RV park electrical loads

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102 Inspector

Senior Member
Location
N/E Indiana
Occupation
Inspector- All facets
I am trying to work with our local park department that runs the campground. Is there a site available to determine basic load calculations for each main run from the service panel. Each pedestal is fed from a double pole breaker at the main panel then daisy chained through seven (7) panels which have 2-30 amp hook-ups each. If I read Article 551.73 correctly, this puts the load calculation at 100.3 amps which exceeds the 80 amp continuous load allowed for the 100 DP breaker. They had numerous times that the breaker tripped during the summer and I feel they need to split the branch lines in half. Like every other community, they have no money to work with but hope to do a total new installation within 5 years to accommodate the larger units people are trying to bring in. Any guidance appreciated. I am the local inspector for the community and have never had to deal with RV parks, this one has been here for 40 years+.
 

102 Inspector

Senior Member
Location
N/E Indiana
Occupation
Inspector- All facets
I guess because I know how most people crank up their electrical when they plug in and don't worry about the meter spinning since it is normally included in site rental fees. I am considering the July 4th weekend when it gets 95 degrees with 90% humidity also. I think they will definitely have to talk to the POCO about additional pad transformers if they want to use what they have and then consider any kind of expansion.
 

david

Senior Member
Location
Pennsylvania
I am trying to work with our local park department that runs the campground. Is there a site available to determine basic load calculations for each main run from the service panel. Each pedestal is fed from a double pole breaker at the main panel then daisy chained through seven (7) panels which have 2-30 amp hook-ups each. If I read Article 551.73 correctly, this puts the load calculation at 100.3 amps which exceeds the 80 amp continuous load allowed for the 100 DP breaker. They had numerous times that the breaker tripped during the summer and I feel they need to split the branch lines in half. Like every other community, they have no money to work with but hope to do a total new installation within 5 years to accommodate the larger units people are trying to bring in. Any guidance appreciated. I am the local inspector for the community and have never had to deal with RV parks, this one has been here for 40 years+.

the calculated load of the feeder being 100.3 or 100.8 would end up being a feeder with a rating 110 amps
based on 240.6
 

iwire

Moderator
Staff member
Location
Massachusetts
I guess because I know how most people crank up their electrical when they plug in and don't worry about the meter spinning since it is normally included in site rental fees. I am considering the July 4th weekend when it gets 95 degrees with 90% humidity also. I think they will definitely have to talk to the POCO about additional pad transformers if they want to use what they have and then consider any kind of expansion.

The load on the feeders is not a continuous load per the definition in article 100. Unless there is a section in 551 requiring it to be traeated as one I would not.

Continuous Load. A load where the maximum current is
expected to continue for 3 hours or more.


I would not expect each of the 14 two pole 30s to be maxed out durring the same period of time.

That being said you mentioned the feeders have tripped, could it be a short circuit in someones camper that was an issue? You can take a main out without tripping the two pole 30.

All I am suggesting is taking some hot day, full campground current measurements before throwing what little money they have at it. :)
 

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
My 2 cents,
be aware of a little footnote that the minimum calculated load for RV parks and the demand factors that can be applied may not work well for all types of campsites. Fairs, special event activities will push and at times blow the calcs out of the water.

Take for example, Over the years we have installed camping sites at fairgrounds all under the load calc requirements set by NEC. Now because all these sites are used/occupied and durring periods of the day (especially if it's above 90*) some of the sections of campsites would trip feeder breakers. We have mostly 400 amp (320a) services which by load calcs worked at the time they were first installed but now we're pulling 390+ amps at times and even fried the POCO secondary in half (even they didn't figure on the load that would be imposed).

So think about going heavier, I don't think the load calcs in the NEC address issues like campers adding beer fridges outside their camper or the ever more increasing size of campers with double/triple A/C's, washing machines, etc.

