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Old 01-26-2016, 02:02 PM   #21
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true dat

Single phase voltage drop
Vd = 2 K x L x I
CM

Three phase voltage drop
Vd = 1.73 K x L x I
CM



Quote:
Originally Posted by Karl4Cat View Post
One thing in this thread that people are a little confused about is the 50 amp RV outlet. It is indeed a 240V. There is no such thing as an RV 4 wire 50 amp 120V plug. So, if your RV has a 50 amp service, your RV connects to a 240V outlet. There is no difference between it and say a grounded range plug in your kitchen. When the 240 volt hits your RV's breaker/fuse panel it splits into two phases just like in your home and half your circuits pull off one phase and half pull off the other since they are all 120V. For more info, photos, and diagrams go to: RV Electric and click on the 50 amp link in the upper left.

Now in an outlet like the OP wants to install with a 30 amp and 20 amp plugs as well, they only pull off a single phase. Only the 50 amp outlet will get both phases. The good thing about these CE panels is they come with all three outlets pre-wired so all you have to do is hook up your wire to the main input lugs and it's done.

As to the run, I have 200 feet from my house to my RV pad. I used #6 and have no voltage drop issues. I can run all three ac's at once and not go below 117 volts on either phase. I also would have no issue using 6/2 and a separate neutral as the OP was wanting to do.

One last thing for the OP. If you haven't already ordered the CE box from Zoro, Amazon has a lower priced alternative that is a touch better quality from Siemens. It would save you $37...

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Old 01-26-2016, 02:22 PM   #22
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I understand voltage drop calculations Mark. However, when looking at the readout on my load management panel or rechecking with a Wiggy, I just don't get that much drop or at least as much as the calculations would indicate I would. (Thank goodness since I had already bought and pulled my 200 feet of it...LOL) Even when I throw everything I can at it to max out load... I agree with you that more distance than the OP is going to have would be required to be reason for concern.

Another thing I forgot to mention is that if someone wires a 50 amp plug incorrectly as 120V (by having both hots on the same phase) because they think their RV should not be on 240V, you run the risk of overloading the neutral. A lot of people are still confused by horror stories on the net about wiring a 30 amp plug as 240V and cooking the RV. (Which it will..) They automatically think that 240V never applies to an RV because of those incidents when in fact 50 amp is always 240V and an RV that is designed to accept 50 amp is designed to accept 240V...
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Old 01-26-2016, 04:46 PM   #23
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Originally Posted by Karl4Cat View Post
I understand voltage drop calculations Mark. However, when looking at the readout on my load management panel or rechecking with a Wiggy, I just don't get that much drop or at least as much as the calculations would indicate I would. (Thank goodness since I had already bought and pulled my 200 feet of it...LOL) Even when I throw everything I can at it to max out load... I agree with you that more distance than the OP is going to have would be required to be reason for concern.

