Home
Shade Tree
Schedule
Scrapbook
Marketplace
Membership
Links
 

More Interior Space:
Relocating electrical equipment


by Jim Peugh
Rancho Cucamonga, CA

If you've lived with a GMC Motorhome for long you'd welcome a bit more interior storage space. This is the first in a series of articles aimed at increasing and optimizing the available storage space in our GMCs.

Have you looked in that lower compartment in the wardrobe to the rear of the range that is crammed with the old iron core converter, the 120VAC distribution panel and the 12VDC RV fuse block and ever wished you could use that space for storage? If so, read on. This artice will show you how I converted it all to storage space.

Finished compartment
Finished Compartment

If you're not comfortable with ripping into the guts of your GMCs interior and very familiar with working with 2-phase electrical systems you may want to hide this article from your spouse... or leave the work to a professional.

Overview:

The existing transformer type converter, 120VAC panelboard and 12VAC fuse block in the compartment are discarded. The new electronic switching type converter is installed in unused space inside behind the motor generator compartment on the drivers side rear. A new flush mount 120VAC distribution panel is installed in the back of the closet where there is wasted space. A new 12VDC flush mount fuse block is mounted in a new panel installed at the rear of the compartment. In the process I replaced the shore cord with a more flexible cord with a higher rating, added a junction box for the receptacle circuit, replaced the electrical hot water heater switch with a timer and added capacity for additional circuits both 120VAC and 12VDC. I consider this about a 4 weekend project give or take.

Converter Replacement

Because I need to use the GMC I broke the project up and did the converter replacement first. I purchased a Progressive Dynamics Model PD9260C 60A unit through a local dealer. After reviewing the installation instructions I finalized the plan to install it in the rear space. This requires the removal of the driver's side rear setee and the heater trim panel behind that. Then the plywood panel can be removed and the wiring installed.

Converter Wiring
Converter Wiring - click to enlarge
I ran a #4 cable I obtained from a local auto stereo installation shop through the aluminum hat section vertical members grommeting as required from the converter to the B+ junction block mounted on the body aluminum frame directly behind the old converter compartment. I bolted the case ground and the negative output ground directly to the aluminum belt rail structure after cleaning off the oxidation.

Also shown here are the seat belt anchorages (an earlier project). On the rear of each seat belt bolt are large steel load plates/washers to prevent pullout and distribute load through the aluminum extrusion.

The yellow romex is the new feed for the new converter receptacle. I added a new circuit just for this receptacle, separating it and the electrical hot water heater. The white romex embedded in urethane foam insulation is the existing (untouched) feed for the blanket locker receptacle at the passenger side rear. The converter should be on its own independent breaker, if possible, as I have done here.

Converter Wiring
Converter Wiring (front)
I suspended the converter from two steel strap supports from the plywood top panel of the compartment. The receptacle to feed it is mounted in a handy box just outboard (at left top of photo). This arrangement allows for air circulation completely around the converter. Access is by removal of the front door and/or removal of the top panel.
Converter Access Door - click to enlarge
Converter Access Door - click to enlarge
The converter access dor is just modified from the original panel by cutting the vent hole with a hole saw and a finger hole. I used an RV furnace vent tube with screen to finish off the air inlet. The original velcro used to retain the trim panel was kept as it was.

120VAC Panelboard Installation

Panel Mock Up - click to enlarge
Panel Mock Up - click to enlarge
First, after removing the carpet and the wood panel at the back of the closet I decided to make sure that this panel would fit with sufficient room for the wires, heating ducts, etc. I made a box out of scrap materials and placed it in location. After doing this I decided to replace the back panel with a new 1/2" plywood panel to get both a better support and a bit more depth. Then I ordered the panel (PD5500) from Progressive Dynamics (through a local dealer). See their Web site for product information, dealers, etc.
Parts Used - click to enlarge
Parts Used - click to enlarge
The photo at right shows some of the parts used in the project. The more flexible 50A shore cord is type S00W bt Carol Cable and I found it at my local electrial supply house. The main breaker is a double or ganged unit rated at 40A (same rating as stock). If you don't have an AC outlet tester then you should get one. This will help you check all your wiring and be useful later whenever you hook-up to make sure shore power is correct (polarity not voltage). You can see the Progressive Dynamics panelboard cover and box at left. Note the split buss at the top of the box and the neutral and ground buss bars at the bottom. No romex entry clamps are required when using this box as it has them molded in. This saves space, time and expense. On the enlarged view of the box you can also see the panel knockouts for the entry cable.

Partially Completed - click to enlarge
Partially Completed - click to enlarge
In the photo above you can see the box installed using a temporary top support to make wiring access easier. The breakers are installed and wired at this point. I made a clearance cut in the closet wall to allow enough space for routing the romex on top of the shore cord box. Here you can also see the shore cord entering through the side of the box via a strain relief.

Receptacle Junction Box - click to enlarge
Receptacle Junction Box - click to enlarge
To cut down on the number of romex cables coming to the new panel I added a junction box in the old compartment. Here you can see it being wired.