The last campground we did actually has demand factors based on all sites @ the 50 amp rating, so the calcs I'm sure should be good for quite a while.
 

kwired

Electron manager
Location
NE Nebraska
My 2 cents,
be aware of a little footnote that the minimum calculated load for RV parks and the demand factors that can be applied may not work well for all types of campsites. Fairs, special event activities will push and at times blow the calcs out of the water.

Take for example, Over the years we have installed camping sites at fairgrounds all under the load calc requirements set by NEC. Now because all these sites are used/occupied and durring periods of the day (especially if it's above 90*) some of the sections of campsites would trip feeder breakers. We have mostly 400 amp (320a) services which by load calcs worked at the time they were first installed but now we're pulling 390+ amps at times and even fried the POCO secondary in half (even they didn't figure on the load that would be imposed).

So think about going heavier, I don't think the load calcs in the NEC address issues like campers adding beer fridges outside their camper or the ever more increasing size of campers with double/triple A/C's, washing machines, etc.

The last campground we did actually has demand factors based on all sites @ the 50 amp rating, so the calcs I'm sure should be good for quite a while.
If they only have a 30 amp receptacle at each site - you are not ordinarily going to run double/triple AC's without tripping the 30 amp breaker for that individual site. I suppose you may be able to plug your 50 amp to 30 amp cheater in and possibly run two AC's but will have little or no capacity for anything else. Then on top of that if you have a 20 amp receptacle at the site as well there could be additional load running on that.


Another thing to consider is load balancing - those 30 amp receptacles are 120 volt - Get too many on one line and not so many on the other line and you may trip the main - load calculations in NEC are typically just VA values and you need to spread that around on multiwire systems or go with a larger system if you are going to have an imbalance.
 

JFletcher

Senior Member
Location
Williamsburg, VA
I am trying to work with our local park department that runs the campground. Is there a site available to determine basic load calculations for each main run from the service panel. Each pedestal is fed from a double pole breaker at the main panel then daisy chained through seven (7) panels which have 2-30 amp hook-ups each. If I read Article 551.73 correctly, this puts the load calculation at 100.3 amps which exceeds the 80 amp continuous load allowed for the 100 DP breaker. They had numerous times that the breaker tripped during the summer and I feel they need to split the branch lines in half. Like every other community, they have no money to work with but hope to do a total new installation within 5 years to accommodate the larger units people are trying to bring in. Any guidance appreciated. I am the local inspector for the community and have never had to deal with RV parks, this one has been here for 40 years+.

During summer, and a busy week/weekend, all pedestals could be in use and near maximum demand. If I understand correctly, there are 14 120V 30A hookups per 100A 2p breaker (or, effectively, 7 240V 30A hookups). 100.3A is probably not going to trip a 100A breaker, even continuously. The amperage draw is probably much higher than your calculation.

Like kwired mentioned, balancing the loads may help quite a bit. Is the main panel in a climate-controlled room? Ambient temperature for the breakers plays a part in their current carrying capacity. Until the totally new install is complete, several ideas come to mind:

1) Climate control for main breaker room
2) Load balancing between legs. If all 14 panels are in use, 7 15A loads on one leg and 7 on another is going to work much better than, say, a 9/5 split.
3) Reducing the number of RVs per main breaker, either by splitting branch lines like you suggest, or not booking all lots (first has capital cost, second has revenue loss). Balancing booking a more even number of smaller and larger RVs per string of pedestals may help, if that's possible.
4) If the existing wiring permits, a larger main breaker would be the cheapest/fastest route. I suspect tho the existing wiring is insufficient for a 125A+ breaker.
 

JFletcher

Senior Member
Location
Williamsburg, VA
Why would you call this a continuous load? Is there a section in 551 that says we have to?

NEC aside, consider this: 95*, 90% RH day (all AC's running). 4th of July weekend (all slots booked). RVs have fairly low insulation, so they bleed heat and cold to ambient. ACs may not run 3+ hours continuous, but if (when) all run 30 minutes at the same time, a tripped main is happening anyway.

