Construction Trailer Power Requirements

[AWinston]

I am reviewing temporary power schematics for a big job. A switchboard (560kVA/1600A (2000A NEMA 3R) 208V/120V 3PH) is to supply 40 construction trailers. Is there a general power requirement for construction trailers? Unfortunately there are a lot of different subs with different sized trailers, so I don't know anything about the trailers. The schematics show a 125A 120V/240V single phase panel for each trailer.

My concern is that the switchboard isn't rated high enough.

 

[iwire]

The schematics show a 125A 120V/240V single phase panel for each trailer. .

That is pretty common for full size trailers with HVAC.

I have not seen one that needed more than that.

 

[Ponchik]

I am sure not a single trailer will draw 125A. In fact I don't think it will ever get close to 50Amps, if it does it will be for a very short period of time. 1600 AMPS of available current is A LOT of current.

 

[iwire]

I am sure not a single trailer will draw 125A. In fact I don't think it will ever get close to 50Amps, if it does it will be for a very short period of time.

Actully the 125 amp ones will often draw close to 100 amps when the electric furnace is running.

The electric heat is about 90% of the load.

 

[AWinston]

I am sure not a single trailer will draw 125A. In fact I don't think it will ever get close to 50Amps, if it does it will be for a very short period of time. 1600 AMPS of available current is A LOT of current.

I figured no one would get close to 125A. I assumed about 80A.

 

[Iron_Ben]

It looks big enough to me. 560 kva spread across 40 trailers is 14 kva per trailer. Yes I know it's not likely that all three phases will be loaded exactly the same. But 14 kva is decent load. A lot of 1,500 to 2,000 sq ft houses will never draw that (over a 15 minute interval). So even on the hottest of hot days or coldest of cold, I think you'll be fine.

 

[AWinston]

Thanks guys. This was my first time dealing with temp power for this many trailers. I didn't want to make any assumptions.

 

[iwire]

It looks big enough to me. 560 kva spread across 40 trailers is 14 kva per trailer. Yes I know it's not likely that all three phases will be loaded exactly the same. But 14 kva is decent load. A lot of 1,500 to 2,000 sq ft houses will never draw that (over a 15 minute interval). So even on the hottest of hot days or coldest of cold, I think you'll be fine.

I would not compare a job trailer with a home.

Homes have real insulation and don't usually have a furnace with a MCA of 90 amps which is what I see very often

That said with 40 trailers there is a lot of diversity.

 

[GoldDigger]

...
That said with 40 trailers there is a lot of diversity.

But not if they are all occupied and a cold snap hits!
The diversity would be limited by the on/off cycle factor of the heating.

 

[iwire]

But not if they are all occupied and a cold snap hits!
The diversity would be limited by the on/off cycle factor of the heating.

No one turns off the heat in a job trailer so it would be unlikely (yes anything is possible) that they will be running in sync.

Another way to do it would be figure for all running all the time but that is going to be about a 3,000 amp 3 phase service at 208.

 

[ptonsparky]

Where is the job? Southern California?