load calculation on 4 unit apartment

[sunny1]

Hello!

New to the forum, relatively new to the trade, first multifamily load calculation I have been responsible for since getting licensed.

I wanted to share my load calculations to invite comments/critiques/laughter at my expense etc. I did both the standard and the optional method for comparison.

A short description is four units with a whole house electric heater, common laundry of two washers two dryers, and an ADA unit with its own laundry. Very basic units no dishwasher, disposal or any other appliances fastened in place. Electric range and ductless heat pump for each unit. One feeder to each individual unit with a separate feeder for the house loads... so I still qualify for the optional method under 220.84 correct?

My service load using the standard method came out to 328 amps while the optional method was 276. This is employee housing for seasonal workers, so the whole place will be under one meter. (Though the facilities manager, my boss, wants the option for future individual metering, which will probably be the subject of another post)

Assuming I did my calcs correct, what are folks opinions on metering this load on a standard 320 meter even though the one calculation came in slightly over?
Doesn't leave much room for expansion but any upgrades after this are unlikely.

Any input is greatly appreciated!

 

[MyCleveland]

Welcome sunny1

Just a few comments to consider.

Standard Calc - seperate out all your house loads like you did in the optional.
House loads do not get access to suite derating factors. You can only use what 220 allows for house.
Optional Calc - appears correct, maybe others can look over. I did not check your math.

You are on 2020 code yes ? If so, how would you use a 320 meter for anything larger than a 300 service…assuming you are trying to use your standard calc data.
See 2020 230.66 B.

Why not just use optional numbers and you then fall into a 300a service, unless you were trying to build in some spare capacity, then go with a 400a.

Not sure how you set up to replace single meter with possible future change to a meter stack. Maybe stand alone main serving panel with feeder CBers to apts and house that gets pulled later and replaced with stack.

 

[sunny1]

Welcome sunny1

Just a few comments to consider.

Standard Calc - seperate out all your house loads like you did in the optional.
House loads do not get access to suite derating factors. You can only use what 220 allows for house.
Optional Calc - appears correct, maybe others can look over. I did not check your math.

You are on 2020 code yes ? If so, how would you use a 320 meter for anything larger than a 300 service…assuming you are trying to use your standard calc data.
See 2020 230.66 B.

Why not just use optional numbers and you then fall into a 300a service, unless you were trying to build in some spare capacity, then go with a 400a.

Not sure how you set up to replace single meter with possible future change to a meter stack. Maybe stand alone main serving panel with feeder CBers to apts and house that gets pulled later and replaced with stack.

Thank you very much for taking the time to look at my calculations. I will amend the house load section of my standard calc. I was unsure how the house load portion worked so thanks for clarifying.

To your point about service size I guess I’ve always just called the standard 400 amp meter from our supplier a 320 meter in reference to its continuous load rating. Maybe thats a local trade term? I’ve always been told this was the highest ampacity you could get before CT metering.

Your point also made me realize I think I need to add a continuous load multiplier to my whole house water heater since it isn’t governed by any demand factor.

I’m not sure if a good solution for having it both ways in terms of metering exists still researching but probably if they really want to be able to have the option They may just have to pay the extra meter fees. I don’t see it getting changed later.

I really appreciate your help!