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Author Topic: 12 volt dc queston  (Read 4402 times)
Bob Gil
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« on: August 31, 2008, 07:44:19 AM »

I know it has been hashed and rehashed that you should not use extension cord for wiring the AC power in a bus.

But my question can they be used for the 12 DC side of it?  I have several 12-3 and 10-3 100 footers  that are not good for cords any more but would work well for this if it is acceptable.   It would help tell the difference from the ac and dc sides.

Did you use the same type switches as you did for the ac side?  Or did you use some kind of auto or truck type switches?

I don't have any dc power grid at this time any suggestions? 

What did you use for a fuse panel? 

I guess I could see if there is a RV scraper around here and see if I can adapt any thing from there. 

What ever I do it is going to be a chore the person that built this thing did some crazy things, glued the headliner over the power wires and the cabinets have bottoms in them under the drawers where you can't pull them out and work with the stuff that runs under them.  Seams like ever thing has a false bottom to keep you from getting to the back side and under it.

He did a nice job but well over done.  I guess it goes back to each person build to what they are planing on doing with the bus.

Bob
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Fort Worth, Texas where GOD is so close you don't even need a phone!

1968 GM Bus of unknown model 6V53 engine (aftermarket) converted with house hold items.

Had small engine fire and had no 12 volt system at time of purchase. 
Coach is all 110 w 14KW diesel genrator
Len Silva
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« Reply #1 on: August 31, 2008, 08:57:17 AM »

I would not use extension cords, not because of any code issues but because some of them tend to deteriorate over a few years.

Switches are rated for AC or DC or both.  DC rated switches are much more rugged that AC, operate faster and have a greater air gap when opened because of the tendency of DC current to arc more than AC.  Typically a dual rated switch might be 10 AMPS AC and maybe 3 AMPS DC.

Use automotive type wire and switches,  search the online surplus places for deals.
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« Reply #2 on: August 31, 2008, 09:00:18 AM »

Bob on a couple items I used wire that was for underground outdoor lighting like patio lights and such and to me its just like extension cord! I have had no problem!
As for my 12v switches, I used a breaker panel from a boat! Neat and easy!
Ace
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DrivingMissLazy
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« Reply #3 on: August 31, 2008, 09:23:54 AM »

I would not use extension cords, not because of any code issues but because some of them tend to deteriorate over a few years.

Switches are rated for AC or DC or both.  DC rated switches are much more rugged that AC, operate faster and have a greater air gap when opened because of the tendency of DC current to arc more than AC.  Typically a dual rated switch might be 10 AMPS AC and maybe 3 AMPS DC.

Use automotive type wire and switches,  search the online surplus places for deals.

My opinion, for what its worth, is that extension cords do not deteriorate over time if they are not out in the elements. The advantage of them is that they are double insulated. The outer insulation covering and then the insulation on the individual conductors.

Richard
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« Reply #4 on: August 31, 2008, 09:58:15 AM »

Bob,
   You said the extension cords were no longer usabale as extension cords, Why?  That may have a bearing on whether they would be OK for DC use.  As far as switches, best to use DC rated switches within the ratings of the switch.  That said, I have used some standard "house type" 120 volt/3 way 20 amp switches.  These switches control a total of 6 amps.  This is much less than their rated 20 amps and are still working fine after 8 years. I would not use 120 volt switches at close to their rated capacity.
   A good source for 12 volt fuse holders, circuit breakers, switches, wire, etc. is WayTek Wire  www.waytekwire.com  I purchased circuit breakers in different amp ratings and ganged them using "buss bar" connector strips.  The breakers are available in automatic or manual reset.  Jack
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Bob Gil
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« Reply #5 on: August 31, 2008, 12:30:45 PM »

Bob,
   You said the extension cords were no longer usabale as extension cords, Why?  That may have a bearing on whether they would be OK for DC use. 

Two of the were cut while triming the hedges with an electric trimer and one has a bear spot where it was pulled across a sharp metal edge.

Other have the same kind of problem in them at one place or another.

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Fort Worth, Texas where GOD is so close you don't even need a phone!

1968 GM Bus of unknown model 6V53 engine (aftermarket) converted with house hold items.

Had small engine fire and had no 12 volt system at time of purchase. 
Coach is all 110 w 14KW diesel genrator
DrivingMissLazy
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« Reply #6 on: August 31, 2008, 12:34:37 PM »

FWIW, I believe Fred Hobe uses extension cords for all his electrical wiring and he has been doing that for many many years. I feel certain that he would have quit that practice if he ever had any problems with it.

