UPDATE GMC MOTORHOME ELECTRICAL PANEL SEMINAR, GMC MOTORHOMES INTERNATIONAL CONVENTION, DOTHAN, AL,

MARCH 2013 RAY SWARTZENDRUBER-PRESENTER

NOTE: Before doing any work on 125 or 250 volt systems, make SURE you know what you are doing. Electrical panels can be very dangerous to work in. Never touch any of the main bus lugs in the panel as they can kill you! The best thing to do is to TURN OFF THE POWER TO THE PANEL before doing any modification or wiring. If you are not SURE of what you are doing, contact an electrical contractor for help. Even if you observe the above warning, your immediate peril is lessened, but a misteak in wiring can be equally deadly to you, the next guy, or the power company guy if he gets any feedback from your inverter or generator while servicing the power lines!!! Be careful and if you are not absolutely positive, get online making sure of your source(s), or ask someone you trust. As my friend and mentor Larry McLaughlin says, if you use a paint brush, you are likely a painter. If you use a screwdriver, you are not necessarily an electrician!

!!STANDARD DISCLAIMER!!

JUST TO ADDRESS SOME CONFUSION:

• If plugged in to a 50 amp outlet, you are plugging into two 50 amp 120V circuits, each of which is 180 degrees out of phase with the other. Each is 120 volts from neutral, but 240 volts from each other so they make 100 amps at 120V available to your panel. •If plugged in to a 20 or 30 amp outlet, only 20 or 30 amps at 120V are available to your panel. •If plugged in to your generator, the two circuits going to your panel are at the same phase with no voltage difference between them and each is 120V from neutral. Thus if you have a 6000W generator, 50 amps (6000W/120V) are available at your panel. P= VI, I = P/V

PLUG ADAPTERS: • 50A male to 30A female – one leg of 50A circuit connected to the only leg of 30A cable. 50A breaker coupled to 30A cable – full length of cable OUTSIDE of coach! I don’t like this approach, particularly if you put 50A main breakers in coach! • 30A male to 20A female – connects 30A hot to 20A hot, again can overload cable, especially a common #14 or #16 extension cord. Use #12 minimum •30A female to 50A male – connects the one 30A leg to both 40/50A legs in your panel •20A female to 30A male – connects leg for leg

!DIFFICULT BUT IMPORTANT CONCEPTS! Neutral and ground are NOT the same, are isolated from each

other, and need to remain isolated for your safety! N & G are both “earth” grounded, but may be grounded at

different physical locations depending on utility and campsite distribution systems

Earth ground for either or both may be at the plug in panel, or may be a few feet away, or a may be a few thousand feet away, but SOMEWHERE, both are at earth ground (earth potential).

N cables carry current, so voltage may be dangerously different where you plug in vs. where it is “earth” grounded due to infamously high voltage drop (read that overload) in campground conducting wires!

G cables carry no current, so are always “earth” grounded everywhere by definition.

! IMPORTANT CONCEPTS CONTINUED! If your G cable or bussbar, or any “touchable”

part of your coach is at any voltage level other than “earth” ground, you have a safety problem that needs to be fixed!!! A quick check that covers all circumstances I can think of, is to use a device similar to that pictured. Or, take a VOM and measure resistance between some grounded part of your motorhome (chrome bumper?) and earth. Should read 0 on lowest ohm setting.

All outlets, and things metal in your coach are hooked to, or should be hooked to ground.

If you stand in wet grass and it tingles when you touch your coach, do something about it!

I am not sure how ground is established when plugged in to generator?

ORIGINAL PANEL •Now to the reason for this seminar….. • Replacement breakers are difficult to come by • In some cases, contacts are corroded, make poor contact, generate heat, even arc sometimes • Not enough breakers • Uses up a lot of space • This seminar applies to GMC converted coaches…others differ!

