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Old 01-07-2013, 10:33 PM   #1
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Default 30/50 Amp Wire

So, currently I have a regular household Standard D breaker box in my truck. A total of 5 20 amp wires connected to it (they will never all be on at the same time, but since I had the 20amp wire, that's what I wired the truck with).
I realized after I had everything set up that I had a problem. Initially I am running a 30amp 50' cord I got for cheap into the box. (Later on, when I run a 50 amp cord into the box, this problem resolves itself). But the wire going into the box will only have 1 hot wire. So that leaves me with 2 possible outcomes. Fold the #10 wire about 3 times and twist so it's wide enough for the main bus and have only half the slots energized, or use a 30 amp breaker and backfeed into the panel using the breaker. Only downside to using the backfed breaker is if someone thought the 'main' 100 amp breaker was off, there would be no power at the panel, and not realize the panel was live.

Until I get a 50amp cord (which happens to have 2 live wires, solving the issues) I was thinking the 30 amp backfeed would be easiest. Any thoughts?
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Old 01-08-2013, 12:22 AM   #2
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Are you planning on running 50 amps of 220 or 110? A standard 50 amp 110 service will have three wires (1)Hot, (1)Neutral, & (1)ground same as the 30 amp only bigger wire. You will still be feeding your panel with only one hot wire & engergizing only one bus (half the panel). if you run hot wires from the same 110 source to both busses you will get a short if a two pole breaker is ever inserted into the panel.

Most panels are designed to be used with 220 volt, although there are some small panels available in 110 only.

Do you need more than half the spaces? you say you have 5 20amp wires (circuits) coming into the panel from the coach. If it is at least a 12 space panel you will have 5 available spaces using only one bus, and using one space for backfed main. If you connect the hot to only one buss, use every other space, and insert blanks covers into any open slots, that should work. best way to do that is to backfeed using a 30 amp single pole breaker. Make sure it is well marked as "main disconnect"

As far as connecting to the bus through the main breaker, what size is your main breaker? Code does not allow for an undersized wire to be inserted into a breaker. If you insert 30amp (10ga) wire into a bigger breaker then you lose overcurrent protection on your shore power cord, as the wire will overheat before the main breaker trips during an overload or short. Especially if you are plugged into a 50 amp campground service with an adapter.
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Old 01-08-2013, 10:13 AM   #3
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The panel is designed for 220, yes. But I dont need the insanely silly 20 slots the panel has. I went with the house type instead of RV type because 1) I dont have any DC needs 2) I needed more than the 3 slots most RV types offered 3) the 20 slot, 100 amp panel was 1/4 of the price of the cheapest RV panel. I paid 39.00 for the panel. I have 5 wires running to the panel atm, and 2 of those are not even used. One was for the future Insolet toilet, and the other was when I still had pipe dreams of using an electric on demand type water heater.

I thought about losing the overcurrent protection, which is why I was leaning towards the 30 amp single pole. But I have not done that before, so I was a little cautious about it.

I dont imagine I will run into too many 50 amp services with this show. I could be wrong. I think I will be using 2 20amp cords to run everything as much as the built-in panel and 30 amp wire. Many places the show is going just wont be set up for 50 amp, another reason I went with the 30 amp wire. (OK, that and I am cheap and just dont *need* 12,000 watts. I dont have an A/C unit.

Edit: So I just had a crazy thought. Dont think I would try it, but in theory it would work. 2 20 amp wires backfed into the panel, one on each bus if I never needed more slots (cant possibly imagine needing more than 10 slots, ever. more power, maybe, more slots, highly doubt it). Obviously, the incoming 20 amp wires would have to be on different circuts, or you would still only get the max output of the circut you plugged into.
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Old 01-08-2013, 02:26 PM   #4
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My concession trailer and my convert both run on 30 amps and have never more.the hardest part is find 30 amp plug ins at the shows.They ask 5-6 months in advance my power needs and I show up and it's 20 amps circuits.Why do they ask?
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Old 01-08-2013, 02:46 PM   #5
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I hear ya there. I am honestly thinking about not even bothering with the 30amp cord. For that very reason. I know I will be able to find 20amp power every stop. And I have enough 20 amp cords laying around to light up a small rock concert, lol.