Richard
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« Reply #7 on: August 31, 2008, 07:01:31 PM »

Correct me if I'm wrong, but I think I just read something on Fred's site the other day about buying good extension cords when they're on sale to use for wiring in your bus to save a few bucks, Will
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Bob Gil
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« Reply #8 on: August 31, 2008, 07:51:23 PM »

Who is this Fred Hobe that you-all speak of?

Bob
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Fort Worth, Texas where GOD is so close you don't even need a phone!

1968 GM Bus of unknown model 6V53 engine (aftermarket) converted with house hold items.

Had small engine fire and had no 12 volt system at time of purchase. 
Coach is all 110 w 14KW diesel genrator
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« Reply #9 on: August 31, 2008, 08:15:39 PM »

Extension cords as hard wired are non code. Check the RV wiring code.

You can do what you want (as in non code--but you assume total liability.)
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Nick Badame Refrig/ACC
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« Reply #10 on: August 31, 2008, 08:57:48 PM »

Who is this Fred Hobe that you-all speak of?

Bob


Hi Bob,

Fred is a long time member here and own's North Florida bus conversions.
http://users.cwnet.com/~thall/fredhobe.htm

Good Luck
Nick-
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« Reply #11 on: August 31, 2008, 09:18:12 PM »

Len,

Thirty years in electronics and AC wiring and I had not a clue that a DC switch had a faster throw time than a comparable rated AC switch.  Now that you mention it, AC does break the arc at the next voltage null and that never occured to me. 

A long while ago I deduced that a camp trailer had LARGE caps in the wiring system due to the behavior of a VOM on the circuit.  They were there as I predicted and the size of those 24 oz. beer cans and there were six of them wired in parallel.  Arc suppression is the only thing I could come up with.  What do you think?

Thanks,

John
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DrivingMissLazy
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« Reply #12 on: September 01, 2008, 05:19:31 AM »

Len,

Thirty years in electronics and AC wiring and I had not a clue that a DC switch had a faster throw time than a comparable rated AC switch.  Now that you mention it, AC does break the arc at the next voltage null and that never occured to me. 

A long while ago I deduced that a camp trailer had LARGE caps in the wiring system due to the behavior of a VOM on the circuit.  They were there as I predicted and the size of those 24 oz. beer cans and there were six of them wired in parallel.  Arc suppression is the only thing I could come up with.  What do you think?

Thanks,

John

I also spent many many years in servicing and building electrical equipment for the regular electrical market place (computer power systems) and for the marine market place (1950-2001). All to UL and/or the applicable marine code requirements (there are several depending on the equipment, the application etc.) 

None of the DC equipment require special DC switches for DC voltage that is under 50 volts dc. Therefore I always used standard AC rated items for anything under 50 vdc.

I also did a lot of work with both 300 vdc and 600 vdc. I can assure that at that level you do not want to use devices that are not rated for that voltage. Please do not ask me how I know. LOL

For the 600 volt equipment it took 50 12 volt batteries in series and we typically would have three or four strings in parallel. With up to 400 batteries in one system you really do not want to ever make an error.

Richard 
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Len Silva
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« Reply #13 on: September 01, 2008, 05:48:10 AM »

I stand corrected.  From the Carling Switch website:

Q:    What DC current and voltage will an AC rated switch handle?
A:    The DC current “rule of thumb” holds that the highest amperage rating on the switch should perform satisfactorily up to 30 volts DC. For example, if you have an F Series toggle switch which is rated at 10A 250VAC, 15A 125-250VAC, the DC rating is 15A up to 30VDC.

My background is in telephony which operates at 48 volts DC and switch ratings were critical.  Apparently not so at 12-24 volts.

Len
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« Reply #14 on: September 01, 2008, 09:55:29 AM »

Len and Richard,

Thank you both.  I sure learned somthing and it looks like you did also.  Great place, this.

John
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"An uneducated vote is a treasonous act more damaging than any treachery of the battlefield.
The price of apathy towards public affairs is to be ruled by evil men." Plato
“We can easily forgive a child who is afraid of the dark; the real tragedy of life is when men are afraid of the light.”
—Pla
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