In the background is the old shore cord entry hole in the shore cord box. I pop-riveted an aluminum plate over this to permanently close it and keep the rodents and vermin out.

Later when installing the plywood back panel in this compartment I added wood cleats to the sides, top and bottom to secure it.

Water Heater Junction - click to enlarge
Water Heater Junction - click to enlarge
Here you can see in the background the junction box for the heater control. I added a 30 minute timer on the front wall of the closet to serve as the water heater control and keep it from running all the time.

You could just as easilly substitute the toggle switch here if that is what you prefer. Here you can see the surface mount wiring to that timer from the junction box.

Romex Routing Along Vent - click to enlarge
Romex Routing Along Vent - click to enlarge
Removal of this top compartment panel gives access to the existing romex so that rerouting can be facilitated.

Here you can also see both junction boxes with their covers installed.

Clip Access Hole - click to enlarge
Clip Access Hole - click to enlarge
Access Hole - click to enlarge
Access Hole - click to enlarge
I removed the drawers from the wardrobe and drilled the backs with a hole saw so that I could remove and reinstall the romex clamp and have access to route the wiring properly.

After completing the work these were covered with sheet metal screwed in place (not shown).

Be careful when working in this area. The fresh water hot and cold lines are adjacent and just forward of the romex. Damaging these would make this a much longer project...

Completed Panel Wiring - click to enlarge
Completed Panel Wiring - click to enlarge
Here you can see the panel box with the wiring completed. I recommend that unlike my wire routing you plan the wire entrances to the box so that you have 4-6" of slack for future unknown situations inside the box. Note the clipping of the romex around the city water entry.

The one area for concern that I can see with this installation is the close proximity of the city water entrance to the shore cord flex conduit. We would not want a leak at the city water entry to cause water to run into the new panel. For this reason I routed the flex conduit up before dropping into the box. You might want to use waterproof comduit here.

Circuit Tester - click to enlarge
Circuit Tester - click to enlarge
I made a new shore cord out of S00W 6/4 cable just 15 feet long. I used a new plug. Then I put a new receptacle on my old shore cord and keep it in the bottom of the shore cord box for the rare occasion when I may need extra length. So far that hasen't happened.

Once it is all hooked up it is time to power up. I have a 50A outlet at my house that I installed when I bought my GMC so it was easy. Start with all breakers off then the main, then a circuit with a receptacle. The tester will tell you whether you got the polarity right. Proceed to turn all circuits on and repair anything with an issue.

Completed Panel - click to enlarge
Completed Panel Wiring - click to enlarge
Here is the finished panelboard. Later I added a new label for the breaker circuits and recarpeted the back wall and floor of the closet.

12VDC Fuse Panel Installation

12VDC Fuse Panel - click to enlarge
12VDC Fuse Panel - click to enlarge
I used a 12V Fuse panel, Progressive Dynamics series PD6000 with screw terminals and 18 fuse holders. I specified no ground buss but it came that way so I took it. While I didn't use many of the fuse locations I had added a couple of circuits and wanted both expansion room and a handy place to store extra fuses so I opted for the box with more locations. It is definitely not the least expensive alternative around but I wanted to have a covered, flush mounted box so I could maximize the storage in the cabinet. Wiring is straightforward. I labeled all wires on the old block with masking tape before removing them and of course disconnected the batteries first. A short at this point would be broken only by the 60A breaker at the RV battery(s).

In the background you can see I split the new back panel into two sections. This was necessary to allow it to enter through the compartment door and also facilitated assembly.

12VDC Fuse Panel Completion - click to enlarge
12VDC Fuse Panel Completion - click to enlarge
Installing the rear plywood back panel, the junction box and the fuse block was straightforward. I used wood cleats secured to the side walls, top and bottom to anchor the back panels. Sectioning the panel into two pieces was an afterthought when it didn't fit through the door. I added a backer board at the center joint for support. If I did this again I would make this a half lap joint. I visited my local laminate supplier and found a close match to the laminate used in the cabinets. It is the same pattern and almost the same color. It's good for inside but you can see the difference under a light if you look closely.

Once the panel was installed I added the new fuse/circuit label. I made a detailed description of all the circuits from the schematic so I wouldn't have to wonder in the future what was where and go consult the schematic. this might work for you but be careful. I've added several circuits.

Finished Compartment - click to enlarge
Finished Compartment - click to enlarge
Here is the finished compartment. The cover of the fuse panel can be removed to get at the fuses with a quarter or a strong fingernail.

I added a battery-powered light secured with stick-on velcro to the panel above the fuse block and some non-skid shelf liner on the floor to polish it off.

                           Home | Shade Tree | Schedule | Scrapbook | Marketplace-GMCs
                          Items for Sale | Items Wanted | Join GMC Pacific Cruisers | Links

Last Change: 4/08/2007
Suggestions/Corrections:
webmaster@gmcpc.org  Copyright 2007.  All rights reserved.  Hot-links welcome.