Custom Coach - electrical questions

[richard5933]

I've searched high and low. Still can't find the fuse panel for the 12v house system. Anyone have experience with Custom Coach conversions that might know where to look?

Here's the main controll panel, which is located above the driver on the side. It contains the 120v breakers. I've opened the front of the panel (it's hinged) but there are no fuses, just terminal strips. Is it possible that they built the coach without fuses?

Richard

1974 GMC P8M4108A-125 (Current bus)
1964 GM PD4106-2412 (totalled Sept 2017)
Located in beautiful Wisconsin
KD9GRB

[luvrbus]

The 12v fuse are in the converter box on my buddy's Custom Coach 4108

[richard5933]

The 12v fuse are in the converter box on my buddy's Custom Coach 4108

Do you mean the bay with the dc power converters/chargers?

1974 GMC P8M4108A-125 (Current bus)
1964 GM PD4106-2412 (totalled Sept 2017)
Located in beautiful Wisconsin
KD9GRB

[richard5933]

I've expanded the title to this thread, as the electrical oddities of Custom Coach go far beyond not being able to find a 12vdc fuse panel. I know that this was the epitome of bus conversions in 1974 when this bus was done, but I would assume that even then there were already some standards for things like connecting an RV to a campsite.

After seeing the details of this Custom Coach conversion first-hand, I'm even more strongly convinced that our 4106 was also done originally by Custom Coach. There are too many similarities, down to the type of wire used and how the vinyl trim is fastened on the ceiling for it to be just a coincidence. The method used to connect the generator to the house wiring is also identical. That's the focus of this post.

The bus has a Kohler 12.5kw genset, same as the 4106. Also like the 4106, the genset is connected to the 120 house wiring panel by using two hot conductors (L1 & L2). Each of these powers one side of the panel. There is a third conductor from the genset, and it is a bonded ground/neutral. It runs to the 120v panel as such, a bonded ground/neutral. If the bus were never to be connected to shore power, then this would be okay. Not ideal, but okay. The problem comes when trying to connect to a modern RV hookup.

Custom Coach used what today would be a 30-amp three conductor receptacle on the bus. There is a 3 conductor cordset that looks like it plugs into a regular 30-outlet. Problem is, the receptacle on the side of the bus is wired with L1, L2, and the bonded ground/neutral. If I use a modern 30-amp cordset to plug into a modern 30-amp outlet, I'm connecting it to L1, neutral, and a separate ground. There is no L2. Only half the 120 panel will have power.

According to the wiring diagrams, it looks like they shipped the bus with a custom made cordset and adapters. I don't have these.

When I got our first bus, the 4106, I worked with an electrician friend of mine to update the bus to modern 50-amp wiring. We separated the ground from neutral on all the 120v circuits. It was pretty easy the 120v panel was a Square D residential box in the closet with lots of room to work. My friend explained that when connected to the house, the bus was essentially a sub panel and should not have a bonded neutral/ground. So that's what we did.

On our new bus the 120v panel is mounted above the driver's seat. It's the part to the left of the photo I posted earlier. I think they used a marine type of panel for this. There is no way to just add a separate bus bar and break out the ground from neutral. Also, the wiring harness/loom is strung so neatly and tucked in so tightly that I don't think there is room to really move things very much at all.

So, finally my question. I'm going to get my electrician to chime in tomorrow, but I want to know from bus people how this sounds.

What if I just use the wiring diagrams to recreate what the bus shipped with originally, and make an adapter that will allow me to pick up L1 & L2 from the 50-amp outlet in the pedestal at our house and keep the bus with a bonded ground/neutral. Apparently it's been used that way for 43 years. There are breakers to protect all the 120v circuits in the bus.

Hope I'm not opening a can of worms, but I would like to know what others would do in a situation like this. My goal is to keep as much as the bus original as possible, and to change what is practical to update for safety.

Richard

[gumpy]

First, the neutral and ground should be bonded at the source. i.e. when connected to shore power, it is bonded in the house panel and should not be bonded in the bus. When the generator is producing power, it should be bonded at the generator, which is appears to be based on your description. When an inverter is producing power, it should be bonded at the inverter. There are a few ways to accomplish this. One is a transfer switch. Another is separate sockets which you manually switch a pigtail between, depending on what source you desire to use. 

