook an extension cord to. Also added 2 air vents to the air box and added dampers on the front and rear outlets to direct more air to the sides of the bedroom. There is a Dometic air box now that works much better than the one I had because it has side air outlets.

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