Amp question

I know, I know, I don’t have any pics…

My question is: How can a 60a panel have A/C on it and be ok?

I know it has to do with load calculations. The unit is 720 sq ft. gas stove, gas hwt, gas dryer, gas furnace. This is brand new construction and I didn’t think any electrician would use a 60a panel. I thought they would at least use a 100a ? Isn’t A/C alone around 40a?

Now you say NEW construction…is this a single family dwelling or a Condo or Apartment setup…their is a difference here…Many times condos and apartments will have a 60A supply…but not NEW construction on a single family dwelling…it should have a minimum 100A service at the least.

As for the AC…well considering everything in the house is GAS…it is entirly possible that it is just fine.

Yes Paul, good point, it’s 5 town houses all connected in a row.

If we are talking a 2.5T AC unit, (2) Small Appl. (1) Laundry and 3VA per sq ft for the 720 sq ft space…and everything else is gas…hmmmm

720- 2,160VA
Sm Ap - 3,000VA
Laund - 1,500VA

Apply the factors and you have - 4,281VA in G & L Loads

now lets just say its a 2.5Ton AC unit ( 4,400VA ) 100% mind you

Add oh…heck atleast a fridge at 1,400VA ( appliance)

Giving you 10,081 VA divided by 240V = 42A Demand

NOW…again with all that said…if this is a Single Family Dwelling it should be ( New Costruction ) minimum 100A…but alas…guess you could find anything anywhere…:slight_smile:

****[FONT=Times-Bold]size=2 One-Family Dwelling. **For a one-family dwelling, the
service disconnecting means shall have a rating of not less
than 100 amperes, 3-wire.

Now their are exceptions for other loads…under 230.79 but if again we are speaking of a single family dwelling…100A is the minimum.

Do they each have their OWN service drop and meter can for each unit…or joined in a group area with a main disconnect ahead of each.

Not sure if that makes a difference or not, but I see where you’re headed.

© One-Family Dwelling. For a one-family dwelling, the
service disconnecting means shall have a rating of not less
than 100 amperes, 3-wire.
(D) All Others. For all other installations, the service disconnecting
*means shall have a rating of not less than 60 *amperes.

The minimum service size for a single family dwelling is 100 amp. The definition for a single family dwelling is:

Dwelling, One-Family. A building that consists solely of
one dwelling unit.

I’m just not sure if one townhouse unit of a long building qualifies as a one-family dwelling under a strict interpretation of this definition. I’d do a 100 amp service, in all likelihood (as there is almost ZERO installed cost difference), but I can make a pretty decent arguement why a small mostly gas townhouse would be legal with a 60.

If there is a shared wall it is not a single family dwelling. This is a 5 unit multifamily dwelling. That would be decided at the zoning phase of the permit process. The minimum size is 60a. If the load calc says this is enough, it is enough. The real decision gets made at plan review.



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yeah…see how hey are done…in this case the 60A is probably fine…BUT when I did my calculations to be under 60A…I did not add in things like Disposals and other specialized appliance loads ( just one fridge )…but chances are it is fine…

The main OCPD’s are located at the meter grouping…

greg is right in that because of this meter setup…I am sure it was approved by the local plans comm.

Agreed… 60’s are okay, only because this is a multi-family building. These little wee garden apartment syle condo’s are fine on 60’s.

We have many condos, built in the 70s, with central AC units, that have 50A service disconnects.

The question I ask is, depending on the age of the dwelling, and what my client may be planning, if the service may be adequate.

I may suggest considering a service upgrade, but it’s kind of hard to argue that the service is inadequate on a hot summer day, when the family is inside the home, cooking is going on, lights are lit, the AC is pumping… and ain’t nothing popping in the panel.

Again, it depends on the age of the dwelling, but a majority of homes I see ate rated at 100 amps, and many of the older condos I see are rated at 50 or 60 ampl (with central AC units!)

Mark, just out of curiosity are those on the West side? Looks kinda like the Tucson mountains in the background.

They are by St Marys hospital on Silverbell.

Thank you: Paul, Marc and Greg!!!