30 AMP Cord Length

[Slow Low]

I have a seldom used 5th wheel (Carriage Carri Lite 28') That is on blocks with a hard skirting around it ( Had to do that to make it a "dwelling" for a permit, long story)

My electric service is 250' from the 5th wheel, I have a 50 amp box there.

Can I run 250' of 30 AMP cord and use an adapter to plug into the 50 AMP box?

Not planning on using too much electric at once i.e. nothing plugged into outlets while using the microwave, fridge on LP etc...

Any thoughts would be appreciated.

[Slow Low]

I have a seldom used 5th wheel (Carriage Carri Lite 28') That is on blocks with a hard skirting around it ( Had to do that to make it a "dwelling" for a permit, long story)

My electric service is 250' from the 5th wheel, I have a 50 amp box there.

Can I run 250' of 30 AMP cord and use an adapter to plug into the 50 AMP box?

Not planning on using too much electric at once i.e. nothing plugged into outlets while using the microwave, fridge on LP etc...

Any thoughts would be appreciated.

[GaryKD]

Hi slow,
Welcome to iRV2. Is the 5'ver a 50 or 30 AMP coach? If it is a 30 AMP coach, your okay with a 30 AMP cord. Except for the last paragraph of this post. If it is a 50 AMP coach, I'd go for the extra cost and run a 50 AMP cord.

A 50 AMP line is really 100 AMPS (50 AMPS on each leg). 100 AMPS is a bunch more than 30. I know you said you'd be using the electric wisely; after time if someone gets careless you could have a problem.

Another thing to consider is that there will be a voltage drop during the 250' run. Go here to calculate the voltage drop. Once you see the drop for a 30 AMP cable you may want to consider the 50 AMP for additional safety. The 50 AMP cord will also provide additional longevity for the appliances in the coach. With the voltage drop combined with runing a few appliances at a time will stress the appliances.

[Slow Low]

Wow, thanks Gary.

It's a 30 AMP system. The boxes the electrician put on my power pole are 50 amp is all.

This will be a temp fix until I can get a hard line in the ground this summer.

It's in Northern Arizona town called Show Low.

I call it Slow Low because well, it's slow.

Great site, found it today.

Thanks again!

[Clay L]

For a 30 amp draw, to keep the voltage drop below the NEC recommended 5% the wire size used should be 04 gauge.
For a 20 amp draw 06 gauge would do.

[Route 66]

I'm with Clay.

At a 250' distance, 30 amp cord, which is #10 wire, is too small for that distance.

[Ray,IN]

This wire size calculator and thisvoltage drop calculator are handy to bookmark for future reference.

I think it is much cheaper to buy 3, 250' lengths of #4 copper wire, or #2 aluminum (required to carry 30A-250') than buy one bundled cable that length.
You are commended for asking before jumping in and destroying your RV components with undersized feed wire.

[Clay L]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Ray,IN:
This wire size calculator and thisvoltage drop calculator are handy to bookmark for future reference.

I think it is much cheaper to buy 3, 250' lengths of #4 copper wire, or #2 aluminum (required to carry 30A-250') than buy one bundled cable that length.
You are commended for asking before jumping in and destroying your RV components with undersized feed wire. </div></BLOCKQUOTE>

Ray you might want to take a look at THIS SITE for a down loadable program that finds the proper wire size for a given set of conditions.

I really like it - of course that may be because I wrote it.

[alvinc]

Note: it is possible to use 10 awg wire, but you need to limit the current to 9 amps (4.7% voltage drop).

There are two alternatives:

1) Use house type wire in conduit or direct burial to get the service connection closer to the RV.

2) Purchase Multi-conductor portable power cable and create your 250' extension cord.

Since you describe a semi-permanent location for the 5th wheel, I would invest the money to install a pedestal with the full 50 amp capability.

General Wire sells power cable like you would need, see their catalog and contact a local electric supply house for a price or something similar. Multi-conductor portable cord Note that 3 conductor, 4 awg wire is 920 lbs per 1000 ft.

[Slow Low]

Hmmmmmmm.

The 30 AMP cords I bought worked just fine. They never got hot, ran a vacuum cleaner and the microwave ( not at the same time).

I will over do it with the big gauge wire when I run it proper in a few weeks.

[alvinc]

The 30 amp cord would not get hot, the effect would be reduced voltage and more stress on the appliances. Motors will heat up a bit when presented with low voltage. A vacuum cleaner should work just fine even on 100 volts, just a little slower.

I would worry more about the microwave, it will not like low voltages and will cook slower.

In my earlier mail I stated that a 10awg 250 ft cord can handle up to 9 amps with no more than 5% voltage drop. Since the nominal voltage is 115 VAC, this would translate to 109 VAC at the end of the cord.

If we allow 100 VAC at the cord end (13%), you could draw up to 25 amps. For 105 VAC (8.8%) you could draw 16 amps.

This means that the 10 awg could be used if you limit your current draw. Note, to make sure you meet this limit, you could install a different breaker in your house panel, use a 15 amp breaker rather than a 30 amp breaker.

Remember the breakers can do two things;
1) they are sized to limit the current to less than the ampacity of the wire. This is where the rule of thumb for 15 amps with 14 awg, 20 amps with 12 awg, and 30 amps with 10 awg.

2) breakers can also be used to limit voltage drop, even though they are current devices. What we do is calculate the acceptable voltage drop and choose a breaker rating that will limit the voltage drop. This is why a 15 amp breaker would help limit the current draw at the end of the 250 ft 30 awg cord.

[alvinc]

Let me clarify why the 30 amp cord (10 awg) would not get hot when using it for a 15 amp load.

The capacity of 10 awg wire is designated as 60 amps, even for a 1 foot length. This means that if you exceed 60 amps on a 10 awg wire, it is considered a fire hazard.

If you draw no more than 30 amps over 75 ft a 10 awg wire is a good choice. If you draw no more than 9 amps over 250 ft a 10 awg wire is a good choice.

Why 75 ft.....most RV cords are 25 ft, and you can buy a 50 ft extension cord. Just don't use more than one.