- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
In addition to less current per phase, if the load is balanced you only need to figure the voltage drop on the phase conductors, not the neutral.
RV Voltage Drop
- Thread starter jmshiller
- Start date
- Status
Have better thinking cap on today...
Distribution at the pedestal feeder level can be 3?.
208Y/120V 3? 4W is definitely permitted at electrical entrance. 120/208 1? 3W is definitely permitted at pedestal. Code does not specifically prohibit 208Y/120V 3? 4W at pedestal... but I can tell you that only customized RV would be wired for a 3? supply. See 551.4(A) & (B), 551.31(C), 551.40, 551.42(D), 551.44(D), 551.46(D), and 551.73.
Obviously, voltage drop considerations would differ for a 3? feeder. Jim has indicated using 120/240 service. So I will table further contribution to that discussion until either warranted or solicited.
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Jim,
See linked Excel file for my idea of calculation...
https://drive.google.com/file/d/0By0rzU3UuNh7cFhSQ2R4S3pEbUU/view?usp=sharing
Note I made no consideration for power factor in the wire size determination. 300kcmil would be more suitable given there will likely be one or more inductive loads.
See linked Excel file for my idea of calculation...
https://drive.google.com/file/d/0By0rzU3UuNh7cFhSQ2R4S3pEbUU/view?usp=sharing
Note I made no consideration for power factor in the wire size determination. 300kcmil would be more suitable given there will likely be one or more inductive loads.
Another consideration you may run into is where the end loads are more heavily loaded than the nearest. Take for example substituting 40A for the last three and 34A for the 4th (0 for first three; total 154A). Rmax for this scenario would be 0.064ohms/1000', which would require 350kcmil AL conductors (0.061ohms/1000') with no consideration for power factor.
Perhaps wisest recommendation is to check with AHJ to see how they want the calculation performed... :angel:
Perhaps wisest recommendation is to check with AHJ to see how they want the calculation performed... :angel:
kwired
Electron manager
- Location
- NE Nebraska
Why is 551.40 worded the way it is if they didn't intend to prohibit 208/120 volt systems? Again I don't know any great reason to prohibit a 208 volt system in the first place but they kind of excluded them the way they worded things IMO.Have better thinking cap on today...
Distribution at the pedestal feeder level can be 3?.
208Y/120V 3? 4W is definitely permitted at electrical entrance. 120/208 1? 3W is definitely permitted at pedestal. Code does not specifically prohibit 208Y/120V 3? 4W at pedestal... but I can tell you that only customized RV would be wired for a 3? supply. See 551.4(A) & (B), 551.31(C), 551.40, 551.42(D), 551.44(D), 551.46(D), and 551.73.
Obviously, voltage drop considerations would differ for a 3? feeder. Jim has indicated using 120/240 service. So I will table further contribution to that discussion until either warranted or solicited.
- Location
- Massachusetts
jmshiller
Member
- Location
- Marco Island
RV Voltage Drop
To all of the professionals that have commented, I got something out of every one, including some good local contacts. For the post from the NW, the names are familiar. I was a contractor in Redmond, WA for 25 years, took the Administrators when it had a 2% passing rate 1st time. To summarize, I am still working through the data but have contacted the pedestal provider, they have agreed to help out. (Gee Thanks) However they do not share their Excel data. To everyone that commented, Thanks and as I work through this be assured that I am always available to help others.
To all of the professionals that have commented, I got something out of every one, including some good local contacts. For the post from the NW, the names are familiar. I was a contractor in Redmond, WA for 25 years, took the Administrators when it had a 2% passing rate 1st time. To summarize, I am still working through the data but have contacted the pedestal provider, they have agreed to help out. (Gee Thanks) However they do not share their Excel data. To everyone that commented, Thanks and as I work through this be assured that I am always available to help others.
RV systems are designed for 120/240 supply connection AFAIK. If I had an RV, that's what I'd want to connect to... but given the option of 120/208 or no connection, guess which I'd choose?
kwired
Electron manager
- Location
- NE Nebraska
Same choice here. For the most part there are no 240 volt loads in them either, I think many units with 50 amp plug still use 120 volt air conditioners, they just have more then one AC and must have more then a 30A 120V supply if you want to be able run all the AC.RV systems are designed for 120/240 supply connection AFAIK. If I had an RV, that's what I'd want to connect to... but given the option of 120/208 or no connection, guess which I'd choose?
kwired
Electron manager
- Location
- NE Nebraska
Pay particular attention to the nonsense Don pointed out in post 10, in that thread: "It appears that the panel's intent is to permit 120/208 volt systems to serve the line to line loads, but the other code sections were not changed to permit this.":happysad:
That was posted about 7.5 years ago probably has comments based on 2005 NEC and I think the wording is or nearly is identical still in 2014.
- Location
- Massachusetts
Nonsense? Are you drinking?
The ROP he posted clearly shows the CMP intends to allow 208 volt supplies at RV parks.
And by the way, that thread also shows I am wrong at times.
kwired
Electron manager
- Location
- NE Nebraska
Nonsense? Are you drinking?
The ROP he posted clearly shows the CMP intends to allow 208 volt supplies at RV parks.
And by the way, that thread also shows I am wrong at times.
The nonsense is if it is their intention to allow 208 volts, why do they specifically only mention 120 volts and 120/240 volts as the only supply voltages that are permitted? Must cost too much extra to print a few extra characters in the final result I guess.
But AFAICT, the mention of 120/240 without including 208 is only for equipment voltage rating, not actual supply voltage. When we do have a 120/208 1? 3W system, we typically use 120/240V rated equipment, do we not?
kwired
Electron manager
- Location
- NE Nebraska
Maybe so. What is the danger if one would use a 600 volt fused disconnect instead of a 250 volt fused disconnect in such an application?
If anything the intentions maybe are that the receptacles are limited to 120 volts or 120/240 volts ratings. Which is all you find in this area of application, 15, 20 or 30 amp 120 volt two wire applications or 50 amp 120/240 for three wire applications - plus ground for all of them.
I do not get into campers/RV's etc. all that often, but from what I have seen they typically have all 120 volt loads anyway, there is just more load possible with a unit with a 50 amp plug so the 208 volt application doesn't really present much issues to actual connected loads.
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