Adding a second roof A/C - Wiring and Electrical Questions

[Lefty]

I've recently purchased a new project to tinker with. It's a 1990 Fleetwood Prowler 34K travel trailer. It's a 34.5' long bumper pull (38' from rear bumper to hitch ball, and 8,900lbs GTW), and currently has a single Coleman Mach III 13.5K btu roof A/C unit installed in the kitchen... which is about 12' back from the front end of the unit. It cools the front half of the trailer great, but it does not cool the bedroom area very much at all due to the distance, and the fact that the air must also pass thru the bathroom before reaching the bedroom. It's about 5' from the front bathroom door, then the bathroom is 6' long, and then the bedroom is another 10' long... so you can see why.
The trailer currently has a typical 30a power distribution box.

In the bedroom area, there is a standard 14" square crankup roof vent (unpowered). I am planning on purchasing and installing a second roof A/C unit in that location.
I removed the interior plastic cover from the roof vent, and the hole is completely framed in with 2"X4" framing. It appears to be very solid, and there is no indication of dry rot, moisture, or any other issue with the ceiling or roof framing.. it appears as brand new wood.
There is however, no electrical power stubbed off in the hole either. I was hoping that maybe a second A/C unit was optional originally, and that the manufacturer would have ran the 110v power to the hole and left the wiring stubbed off for the A/C regardless if it came with two units or just one.... But alas, I was wrong.

So,
Here's my options, and here is where I need advice.
I can replace the current 30a distribution box, and the existing 30a power cable. Replacing it with a 50a distribution box and new 50a service cable. Then wire a new 12/2 wire from the rear roof A/C to a dedicated 20A circuit breaker located in the new distribution box.  Cost: about $400 for the box, new 50a service wire, and misc. other wiring bits.

I can keep the current 30a distribution box, and wire the new roof A/C to a smaller breaker box which contains only a single 20a breaker, and then use two service cables... the original 30a, and a second HD extension cord cable with a standard 20a plug end. which would plug into the other socket in the campground hookup box. Cost: about $75-$100 for a small breaker box, breaker, and a new HD extension cord to use for a 20a service cable.

Anyways, my main concern is with option #2. I've been to campgrounds where the boxes did not have a standard duplex 110v outlet in them... containing only a standard 30a outlet. So I'd run the risk of not having a way to plug in the second unit.  Also, I don't like the idea of paying for 30a service and possibly using 50a. To me thats theft.

Either way, I need to run new 12/2 wiring from the roof vent hole to the distribution box. Without damaging the ceiling or walls. Ideas? Special Tools? I can handle boring a hole for the wire thru the 2"X4" framing... but how do I get the wire thru the ceiling over to the wall, and then down the wall to the box? I'm sure I would have to somehow drill a hole in the header at the top of the wall where the roof and wall joins for the wire to pass thru...but I'm stumped on how.
I really don't want to have to drop the ceiling and wall panels... as they are in perfect condition, and I'd most likely never get them off and back on without damage.

Could an electrician do this type of thing? Do they have a way of fishing the wiring thru without damaging the wall or ceiling?

That's my question.

[eXodus]

I won't answer your questions Just give you a hint to maybe safe some money and work.

do you need to run both A/C at the same time ?


if you are only cooling the bedroom get a small 9000 BTU Roof A/C then you should be fine running both together.
Or if you don't want to mess with the roof consider a Mini-split A/C



For $500 you get heating and a lot of cooling and still be able to use your ceiling vent and don't have to compromise the roof.

[Lefty]

Thanks Exodus,
I had not thought about a split unit. Unfortunately, after looking at them, I see no place where I could practically mount the interior unit part in the rear of the trailer, as there is cabinetry all along the walls.
Interesting idea, and one I had not considered, but I don't think that would be a practical solution in my case.

[Froggy1936]

Another option ! Outside the box, Keep all new A/C wireing on the outside of the vehicle . A Connection right on the A/C case with an extension of whatever length would be necc to run to the power supply !  Extension stored inside a compartment ! Frank

[DaveVA78Chieftain]

Cost: about $400 for the box, new 50a service wire, and misc. other wiring bits.

