Electrical Question - Page 2 - Fiberglass RV


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Old 12-08-2011, 02:03 AM   #15
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Your plug must match your service

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Originally Posted by Ralefan46 View Post
WOW Thanks everyone, allot to think about, and allot learned. I think I am gonna take Jons suggestion and upgrade to a 30 amp circuit, adding breakers. Seems like the safest thing to do, and will give me more versatility in the future. As for the 12v system, for right now think I will make that an independent circuit that I will just charge as needed. Heading to Home Depot to see if I can find a breaker box that will work. Thanks all
How does the power get into your trailer? Do you currently have the standard electrical connector that you see in a house? Possibly on a cord of some sort? If so, you will need to change it for a 30A service. A twist lock connector is best.
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Old 12-08-2011, 02:46 AM   #16
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Yes, that's exactly what I have. The power cord to the trailer is just a heavy like extension cord that plugs into a standard house outlet. Thinking back when I was using my pop-up which was a 30 amp service I seldom ever used the 30 amp hook-up,(because it wasn't available) instead I would use the adapter that allowed me to change the 30 amp plug on power cord to a standard house type plug. With this I would run my A/C (roof mounted) and a couple of small appliances with no problems. But I think upgrading to a 30 amp service would be smart
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Old 12-08-2011, 10:15 AM   #17
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I do have a question about the 12v system. What size wire would you recommend to wire from the battery to the fuse block??
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Old 12-08-2011, 02:22 PM   #18
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Originally Posted by Ralefan46 View Post
I do have a question about the 12v system. What size wire would you recommend to wire from the battery to the fuse block??
I would recommend at least a 10 Ga wire.

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Old 12-08-2011, 03:04 PM   #19
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I would recommend at least a 10 Ga wire.

Spanke
Why?
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Old 12-08-2011, 04:50 PM   #20
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Why?
Why Not?
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Old 12-08-2011, 05:26 PM   #21
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Originally Posted by Spanke View Post
Why Not?
You made the statement and I would like to know your reasoning. But since you why not here's my reasoning.

Here's my reasoning for use either 12 awg or in some cases 14 awg. You can even go all the way to 16 in many cases.

Most 13' fiberglass trailers have a 20 amp 12 volt service. The maximum expected to draw is around 20 amps.
Lets take a look at some common current draws expected.
Standard 12Volt automotive incandescent lamps 1.5 amp each.
LED light replacement bulbs 0.2 amps each.

Furnace fan 3.5 amp (approx.)

Other items like a lap top computer 3 to 7 amps.

The larger gauge wire is more expensive, which is good for the metal thieves.
Larger wire is harder to handle get into small spaces, larger bend radius, and stiffer.

So it just doesn't seem practical to spend the extra money and effort to use the larger gauge wire.
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Old 12-08-2011, 05:27 PM   #22
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The choice of wire size depends on what you expect to pull from (and put back into) the battery. #10 or even smaller would be OK for LED lighting & most loads - using the wire sizing tables at Powerstream shows #10 wire good for as much as 55 amps for chassis wiring.

Unfortunately, it isn't quite that simple because you also need to consider voltage drop. Wire has resistance & some voltage is going to be dropped across the wire in order to push current through it. For some devices even a large amount of voltage drop is OK but for others it will be a problem.

For example, most large inverters shut down when the input voltage drops below a preset amount. If your wire is too small, you may find the wire loss is enough to shut down the inverter before the actual battery voltage is lower than the preset amount.

If you have a 3 stage converter to recharge your battery, too small a wire between the converter & battery may prevent it from going into the "Boost" mode - the fastest charging stage.

For most branch circuits from the fuse panel to most devices the general rule of keeping voltage drop to less than 3% works. There is a calculator at the bottom of the wire size table linked above that lets you enter current, wire size, voltage & wire length to calculate drop. You will find that for most runs over a couple of feet you need to stay well under the maximum current for the specific wire size to keep the voltage drop under 3%.

For example, that 55 amp rating for10' of #10 would result in a voltage drop of 1.13 volts or 10.86 volts at the load (an 9.42% drop). To stay within the recommended 3% the maximum current you could draw would be around 18 amps.

I agree with Byron that you can use wiring smaller than #10 to save money & ease of wiring, however for large loads such as 12V refers, converters & inverters actual calculations will produce better results.

All in all, spending some time planning 12V wiring will save you needing to rewire things in the future. A very useful site for more information is The 12 Volt Side of Life, Part 1 & 2 by Mark S. Nemeth.
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Old 12-08-2011, 05:46 PM   #23
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Originally Posted by Jon Vermilye View Post
The choice of wire size depends on what you expect to pull from (and put back into) the battery. #10 or even smaller would be OK for LED lighting & most loads - using the wire sizing tables at Powerstream shows #10 wire good for as much as 55 amps for chassis wiring.

Unfortunately, it isn't quite that simple because you also need to consider voltage drop. Wire has resistance & some voltage is going to be dropped across the wire in order to push current through it. For some devices even a large amount of voltage drop is OK but for others it will be a problem.

