Load calculation with unknowns

[nizak]

What is a ‘reasonable” load to assign to a residential outbuilding that the owner wants a 100A sub feed installed in.

Using a full load in the calculation always jacks it up to a seemingly ridiculous number.
Most always bumping into a 320/400A meter base.

Our utility has 100 and 200A meter bases available on a walk basis.

Larger ones now need “design criteria” and take weeks to get.

Is using the first 10K watts at 100%
and the balance at 40% reasonable?
Opinions welcome

 

[retirede]

What are the loads? Is there even 10K worth?

My philosophy is that there’s not much reason to install a subpanel smaller than 100 A in an outbuilding. Allows for future-proofing.

 

[Dennis Alwon]

What is in the outbuilding or what is it used for? It really depends, for instance, a wood shop that will only have one machine at a time being used could be calculated as coincidental loads

 

[nizak]

Currently going to be a man cave.
Microwave
Refrigerator
30 LED recessed cans
15 duplex receptacles
18K BTU mini split 16A 230V


Then there's the ever present:

May put a welder and air compressor in down the road in the unfinished part. Maybe a hot tub, but probably not.

Blah Blah Blah

 

[Dennis Alwon]

I would certainly figure the man cave area as a dwelling assuming it meets the definition of dwelling.

Dwelling Unit. A single unit, providing complete and independent
living facilities for one or more persons, including
permanent provisions for living, sleeping, cooking, and sanitation.

 

[retirede]

That’s a fraction of what I have on my garage 100A subpanel with a 200A service (2500 ft2 home).

 

[petersonra]

Currently going to be a man cave.
Microwave
Refrigerator
30 LED recessed cans
15 duplex receptacles
18K BTU mini split 16A 230V


Then there's the ever present:

May put a welder and air compressor in down the road in the unfinished part. Maybe a hot tub, but probably not.

Blah Blah Blah

I would not get all worried about what "might" happen in the future.

I suggest a load calculation based on what he wants right now.

Is there a bathroom or kitchen as defined in the code?

There is no rule that says that is you use 180 VA per outlet that they have to all be on the same circuit.

 

[DrSparks]

I would certainly figure the man cave area as a dwelling assuming it meets the definition of dwelling.

I think he would need a range or cooktop to qualify as a dwelling. If the OP is trying to get this zoned as an ADU then he'll have to have these provisions.

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[DrSparks]

I would not get all worried about what "might" happen in the future.

I suggest a load calculation based on what he wants right now.

Is there a bathroom or kitchen as defined in the code?

There is no rule that says that is you use 180 VA per outlet that they have to all be on the same circuit.

180VA for receptacles is for non-dwelling units. Dwelling units go by the 3VA/Sq
Ft. Rule. But you can have unlimited receptacles on general lighting circuits.

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[DrSparks]

What is a ‘reasonable” load to assign to a residential outbuilding that the owner wants a 100A sub feed installed in.

Using a full load in the calculation always jacks it up to a seemingly ridiculous number.
Most always bumping into a 320/400A meter base.

Our utility has 100 and 200A meter bases available on a walk basis.

Larger ones now need “design criteria” and take weeks to get.

Is using the first 10K watts at 100%
and the balance at 40% reasonable?
Opinions welcome

The method of load calculation you're referencing is for a complete dwelling unit with range, laundry, bathroom, 2 kitchen appliance circuits, etc. I don't think it would apply to a man cave out building.

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[Dennis Alwon]

I think he would need a range or cooktop to qualify as a dwelling. If the OP is trying to get this zoned as an ADU then he'll have to have these provisions.

Sent from my SM-A326U using Tapatalk

That's correct. That is part of what I meant when I said did it qualify as a dwelling