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Old 01-21-2008, 07:13 AM   #1
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20 Amp or 30 Amp, that's the question

Here's one for the experts to noodle out. The main circuit breaker coming into the 110v panel from the shore power is only a 20 amp breaker. Coming out of the panel there are two 20 amp breakers that feed the interior of the camper. One of these 20 amp branch circuits feeds the air conditioner. The other 20 amp branch circuit feeds all of the other 110v outlets.

So the question is, why only a 20 amp for the main, shouldn't it be a 30 amp? Is there any reason why I can't replace it with a 30 amp?

The shop manual isn't much help here. The wiring diagram in the manual shows the circuit layout to be exactly what I have (wiring only). The diagram of the breaker panel (panel only)shows only 2 20 amp breakers, one to the shore power and one to everything else inside the camper (obviously this isn't correct).

As always, thanks for the help!

Jim
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Old 01-21-2008, 07:17 AM   #2
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the reason for this is because the air conditioner is completely separate from the rest of the wires. The wiring in the trailer is only supposed to be able to handle 20 amps.
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Old 01-21-2008, 07:23 AM   #3
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I understand that part of it; the air conditioner should have its own dedicated circuit from the panel. What I don't understand is why the shore power breaker is only 20 amp. If the camper is supposed to be 30 amp, why wouldn't the main breaker be a 30 amp? The mystery continues....
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Old 01-21-2008, 07:26 AM   #4
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My trailer is the same; however, we had an additional plug installed on the AC circuit for use in the winter. Since we have the elect/LP water heater on the other circuit, we were limited in our use of the 20amps. In the winter we use the AC circuit for an electric heater. We have not put in a new furnace and have been hesitant about using the original central heat in the Argosy. Actually we don't use the trailer much in the really cold part of our winters, so with the cat heater and the electric space heater this has worked out well.
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Old 01-21-2008, 07:32 AM   #5
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Jim,

Look at the guage of the wire that is feeding the breaker box from the street connection. The breaker on that lead should the wire guage.....20 amp for 12 guage and 30 amp for 10 guage.
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Old 01-21-2008, 07:42 AM   #6
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I just went out and checked, the street connection is 10 guage and printed on the wire it reads "30 amp" service. SO that means that I can replace the 20 amp street side breaker with a 30 amp, right?
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Old 01-21-2008, 08:06 AM   #7
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Our '77 has 10 ga. service wire & 30A main breaker.

The individual circuits are protected at 20A so I (not being an electrician) would feel comfortable changing the main to 30A.

Seems like you should be able to maximize the use of 30A service offered by campsites.
For example:
If you are using the AC (has it's own 20A circuit) and a microwave (let's say 800 watt size) on the receptacle circuit; the 30A main would allow this when the existing 20A may not. right?

Qualified advice is needed here. Amateur electricians can burn things up.

martin.
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Old 01-21-2008, 08:14 AM   #8
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Well, I just went back out and looked at things again. Then looked back at the shop manual. Seems things got a little confused here because of a PO's "creative wiring". Let me see if I can explain.

First, there is no "main" breaker facing streetside. The shop manual shows a direct feed from the street to the main buss without a circuit breaker. Then, there are 2 20 amp breakers that feed the two branch circuits described above (one for the air conditioner, one for everything else). This is actually how things are wired in the panel.

Seems a PO rewired things and left an extra 20 amp breaker in there that is not wired to anything.

So I suppose the real question now is, should I rewire the streetside connection so that it actually has a true "main" circuit breaker that can trun the power off coming from the street. Weird.

Jim
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Old 01-21-2008, 08:29 AM   #9
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Jim,
Considering the age, capacity & limited utilization, I would suggest replacing
with something you can have confidence in.
Try an elec. supply house for a better selection of panels and... I bet you can get a small panel and necessary breakers for under $100. If McDonough doesn't have a large commerical supplier we have several in Macon & I can pick one up for ya.
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Old 01-21-2008, 08:38 AM   #10
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I think you're probably right, Martin. The idea of not being able to cut main power at the box isn't very appealing. On the other hand, I could just unplug the dang thing!
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Old 01-21-2008, 09:20 AM   #11
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If the service cord is connected directly to the buss, and the two 20a circuits are connected to the buss, you should install a 30a main breaker.

If the box has room for another breaker, you would install the 30a breaker on the buss, adjacent to the branch service breakers. Then you connect the hot wire from the service cord to 30a breaker.

It may look unusual. It will look like you are running the power "backwards" through the main breaker. This is how it is done.

Be sure that you have the ground and neutral wires separated. Sometimes a PO, or even a residential electrician, will bond the ground and neutrals together.
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Old 01-21-2008, 10:09 AM   #12
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Quote:
Originally Posted by markdoane
...Sometimes a PO, or even a residential electrician, will bond the ground and neutrals together.
This is exactly what happened about 7 years ago when I developed a short in the 30 amp power cord plug. It kept tripping the campground circuit GFIC so a well meaning factory maintenance electrician ran a jumper wire from ground to neutral. It kept tripping the campground circuit even after I replaced the power cord plug. Once home, I compared the breaker box to the schematics in my manual. Funny thing, there was an extra wire in there that was not there before. I know it was not there prior to this incident because I had replaced a 30 amp main breaker and decided to draw a diagram of the wiring just for the heck of it. Fortunately I kept the drawing and it matched the factory diagram. I removed the jumper and everything worked fine.
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Old 01-21-2008, 10:09 AM   #13
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I agree with EMPRESLEY on replacing the whole box with a new box. I am goimg to go a step further on my GT resto, and go with a 50 amp box to add a dedicated circut to the electric portion of the new hot water heater, fridge, and the micro wave, along with the air conditioning circut, and then a GFI breaker for all the regular outlets. The hot water heater will also have a GFI breaker. I am a strong believer in the saying "better to have and not need then to need and not have"

Kip
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Old 01-21-2008, 10:57 AM   #14
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The limiting factor in your wiring is the wiring. you can't have more than a 20 amp breaker if the wiring will only handle 20 amps. From the breaker out to the pole the wiring is rated at 30. If you put a 30 amp inside the triler, the 20 amp rated wires will melt before the breaker will trip. The 20 amp main interior breaker is only for the trailer wiring, not the air conditioner, that wiring is completely seperate.
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