Custom Coach - electrical questions

Oonrahnjay · October 20, 2017, 05:55:40 AM

Quote from: j.m.jackson on October 20, 2017, 05:34:06 AMYes, 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

Yeah, this is a confusing mess. The 30-Amp TT-30 connectors (round ground, two angled blade pins - one hot, one neutral) looks very much like the 5-50 connector (blade ground/neutral together, two angled blade pins, both hot at 120V) and the 6-50 connector (round ground, two parallel blades, one wide and one narrow). If Richard's new bus is indeed 240V wired at the breaker box then he needs a 4-conductor cord with a 14-50 four-pin plug on it and a compatible 4-pin socket to plug it into. If it's wired 120V by separating the legs at the breaker box, he needs the same kind of cord and plug. If it's wired for 120V at the breaker box, and he puts that cord and plug on it, he can plug into a 240V outlet and be OK, or he can use a dogbone plugged into a 30Amp socket and connect his shore cord to the 4-pin socket on the dogbone. Only thing is, wired for 120V on the bus and plugged into a 30Amp receptacle on the pedestal, he can't run 240V appliances, even though he's got 240V connectors on his shore cord.

richard5933 · October 20, 2017, 06:15:37 AM

Maybe these photos will help.

The bus is wired like a modern 50-amp coach, except for the connections being 3 conductor instead of 4. They did that by using a bonded neutral/ground.

If there's room, maybe the simplest thing to do is swap the receptacle on the side of the bus for a modern 50-amp version. Othwise, I could create my own adapter.

Can you guys verify which type of connector they used from the photos? There's two of the receptacle (one open, one closed), on of the other end of the cordset, and one of the appropriate wiring diagram.

Richard

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

j.m.jackson · October 20, 2017, 06:46:33 AM

That's a hubbell twist lock connector, rated for 50 amps at 250vdc/600vac. If that cap is threaded, it may be the 'standard' marine 50 amp hookup.

It's actually pretty nice in that it won't fall or pull out. It can actually support a separate neutral and ground connector, if you want to make up an adapter cord for it. The diagrams you included above show that.

Below is the current 'standard' 50 amp marine locking socket and lineset. I don't know if it's exactly the same, but it's very similar (with the sliding ground connector on the shell)

Socket:

http://www.adventurerv.net/cynder-rvmarine-easy-twist-lock-inlet-standard-amp-125250-marine-p-33151.html

Pre-Made cord to standard 50 amp RV plug:

http://www.adventurerv.net/marine-power-cord-amp-with-marinco-hubbell-locking-connector-p-22804.html

eagle19952 · October 20, 2017, 09:27:30 AM

how do you get 50 amp service from 3 wires...?

j.m.jackson · October 20, 2017, 10:30:42 AM

The case of the connector is ground. L1, L2, and neutral are the pins.

Look at the adapter diagram, you'll see the adapter in the upper left is the 5-15 plug (110v) and they short the L1 and L2 pins together to power both sides of the panel.

The diagram in the middle of the page shows all 4 conductors with L1, L2, Neutral, and Ground. Ground doesn't have a separate pin, it's the case of the connector. But from the diagram, Neutral and Ground are not connected together.

Edited to remove "not ever", as we don't know if neutral is connected to the body at any point, or if the sockets in the unit are grounded to ground, or connected to neutral. It would be interesting to see if there is continuity between the neutral pin and the body.

windtrader · October 20, 2017, 12:37:58 PM

Richard,
Here's the link to the CCC FB group. https://www.facebook.com/groups/542130302637631
Buck trout admins this group. https://www.facebook.com/buck.trout.7

If you have trouble getting in let me know.

Don

richard5933 · October 20, 2017, 02:44:03 PM

Quote from: j.m.jackson on October 20, 2017, 10:30:42 AM
The case of the connector is ground. L1, L2, and neutral are the pins.

Look at the adapter diagram, you'll see the adapter in the upper left is the 5-15 plug (110v) and they short the L1 and L2 pins together to power both sides of the panel.

The diagram in the middle of the page shows all 4 conductors with L1, L2, Neutral, and Ground. Ground doesn't have a separate pin, it's the case of the connector. But from the diagram, Neutral and Ground are not connected together.

