Load Calculation Of Residential Wood Working Shop

[Ravenvalor]

I have a customer who wants to run power to his 950 SQ FT detached garage and turn it into a woodworking shop. He could have as many as 6 - people working in the shop at one time. They build wooden toys and give them to kids.
What would be the best code references for determining how to calculate the feeder load for this shop?
Should I use 220.82?

Thanks for the awesome help...

 

[coop3339]

You could do a load calc but I were you, I would consider running the full size service to the gearage. You could install an exterior disconnect, hopefully the house has a 200A service, add a splice box under this and run the full 200A to the garage. The biggest issue would be you will have to separate the grounds and neutrals in the house and the garage load centers. The other trick will be load balancing the garage panel so that the biggest loads will be on different phases. Better yet buy 240V equipment if possible.

 

[letgomywago]

Other option is plan on a 200 amp service and get them a second meter. If they're using it only for charity they can tax deduct certain parts of it.

 

[Ravenvalor]

So I called the NCEIA North Carolina Electrical Inspectors Association and spoke with someone whom I was told was an expert in the NEC and the NC state amendments. He was actually very knowledgeable in load calculations. He said that residential detached garages do not get calculated as a residence (which makes sense), they are considered accessory buildings. And there is not much in the code for load calculations pertaining to accessory buildings. He recommended calculating all of the equipment at 100%.

I will recommend to the customer about your 240v and charity tax deduction suggestions.


Thanks

 

[Eddie702]

Find out what they have for equipment. It could range from very little load to a fairly large load.

 

[ptonsparky]

Find out what they have for equipment. It could range from very little load to a fairly large load.

For sure. My guesses as to load in watts when everyone is hard at it.
7200 Misc
2800 Lighting
2400 Air Comp
2400 Dust Vac
9500 Htg/Air
Works out to a 100 amp service in a hurry. YMMV

 

[Ravenvalor]

He wants to put a ton of stuff in there. Including 2 - 48-amp car chargers. The total load came up to 296-Amps. So now he is re-thinking the whole setup to see what he can subtract from the equation. One thing for sure, he won't be charging his cars while they're in there working.

 

[Fred B]

This sounds like it might fall within a commercial/manufacturing occupancy or Workshop occupancy, might want AHJ input for occupancy type as some significant variations between the 2 are there. Review of article 220 would be helpful for load calculations
Around me additional consideration of air handling/ventilation need addressing for a wood working shop. You have sanding dust, potential high VOC glue and finishes, flammable finishes and thinners, all potentially explosive/flammable. And with multiple persons working in the somewhat more confined area mentioned given the building dimensions more mixed operations will be taking place.
AFA loads calculation, you need to have a list of all the equipment that will be used with specifications and also consider how many smaller hand held tools used simultaneously will be involved adding capacity for multiple users. Likely with size of space you won't have a lot of fixed in place equipment so need to plan for equipment movement and use in multiple locations consideration for different equipment requirements.
Some of the processes involved also need consideration for extra lighting levels and "color" quality that wouldn't be there for other occupancies.

 

[Fred B]

He wants to put a ton of stuff in there. Including 2 - 48-amp car chargers. The total load came up to 296-Amps. So now he is re-thinking the whole setup to see what he can subtract from the equation. One thing for sure, he won't be charging his cars while they're in there working.

are you giving allowance for demand factors and largest motor? What likelihood for multiple large motor operating simultaneously is there?
2 EVSE operating simultaneously is a large add on for loads. He wants to keep it as a residential garage also? Then most likely will not be adding really big equipment loads more likely small portable loads non-simultaneous use reducing overall loads.

 

[retirede]

Most woodworking equipment never draws full power. This is probably even more true when making toys (as opposed to furniture, for example). Adding up everything at 100% of nameplate will result in a grossly oversized result.

Even with the 2 EVSEs, I’d bet a 200A sub is sufficient.

 

[petersonra]

A few dpdt switches would insure non-simultaneous operation of various pieces of equipment so they would not need to be counted in your load calculations.

 

[jaggedben]

You don't get to use 220.82 because it's not a dwelling.

You would probably get to use the demand factor for 4 or more appliances.

 

[letgomywago]

Ligniting loads are

You don't get to use 220.82 because it's not a dwelling.

