Feeding new manufactured building or home

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Mustwin351

Senior Member
Location
Texas
Here is the situation. I maintain a camp on a large military installation. There is one service for my camp that feeds 6 large transformers that feed buildings and areas throughout. One of these transformers feeds a large panel that then feeds two smaller 200A panels that fed laundry tents. Now these tents have gone a way and they've brought in a single wide building with a 100amp panel. This building sits about 10 feet from the dual 200A panels. I wanted to run power to this new building but was unsure on a couple of things. I know running a single branch circuit or multiwire circuit is no problem but unfortunately the 100 amp panel in the new building will not support my load which will contain 3 dryers and 3 washers. I'm guessing it's not legal to run more than one branch circuit (one for the 100amp panel and then one for a new panel I will set on the outside of the building to supply the washers and dryers.)?

I'm sure this is about as clear as mud but a little discussion may help me.

Thanks.
 

qcroanoke

Sometimes I don't know if I'm the boxer or the bag
Location
Roanoke, VA.
Occupation
Sorta retired........
but unfortunately the 100 amp panel in the new building will not support my load which will contain 3 dryers and 3 washers. I'm guessing it's not legal to run more than one branch circuit (one for the 100amp panel and then one for a new panel I will set on the outside of the building to supply the washers and dryers.)?

I'm sure this is about as clear as mud but a little discussion may help me.

Thanks.
Why do you think that? Have you done a load calc?
Funny thing me asking that. I don't know how without a lot of help.
AKA someone else doing it for me......
 

JFletcher

Senior Member
Location
Williamsburg, VA
Why do you think that? Have you done a load calc?
Funny thing me asking that. I don't know how without a lot of help.
AKA someone else doing it for me......

Ditto. But a load calc may not cover real world operation anyway. Off the top of my head, I'd think you could run all three dryers, 2 of the 3 washers, and a small lighting load and stay under or just at 100A in a 240V panel, which is probably worse-actual-case loading. Besides, what are the odds that all 3 dryers are running and have their heating elements on at the same time?
 

kwired

Electron manager
Location
NE Nebraska
Ditto. But a load calc may not cover real world operation anyway. Off the top of my head, I'd think you could run all three dryers, 2 of the 3 washers, and a small lighting load and stay under or just at 100A in a 240V panel, which is probably worse-actual-case loading. Besides, what are the odds that all 3 dryers are running and have their heating elements on at the same time?
3-5500 watt dryers will pull about 69 amps. They may all pull this at same time for a little while if all started at same time, but once they reach operating temp the heat elements will cycle as needed. Washers don't have a lot of demand anymore unless they have a water heating feature. Motor has most demand during spin cycle.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
What type structure are supports your 200 amp panels ?
Sounds silly to ask, I know, but I have encountered similar situations and used a little "trick" to meet Code. Since they are only 10 ft away you might structurally connect the 200 amp panel support to your new building (a couple of 2 x 12s etc) Walla! Two structures now are one :)
You have a route to run your circuits and can install as many as needed.

Food for thought :)
 

kwired

Electron manager
Location
NE Nebraska
Here is the situation. I maintain a camp on a large military installation. There is one service for my camp that feeds 6 large transformers that feed buildings and areas throughout. One of these transformers feeds a large panel that then feeds two smaller 200A panels that fed laundry tents. Now these tents have gone a way and they've brought in a single wide building with a 100amp panel. This building sits about 10 feet from the dual 200A panels. I wanted to run power to this new building but was unsure on a couple of things. I know running a single branch circuit or multiwire circuit is no problem but unfortunately the 100 amp panel in the new building will not support my load which will contain 3 dryers and 3 washers. I'm guessing it's not legal to run more than one branch circuit (one for the 100amp panel and then one for a new panel I will set on the outside of the building to supply the washers and dryers.)?

I'm sure this is about as clear as mud but a little discussion may help me.

Thanks.
I think I can see through your mud:)

As I said in my other post 100 amps very possibly is enough to handle the washers/dryers, but won't have much extra capacity. If there is much other load then you probably are in that marginal area of being able to handle it - especially if there is electric water heating or space heating/cooling that hasn't been mentioned.

One of my ideas without knowing any more about it is to supply a 200 amp panel from your old 200 amp feeder and sub feed the existing panel with a 100 amp breaker.

You can't have two feeders to the building but you can split up the one feeder you do run. You can also tap the main feeder and not put in the 100 amp breaker, but the two (up to six permitted) mains must be grouped in one location so you couldn't put one inside and one outside with this method.
 

Mustwin351

Senior Member
Location
Texas
I think I can see through your mud:)

As I said in my other post 100 amps very possibly is enough to handle the washers/dryers, but won't have much extra capacity. If there is much other load then you probably are in that marginal area of being able to handle it - especially if there is electric water heating or space heating/cooling that hasn't been mentioned.

One of my ideas without knowing any more about it is to supply a 200 amp panel from your old 200 amp feeder and sub feed the existing panel with a 100 amp breaker.

You can't have two feeders to the building but you can split up the one feeder you do run. You can also tap the main feeder and not put in the 100 amp breaker, but the two (up to six permitted) mains must be grouped in one location so you couldn't put one inside and one outside with this method.


Yeah there is an hvac unit that on heat will draw 44 amps according to the nameplate but since it's a continous load it is subject to the 125% so for load calculations it becomes 55 amps. Forgot to mention that the service is single phase 120/208. So based on the code book I figure my dryers drawing 72 amps and my washers at 38 amps (again based on the calculation from the NEC.) All of which totals 154 amps. This is without my lighting and outlet load calculations. Of course real world the load will be much less but we go by the book.

Im thinking of feeding the inside 100 amps panel from one of my outside 200 amp panels and run a second conduit to feed my washer and dryers.

Only issue I think are the panels being about 10 feet away from the building (which Augie47 addressed but that option is not preferable). If I set a separate 200 amp panel on the building and fed it that would solve it but then it's not crystal clear if I then need a ground rod.
 

kwired

Electron manager
Location
NE Nebraska
Yeah there is an hvac unit that on heat will draw 44 amps according to the nameplate but since it's a continous load it is subject to the 125% so for load calculations it becomes 55 amps. Forgot to mention that the service is single phase 120/208. So based on the code book I figure my dryers drawing 72 amps and my washers at 38 amps (again based on the calculation from the NEC.) All of which totals 154 amps. This is without my lighting and outlet load calculations. Of course real world the load will be much less but we go by the book.

Im thinking of feeding the inside 100 amps panel from one of my outside 200 amp panels and run a second conduit to feed my washer and dryers.

Only issue I think are the panels being about 10 feet away from the building (which Augie47 addressed but that option is not preferable). If I set a separate 200 amp panel on the building and fed it that would solve it but then it's not crystal clear if I then need a ground rod.

Something tells me you are overlooking the fact that your electric heating will be less if supplied with 208 volts - same with the dryers. May not be enough to make much difference in what you decide to do, but just keep in mind they will draw less like ~ 25% less VA.

As mentined separate building or structure - needs it's own grounding elecrode system whether service or feeder supplied. If supplied by a branch circuit - usually not, but that doesn't fit what you have here.
 
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