So, you may not have to size for continuous per the NEC. But the 1 and 2 star on-line reviews and complaints your campsite gets for not being able to keep the power on has far more impact on the owner's bottom line.
 

mgookin

Senior Member
Location
Fort Myers, FL
You can put any size receptacle you want and it's not going to change the load the customer pulls. You can only limit that with the breaker at their pedestal. Those motorhome people have every adapter under the sun to be able to connect to anything you provide. Motorhomes have certainly grown in size over the past few decades. They are bigger today and full of luxury which includes lots of ice cold A/C.
 

iwire

Moderator
Staff member
Location
Massachusetts
NEC aside, consider this: 95*, 90% RH day (all AC's running). 4th of July weekend (all slots booked). RVs have fairly low insulation, so they bleed heat and cold to ambient. ACs may not run 3+ hours continuous, but if (when) all run 30 minutes at the same time, a tripped main is happening anyway.

So, you may not have to size for continuous per the NEC. But the 1 and 2 star on-line reviews and complaints your campsite gets for not being able to keep the power on has far more impact on the owner's bottom line.

I have consider it and there is no way the feeder breaker supplying 14 RVs going to be a continuos load per NEC defintion even if every RV leaves the AC on with the doors open.
 

iwire

Moderator
Staff member
Location
Massachusetts
Let me ask this question.

Does it make sense to just assume it is an overload issue without some sort of measurements taken?

Again, a short circuit in a branch breaker can drop a feeder breaker.
 

Smart $

Esteemed Member
Location
Ohio
I have consider it and there is no way the feeder breaker supplying 14 RVs going to be a continuos load per NEC defintion even if every RV leaves the AC on with the doors open.
So... having considered it, what factor(s) do you believe is(are) going to make the AC units a noncontinuous load under those conditions?
 

iwire

Moderator
Staff member
Location
Massachusetts
So... having considered it, what factor(s) do you believe is(are) going to make the AC units a noncontinuous load under those conditions?

The ACs may well be continuos but that is not the max load is it? Campers have other loads that will be cycling such as refrigerators, lighting etc. But that issue aside, the calcultion is 0.3 amps over 100, is it really that imaginary .3 amps tripping the breaker?

And again we have no measurements of the actul load being drawn so in my own opinion we cannot tell why these breakers are tripping.
 

Smart $

Esteemed Member
Location
Ohio
The ACs may well be continuos but that is not the max load is it? Campers have other loads that will be cycling such as refrigerators, lighting etc. But that issue aside, the calcultion is 0.3 amps over 100, is it really that imaginary .3 amps tripping the breaker?
The calculation result is all that is provided. We do not know how it was calculated. A 100.3A result indicates a overloaded 100A circuit. FWIW, a 551.73 load calculation makes no consideration for continuous vs. noncontinuous load. We are also left assuming Table 551.73(A) demand factoring has been applied, but until stated, we do not know for certain.

And again we have no measurements of the actul load being drawn so in my own opinion we cannot tell why these breakers are tripping.
Yes, more details or some investigation appears required, especially since this park has been in service for 40yrs.
 

iwire

Moderator
Staff member
Location
Massachusetts
I know... the statement sounds ridiculous taken out of context. But it is not a matter of in-the-field use, rather the application of Code, which is essentially the same as a "textbook application".

Fair enough, and you are right of course 100.3 is greater than 100.


I just keep thinking of the same thing you also pointed out.

this park has been in service for 40yrs

To me that suggests it is something other than the peak load that is tripping the breaker.

That said, I certainly could be wrong again. :)
 

kwired

Electron manager
Location
NE Nebraska
Weak connection on a main breaker termination causing enough heat to trip the breaker?

Bad contact within the breaker doing the same?

I had a 200 amp main breaker on some ball field lights only installed 5 years ago that kept tripping all of a sudden this past summer. Line/load terminations seemed good but fall of potential test across breaker indicated there must be something wrong inside. Don't remeber the load - probably between 120 to 150 amps and was a fixed load unlike OP where the load can vary.
 
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