You would probably get to use the demand factor for 4 or more appliances.

Lighting loads are different and you just need the 180va per yoke calc for general purpose receptacles. That knocks you down too

 

[zbang]

A bit off-topic, but your friend should really run this by a qualified tax advisor, while he might do this work for charity doesn't make him the charity and thus allowed the deductions. The IRS is quite picky about this kind of thing (like deduction home-office space and equipment).

 

[letgomywago]

A bit off-topic, but your friend should really run this by a qualified tax advisor, while he might do this work for charity doesn't make him the charity and thus allowed the deductions. The IRS is quite picky about this kind of thing (like deduction home-office space and equipment).

He could donate the use of the shop for a market share of what a the lease would be to the charity though. An accountant would be best for checking that though.

 

[cmoreno58]

Calculating the receptacle LOADS for a GARAGE workshop is not the main problem.
Getting CITY approval to run a new second 200A 240Vac service drop from the power pole to the GARAGE-shop RISER is the problem.

If you live in a small town or on a ranch property, maybe it is easy for the CITY and LOCAL power company to approve a dedicated RISER CONDUIT on the garage (that provides a 200A 240Vac service drop from the power pole).
With a service drop to the GARAGE, the owner can install a MAIN service panel, that comes with its own METER and MAIN 200A Circuit Breaker for shutoff. Then the owner can install a 50Amp breaker for a WELDER, 50A breaker for an Air compressor, four 20Amp 120Vac breakers to control the lights, and four 20Amp 120Vac breakers to dedicated outlets (for a grinder, sander, hand drill, small saw).


I live in a big city (Santa Clara CALIF), and the CITY is very strict about the POWER delivered to a residence. There is a single service drop from the power pole to the property; a separate drop to the detached garage is not allowed.
Most new homes have a 200A 240Vac service drop from the power pole to the RESIDENCE CONDUIT RISER. If the owner wants to share this power with a detached garage, then the owner has to dig a trench for conduit, and run (100Amp 240V conductors) via conduit from the Main Service Panel to the GARAGE Sub panel, and then provide breakers for the GARAGE, and scale down the use of power in the HOUSE.
The City does not easily approve a new 400A 240Vac service drop from the power pole to the HOUSE RISER, so that the owner can run (200Amp 240V conductors) via conduit from the Main Service Panel to the GARAGE Sub panel, and still have a 200A 240Vac service for the HOUSE. Again, maybe separate service drops are allowed to a ranch property.

 

[retirede]

Calculating the receptacle LOADS for a GARAGE workshop is not the main problem.
Getting CITY approval to run a new second 200A 240Vac service drop from the power pole to the GARAGE-shop RISER is the problem.

If you live in a small town or on a ranch property, maybe it is easy for the CITY and LOCAL power company to approve a dedicated RISER CONDUIT on the garage (that provides a 200A 240Vac service drop from the power pole).
With a service drop to the GARAGE, the owner can install a MAIN service panel, that comes with its own METER and MAIN 200A Circuit Breaker for shutoff. Then the owner can install a 50Amp breaker for a WELDER, 50A breaker for an Air compressor, four 20Amp 120Vac breakers to control the lights, and four 20Amp 120Vac breakers to dedicated outlets (for a grinder, sander, hand drill, small saw).


I live in a big city (Santa Clara CALIF), and the CITY is very strict about the POWER delivered to a residence. There is a single service drop from the power pole to the property; a separate drop to the detached garage is not allowed.
Most new homes have a 200A 240Vac service drop from the power pole to the RESIDENCE CONDUIT RISER. If the owner wants to share this power with a detached garage, then the owner has to dig a trench for conduit, and run (100Amp 240V conductors) via conduit from the Main Service Panel to the GARAGE Sub panel, and then provide breakers for the GARAGE, and scale down the use of power in the HOUSE.
The City does not easily approve a new 400A 240Vac service drop from the power pole to the HOUSE RISER, so that the owner can run (200Amp 240V conductors) via conduit from the Main Service Panel to the GARAGE Sub panel, and still have a 200A 240Vac service for the HOUSE. Again, maybe separate service drops are allowed to a ranch property.

He’s running a feeder from the house. There is not a second service.