Posted By: BigB
Multi Family Load Calcs - 12/14/14 07:30 PM
Working on some load calcs for a group of multi family dwellings. Each building has 6 small units @690 square feet each. The hot water, cooking and heat(wall furnaces with no fans) are all gas. The cooling is evaporative. I am figuring in a laundry circuit per unit as everyone has a clothes washer on the back porch. So at 690 Sq ft with 2 SABC and 1 laundry I get 4,250 VA after the deduction, plus the full 1,320 VA for the evaporative cooler for a total of 5,570 VA per unit, or 23.2 amps.
For the service I get 41,340 VA X .44 (220.84) for a total of 18,603 VA or 77.5 amps.
Have not done calcs for multi family so just putting this out there to make sure this is correct. Presently these units each have a single 20 amp circuit. We are proposing 2 SABC, 1 laundry, 1 cooling, 1 bath and 1 more lighting circuit in addition to the original circuit.
Posted By: gfretwell
Re: Multi Family Load Calcs - 12/14/14 07:51 PM
No dryers? No dish washers? No disposals? (fixed in place equipment)
I think I would present the low ball 100a bid and I would bump it up to 200a and show them it is not that much more.
Posted By: BigB
Re: Multi Family Load Calcs - 12/14/14 08:14 PM
None of the above. This is a privately owned complex in a low income area, built in 1950. The city is requiring the upgrade in order for them to retain occupancy, they have 60 days to comply. They are not interested in anything over and above, just enough for safety and compliance. We are planning on a 200 amp six pack on each building with a 50 amp sub panel to each unit. Actually that is more than double what my calcs require, if I am correct. I take it you meant 200 amps for each service?
Posted By: Tesla
Re: Multi Family Load Calcs - 12/15/14 02:28 AM
I'm in a EUSERC Poco state.
I thought that Arizona's utilities had adopted EUSERC, too.
In which case, your calculations are pretty irrelevant.
It may prove out that it's the Poco that's driving this 'City mandate.' (Which is very, very, likely linked to the Federal program to mandate "the Smart Grid.")
Both the Poco and the City are being driven by the Feds to ENTIRELY eliminate 'grandfathered' Services that don't meet "Smart Grid" standards.
If this is indeed the case, then you need to head right on over to the EUSERC web pages/ talk to your electrical distributors to get the heads-up. For you can hardly be the only contractor getting these phone calls.
One aspect of the "Smart Grid" is digital metering to each Service -- as THEY define it. I rather suspect that the wording is over-broad.
There are no end of ironies here: for the end-users in this situation are ALREADY at the very bottom of the scale of power consumption. (!)
If the heavy-up is driven by this political pressure (the timing is suspect) then you'll be compelled to build to their calculations... which will (magically) entirely override the NEC calcs.
The 'Greens' have politicized power consumption. They are an international force. You'll find similar 'political' (doctrinal) interventions across the Western world. What started in Europe has come to America.
This (Greens) doctrine is reality inverted. Electrically powered devices are the MOST efficient in almost all applications. No industry has done more to improve the quality of life than the electric industry.
The Greens in Germany found out the hard way that they had to stop. Their policies became so significant that 'sustainable energy' was destabilizing the national power grid! (Wind power, in bulk, is impossible to utilize. It's too chaotic.)
Seimens and the rest of the German electrical 'heavies' promptly left the business -- taking multibillion dollar write-offs at the same time. They realized that they'd guessed wrong -- and had already reached the end of the 'sustainable' road.
The Greens are pretty much stumped -- and the "Smart Grid" is Plan B. I suspect that we'll be seeing a persistent roll out of Smart Grid devices -- especially at the Service -- for the rest of our careers.
I'm an old clod. If I were a younger man -- this is what I'd study up on. It's going to be a HUGE (Service) design feature from now on.
Posted By: Tesla
Re: Multi Family Load Calcs - 12/15/14 02:52 AM
I'm in California.
Political decisions override the NEC practically everywhere you care to turn in California:
Illumination levels at
Cold boxes -- when showcases
Auto lots -- when showcases
Parking lots -- all
Illumination types -- especially in commercial use
EUSERC rules Service calculations -- de facto
125 A 240V or 208V one-phase minimum (condos/ apartments)
200 A 240V one-phase minimum (SF home)
Because of the political interventions -- drastically increasing power rates above all prior norms -- no landlord dares wrap electric power into the rent. All tenants are individually metered. (whenever practical)
The above political situation spans all political parties and is most unlikely to change. It's not even controversial.
So, for us, we put our efforts into staying ahead of these legally mandated design standards -- which supercede the NEC in every case.
The ECN house expert for California is Scott35. I strongly recommend paging through the ECN Technical Reference Area. It's priceless. Many a query is already answered -- in depth -- right there.
The NEC was drafted by the insurance industry more than a century ago -- for safety -- above all fire prevention.
In our time, that's no longer deemed enough. So politicians are drafting statutes and programs that top the NEC with energy efficiency in mind. I can't imagine any twist in political fortunes that would ever reverse that drive.
Our 'design Bible' is being overwritten.
With that in mind, it might be time for the ECN to establish a technical forum specific to this new reality.
Fellow electricians: let's kick the idea around.
Posted By: gfretwell
Re: Multi Family Load Calcs - 12/15/14 05:44 AM
Bob, we are on the same page here. I meant 200 for the building. Your calc would let you use 100 (the NEC minimum)
I am not sure how EUSERC might apply. We don't do that here.
Tesla seems to be saying you would need 125a per unit and that does sound silly in your circumstance.
As to the idea of a EUSERC forum, if we have enough people affected, why not.