Are you needing a distribution panel with converter installed?  You can get the WFCO WF-8930/50 AC/DC panel (http://www.wfcoelectronics.com/UI/Distribution-Panels-WF-893050.aspx?ptype=3&pid=18) for around $100 (http://www.ebay.com/itm/WFCO-55-amp-POWER-CENTER-Converter-Battery-Charger-RV-52-New-enclosure-/151435585976?pt=Motors_RV_Trailer_Camper_Parts_Accessories&hash=item234243a9b8&vxp=mtr)

That provides a large range of options for converter selection.  You maybe able to reuse the AC breakers you already have in your existing panel in it to save additional cost.  Unless you buy used on ebay, distribution panels rarely come with AC breakers.

Dave

[Lefty]

That's a lot better price than what I had found...  and yes, I am hoping to reuse whatever breakers and fuses I can in the install.

Any ideas on how to get the new wiring from hte vent hole thru the ceiling, and down the wall without damage? The power center is currently located under the left side rear twin bed. The bed also has storage access both outside via a large door, as well as a door beside the power center (which is flush mounted in the face of the bed near the floor).
As said, I have room to drill a hole thru the wood framing around the vent hole... to get the wire into the ceiling. I also have access to the wall framing via the compartment under hte bed (I can lift the base of the bed up, exposing the entire compartment, and drill a hole in the wall somewhere inside the compartment.) What I can't do, is drill a hole in the framing at the top of the wall where the wall and ceiling join. At least, not with anything I have. But, I was thinking on this tonight, and I remember seeing a long, flexible drill and cable wire fisher for sale at a electrical supply near me. It was about 10' long, and made of a flexible steel cable, with a 1/2" or 5/8" bit on the end. The end also had a small hole for attaching an electrical wire to it, so a wire could be pulled thru. I think tomorrow I'm going to go there and see what other wire fishing products they have, and go from there.

[DaveVA78Chieftain]

Use a surface mount cover (http://www.midlandhardware.com/198553.html?gclid=CI6vyY-BnMECFaZj7AodTjwAuQ#.VDSh3FeKUW0) across the ceiling to say a closet on the panel side.  THen run down inside closet back to floor area where you an run it to the panel easier.  Even under the rig if need be.  You can even use 10 gauge outdoor extension cord for flexible wiring.  Many bus conversionist use it.

Dave

[TerryH]

 What I can't do, is drill a hole in the framing at the top of the wall where the wall and ceiling join.

Suggestions:
If your build is somewhat similar to mine, take a look in the upper inside corners of your upper cupboards. You may find a few  plastic 90 degree corner wiring covers that cover the in coach wiring that may work for your needed corner connection. If so, would eliminate the need to drill thru ceiling to wall connection to a degree. Also covers the 90 deg. wire bend.

Through the ceiling and through the wall should not be a major problem for running and fishing required wiring by themselves. Connection between the two would be quite a different situation.

Flexible drill bit - consider possible roof/side wall damage - you're not dealing with a stick built house.

Another alternative may be wood strips along the ceiling and walls with wiring cut into the wall behind. I did something similar to cover the plastic strips between headliner panels. Gives it a "Tudor" look, and far nicer than  the OEM yellowing plastic. Did it throughout, and to me looks far better than original.

Terry

[Lefty]

Yeah, drilling with a 10' long floppy drill bit spinning wildly in the wall, with it punching thru the side of the trailer, would be a worst nightmare come true situation...That would be a little worse than if I drilled straight thru the top of the wall framing, and right thru the roof, which was also something I feared.

I had already considered doing the wiring externally on the wall, inside plastic ducting like Dave suggested. I was just hoping somebody here had an idea for how to do it internally... so the wiring didn't show.   I guess it's the OCD in me.
Anyways, I'll get the box and wiring upgraded... and then I'll probably go with the surface mount tracking to hide the wiring.

[eXodus]

Thanks Exodus,
I had not thought about a split unit. Unfortunately, after looking at them, I see no place where I could practically mount the interior unit part in the rear of the trailer, as there is cabinetry all along the walls.
Interesting idea, and one I had not considered, but I don't think that would be a practical solution in my case.

thanks for considering    Maybe mount the inside unit under a cabinet ?


Ever worked with a oscillating tool ?



with this you can just cut out at the surface to run a cable.