Sizing RV-Park Electrical Services Using NEC Table

By: Jerry Durham | Oct 05, 2018

The Electrical Service supplying an entire RV park must be sized to accommodate the electrical demands of multiple modern recreational vehicles drawing power simultaneously from the individual park sites. The sum of the individual sites within the park, with some additional math applied, determines the total service size for the park.

Per the 2017 NEC, when calculating an RV park service, the load that you count for a single RV site equipped with a 125/250 volt, 50-ampere receptacle has been increased from 9600 volt-amperes to 12,000 volt-amperes.

The load you count for a single RV site equipped with both 30-ampere and 20-ampere receptacles remains unchanged at 3600 volt-amperes. The load counted for a 20-ampere RV site receptacle is 2400 volt-amperes. And the load counted for each 20-amp supply provided at each dedicated tent site is 600 volt-amperes.

The individual RV sites within an RV park are equipped with “supply-equipment” so that the RVs can connect to the available electric. These individual supply enclosures typically consist of more than one receptacle. When a multi-receptacle supply enclosure is dedicated to just a single RV, the load that you count toward determining the size of the entire park service is based on the single highest rated receptacle within that multi-receptacle enclosure. For example, if it contains a 50-ampere as well as a 20-ampere receptacle, you would only count the 50-ampere. However, where the supply enclosure is expected to serve two recreational vehicles, the load you count toward sizing the park service is calculated using the two highest rated receptacles within that enclosure and not just the one.

After adding up the individual sites throughout the park, the next step is to apply the demand factors found in Table 551.73(A). This Table allows for the derating of the park’s service amps based on the total number of individual sites within the park. For example: The demand factor for a service supplying just 1 RV site is 100%, which is just another way of saying that there is no allowable demand factor at all. But when there are 36 or more sites in the park, the demand factor from the Table is 41%, regardless of how many sites there are beyond 36. This means the park electrical service can be sized at an ampacity no greater than what is necessary to adequately supply just 41% of the total load of 36 RV sites, instead of 100% for all 36 sites. This derating is permitted because the NEC assumes that all 36 sites won’t be occupied and in full use at the same time.  Note: The derated demand factors found in this Table are not applied to loads such as RV park bathrooms, recreational buildings, swimming pools, or similar amenities. These loads are calculated separately.

 

Here is an RV Park Service Calculation Example: 

20 sites, and each site is equipped with:

One 50-ampere, 125/250-volt receptacle.

One 30-ampere, 125 volt receptacle.

One 20-ampere, 125 volt receptacle.

You just count the largest receptacle of the three, which is 50-ampere: (20 sites x 50 amp receptacles, worth 12,000 va each: 20 x 12,000 = 240,000 VA)

—————————————-

15 sites, and each site is equipped with:

One 30-ampere, 125 volt receptacle.

One 20-ampere, 125 volt receptacle.

Remember, when both 20-ampere and 30-ampere receptacles are present at one site, the value is 3600VA: (15 sites x 3600va = 54,000 VA)

————————————–

15 sites, and each is equipped with:

One 20-ampere, 125 volt receptacle.

A 20-ampere receptacle is worth 2400va: (15 sites x 2400va = 36,000 VA)

—————————————-

10 sites for tent camping, each equipped with 20amps of power:

Each tent site supplied with 20 amps, counts as 600va: (10 sites x 600va = 6000 VA)

TOTAL VA FOR THESE 60 SITES = 336,000 VA

Demand Factor from Table 551.73(A) is 41 % for 36 or more RV sites, so 336,000 x 41% =137,760 VA

 Finally:  If the RV park’s service is going to be 120/240 single phase, then the minimum ampacity for that service would be determined by taking that 137,760 VA and dividing by 240 V = 574 AMPS

A 600 Amp service would be adequate.

12 thoughts on “Sizing RV-Park Electrical Services Using NEC Table

  1. In the last example, the calculated ampacity was 574 amp. At this point, do I consider the load to be continuous and multiply 574 amps by 125% to get a load of 717.5 amps and use 717.5 amps to size the conductor and breaker or does the calculation that leads to 574 amps take into account weather the load is continuous or non-continuous.

    A similar question is with regards to the branch circuit conductors feeding the pedestal for an individual lot. If the receptacle is 30 amps at 125 volts, is the conductor sized for 30 amps continuous ie 30 x 1.25 = 37.5 amps (#8 wire) or is it sized for the size of receptacle, 30 amps (#10 wire) or is the receptacle considered non-continuous and the conductor is sized to 80%, 30 x 80% = 24 amps

  2. What if your RV Park is all long-term residents and larger than 36 spaces. Would you still have a demand factor from the table or would you consider it 100%.