For example, most large inverters shut down when the input voltage drops below a preset amount. If your wire is too small, you may find the wire loss is enough to shut down the inverter before the actual battery voltage is lower than the preset amount.

If you have a 3 stage converter to recharge your battery, too small a wire between the converter & battery may prevent it from going into the "Boost" mode - the fastest charging stage.

For most branch circuits from the fuse panel to most devices the general rule of keeping voltage drop to less than 3% works. There is a calculator at the bottom of the wire size table linked above that lets you enter current, wire size, voltage & wire length to calculate drop. You will find that for most runs over a couple of feet you need to stay well under the maximum current for the specific wire size to keep the voltage drop under 3%.

For example, that 55 amp rating for10' of #10 would result in a voltage drop of 1.13 volts or 10.86 volts at the load (an 9.42% drop). To stay within the recommended 3% the maximum current you could draw would be around 18 amps.

I agree with Byron that you can use wiring smaller than #10 to save money & ease of wiring, however for large loads such as 12V refers, converters & inverters actual calculations will produce better results.

All in all, spending some time planning 12V wiring will save you needing to rewire things in the future. A very useful site for more information is The 12 Volt Side of Life, Part 1 & 2 by Mark S. Nemeth.

Voltage drop in most cases is insignificant, that's why I didn't mention it. What in your trailer is going to draw 55 amps?????

Larger loads, refers = 9.5 amp.
converter ???? Wrong direction
Inverter... Maybe if you have a big one. But you won't use it very long before the battery is dead.
Think Practical....
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Old 12-08-2011, 06:01 PM   #24
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Quote:
Originally Posted by Byron Kinnaman View Post
Voltage drop in most cases is insignificant, that's why I didn't mention it. What in your trailer is going to draw 55 amps?????

Larger loads, refers = 9.5 amp.
converter ???? Wrong direction
Inverter... Maybe if you have a big one. But you won't use it very long before the battery is dead.
Think Practical....
I'm not sure what you mean by the wrong direction for the converter - when charging the battery the DC is going over the same wires to get from the converter to the battery. Many converters can charge at 40 amps or better in the boost mode.

As to the inverter, many individuals use a large inverter for short periods of time without problems. I have a 900 watt inverter that lets me make a pot of coffee. It does draw 600 watts for around 5 minutes - that works out to around 4.2 amp hours which my solar system puts back in the batteries in an hour or so.

Again, I'm agreeing with you in most cases, but there are times large wires are useful.
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Old 12-08-2011, 07:44 PM   #25
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Originally Posted by Byron Kinnaman View Post
You made the statement and I would like to know your reasoning. But since you why not here's my reasoning.

Here's my reasoning for use either 12 awg or in some cases 14 awg. You can even go all the way to 16 in many cases.

Most 13' fiberglass trailers have a 20 amp 12 volt service. The maximum expected to draw is around 20 amps.
Lets take a look at some common current draws expected.
Standard 12Volt automotive incandescent lamps 1.5 amp each.
LED light replacement bulbs 0.2 amps each.

Furnace fan 3.5 amp (approx.)

Other items like a lap top computer 3 to 7 amps.

The larger gauge wire is more expensive, which is good for the metal thieves.
Larger wire is harder to handle get into small spaces, larger bend radius, and stiffer.

So it just doesn't seem practical to spend the extra money and effort to use the larger gauge wire.
Referring to the picture of wire sizes, in my area for house wiring 14 gauge is rated for 15 amps and 12 gauge for 20 amps.
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Old 12-08-2011, 08:27 PM   #26
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Automotive chassis wiring is generally rated at higher currents than NEC uses for household wiring.
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Old 12-08-2011, 08:30 PM   #27
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Originally Posted by Laura & Rick View Post
Referring to the picture of wire sizes, in my area for house wiring 14 gauge is rated for 15 amps and 12 gauge for 20 amps.
That's pretty much "electrical code" for breaker sizes as associated with wire size. Code is developed by a bunch of people deciding what would they would make legal and what they would make not legal.
Then there's the physics. I'm not sure what criteria was used for the picture but, my guess is that has to do with heat rise.
I'm probably getting way too technical for most people, so I'll drop out this subject at this time.
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Old 12-08-2011, 09:09 PM   #28
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Quote:
Originally Posted by Byron Kinnaman View Post
That's pretty much "electrical code" for breaker sizes as associated with wire size. Code is developed by a bunch of people deciding what would they would make legal and what they would make not legal.
Then there's the physics. I'm not sure what criteria was used for the picture but, my guess is that has to do with heat rise.
I'm probably getting way too technical for most people, so I'll drop out this subject at this time.
The question was about the wire from the battery to the converter.That wire would feed all the 12V circuits in the trailer.
Before answering the question correctly, other questions must be answered...
1] how far from the battery to the converter?
2] how many 12V cicuits do you use coming off the converter?
3] what loads are supported on those circuits
4] How much power is supplied from the converter to charge the Battery?

Of course if you could answer all those questions you would not need to ask the first one!

Answer... 12ga.
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