Maximum Amperage Draw

[TheNescios]

Am working on figuring out how many amps an RV typically draws during high usage - anyone have information on this?
It all stems from needing to calculate the line loss on a 330-350 foot long feed from the panel to the 50amp power pedestal.
With both AC's, fireplace, and almost everything but the microwave running I got 22.46 on L1 & 16.34 on L2 for a total just under 40amps.
Unless I'm missing something, only way I'd see a true 50amp draw is if every system started at the same time?
Is this typical of what others have seen?
Reason for the questions are the cost of the wire for the location I'm hoping to use next year could be as much as $3 per foot x 3 legs x 330 LF or a potential swing of $3000 to get power to the pedestal.
And I may go for something other than what I currently have right now so want to make sure I don't have issues in the future?
Appreciate any information or feedback I can get on this.
Chris

[Scott'n'Wendy]

If you are plugging into a 50A plug, code requires you to use wire capable of handling 50A. Over 350 feet, there are code requirements for line loss that will dictate an increase in wire ga.....or not...depending on location.

[TedS]

If you are wiring to code then it's driven by rated capacity, not actual demand. Otherwise, it's a bootleg project and you are on your own.

[Jkwilson]

The total current is not relevant here. It’s 50A on a 120/240 circuit which is 50A on each leg.

You need to be concerned about having enough wire to prevent sag when the ACs are starting which will be about 5 more Amps each. I’d be a little worried you might get a different rig and end up spending the money twice.

Any possibility you can just put another service line closer? Here it costs about $15 a month plus electrical usage. It would take a long time to spend that $3000 at $15 a month.

[TheNescios]

Agree with the code requirements, and unfortunately in this area everything beyond the meter is the owner's to deal with.
With residences there is a factor that gets applied for usage which is why we don't have quite a bit larger wire diameter feeding our homes.
Same factors don't seem to exist for RV's so the electrical design person I'm working with is applying essentially industrial loading factors.
Seems reasonable to me that the same factors of usage vs total value should apply to RV's - but I'm still new enough to full time RV'ing (little over a year) that I'm looking for input.
Key is what percent of the time 100% of the capacity will be required and from my limited investigation I'm wondering if there are any RV's that actually max out a standard 50amp supply?

[Scott'n'Wendy]

I'm wondering if there are any RV's that actually max out a standard 50amp supply?

I doubt it. How many people would have the fireplace, the furnace and the A/C on, with the fridge on max while microwaving a sandwich?
But the RV manufacturer probably has to size the wire/plug according to possible loading

[TedS]

Max voltage drop should be 3 to 4 volts at the current you expect to draw. Size the wire based on that.

[JBill9694]

Let's not forget that the breaker protects the devices down line of the breaker. If you have a 50-amp breaker in the subpanel then the wiring upline of it better be capable of carrying 50-amps plus line lost. Similarly, the breaker(s) in the main panel will need to be sized for the 50-amps plus line lost.

[TheNescios]

Closing the loop on this, turns out there is a "diversity" calculation used for residential applications which looks at not only the maximum potential electrical usage/load but also the typical usage/load plus there are some additional calculations for allowable voltage drop - I won't pretend to understand all the nuances but the electrical engineer did and he's a pretty smart person.
When this was applied to what I'm trying to do, it got things to a reasonable compromise between gold plated and sketchy - and meets all the applicable electrical codes & standards.
So, bit more $$ than I was hoping for, but less than the $$$$ initially being called for?

[ncitro]

TheNescios While everyone is right here that the wire size is based on the breaker protecting it (technically its the other way around), the thing to do if you are looking to use smaller wire is use a smaller breaker. If you can get by with 30 amps on each leg, you could use a double pole 30 amp breaker and then run smaller wire. You could still use a 50 amp outlet, so no dog bone would be needed, and you would still have 30 amps on each leg, and would be able to use smaller wire (as small as #10 instead of #6 if the run is short enough). I frequently do this when I moochdock and need to wire into someones panel in the garage. Since I only have two AC units I do not ever need more than two legs of 30 amps.

[TheNescios]

Neil,
You hit on an important point - the breaker is protecting the wire - and while not for my own RV, have done something similar for others and project trailers over the years.
What I wasn't aware of was the diversity calculation which I think has given me a good balance of "needs & wants" for the installation - how often will I run the AC units, convection microwave, electric fireplace, and a washer/dryer and have a crockpot or other countertop appliance running? Based on the information I got from my amp meter and lacking additional data, starting to think the standard 50 amp service has a reserve factor that most of us would struggle to max out - how often do multiple AC units kick off at the same time while pushing the start button on the convection microwave?
Plus, if it doesn't work like it's calculated to, I can always put a smaller 2 pole breaker in like you described and deal with it that way?
Do feel fortunate I was able to trade some tractor work and get input from an electrical engineer I know - they understand the details much better than I do!
Chris

[Guest]

I just paid for a 50amp 230V system install with a GFCI and it was painfully expensive. The electrician wanted to use aluminum and I insisted on copper so the price reflected that choice. Not a good time to buy copper.

Jim

[Scott'n'Wendy]

In larger gauges, nothing wrong with aluminium. I would have had no problem with aluminium. Smaller gauges, a little more problematic.

[Guest]

In larger gauges, nothing wrong with aluminium. I would have had no problem with aluminum. Smaller gauges, a little more problematic.

Scott,

I agree but corrosion can be a problem where aluminum oxidation is not conductive. And aluminum creeps.
I just did not want to deal with it and it bothers me enough that the 200amp main coming in is aluminum. That I could live with if the aluminum main used copper ferrules. I'm not an EE or an electrician but I did see a competitive auto maker use aluminum wire in a hybrid vehicle application and it melted down which grossly delayed their launch. We used copper.

Perhaps this is the cause of my aluminum phobia. LOL.

Jim

[Scott'n'Wendy]

No doubt. Copper is better. But aluminium can be installed safely/correctly as well. Not sure what you mean by 'Aluminium creeps'?