ejforwood
Littleton (Denver) Colorado
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Rick Jay wrote:ejforwood wrote:The amperage capacity of a wire does not double by using two wires. Check the Code! A 30 amp circuit requires that you use ONE set of wires of sufficent size to carry the entire load from the source (breaker panel) to the load (outlet).
I agree, the NEC does not allow you to parallel wires (in most cases) to increase ampacity. But "splitting hairs" here and looking at the theoretical limits, according to this chart, the maximum amps for an enclosed copper conductor of 14 gauge (typical 15A wiring) is listed at 17 Amps. The maximum amps for an enclosed copper conductor of 10 gauge (typical for 30A wiring) is listed at 33 amps. So, technically, two paralleld 14 gauge wires would equal the ampacity of a single 10 gauge wire.
Should this be done? Of coure not, for all of the reasons mentioned in this thread. It's just one of those things that might look good on paper, but is apt to be very problematic (and unsafe) in practice.
~Rick
The reason the NEC won't allow it is simple. If something happens to one of the wires in a 30 amp circuit using #10 wire you have a dead circuit, nothing more. If something happens to one of the hot wires in a 30 amp circuit using #14 wire, you have an overloaded wire and a fire!
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MrWizard
Van Nuys, Ca
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assuming you are talking about your HOUSE, and trying to make a 30amp circuit for your RV, ( with out new wiring ) , chances are you would end up with a 220 volt circuit and fry your RV
even if you got the wiring correct, what you want to do is against 'code'
you should run new 10ga wire from a NEW 30 amp breaker
* This post was
edited 08/18/08 09:55pm by MrWizard *
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jhilley
Buxton, ND
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MCrankyPants wrote:Good enough for me...Thanks for the help!!
What exactly does that Power Service box do?
I have a box that uses a 30 and 20 amp box going in and converts to 50 amp going to the coach...is this the same thing?
No, it allows you to power your RV like the built in genset. It allows you to connect the 30 amp to one receptacle and the 20 amp normally supplied by the genset to the rear AC to be connected to a 20 amp receptacle. This puts the rear AC on its own separately supplied circuit.
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Rick Jay
Greater Springfield area, MA
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MCrankyPants wrote:In layman's terms...how is achieving what I'm curious about different than linking two gennies? (not being antagonistic...am just truly curious...who knows, I might be able to understand).
I'll do my best to keep it as simple as possible, knowing that I'll probably get blasted for leaving out a few details...but here goes...
First of all, normally you can't "parallel" generators. In order to put two voltage sources (batteries, generators, etc.) in parallel, they must be properly matched for voltage and (in the case of AC) frequency & phase. Standard generators do not allow this because there is no easy way to keep the outputs exactly equal in voltage, frequency & phase. For most generators, this would require mechanical synchronization of the engine speed and even rotor position to keep the frequency and phase locked together. That's just not easy to do. Possible, yes, easy (as in cheap) no. 
The Honda generators (I think that's the brand that was mentioned earlier) and some others make use of an "inverter" to convert DC to AC. That is the generator first makes a DC voltage and feeds that to an electronic circuit called an inverter to make it AC. The key difference here is that to synchronize two such generators, it's a matter of synchronizing the electronic modules of each to the same frequency and phase. Since there doesn't have to be any mechanical synchronization, the process is much easier. It's just a matter of one generator being the "master" and the other being the "slave" so that they operate at the exact same frequency with the same phase relationship. (I know I may be using the word "phase" loosely here as the signals may not be pure sinusoids. But I think the concept gets across. )
ON EDIT: (Please read Wayne's post below for a better explanation of the output of the Honda generators. I don't have one and was just repeating what I had read elsewhere.)
One other issue that I'm not sure matters in the synchronization aspect, is that the Honda generators do not supply a "hot, neutral, ground" output as is typical of AC power. Rather, they put out a "+ 1/2 voltage, - 1/2 voltage, ground" output. So there is no "neutral" in the conventional sense.
OK...did that help? I think I got most of it right.
~Rick
* This post was
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wa8yxm
Wherever I happen to park
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MCrankyPants wrote:Good enough for me...Thanks for the help!!
What exactly does that Power Service box do?
I have a box that uses a 30 and 20 amp box going in and converts to 50 amp going to the coach...is this the same thing?
NO, it does something different
Standard 50 amp RV service is 120/240 volt at 50 amp, this gives you TWO seperated legs, 50 amp each, but the two legs are independent save the have a common "Neutral" lead (Which by the way is also rated 50 amp)
Your BOX, depending on which of two systems it is, either 1: supplies 30 amp to one leg and 20 to the other, giving you exactly 1/2 the total power capability of your 50 amp service.
or 2: (http://www.psrv.net) takes one big ticket item and "isolates" it from your RV completly NOTE that this device actually WORKS
The "dual power adapters" for the most part do not work as you suggest (They will trip the 20 amp GFCI 100% of the time, in fact, they SHOULD trip it, if they do not then something is wrong)
Nothin adds excitment like something that is none of your business
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MCrankyPants
Dayton OH USA
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I actually understood that info...thanks guys!!
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Wayne Dohnal
Banks, OR.
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Quote:....the Honda generators do not supply a "hot, neutral, ground" output as is typical of AC power. Rather, they put out a "+ 1/2 voltage, - 1/2 voltage, ground" output. So there is no "neutral" in the conventional sense. Not sure if I'm debating substance or terminology, but here goes. There is no 1/2 voltage output on the Honda eu-series generators. The output is 120 vac floating. The 1/2-voltage myth (more often called the 2-leg myth) keeps getting reborn when an eu-series owner uses a high-impedance meter (which most are now days) to measure between the AC outputs and chassis ground. Each reading is about 60 volts nominal, and the leg theory rises again. When the owner doesn't realize is that the voltage readings to chassis ground are from stray coupling and the available maximum current is under 2 milliamps. I've debated this a lot on the forum and the argument that seems to work best is pointing out that if the leg theory were correct, an eu-series generator would have one of its legs shorted to ground when properly wired to a premises for backup power, resulting in the product being a total dud in the marketplace.
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nbounder
Arizona mountains
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Crankydroomers - heed Mr. wizard. . . . ...... he has a knack of 'splaining things clearly. Not all other posters have this knack - he always hits the screw right on the head.
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Rick Jay
Greater Springfield area, MA
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Wayne,
Your explanation makes sense. I had always wondered about what would happen if you connected the output to premises wiring for backup if it were as I had originally presented. The output being "floating" makes sense, although I believe that concept may be a bit beyond what most people would understand about electronics.
I edited my post above to reference to yours. Thanks for the clarification.
MCrankyPants, see...we all learn on this forum. That's what makes it such a great place!!!
~Rick
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Bob Landry
Austin, texas
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I'm sorry. I thought the thread pertained to currently available materials and current installation practices..
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