Second, If your bus is wired for 50 amp service to shore line, just buy a dogbone connector for 30 amp service. This connection has the two hot wires tied together internally, so when you plug into 30 amp post, it will power both sides of the breaker box on the one hot leg coming from the power post. If your bus is only wired for 30 amp shore power, then consider the individual sockets I alluded to above and to the crossover inside the shore power plug.

[richard5933]

First, the neutral and ground should be bonded at the source. i.e. when connected to shore power, it is bonded in the house panel and should not be bonded in the bus. When the generator is producing power, it should be bonded at the generator, which is appears to be based on your description. When an inverter is producing power, it should be bonded at the inverter. There are a few ways to accomplish this. One is a transfer switch. Another is separate sockets which you manually switch a pigtail between, depending on what source you desire to use. 

Second, If your bus is wired for 50 amp service to shore line, just buy a dogbone connector for 30 amp service. This connection has the two hot wires tied together internally, so when you plug into 30 amp post, it will power both sides of the breaker box on the one hot leg coming from the power post. If your bus is only wired for 30 amp shore power, then consider the individual sockets I alluded to above and to the crossover inside the shore power plug.

I understand what you're saying that only the source should be bonded, whether it be the generator, the shore power, or the inverter. Unfortunately they didn't know that at Custom Coach in 1974. Actually, I have heard that in some areas of the country things used to be done differently with regard to bonding neutral/ground. The 120v panel on the bus has bonded neutral/ground. It would need to be totally redone to change that, as the wiring hasn't got a spare inch to move any thing to separate things out.

It appears that the bus is wired for 50-amp service. However, this was accomplished through the use of a 3-conductor receptacle - I'm guessing because that's all they had in 1974 to work with. The 3-conductor is wired L1, L2, bonded neutral/ground. I know that's not what it should be, but it is. Apparently they've used it for 43 years this way.

I checked with the electrician that helped me re-do our first coach to bring it into this century. He said that while not ideal, continuing to run as is will work for the short term. All I need to do is re-create the original adapter spec'd out in the wiring diagram so that I can plug the bus into a modern 50-amp outlet. Eventually we'll figure out how to break out the ground/neutral and run a proper 50-amp setup throughout the bus.

There are so many oddities of the electrical system on this coach that I want to run as is if possible just to see what is powered by what. For example, there is really no house battery setup. There is a 12v 8D battery on the generator. It's not deep cycle, but it is used to run the 12v systems on the bus. I think that they planned to be on generator or shore power nearly all the time. There are also a lot of house systems running on the chassis 24v battery bank. Also not deep cycle. These are mainly lights but also include the water pump and some of the solenoids for the pneumatic controls for things like the stair well cover.

Once I fully understand how things are currently running I'll start drawing up plans to break it down and create it with a proper house battery bank.

Any insights would be welcome.

[gumpy]

Again, before you recreate the adapter from their drawings, maybe you can post the drawings here. I suspect the standard 30-50 amp dogleg adapter from any RV supply store and most WalMarts will probably do what you need.

[j.m.jackson]

I bet Grumpy is right, a 30 -> 50 dogbone should connect L1 on the 30 amp side with L1 and L2 on the 50 amp side. I have two adapters plugged into mine right now, a 15 -> 30, and then a 30 -> 50, and both L1 and L2 have power.

The 30 -> 50 was $15 from amazon.com, seems up to the task.

https://www.amazon.com/Camco-55185-PowerGrip-Dogbone-Electrical/dp/B000BUQOGI/ref=sr_1_3?ie=UTF8&qid=1508468086&sr=8-3&keywords=30+to+50+amp+rv+adapter

[j.m.jackson]

BTW, that electrical panel is dead sexy. That coach is a pure time capsule, what a find!

[gumpy]

I bet Grumpy is right, a 30 -> 50 dogbone should connect L1 on the 30 amp side with L1 and L2 on the 50 amp side. I have two adapters plugged into mine right now, a 15 -> 30, and then a 30 -> 50, and both L1 and L2 have power.

