# RV park transformer



## besc (May 16, 2010)

Surfed youtube and elsewhere. Need overview of RV transformers.
1. Are they usually 3 or single phase
2. Nominal input voltage
3. Y or Delta primary and secondary
3. Any links I can go to to get info
4. Oh. Hard packed gravel on sight. Ditch witch won't handle it. Any ideas. 
5. Anything else that comes to mind.


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## backstay (Feb 3, 2011)

besc said:


> Surfed youtube and elsewhere. Need overview of RV transformers.
> 1. Are they usually 3 or single phase
> 2. Nominal input voltage
> 3. Y or Delta primary and secondary
> ...


1-3 The answer is the power company. 
4. I never use a chain trencher because of our soil. Mini excavator, I rent at about $350 per day. 
5. What are you doing or want to do. 

As far as the tranny goes, who cares about most of your questions? You want it to be large enough to handle the load and the right secondary voltage. 3 phase would be a plus on large sites.


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## besc (May 16, 2010)

A local RV park owner wants to expand and needs to rplace2 37kw transformers and install a 3rd new one.


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## catsparky1 (Sep 24, 2013)

voltage is ?


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## Southeast Power (Jan 18, 2009)

We have quite a few parks here and I can tell you that I haven't seen a single exception of the POCO here using single phase.
They seem to set a tx for every 8 to 16 trailers depending if they are double wide or not.
If it's campers, no doubt it's 120/240. It's just cheaper to install less primary.


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## backstay (Feb 3, 2011)

I just built one last year for a new 40 site RV park. 800 amp single phase 120/240 service. The PoCo had 3 phase running past it, but put single phase in.


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## besc (May 16, 2010)

Thanks guys


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## MechanicalDVR (Dec 29, 2007)

Suncoast Power said:


> We have quite a few parks here and I can tell you that I haven't seen a single exception of the POCO here using single phase.
> They seem to set a tx for every 8 to 16 trailers depending if they are double wide or not.
> If it's campers, no doubt it's 120/240. It's just cheaper to install less primary.


I've also seen pole mounted transformers here for 3 or 4 doublewides and discos mounted below. Seems like overkill.


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## sbrn33 (Mar 15, 2007)

An RV park is way different from a mobile home park. As in a MH park normally each site is metered and the POCO provides the trans.
A RV park is normally only metered in the service. I have never needed to set transformers for an RV park just the service and separate breakers to each pedestal. There are derating factors that come into play but I normally figure around 3KVA for each site, but that is assuming it is a warm area and they will be using AC quite a bit.


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## backstay (Feb 3, 2011)

Code for a 50 amp receptacle site is 40 amps. Then derating from there.


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## sbrn33 (Mar 15, 2007)

Yep, and 20 units would be right at 3kva. Really nowadays all you need to worry about is AC load.....


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## Cl906um (Jul 21, 2012)

backstay said:


> 1-3 The answer is the power company.
> 4. I never use a chain trencher because of our soil. Mini excavator, I rent at about $350 per day.
> 5. What are you doing or want to do.
> 
> As far as the tranny goes, who cares about most of your questions? You want it to be large enough to handle the load and the right secondary voltage. 3 phase would be a plus on large sites.


We had a campground that was wired years ago someone wired 120/208 3 phase y. Had to change it out and put in single phase 120/240 because all the bigger campers that took 240 were burning out their inverters on 208.


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## Cl906um (Jul 21, 2012)

Cl906um said:


> We had a campground that was wired years ago someone wired 120/208 3 phase y. Had to change it out and put in single phase 120/240 because all the bigger campers that took 240 were burning out their inverters on 208.


I think most campers even the higher volt ones will work off of 1 leg jumpered over though. Just a few were having this problem. Article 551 does tell you to provide 120/240 nominal.


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## besc (May 16, 2010)

Hay Backstay. That seems to be a really big derating factor. Is that something unique to RV parks. And hay sbrn23. Could you show me how the 3kva calculates to 20 units? Sorry for the ignorance.


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## sbrn33 (Mar 15, 2007)

besc said:


> Hay Backstay. That seems to be a really big derating factor. Is that something unique to RV parks. And hay sbrn23. Could you show me how the 3kva calculates to 20 units? Sorry for the ignorance.


I doesn't, that is based off experience. I actually calcs out to around 4,300 each. Read art.551 and make sure to check out table 551.73A.
In my experience most campers only draw around 3,000 watts. most less and some big ones way more. If it is a campground that number is fine if it is a live in campground you may want to bump it up a bit.


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## backstay (Feb 3, 2011)

besc said:


> Hay Backstay. That seems to be a really big derating factor. Is that something unique to RV parks. And hay sbrn23. Could you show me how the 3kva calculates to 20 units? Sorry for the ignorance.


Seven sites and up are 55% of 9600VA. It's in the book. If you had mostly big 5th wheels, and you were somewhere far south. You may need more power. But that number is the minimum NEC allows. And yes, RV parks not trailer parks.


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