    1. Greetings,
      The NEC makes no concessions for “long-term residents” in an RV park when it comes to sizing the service and/or feeder conductors serving the entire park – It actually makes no difference if they are long term or short term. Think of it like this- If all 36 spaces are filled for just one day, then that one day either overworks those conductors feeding the RV park, or it doesn’t. One day is more than enough time to overheat conductors and burn an electrical service to the ground. So the issue here is not how long the RV park residents stay. However, I do get where you are going with your question, so stay with me and I will explain to you what the mindset is here, and shall do so by answering your next question regarding RV parks having more than 36 spaces, which is the largest number provided in Table 551.73(A), which we are required to use when calculating the demand on service and feeder conductors serving entire RV parks.
      An RV Park “larger than 36 spaces” as you have mentioned, would actually trigger more leniency from the Code – not less, when it comes to sizing feeder or service-entrance circuit conductors – if we are to use the applicable Table from 551.73(A) to guide us. You notice from that RV park table that, as RV spaces increase within the park, the anticipated demand (meaning the percentage of use expected) on the service and/or feeder conductor(s) feeding that entire park decreases. The reason for this is the same logic that is applied in the construction of the Range Table, found in NEC 220.55. In that range table you see that, as the number of appliances being served by that one service/feeder circuit increases, the overall percentage of anticipated demand on that service/feeder circuit decreases – there is a logical reason for this. The NEC Code-Making Panel(s) make a fair assumption that, when more loads are attached to one circuit, (for example: more ovens being served by one set of electrical service conductors) the likelihood of 100% of those ovens being used/energized at the same time diminishes. So, the NEC requires that service/feeder conductors for multiple ovens be sized based on the percentage of ovens they think will be turned on at any one time. The same logic is at work for the RV park spaces. More spaces in the park means that -odds are- less spaces will be occupied at any one time, and even less of those spaces will be drawing a lot of power at the same time. Yes, there are of course exceptions, but the NEC engineers are working off a calculated average that they have determined.
      Now, don’t misunderstand me, of course the service/feeder conductor size increases every time the number of RV spaces or (or ovens) increases, it is just that the increase gets less and less with the addition of each new RV space (or oven) placed on that one circuit.
      So, to answer your question- “No.” If the RV park has more than 36 spaces it will not change the demand percentage applied to the conductors feeding the park. Remember, the last entry in the RV park demand table says “36 plus” RV sites shall be calculated at 41% of the calculated volt-amps. There is no adjustment to that 41% beyond 36 RV sites.
      Let’s summarize what we have discussed. The service conductors / feeder conductors serving an entire RV park service are calculated by assuming 12,000VA, 3,600VA, 2,400VA or 600VA, for every individual RV parking site in that park, (that wide range of volt-amp values is based on whatever receptacle configuration happens to be available at each individual parking site.) Now, if there was no RV park demand factor that existed (in other words, no Table 551.73(A) to take into consideration) calculating the size of conductors to feed the Park’s electrical service would be easy, for example: If there were 10 RV sites worth 600VA each we would simply multiply 10 sites x 600 volt-amps, and then size the service conductors feeding the entire park at 6000 volt-amps. However, there is a demand factor, and it allows that total volt-amp number to diminish as the number of sites in the park increases; you are only required to size the conductors feeding the whole park at a percentage (or in other words a fraction) of the total volt-amps determined by adding up all of the individual sites in the park. That percentage, or fraction that you are to use is specified in T551.73(A), and it grows smaller as the number of individual RV sites in the park increases. Furthermore, once you reach 36 RV sites or more (per the aforementioned Table), your conductors feeding the RV park’s service are only required to be sized at 41% of the total calculated load for all of the RV sites, no matter how many sites exist beyond that 36.
      If you have 36 RV sites in the park and they add up to 129,600 volt-amps, you must size your service conductors at 41% of 129,600VA – per the Table. If you have 136 RV sites in that same park and those sites add up to a whopping 518,400 volt-amps, you are still required to size your service entrance conductors at 41% of that number. So you see, the conductors feeding the service do get bigger, it is just at what percentage that they grow that the Table determines, and that based on the number of sites in the park.
      Thanks for your question!
      Jerry Durham
      JADE Learning Instructor

  3. If each RV space is equipped with a 50amp,30amp and 20 amp setup do you still count the highest amp. This is for an RV that will have either a 50 or 30 amp service setup.

  4. How many 50 amp RVs can i run off of a 225 amp service in north east Texas given the extreme heat an AC units running constantly?

  5. If I am doing a load calculation on an expansion of (15) 50A pedestals to an existing park, do I use the demand table percentage of .48? What if they expand again the following year with another (15) 50A pedestals, same .48%?

  6. Have an RV park with 131 total sites and using 400 amp meter with 2 200 amp breakers for feeders
    How many sites can we use per 400amp service ? or each 200 amp breaker?

  7. I dont understand your math because I did 20 sites times 50 amp I come up with 1,000 how did you come up to 12,000 VA

    1. Per the 2017 NEC, when calculating an RV park service, the load that you count for a single RV site equipped with a 125/250 volt, 50-ampere receptacle has been increased from 9600 volt-amperes to 12,000 volt-amperes.
      20 sites x 50 amp receptacles, worth 12,000 va each: 20 x 12,000 = 240,000 VA

  8. I am a RV park owner. I have expanded my park twice since I purchased it 5 years ago. The original 19 sites are broken up into 2 200 amp services. 1 200 amp service runs 4 50 amp sites and the other 200 amp service takes care of the 15 30 amp sites. I am having a problem that just started this May. my electric bill doubled and now my 200 amp main breaker pops. None of the breakers at the pedestals or smaller breakers in the box. I have replaced the 200 amp breaker just because it was old (20 years) that didn’t help. I check the amp draw at each wire in the box to see which leg is drawing too much. each leg has 3 sites and they are in a 70 amp double pull breaker. So there are 3 70 amp double pull breakers. I did have a 70 amp breaker drawing 83 amps for more then 5 minutes and the breaker did not pop. That guest and a couple more have since checked out and I am still having the main breaker pop. When I put my amp meter on each wire coming in they are all between 0-40 amps. What ever is causing the spike is impossible to find. Is there a good way to find the spike? I have ordered sense electric monitor but it doesn’t want to blue tooth connect so I am waiting on that reply from them. Any tricks or things I could try short of moving people?

Leave a Reply

Your email address will not be published. Required fields are marked *