On a slightly different note, but related to electrical, has anyone tried using the induction cooktop? I know it needs metal cookware to work, but it seems like a solution to having no propane tanks..
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Old 01-08-2013, 04:03 PM   #6
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seems to me that if you could wire for 30a (or even 50a) and never used it, youd
be money ahead for future upgrades that may require more current.

you can always use a plug adapter -

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Old 01-08-2013, 05:50 PM   #7
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Quote:
Originally Posted by bushpilot View Post
seems to me that if you could wire for 30a (or even 50a) and never used it, youd
be money ahead for future upgrades that may require more current.

you can always use a plug adapter -

I partially agree. But as we all know, 50amp wire is about 3 bucks a foot. 30amp wire is around a dollar a foot. And swapping that end of it out is quite easy with the current set up (no pun intended). Swapping the wire going into the box to power the RV is easy and simple. Swap breakers, and plug in.

The catch, and there is always a catch, is knowing what type of power will be available at each location. I would be wasting money to set up 50 amp wire from the breaker box to the camp power if there is no 50amp available. And you always have to be very careful if you downsize your plug at the power input. You can accidently melt adapters and burn wiring by drawing too much power through a 'lesser' adapter, ie pulling 50 amps through a 30 amp adapter, or 30 amps through a 20 amp adapter.. I would much rather play it safe, run a couple 20 amp cords, place 15 breakers in the box, and have 30 amps available on a single bus. That way I know I am not going to overburden the system coming in, because the breakers will trip if more than 15 amps is pulled into the RV per leg.
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Old 01-08-2013, 10:51 PM   #8
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I ordered my first trailer with 50a service, cuz it was only $20 more than 30a service, and bigger is always better, right? But the 50a plug was a pain as there was never anywhere to plug it in, and way overkill anyway. Just go with the 30a rv style cord, they are cheap and plentiful and you can plug in directly most places. And if not the 15a adapter is only about $5 at walmart, so easy to adapt down. The 30a setup is big enough for your future needs and easy to install now instead of changing later. I would suggest just getting a 50' sealed connector rv extension cord and just cut off the camper end and wire it directly to your panel. Cheaper and easier than building the cord yourself, plus the outdoor end will be factory sealed and waterproofed. They are under $50 on ebay if you shop. On mine I looked into using a marine type sealed connection on the outside of the trailer to plug the cord into, but that stuff ain't cheap. So I just have a short cord like I described from the box rolled up in the storage compartment and I just pull that out and plug it into my 30a extension cord. I carry 100' of 30a cord, and that is more than enough to run roof air, appliances, etc. without getting hot.
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Old 01-09-2013, 12:45 AM   #9
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Quote:
Originally Posted by hot rod View Post
I ordered my first trailer with 50a service, cuz it was only $20 more than 30a service, and bigger is always better, right? But the 50a plug was a pain as there was never anywhere to plug it in, and way overkill anyway. Just go with the 30a rv style cord, they are cheap and plentiful and you can plug in directly most places. And if not the 15a adapter is only about $5 at walmart, so easy to adapt down. The 30a setup is big enough for your future needs and easy to install now instead of changing later. I would suggest just getting a 50' sealed connector rv extension cord and just cut off the camper end and wire it directly to your panel. Cheaper and easier than building the cord yourself, plus the outdoor end will be factory sealed and waterproofed. They are under $50 on ebay if you shop. On mine I looked into using a marine type sealed connection on the outside of the trailer to plug the cord into, but that stuff ain't cheap. So I just have a short cord like I described from the box rolled up in the storage compartment and I just pull that out and plug it into my 30a extension cord. I carry 100' of 30a cord, and that is more than enough to run roof air, appliances, etc. without getting hot.
If I use the 30amp wire, I will buy an extra 25' cord. I will cut the end off that, hardwire it into the box, that way I can put the surge protector/power conditioner at the end, and then connect the 50' cord to that and plug into the camp power. I just know the first 10 stops on the road will all not have the 30amp connector, lol. Murphy's Law.
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Old 01-09-2013, 03:56 PM   #10
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The adpater for the 30 amp will do just fine I use it at most stops too. and +1 to the cord.
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Old 01-09-2013, 04:46 PM   #11
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Update: Bus1 is live and operational, at a whopping 15 amps. Just for testing purposes, I am going to add another 15 amp line onto Bus1. First test will be checking if it will actually hold a 3600 watt load. But in the end, I will end up moving the additional cord to Bus2.

Reason for this is I have a space heater that calls for 1500 watts, but the owners manual says it needs a dedicated 15amp circut, which is 1800, not 1500. I am guessing the heater must surge when it first comes on to 1800, so the heater will stay on Bus2 by itself.