Edited to remove "not ever", as we don't know if neutral is connected to the body at any point, or if the sockets in the unit are grounded to ground, or connected to neutral. It would be interesting to see if there is continuity between the neutral pin and the body.

The 15-amp adapter does bond L1 & L2. That's not my worry.

If you look at the bottom right of the diagram, you'll see that from the input receptacle to the transfer switch they use only three wires.

Here's a photo showing the inside of the panel where those three wires go after the transfer switch. Left side of panel is fed by black. Right side by white. Top (bonded neutral/ground) is fed by green.

Richard

Dave5Cs · October 20, 2017, 03:04:13 PM

On genny that's OK but not on shore or some inverter's. It could create a hot-skin condition. Shore power should only be bonded at the pole or house main panels.

richard5933 · October 20, 2017, 03:38:14 PM

Quote from: Dave5Cs on October 20, 2017, 03:04:13 PM
On genny that's OK but not on shore or some inverter's. It could create a hot-skin condition. Shore power should only be bonded at the pole or house main panels.

I agree. Any idea when they stopped making them this way?

Until I can figure out how to separate neutral/ground, I need to figure out how to use this as is so I can charge batteries and test the systems.

If I understand what you're saying, if we have a short from hot to neutral/ground in the bus, the skin will be energized. I imagine that the biggest danger is being in contact with the bus skin and earth simultaneously. Correct?

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

Dave5Cs · October 20, 2017, 03:56:13 PM

Especially when wet or if raining and say you touch the skin and are standing in a puddle. People have actually died this way.
Please test the skin. If you have a Multimeter. Plug the shore cord into the bus first and then with no one on board or around the bus but you plug the house side in.
Use the + prob and touch the metal skin of the bus and put the other prob into the neutral of a cord plugged into a grounded outlet. If there is a hot-skin condition you will see a current reading on your meter. if it is a GFCI outlet it should pop the breaker. HTH

j.m.jackson · October 20, 2017, 03:59:42 PM

Also check if there is continuity between the skin (ground) and the neutral leg. You should be able to do that without plugging it in at all.

richard5933 · October 20, 2017, 04:28:52 PM

Quote from: j.m.jackson on October 20, 2017, 03:59:42 PMAlso check if there is continuity between the skin (ground) and the neutral leg. You should be able to do that without plugging it in at all.

If the bus has a bonded neutral/ground, then won't there always be continuity between them?

Isn't it current between hot and bus skin (neutral/ground ) that I'm worried about?

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

richard5933 · October 20, 2017, 05:42:52 PM

In looking over the wiring diagram again, I see mention of 'grounding clip'.

Did they used to run the fourth (ground) wire from bus chassis to pedestal ground this way? I'm going to crack open one of the ends of the original shore cord tomorrow and see what's inside. Maybe there is a fourth conductor?

j.m.jackson · October 20, 2017, 06:12:48 PM

The diagram shows four wires in the shore cord, I suspect you'll find 4. The 4 th wire should goto the shell of the connector, for ground. The connector on the side of the bus is 4 conductor. Three pins plus the shell for ground. The 'clip' I suspect would be on the shore end of the cord to clip to the conduit or something on the shore end for ground.

Nowadays, there is a dedicated ground pin on the shore side.

Yes, hot on the skin is a worry, but the ground should drain that away.

The transfer switch may connect neutral to ground when switched to gen, but may separate them when set to shore. It's definitely something to check so you know.

gumpy · October 20, 2017, 09:25:56 PM

According to what I see in the drawings, the neutral and ground are separate, not bonded. Neutral comes into the bus in the cable as white, but they run neutral from the inlet to the panel as green. This is the biggest problem I see. The color of neutral should be white, not green, and the color of the hots should be black and red, not white. Ground comes in from the cable as green and is bonded to the case of the connector, which is bonding the entire bus frame to ground by the fact that the connector is attached to the body. Now, if there is not a neutral to ground bond within the panel or elsewhere in the bus (e.g. in the generator), then the bonding will be properly NOT bonded. However, I think we've already seen that they are bonded in the generator. I suspect they simply used a 3 conductor 120v 8 ga cable to run from the inlet to the panel rather than a proper 4 conductor 240v cable of proper size.