Figuring Power Needed

A

Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
Have a unique situation where existing modular buildings( about 15) are being relocated and we need to temp them out. All I have is an existing one line showing different boards feeding the buildings to be relocated. Not all are being relocated.

If I just have below and say there are, (as an example), 15 of them like this being fed from 100A breaker that would not necessarily mean I need 1500A source of power correct? It would never demand that much at once? With the limited info I have could I just take 80% of the total amperage and say I need that much power at the source? Thanks

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It's safe to assume you don't need 1500 amps but without more information it's just a SWAG.
80%, 50%, 30%, who knows.
There is no way of knowing until you get more input,,,,what are they used for ?, heat and air conditioning involved, any process equipment, etc ?
 
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As Augie stated based on your limited information there is no way to determine what the minimum ampacity would be. Someone would need to look at the existing modular units and try to come up with a load.
 
When you say temped out, what do you mean? You are wiring them temporarily? Because if so, I wouldn't dwell much on the loads. Find the minimum ampacity of the HVAC unit, add 3VA per square foot for lighting and go with that. If it is for permanent, then either do a proper load calculation, or install a 30 day monitor, or possibly ask the provider of the modulars and see if they already have the load calculations.
 
Strathead said:
When you say temped out, what do you mean? You are wiring them temporarily? Because if so, I wouldn't dwell much on the loads. Find the minimum ampacity of the HVAC unit, add 3VA per square foot for lighting and go with that. If it is for permanent, then either do a proper load calculation, or install a 30 day monitor, or possibly ask the provider of the modulars and see if they already have the load calculations.
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Thanks. HVAC and lighting you mention but what about receptacles?
 
augie47 said:
It's safe to assume you don't need 1500 amps but without more information it's just a SWAG.
80%, 50%, 30%, who knows.
There is no way of knowing until you get more input,,,,what are they used for ?, heat and air conditioning involved, any process equipment, etc ?
Click to expand...
Thanks Augie.
 
Alwayslearningelec said:
Thanks. HVAC and lighting you mention but what about receptacles?
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It's dangerous to assume anything but your lighting and receptacle loads are likely minimum. My concern would be HVAC (air c & heat) and any equipment they might power.
Do you have any idea what purpose these units serve ? There's a huge difference between storage, classrooms and bitcon centers :)
 
augie47 said:
It's dangerous to assume anything but your lighting and receptacle loads are likely minimum. My concern would be HVAC (air c & heat) and any equipment they might power.
Do you have any idea what purpose these units serve ? There's a huge difference between storage, classrooms and bitcon centers :)
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LOl..yes I know use of space is important. Don't know at this point.
 
Since it's getting cooler, if they are office trailers, probably your biggest load is going to be I2R heating. and better figure for a some portable space heaters if there a lot of women working in them. Old building engineers always told me that "Women don't like to be cold" and they are going to have space heaters no matter what you do.
 
Joethemechanic said:
Since it's getting cooler, if they are office trailers, probably your biggest load is going to be I2R heating. and better figure for a some portable space heaters if there a lot of women working in them. Old building engineers always told me that "Women don't like to be cold" and they are going to have space heaters no matter what you do.
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If there are women, they will never be happy. If you tell the women, it is temporary they will whine and go home.
 
Eddie702 said:
If there are women, they will never be happy. If you tell the women, it is temporary they will whine and go home.
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I had one guy from the city tell me how hard it was to have stable temperatures and how widespread it was in his building. He was showing me graphs of his steam and electric usage and telling me the demographics of who worked there. Sounded like he put a lot of thought into it. Made a good argument for his position on it. Also made it sound like it was like trying to fight the weather
 
Had a job once in a Town Hall. They had 2 steam boilers 1 heated floor 1,2 & 3. The other boiler did the 4th floor only. The 4th floor boiler quit in the middle of the winter. Big boiler that would take 4-5 days to change out + it wasn't stock had to be ordered.

I told them I could temporally cross connect the supply and return pipes to get the 4th floor heat off the other boiler and I did it with pipe a lot smaller than it needed to be anything larger was not practical.

It worked fine. The day we delivered the new boiler the top floor people Mayor's office etc, were all going home they said it was cold.

I went upstairs and put a thermometer on the secretaries desk it was 71 degrees. They all went home anyhow. It was just an excuse when they saw us deliver the boiler they went home.
 
Alwayslearningelec said:
Have a unique situation where existing modular buildings( about 15) are being relocated and we need to temp them out. All I have is an existing one line showing different boards feeding the buildings to be relocated. Not all are being relocated.

If I just have below and say there are, (as an example), 15 of them like this being fed from 100A breaker that would not necessarily mean I need 1500A source of power correct? It would never demand that much at once? With the limited info I have could I just take 80% of the total amperage and say I need that much power at the source? Thanks
Click to expand...

Are the buildings in typical use?
Measure the actual load.

Get utility data for a year.
 
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