Another thing I forgot to mention is that if someone wires a 50 amp plug incorrectly as 120V (by having both hots on the same phase) because they think their RV should not be on 240V, you run the risk of overloading the neutral. A lot of people are still confused by horror stories on the net about wiring a 30 amp plug as 240V and cooking the RV. (Which it will..) They automatically think that 240V never applies to an RV because of those incidents when in fact 50 amp is always 240V and an RV that is designed to accept 50 amp is designed to accept 240V...
the statement about overloading the neutral is very wrong on an RV. There are two separate 120 circuits in RV and no 240 Volt appliances. The only way the interconnection between the phases would take some load off the neutral is if it was a 240 Appliance in use. The ideal set up would be to have two separate 120 volt services with each having its own neutral as it is in home wiring. Problem would be it would need a six wire service from 50 amp service plug into RV and I have enough problems lifting the 4 wire. Can't imagine how heavy it would be. There are many RV parks that only have 120 volts run to their 50 amp 4 wire service.
Most RV's I have looked at with 50 Amp service only run the 2nd air and maybe one outlet usually to the Wash dryer off the extra leg. I had problems in a Sierra tripping breaker on inside breaker box.. That is when found the less than desirable wiring. When running Main Air conditioner and a hair dryer or Microwave it would trip a breaker. Everything in camper was on that side of circuit except the 2nd AC and Wash Dryer hook up. I moved the converter from the circuit to the 2nd and no more tripped breakers. Don't ever assume anything when it comes to camper wiring.
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Old 01-26-2016, 05:09 PM   #24
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The reason you don't have to double the size of the neutral in a split phase 240 volt service is that the hots are 180º out of phase and therefore the current the neutral carries is not the sum of the two phases. As long as the 50 amp service to an RV is derived from the split phases (the double pole breaker makes sure that happens) the neutral won't be overloaded.
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Old 01-26-2016, 05:09 PM   #25
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the statement about overloading the neutral is very wrong on an RV. There are two separate 120 circuits in RV and no 240 Volt appliances. The only way the interconnection between the phases would take some load off the neutral is if it was a 240 Appliance in use. The ideal set up would be to have two separate 120 volt services with each having its own neutral as it is in home wiring. Problem would be it would need a six wire service from 50 amp service plug into RV and I have enough problems lifting the 4 wire. Can't imagine how heavy it would be. There are many RV parks that only have 120 volts run to their 50 amp 4 wire service.
Most RV's I have looked at with 50 Amp service only run the 2nd air and maybe one outlet usually to the Wash dryer off the extra leg. I had problems in a Sierra tripping breaker on inside breaker box.. That is when found the less than desirable wiring. When running Main Air conditioner and a hair dryer or Microwave it would trip a breaker. Everything in camper was on that side of circuit except the 2nd AC and Wash Dryer hook up. I moved the converter from the circuit to the 2nd and no more tripped breakers. Don't ever assume anything when it comes to camper wiring.

Actually, it's VERY right. If you have two individual 50 amp breakers on the same phase to try to create a 120 volt service they will in effect share the neutral and can overload it. If wired correctly to a double throw 50 amp breaker supplying 240V with both circuits being out of phase, then no, in a correct wiring situation it can not overload the neutral. So you have it exactly the opposite of correct. 240V 50 amp can not overload the neutral. 120V 50 amp wired incorrectly can.

As to RV parks, if they have a 50 amp outlet wired in phase feeding 120V it is wired incorrectly and has the potential to overload the neutral. Likely? No. But possible and for that reason incorrect. If it is to be wired that way you'd technically need #2 for the neutral as the max potential draw is 100 amps. However you'd still be overloading your RV cord's neutral.

For my RV, both phases in my breaker box are full so I need true 240V 50 service. Also, my load management system will not function correctly if it's not true 240 volt service as it needs to see both phases to know it's running on 50 amp. If the LM center sees 120V it will default to 30 amp and limit AC and electric HW function as it doesn't know 50 amp is available.
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Old 01-26-2016, 05:11 PM   #26
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The reason you don't have to double the size of the neutral in a split phase 240 volt service is that the hots are 180º out of phase and therefore the current the neutral carries is not the sum of the two phases. As long as the 50 amp service to an RV is derived from the split phases (the double pole breaker makes sure that happens) the neutral won't be overloaded.

Exactly, which is why I said if it's wired "incorrectly" as a 120V in phase outlet, it can overload. Wired correctly as a 240V there is no danger of overloading as both 50 lines are out of phase.
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Old 01-26-2016, 05:21 PM   #27
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Exactly, which is why I said if it's wired "incorrectly" as a 120V in phase outlet, it can overload. Wired correctly as a 240V there is no danger of overloading as both 50 lines are out of phase.
You guys need to study up on how the phases of 240 vs 120 works. There is no way the 50 amp breaker mixes the phases. This is only done in the 240 equipment where the 180 degrees out of phase comes into play. You can use two separate single 50 amp breakers if you can find them and they will work just fine. Not saying it is right.
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Old 01-26-2016, 05:25 PM   #28
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You guys need to study up on how the phases of 240 vs 120 works. There is no way the 50 amp breaker mixes the phases. This is only done in the 240 equipment where the 180 degrees out of phase comes into play. You can use two separate single 50 amp breakers if you can find them and they will work just fine. Not saying it is right.