TOP BREAKERS • Two center lugs are 40 amp main breaker

•The right 20 amp breaker is for the water heater and converter

•The left 20 amp breaker is for the roof A/C

BOTTOM BREAKERS

• Left 20 amp breaker services all recepticles – BR, ceiling, LR, DR, outside, Ref, kitchen •Right 15 amp breaker services the central vac if you have one, not sure otherwise •Only four breakers total to service 115V living area •Another breaker is present for a second roof air

BOX LOCATION

•Facing aisle, change to mount on closet wall

•Remove old panel, take out old panel mounting board

•Opens quite a bit of room in electrical compartment

SALVAGE OLD PANEL PARTS • Remove the neutral strip from old panel to use as grounding strip in rebuilt panel • •Remove insulation to isolate neutral strip from panel in rebuilt panel • •Save breakers for someone who has not rebuilt his panel (Valuable if you catch them at the right time!) {:>)

OLD NEUTRAL BAR

• This shows the old neutral strip – remove and use as ground strip in rebuilt panel

NEW PARTS

• Procure HOM612L100SCP I got mine at Menard’s • Remove the bussbar • Comes with no main breakers, so purchase 40 or 50 amp double breaker for main •It’s way to big for our compartment, so take out guts and put in your old panel

MOUNT NEW PARTS IN OLD PANEL

•Place the new parts loosely in the old panel •Place the insulation strip from old panel between panel and neutral wire bussbar •Align with cover to minimize cutting •Leave room (more than I did) to install neutral wires into bussbar •Drill holes in panel and attach bussbar

INSTALL TO CLOSET WALL

• Locate high enough to get wires out of the bottom • Locate back from opening enough to install toggle switches (later) • Attach panel to closet wall •Be aware screws will come out in closet{:>) I used 10-24 nuts and bolts •Hook up supply wires •Note panel box is upside down from original!

MICROWAVE/ INVERTER CIRCUIT

• Move the handibox for the inverter, and in my case the microwave out of the way.

HOOK UP BREAKERS • Plan what you want on each circuit • Procure your breakers and wire them • Here is my scheme:

• 15a vacuum • 15a uwave & converter • 20a empty • 20a kitchen/LR receps • 20a water heater • 20a ref/outside receps • 20a A/C • 20a hall/BDRM receps

A NOTE ABOUT WIRE SIZES #14 wire should never be on a breaker greater than

15A #12 wire – 20A breaker #10 wire – 30A breaker #6 wire – 50A breaker Vacuum is wired with #14 wire, thus the 15A double

breaker on the previous slide Be careful about looping wire in a coil that is carrying

high current such as behind our outside electrical access door– fire hazard from heat generated in a concentrated area with no ventilation!

LOTS OF ROOM •Notice how much room this makes available for other “stuff” such as an auto transfer box – next slide

SWITCHING POWER SOURCE •To my knowledge there are only a couple ways to switch from land line to genset: •1) Manually unplug and plug to desired power source •2) Purchase a device ready made for this task auto transfer switch such as the Powermax PMTS-50 shown, available from Camping World for about $130 •3) Cobble something together with contacters…see slides 2 - 5!!

OPTION #1 • Get rid of the handibox that contains the water heater toggle switch and put it in the side of the panel.

• Install inverter switch • Double throw, dbl pole switch

• Kitchen/LR receps to common • Conv output to one set terms •Breaker, N to other set terms

!NOTE! YOU MUST SWITCH BOTH HOT AND NEUTRAL TERMINALS OR YOU WILL BLOW YOUR INVERTER!! ASK ME HOW I KNOW THAT{:>(

OPTION #2

INVERTER • Notice this is not the same inverter as the one shown in earlier pictures • To use converter, turn on converter power switch, toggle source switch. •To use shore power, turn off converter, toggle source switch.

NEAT, TIDY, LOTS OF ROOM

COVER

• To wrap things up, cut out the cover with a sabre saw, file edges smooth

•Make tags identifying breakers

•Put on switch instructions if you did the options

•DONE!