Can I go over 100 feet with AC extention?

kcaravelli · 07-18-2010, 10:49 PM

I am at about 100 feet with my AC extended from the house out into our field where the motorhome is.

We live full-time in the HM.

I have the stock cord coming from the coach, 33' Suncruiser (30amp) service. In addition to that I have 50' 30amp cord purchased from Camping World and a 25' also purchased from Camping World. That last one is plugged into the 30amp receptable on the outside of the house which is on the other side of the wall from the actual electric panel in the house.

I am very close to the length I need to be ideal. I can pull the coach a few feet forward to make it work better (it's a close fit right now"). I would like to think that I can use my extra 25' power cord to make it a total of 125 but somehow that seems like someone is going to tell me it's too far.

I run my computer and of course the heat exchangers and so forth. As I mentioned, we are full-timers.

Can I get a 4 foot extension and make it work or is the 100' limit I have heard about theoretical?

I am wondering if this cord is going to over heat drawing across that distance or if my appliances will get damaged by low voltage?

Because this one is a safety issue in my opinion, please qualify your background. I really need to know what the correct answer is. I have thought of calling my electrician but I'm not sure it warrants that. Sometimes these folks just don't understand how these coaches run.

Thanks, sorry for the long post.

RJay · 07-18-2010, 11:03 PM

Since you already have the cord, go ahead and hook it up and take voltage readings at a kitchen receptacle with no load and then run the microwave or coffee maker or A/C or any combination and see what the voltage is at the same receptacle. I think you'll see a difference between no load voltage and the voltage when you have the appliances running. If the voltage is below 108 volts you will have to either increase the wire size, shorten the distance from the house to the RV or be selective in what loads you run at the same time.

1ciderdog · 07-18-2010, 11:26 PM

I don't know if this will apply to your situation but this past week we visited daughter and family in Tracy, CA and outside temp was at 100 or slightly above in the late afternoon. I have basement air that pulls according to the wall gauge 23 - 24 amps. I installed a 30 amp RV plug in the shop. I was parked far enough away from the shop that I needed to add a 50 foot heavy duty (#8 wire) extension cord to the RV cord. This ran the A/C for a couple of hours then apparently the heat build up restriction was enough to drop the amperage to where the A/C would not run. I moved the RV closer to the plug - removed the extension cord - and attached the RV cord directly to the 30 amp plug. That ran the A/C and everything else for the rest of the time we were there, another two days without problem. You will get your voltage but you may lose to much amperage to run heavy draw items you want to use.

RVDude · 07-18-2010, 11:41 PM

Here's a very comprehensive voltage drop calculator.
Voltage Drop Calculator

NeilV · 07-19-2010, 04:52 AM

If you are full time and that is your regular location then have a proper service run to your rig that will support you within reach of your coachs built in power lead. Even if you have the proper wire size in your extension cords you will not be really kosher unless there are waterproof connectors on the connections exposed to the weather.

I help with disaster relief and in most parts of the country the standard RV extensions sold at Camping World for example will not pass muster with a safety inspector unless you raise the connections off the ground in a water resistant enclosure of some kind.

Clay L · 07-19-2010, 09:43 AM

You can download a program HERE that will calculate the wire size necessary. I would use 114 volt as the desired voltage at the load (a five percent drop). That would give you some leeway since a ten percent drop is the maximum I see recommended.

Always-RVing · 07-19-2010, 10:09 AM

The most simple thing to remember is: The Longer run needs a larger, heavier gauge wire to compensate for the voltage drop.

More appliances and electronics are damaged due to low voltage than high or over voltage.

Always-RVing · 07-19-2010, 10:53 AM

Here is an example:

Say you're running a standard typical copper 2 conductor wire, pushing 125 volts over 12 AWG gauge, single phase for 100 feet, load current at 25 amps. You voltage drop or loss is:

7.6% or 9.5 voltage loss and the other end. The 125 volts is now 115.5v as seen at the load end.

Take the same and go 200 feet. Drop or loss is now 15.2% and now at 106v

Take the same and now use 8 AWG gauge wire instead of 12 awg: 200 feet the drop is: 5.9% or 117v

Think of voltage as water pressure, current as the water flow and the pipe as the wire that carries the flow. Trying to push too much water through too small of a pipe may cause a burst where in the electrical would it would heat up and burn up.