Be careful of those 15 -> 30 adapters. Some have been known to get hot and melt the cover, even without an excess load on them.

[j.m.jackson]

The 15 -> 30 cord I use looks just like the 30 -> 50, it's a plug, 1ft of cord, and a socket. Ive run a 13500 btu ac, drill, 4.5" grinder, and shop vac on it. I've purposely checked the temp of the plugs and extension cord I use after running the above to make sure nothings getting hot. I've had good luck so far. I'm about 75ft away from the gfi socket that I'm plugged into. Purely temp tho while remodeling the 5303, need to put a 50 amp socket on the house.

[windtrader]

Sounds like a lot of unique build methods of the CCC. Did you get connected to the CCC Facebook group? It seems topics like this would get responses from those who have wrestled with this sort of thing

[richard5933]

Sounds like a lot of unique build methods of the CCC. Did you get connected to the CCC Facebook group? It seems topics like this would get responses from those who have wrestled with this sort of thing

Couldn't find the Facebook group for them.

Richard

[Oonrahnjay]

I bet Grumpy is right, a 30 -> 50 dogbone should connect L1 on the 30 amp side with L1 and L2 on the 50 amp side. I have two adapters plugged into mine right now, a 15 -> 30, and then a 30 -> 50, and both L1 and L2 have power.

The 30 -> 50 was $15 from amazon.com, seems up to the task.

https://www.amazon.com/Camco-55185-PowerGrip-Dogbone-Electrical/dp/B000BUQOGI/ref=sr_1_3?ie=UTF8&qid=1508468086&sr=8-3&keywords=30+to+50+amp+rv+adapter   

     Something about this bothers me.  Richard ways that his coach was wired for 50Amps with a three-pin socket/plug.  That would be a NEMA 10-50 (if the ground terminal is flat and the other two at an angle to each other) or 6-50 (if the ground terminal is round or "arched" - half a square with a radiused top side - with the other two terminals parallel to each other).  The dogbone that you show here* has a NEMA TT-30 (the "standard" RV/Trailer 30Amp/120V plug socket) but is had the other end a NEMA 4-pin, 10-50 socket.  If Richard has the three-pin plug (of either type), it's not going to fit into the four-pin socket on the dogbone. 
      He'll have to make up a special connector with a socket that matches the plug on his cord (including checking that it is actually 50Amps/240Volts on a three-pin plug and not 30Amps/120Volts on the three-pin RV plug -- MANY people have burned out RV systems --
see http://noshockzone.org/accidentally-plugging-into-240-volt-outlet/ -- by plugging a 120V system into a 240V outlet) with a RV-type TT-30 plug on the other end.

      It's always something that gets in the way of making it simple. 

(Speaking of this dogbone that lets you connect a plug on your shore-cord that's 4-pin/50Amps on a system that wired at the breaker for two split 120V legs and plug the other end of the dogbone into a 30Amp RV socket, isn't there a reverse?   If the only receptacle available is 240V/50Amps and you have a three-wire 120V system on your bus/RV/trailer with a three-pin TT-30 plug on the shore cord, you'd need a dogbone that gives you a 4-pin plug on one end with a connector to only one hot leg that goes to a 30Amp RV socket to match the shore cord's plug, right?  I know that most campsites with pedestals for RV's that have 240/50Amp/4-pin sockets usually have a 120/30Amp/3-pin socket and also a "household" 120/15Amp/3-pin extension cord socket, but I bet that there are some situations where you may have only  240/4-pin socket and  15Amp socket but if a vehicle is wired with the 30-Amp plug on the shore cord, you need an adapter for that situation.)

[j.m.jackson]

Yes, Richard stated that the plug on the bus looks like what is today a 30 amp TT plug, but is not wired as such. If it were mine, I'd swap that out for a standard 50 amp inlet plug so that there is NO CONFUSION when plugging into today's adapters, cords, and TT outlets. IF the coach is only rated at 30 amps, then use a proper 30 amp breaker on the bus side to protect it, maybe in a disconnect box near the inlet