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10-2 with ground
I want to run a 30 amp 220 line to my bus to charge my batteries with the inverters on the coach. I have enough Romex 10-2 to do the job. Can I use it or do I need to use 10-3?
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16 Replies
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I think the 10-2 with ground will work because 30 amp in a temporary service box like we use in campgrounds is only a single leg. But you do need the ground. That is for 120 into the coach and as long as the batteries are charged when you plug in, or the inverters are set for a relative low charging current you will be OK. That will be for a 30 amp adapter on your cable.
If you need 240 into the coach (you shouldn’t) you need 3 wires plus a ground and then you definitely need a 50 amp plug.
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I assume you just want to plug in the bus which has a 240V/50A plug. For that you’ll need 3 wires plus ground. My bus uses both sides of the split 240V phase including neutral. I assume yours is similar. Wire gauge depends on how long the wire run is. Lots of calculators on the web.
Gerald
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If you want 220 volts, you’ll need 10/3 plus ground. Black = hot 110 volts, red = hot 110 volts, white = neutral, bare = ground. A 10 wire is correct gauge for 30 amp breaker unless your run is more than about 250 feet (voltage drop). That being said, I defer to other responders.
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Jon
just to be sure, are you saying to run the 10-2 w/ground as a 30 amp 110 line using the 110 volt adaptor from my 50 service cable? I am using it that way now but tapped into an existing outlet in a building 12-2. Depending on what is going one in the building we occassionally trip the breaker. I am going to put in a designated circuit just for the bus. Part of the run is underground where I already have 10-2 ran. Would rather not have to dig that up. It is not necessary but I’d like to be able to merg and charge the start batteries. Note they were low after setting awhile and when I merged them to the house the breaker popped when the charger stepped up. May be time for new start batteris. they are about 4 or 5 years old. appreciate your help.
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If you have what is a standard 30 amp receptacle it will have 3 wires going to it, a hot, neutral and ground. It will be 120 volts. If you use an adapter to your normal 50 amp cable those 30 amps and 120 volts will power both legs of your electrical system so any loads typically powered up are drawing from that 30 amp source regardless of which leg they are on.
It may be possible with your coach you have loads such as inverters, plus other not recognized loads such as power to the TVs used to retain memory, refrigerator, etc. When you add a charger that is trying to recharge nearly dead batteries the total load can go up and trip breakers at the source.
You may have to do some power management to keep the total current draw below 30 amps (consider 24 amps a good limit) when you need to charge batteries. Aging batteries, house and chassis are going to pull more charging current when they are drawn down so that might contribute. At the age you said, especially if they have had a history of deep discharge might well be the end of life for your batteries.
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Jon
I understand, and a 30 amp 110 volt is the way I will go and will have the batteries checked or just go ahead and replace them. Thanks for your input, You are Da Man!
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Depending on what inverters you have, you can also limit how much charging current they draw, say 10A each.
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Jon
Just got a look at a voltage drop table. My total run is 175 ft. and at 110 volts it says it requires a #3 or #4 wire and at 220 volts it requires #6 wire. Am I missing something?
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The longer runs are going to cause a voltage drop. that is a given. But those wire sizes are not for 120V, 30 amp.
I think the question you have to answer is what are your electrical loads going to be? If you can limit the loads to something well under 30 amps you likely are OK. As a rule you never want to contiuously exceed 80% of the circuit breaker rating anyway (24 amps) and with the long run you may want to remain below 20 amps. You have a double whammy to deal with. You want the amps to be as low as practical, yet over a long run like you have the voltage drop is going to cause the amps to increase so if you do not want to dig up the line and replace it you will have to keep loads to a minimum.
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Jon
Let’s say that I do dig up the 10-2 that I already have. Would I be better off in going ahead and put in a 220 volt line? With say an 8-3? It only money right?
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My biggest loads are two 2800 watt inverters that I run in the low charge position. everything else (when I use it ) run off the inverter, ae lights, tv’s, and Aquahot blowers.
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I cannot address your Marathon power needs, but if I had to rely on what I will guess might be a 20 amp, 120V power supply I would be uncomfortable. If I set my inverter (run only one) to its lowest setting I could keep my house batteries charged and that would include handling the phantom loads on my house that are always present.
I would not be able to trust it to handle the Webasto in cold weather because like the Aquahot there are the current draws of the blowers, circulating pump(s), etc. and I couldn’t run the refrigerator, water pump, or other things I would have the potential to need. Without the Webasto I think it would be OK but I don’t think I could maintain both the house and chassis batteries.
So if you are going to want to be less fearful and have some flexibility running a new cable would be far and away the best option. I would run at least #6 so I could protect the coach by running one or two A/C’s and still allow for plenty of additional capacity for the refrigerator and other loads that you might want to run from time to time.
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Jon
That is probably what I will do. One last question on the #6 wire are you talking a 110 or 220 line to the coach?
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Tony, Jon is giving you good advise on the num,ber 6 (3 conductor + ground) 50 amp / 220/240 volt service can be handled by #8 wire, but you are talking about a 175 foot run which would probably require at least one size larger wire due to induction loss, hince the #6 recommendation. Since you are replacing wire, it only ,makes sense to wire for 50 amp / 220/240 volts.
I am not an electrician, but I did play one on TV.
Good luck on your project and keep us posted.
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What Fred said.
With that run you will get some voltage drop, but unless you have to run all airs or use heavy power devices like the cooktop or an outdorr grill you are easily going to handle 30 to 40 amp loads on both legs. That will keep the coach heated in the winter and cooled during the summer which goes a long way to protecting the interior.
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