Your not following. A double throw 50 amp breaker can not cause an issue as it by nature has to pull from each buss and therefor provides 240V with 50 X 2 out of phase. If you have two single 50 amp breakers on the same buss (say in location 1 and 3 of your breaker box) feeding the two hots then each is capable of pulling 50 amp on the same phase thus overloading the neutral. If you put them side by side in your breaker box then, no, they will not be on the same phase just like a double throw and then it is a safe install.

Plus, as I said a couple posts back, if a campground was incorrectly wired as you said you've come across and it was a hot time of the year, I would not be able to stay as I'd loose one ac and my electric HW as my LM center would drop those two circuits assuming I was on 30 amp. This has not happened to me to date though. Every park I've been to with my current RV has had their 50 amp outlet wired correctly for 240V.

Lastly, let's not forget, you're not just able to overload the neutral on the feed to the outlet. You also have the potential to overload the neutral on your RV's umbilical.
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Old 01-26-2016, 09:07 PM   #29
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Your not following. A double throw 50 amp breaker can not cause an issue as it by nature has to pull from each buss and therefor provides 240V with 50 X 2 out of phase. If you have two single 50 amp breakers on the same buss (say in location 1 and 3 of your breaker box) feeding the two hots then each is capable of pulling 50 amp on the same phase thus overloading the neutral. If you put them side by side in your breaker box then, no, they will not be on the same phase just like a double throw and then it is a safe install.

Plus, as I said a couple posts back, if a campground was incorrectly wired as you said you've come across and it was a hot time of the year, I would not be able to stay as I'd loose one ac and my electric HW as my LM center would drop those two circuits assuming I was on 30 amp. This has not happened to me to date though. Every park I've been to with my current RV has had their 50 amp outlet wired correctly for 240V.

Lastly, let's not forget, you're not just able to overload the neutral on the feed to the outlet. You also have the potential to overload the neutral on your RV's umbilical.
You are correct I was not following what you said. I did the way you put it here. We are on the same page. I have seen 50 amps wired to the same buss. It was in an old park and the 50 amp plug was not in the same junction box, but the conduit feeding the new 50 came from the old 30 amp box. Didn't take a rocket scientist to figure that one out. This was back in the early 90's when 50 amp was becoming popular. Not many LM centers around back then. I haven't seen too many in a TT or FW either. Where I said that about the two separate breakers was putting them on the same leg would work on RV. Not saying it is right and it will over load the neutral. What is helping with the load on the neutral is the neutral and ground are connected to the same ground buss and the ground is helping carry the load on the neutral on the 120 same leg mis wired 50 amp plug. Not saying it is right at all. Using two separate breakers for 50 amp 120 or 50 amp 240 is an absolutely dumb thing and will present one big time safety hazard.
In the US we do not call anything two phase unless we are only using two conductors derived from a 3 phase system. It's either single or three phase.
That may be what is confusing the issue also.
We have gotten a long ways off the subject of the original post. I have a RV shed with a single 30 amp service and just use the 30 to 50 adapter as I don't live in it and being under shed never try to run both AC's at the same time. Original camper was a 30 amp is why it is set up that way.
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Old 01-27-2016, 12:48 AM   #30
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I thank all of y'all for the good info posted and I've learned a lot. Not saying I understand all of it but I have enough info to proceed.

My friend who is a county building inspector and former electrician came by today to look over what I have planned and said go for it. Unfortunately, since he is an inspector he cannot do any of the work himself or he would just do it for me.

After reading all the comments about the wire gauge/quality/etc I decided to just bite the $$$ bullet and got the 6/3 UF underground wire. Found 125 feet at a flea market for $175 (and I didn't ask where it came from). Changed the outlet box to the one from Lowes ( Shop Eaton 50-Amp, 30-Amp, 20-Amp Overhead or Underground Temporary Power Panel at Lowes.com) and, as mentioned earlier, it's all pre-wired for the hard to do stuff.