Electrical to water: Valve is to water as a resistor is to electricity. Water flow one way check valve is to water as a diode is to electricity. It only allows flow in one direction.

Taking this just a little more... What would you have if say the voltage was around 240v, but the current or flow is a whopping 300 amps? -> Arc Welder

The opposite... Say you have a device that has millions of volts but next to nothing in current?

RocketDork · 07-19-2010, 11:31 AM

The 100' limit is something I've never heard of...not that it matters. 100' is not a limit if things are designed properly...how many MILES of wire delivered the power to your house?

A 10 gauge extension cord from Camping world will work just fine, as long as the CURRENT you are drawing is low, say, less than 10 amps. It's not going to be suitable for the full 30 amps.

The question about your appliances is best answered by "it depends". That's the best I can give you.

If you want to be sure that you are going to be OK on the full 30 amp draw, without tripping breakers in the house, over heating the cord and possibly damaging some of the appliances in your coach, you should either have a custom cord made that is 6 gauge, or run a buried set of wires of the same gauge. Think of a power post like you'd see at a camp ground. Neither is cheap, but your safety is at stake.

I'm not an electrician, I don't even play one on TV...nor did I stay in a Holiday Inn Express. I am a Electrical Engineer by trade...

As much as you hate to hear it, I'd hire an electrician to run the wire and make the connections. He's going to be familiar with local code, along with the best way to get the power you need to your coach (house!)

kcaravelli · 07-20-2010, 12:31 AM

I like your idea of a custom 6 gauge cord. I can afford the cord. I can't afford the damage to the coach. I also can't run the conduit under the ground in this case. If a custom cord will do then that is great. Thanks. I can take the 50' entension I purchased back to camping world. I will call the Electical shop I hired to put in the 30amp service and discuss this with them. Thanks again.

1ciderdog · 07-22-2010, 02:14 PM

I stumbled on this while looking for something else. It has a voltage drop calculator. You put in wire type: copper or aluminun; wire size; amps; & distance and it will tell you the voltage drop. So easy even I can do it.

American Wire Gauge table and AWG Electrical Current Load Limits with skin depth frequencies

Dagwood · 07-22-2010, 05:28 PM

According to the calculator rvdude linked to you will be marginal at 30 amps, 113 degrees and 150 feet with 10 guage wire. Some things like the ac may be a little anemic.

mudpuppy · 07-22-2010, 07:10 PM

First let me say you do not get something for nothing. I often find myself a long way from the outlet provided by my host. Here is my solution. I have two custom made 10/3 cords. One is 100 feet the other is 50 feet. To overcome the voltage drop at the end of such a long run ether 100 or 150 feet I use an auto-transformer to bring the voltage back up to acceptable levels. Now here's the rub, as I boost the voltage I increase the current draw at the input to the auto-transformer up to 30 amps but have less available in the MH. Simply put at 150 feet I now have a 25 amp MH. If you are in a semi permanent situation I would opt for the bigger wire.

wa8yxm · 07-22-2010, 09:15 PM

Try this.. Plug in a volt meter. one of the best is the popular Kill-A-Watt, Push the VOLTS button and try a few things.. Start with everything major turned off (This does not include televisions) and the water heater COLD..

Let the batteries charge overnight unless they are already full up. Then note the AC voltage on the Kill-a-watt.

Turn on the water heater, Note the voltage when the heat element kicks in

Subtract, this gives you a voltage drop, Now double it.. And subtract that number from the first number. (No load voltage)

Example. NO load 125,, Water heater on 120,, Difference 5, double that to 10, subtract from 125 gives 115

Safe to use that cord set

Example, no load 125, Water heater on 111, Difference 14, double that 28 Subtracted from 125 = 97.. You need heavier cord.

I would want at least 110 volts, for the final calculated voltage

NOTE that running the water heater on GAS only reduces the load,,, If the loaded voltage is too low you can try running the water heater on gas, then use EITHER the Microwave OR the air conditioner, but never both.