All in all, a satisfying experience finishing it this way. I will still have the 30amp cord on standby in case I decide to upgrade on the road.
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Old 01-09-2013, 05:26 PM   #12
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There should not be any surge on start up with the small electric heater as the bulk of the load is a resistance load. Surges at start up come from electric motors (induction loads) (the small fan in those heaters is insignificant.) Large motors can draw up to 3 times their running load on start up. Most breakers in panels (especially breakers with HACR ratings) will allow a short period of overload without tripping to allow for motor start up on larger appliances. The duration of the load is so short there is no risk of overheating or damaging the wires.

Code only allows for 80 percent of the rated breaker capacity as a safety factor, so a 15 amp breaker can handle 1800 watts x .8 or 1440 watts. usually the heaters actually pull slightly less than the 1500 watt nameplate rating, so they sneak in on a 15 amp circuit and get their UL listing.

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Old 01-10-2013, 01:33 PM   #13
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Dave, I understand what you are talking about, and have read similiar facts in trade manuals and the like. But I dont understand why the manufacturer of the heater would say it requires a 15 amp dedicated circut if it only is rated for 1500 watts (which is on the UL label on the back of the heater).

No worries, I will have the heater on it's own circut (all of Bus2) and wont have any issues with it.
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Old 03-20-2013, 05:22 PM   #14
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Update.
So the show suprised me. The setup here is almost the same as the circus I worked for. 3 gennys 2 for the show and one dedicated for the RVs. And I can pick whatever size cord I want to spend money on.
Now I just need to size the wire and install it. Going to install a couple boxes under the truck first, so I have someplace to put all the wire.
In a different thread I was discussing a mini split AC unit. Very modest draw of 800 watts (Either crazy efficent or dont work lol) plus water heater 1500 plus 1500 for cooking and a couple hundred in extras here and there (TV, computer, etc etc..it all adds up). Can *almost* get away with 30 amp service. No, not everything will be on at the same time. But I want to make sure that the wire can handle the load *if* they are all on at the same time.
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Old 03-22-2013, 10:15 AM   #15
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If you have 30 amp plug and wire coming into the unit. And you plug that into a 30 amp supply. That's all that is going to flow into the unit and it won't (shouldn't anyhow) overload or heat up. No matter how many things you plug in and turn on in the truck. It's still only going to be able to get 30 amps from the supply.

I've also seen an adapter that has two male 20 (maybe 15 since both blades were parallel) amp plugs that wire directly together to a box that then has a 30 female socket to plug your 30 amp line to. If you can find 2 separate 20 (or 15) amp circuits to plug each of those males into your then going to have enough to run your 30 amp system.

Oh snap, I just did a google and here is the deal: Dual 15 - 30 AMP RV Adapter For Honda, Yamaha, & Kipor Generator - Convert Two 15/20 AMP Outlets To One RV 30 AMP Outlet - Reviews & Prices @ Yahoo! Shopping

For you guys that "camp" and shows and stuff like that where they don't usually have a 30 amp rv hookup this would be a good thing to have. My brother goes to dog shows and he's used one similar to this. Key is to find two separate 20 amp plugins.
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Old 03-22-2013, 10:28 AM   #16
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bob those two plug cheater boxes wont work if theyre plugged into a outlets that share the same circuit (and most pedestal outlets do, in my experience). If the outlets are GFCI'd you can 'fget about it....itll trip the GFCI every time.
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Old 03-22-2013, 10:38 AM   #17
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No, I know. That's why you gotta find two separate circuits to plug into. I'm thinking they both might need to be on the same phase too? Or opposite phase? Maybe it doesn't matter? I know not the same one tho.
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Old 03-22-2013, 11:05 AM   #18
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dont know about phase never heard of 110s being in diff phase (but again i dont know).

i know at my house, i wired my garage w/ alternating outlets on one wall (can never have enough power in a garage & i use 'em to isolate battery chargers)... I have TWO 20a circuits (sep breakers), close to my garage door...and the cheater box will work there...but those circuits are not GFCI'd either.

these days you wont find an outlet (that can be exposed to weather or water) that isnt GFCI'd.
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Old 06-09-2013, 01:43 PM   #19
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Quick update on the wire situation. Found some 8/4 wire on eBay for 2.20 a foot new. Company was Tempco. Will post later on the quality. I suspect its cheap because I am buying the leftovers from a spool...which is ok with me. 175 feet total is way more than I will ever need. And more power than I should never need as well. Going with a double pole 50 amp breaker to get the full power. Will never use all the slots, but its nice to have the power available.
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Old 06-10-2013, 12:41 AM   #20
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I'll buy left over if you have a least 50-100ft. PM me.
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