Contractor is supposed to show up Thursday or Friday to put up the RV carport. I have to wait for that completion so I can get the exact location to dig the trench to bury the wire and water lines.

Once I get the lines all run and the other wiring done in the carport the local electric company is going to come out and remove the meter to ensure there's no power to the entrance service panel before I make the final connections. I know that's not necessary but there are way too many wires in that panel and y'all need to understand I can be really clumsy at times. They even said they would wait up to 30 minutes for me to make the final connection then they'll re-install the meter. I assume they'll look at what I've done to make sure it's correct before they put the power back. Not even charging me for doing that.

I'll post some pix when the project is completed.
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Old 01-27-2016, 07:59 AM   #31
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Voltage drop does not come into play usually until after 500 ft. Usually if there is a drop it is because of low voltage in the first place,

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Originally Posted by karl4cat View Post
i understand voltage drop calculations mark. However, when looking at the readout on my load management panel or rechecking with a wiggy, i just don't get that much drop or at least as much as the calculations would indicate i would. (thank goodness since i had already bought and pulled my 200 feet of it...lol) even when i throw everything i can at it to max out load... I agree with you that more distance than the op is going to have would be required to be reason for concern.

Another thing i forgot to mention is that if someone wires a 50 amp plug incorrectly as 120v (by having both hots on the same phase) because they think their rv should not be on 240v, you run the risk of overloading the neutral. A lot of people are still confused by horror stories on the net about wiring a 30 amp plug as 240v and cooking the rv. (which it will..) they automatically think that 240v never applies to an rv because of those incidents when in fact 50 amp is always 240v and an rv that is designed to accept 50 amp is designed to accept 240v...
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Old 01-27-2016, 08:00 AM   #32
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Using the calculator I linked to; the return is there; so don't double the distance.

K4C, I plugged in your data; you would have at least an unloaded 122Vac... Voltage drop a little over 6 at 35A load. Also, that panel is a steal! Thanks pointing that out.

However the OP should be in high cotton running on 6AWG.

Voltage drop comes into play no matter the distance. The smaller the gauge the shorter the distance it stops playing nice. When gauge is too small, it warms up it is wasting $$$ when it melts it costs even more dollars. When appliances and expensive electronics gets low voltage, current rises proportionately and can really get into your wallet. That said, if you manage your usage you can get by with less gauge that is recommended.

I only have 30A service and am running on 10AWG for 65'... Only pulling 20A with lights fridge and A/C running, but I make sure that's all.
My voltage drop is less than 3.
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Old 01-27-2016, 08:19 AM   #33
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As I said, I know what the calculation says. However, I start out with about 119-120V and end up around 117 with all three AC's running. I have a magical setup I guess. LOL.
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Old 01-27-2016, 08:28 AM   #34
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Voltage drop does not come into play usually until after 500 ft. Usually if there is a drop it is because of low voltage in the first place,
I'm not sure how you figure that. If that were true I could run 30 amps at 120 volts on a #10 wire 500 feet and still have acceptable voltage at the destination.

According to my calculation the voltage drop would be 35.4 volts so the final voltage would be 84.6 volts. No 120 volt device that I'm aware of would like that.

One should always consider voltage drop when running more than about 20' of wire.
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Old 01-27-2016, 08:30 AM   #35
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I thought a 3 a/c units are managed and don't run at once??? I just read a 15K btu pulls only 11Amps - running. Startup about 16/17. I don't think your EMS will see startup loads. You didn't say how many amps you are pulling when you see that 6 volt drop. Also, could the 200 feet distance be slightly shorter? More than likely the gauge you bought is no more than and could measure no less than. Conductivity of wire is temperature dependent; usually rated at 70°

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Old 01-27-2016, 08:34 AM   #36
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Were never going to agree, to each his own, seen it, done it, its all good,,,,

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i'm not sure how you figure that. If that were true i could run 30 amps at 120 volts on a #10 wire 500 feet and still have acceptable voltage at the destination.

According to my calculation the voltage drop would be 35.4 volts so the final voltage would be 84.6 volts. No 120 volt device that i'm aware of would like that.

One should always consider voltage drop when running more than about 20' of wire.
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Old 01-27-2016, 08:55 AM   #37
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I thought a 3 a/c units are managed and don't run at once??? I just read a 15K btu pulls only 11Amps - running. Startup about 16/17. I don't think your EMS will see startup loads. You didn't say how many amps you are pulling when you see that 6 volt drop. Also, could the 200 feet distance be slightly shorter? More than likely the gauge you bought is no more than and could measure no less than. Conductivity of wire is temperature dependent; usually rated at 70°

It can't be magic... Its science
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No, all three can run at once which was the case on our trip to FL where we met up. Man you guys got some heat down there! The management system only sheds one AC (or my electric HW element) if it senses low voltage. I had more than just the three AC's on when I checked voltage too. I can't remember the amps from the readout. A lot can disappear from the mind in a year when it's not that important to you...LOL.

On length, yep, it's about 196 feet. Bought 200 and had a couple feet leftover. And, that's only to the house. Another 20 feet or so to my breaker box from point of entry. THHN from outlet to house and 6/3 Romex from point of entry to breaker box. Oh and then another 50 feet of RV umbilical from the outlet to the RV. So, closer to 300 feet total of #6 plus all the trailer wiring it has to go through...

Now, here's some more magic that most people never see. The wiring supplied by Onan that runs from the genset to the J-box installed by XLR is tiny stranded wire that looks to be the size of lamp cord. It's commical to see it tied to the #6 in the J-box where it meets XLR's wiring. My last Onan 5500 in my previous hauler was the same. I'm guessing they get away with it because it's such a short run?
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Old 01-27-2016, 09:59 AM   #38
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The calculator produces typical values because the conductor values differ. The type of wire; the conduit, the connects; besides the advertised gauge can make a difference, but these are usually close. I don't doubt for a second what you said is your net voltage. Thanks for explaining about multiple a/c units. If its for me I might skimp on the gauge. The guy that wired up my menagerie if buildings used a voltage drop calculator and he has 39 years experience so; I figured it must be important. The experts say a maximum drop us 3%, but if I came up with 4% at the RV shed, I would do that and not be at all concerned.. it seldom is used and never stressed.

12awg will run 50amp load for 25 feet and stay under 3%
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Old 01-27-2016, 10:09 AM   #39
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I too had an experienced friend help with pulling the wire to my shed and RV outlet. He actually used his discount to get me the wire. Licensed electrician over 20 years and now works high voltage for Eversource for about 5 years, our big utility in the area. Man, his job scares me. You don't just get shocked due to a fail. You don't go home. I can't imagine working on high voltage never mind high voltage transmission and switching. 33-330k. Yikes!
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Old 01-27-2016, 10:10 AM   #40
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The calculator produces typical values because the conductor values differ. The type of wire; the conduit, the connects; besides the advertised gauge can make a difference, but these are usually close. I don't doubt for a second what you said is your net voltage. Thanks for explaining about multiple a/c units. If its for me I might skimp on the gauge. The guy that wired up my menagerie if buildings used a voltage drop calculator and he has 39 years experience so; I figured it must be important. The experts say a maximum drop us 3%, but if I came up with 4% at the RV shed, I would do that and not be at all concerned.. it seldom is used and never stressed.

12awg will run 50amp load for 25 feet and stay under 3%
Brings up another question. I keep seeing and hearing about 110/120 volt or 220/240 volt. It appears we say 120 (or 240) when referring to the voltage output at the entrance service panel. But, it seems most consumer electrical products refer to everything as 110/220.

Would that mean the minimum voltage for that particular device is 110/220? If so, using the 3% drop factor results in a 200 foot run losing 7.2 volts (120 line) or 14.4 volts 240. Either would result in adequate power for the end consumer when thinking about 110/220 (I think).
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