Minimum supply to a residential occupancy

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mbrooke

mbrooke

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What would the minimum supply be to say an apartment or condominium where the service disconnect and meter feeds many dwelling occupancies including building services?


Would a meter pack with over 6 throws (forcing a main disconnecting means) still have the feeder breakers classified as a feeder disconnecting means or would 225.39 (C) be ignored?


Much help needed :?
 
The minimum feeder size would be what is determined by Art 220.
225.39(C) would not be ignored however that provides the minimum disconnect size not the OCP rating.
 
mbrooke said:
What would the minimum supply be to say an apartment or condominium where the service disconnect and meter feeds many dwelling occupancies including building services?
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60A [230.79(D)]

mbrooke said:
Would a meter pack with over 6 throws (forcing a main disconnecting means) still have the feeder breakers classified as a feeder disconnecting means or would 225.39 (C) be ignored?
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If any part of the feeder circuit is 'outside', you cannot ignore 225.39(C). The scope of Article 225 [225.1] covers feeder circuits run on or between buildings, structures, etc.
 
Smart$ and I will have to disagree on this one at the moment. 230.79(D) is for SERVICES, not feeders.
As I recall this has been discussed previously and it was determined that the minimum was the Art 220 calculation.
Difficult to think of a dwelling unit smaller than 60 amps but consider a minimum size dwelling with gas heat & all gas appliances. Two S/A branch circuits, a bath circuit.
800 ft sqft (just to pick and number) is 1 circuit + 2 for S/A + 1 for bath = (4) 20 amp 120v circuits.
The Code is minimum :)
 
augie47 said:
Smart$ and I will have to disagree on this one at the moment. 230.79(D) is for SERVICES, not feeders.
As I recall this has been discussed previously and it was determined that the minimum was the Art 220 calculation.
Difficult to think of a dwelling unit smaller than 60 amps but consider a minimum size dwelling with gas heat & all gas appliances. Two S/A branch circuits, a bath circuit.
800 ft sqft (just to pick and number) is 1 circuit + 2 for S/A + 1 for bath = (4) 20 amp 120v circuits.
The Code is minimum :)
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We don't have to disagree. I was just looking at the first question differently, and changing that as this thread continues. I took the first question to be inquiring about the minimum rating for a service disconnecting means... and the second regarding the feeder disconnecting means thereafter. Note in many cases regarding MFD's, the service disconnecting means and the feeder disconnecting means are one and the same.
 
Since we are off topic on Service I would have to comment that although T 230.79 req. 100 amp disconnect for a residence the conductor size must also be sized to 100 amps, IMO

230.42 (B)

(B) Specific Installations. In addition to the requirements
of 230.42(A), the minimum ampacity for ungrounded conductors
for specific installations shall not be less than the
rating of the service disconnecting means specified in
230.79(A) through (D).
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But doesn't everything become a feeder after the first disconnect?


Therefore, if I had over 6 throws, the sub breakers are technically feeder breakers?
 
Smart $ said:
60A [230.79(D)]


If any part of the feeder circuit is 'outside', you cannot ignore 225.39(C). The scope of Article 225 [225.1] covers feeder circuits run on or between buildings, structures, etc.
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But, if the meter and main disconnect feed into a switchboard inside the building, doesn't 230.79 (D) automatically become irrelevant since the service disconnect has already been passed?


At that point, Id think only an article 220 load calc would suffice, so in theory a small studio apartment with onsite laundry would be ok with a 40 amp service?
 
mbrooke said:
But, if the meter and main disconnect feed into a switchboard inside the building, doesn't 230.79 (D) automatically become irrelevant since the service disconnect has already been passed?

At that point, Id think only an article 220 load calc would suffice, so in theory a small studio apartment with onsite laundry would be ok with a 40 amp service?
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No... the service disconnecting means cannot be rated less than 60A... this also complies with 225.39(D) because the SDM is also the FDM.

225.39 does not apply to or after inside distribution equipment as long as load-side circuits do not run on or between any 'structures'.

EDIT: You're going to have to be more specific in your posts. It's hard to tell whether your talking about a multi-dwelling building, a single apartment in that building or what. For example, did you mean apartment service or feeder? If feeder, all inside or some outside?
 
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mbrooke said:
What would the minimum supply be to say an apartment or condominium where the service disconnect and meter feeds many dwelling occupancies including building services?
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SArt. 230.79 would require a 100 amp minimum to the service only however 228.39 for some reason, only requires the disconnect to be 60 amps. This is absurd because I can use 40 amp conductors and overcurrent protective device or less and install a 60 overcurrent protective device at the apartment and be compliant


Would a meter pack with over 6 throws (forcing a main disconnecting means) still have the feeder breakers classified as a feeder disconnecting means or would 225.39 (C) be ignored? :?
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You still need no more than 6 disconnects at the service.

I am still confused as your first sentence seems to imply that you have one meter and one service disconnect feeding many apartments or condos.
 
Smart $ said:
No... the service disconnecting means cannot be rated less than 60A... this also complies with 225.39(D) because the SDM is also the FDM.

225.39 does not apply to or after inside distribution equipment as long as load-side circuits do not run on or between any 'structures'.
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But what qualifies as a service disconnecting means vs feeder disconnecting means? To me it has always been the main disconnect, ie the very first disconnect after the utility feed.


In the first scenario I take away that once the meter and disconnect is passed, that anything leaving the switch board is no longer considered a service and therefore 225.39 A, B, C, and D no longer apply.






Dennis Alwon said:
SArt. 230.79 would require a 100 amp minimum to the service only however 228.39 for some reason, only requires the disconnect to be 60 amps. This is absurd because I can use 40 amp conductors and overcurrent protective device or less and install a 60 overcurrent protective device at the apartment and be compliant
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I get you, that is confusing me. But, in more complicated is that the panel doesn't even need a main, so if I put a main than that becomes my service disconnect and not what ever is feeding it?



You still need no more than 6 disconnects at the service.

I am still confused as your first sentence seems to imply that you have one meter and one service disconnect feeding many apartments or condos.
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My apologies, these are 2 different scenarios since several different (not related) buildings are involved.


Scenario one:

1200 amp 120/240 service comes into the building underground. A hot sequence metering takes place via CT cabinet which then hits a 1,200 ampere OCPD disconnect.


After the disconnect the conduit feeds into a switch board which has branch breakers. Breakers feed individual studio apartment, while 4 of them feed separate subpanels for building services like on premises coin laundry, gas boiler room and hall/exterior lights.


Electric and gas is payed by land lord.


Scenario two:


Involving larger units ('luxury' condo style) apartments the setup is different.


An 800amp service hits a meter main combo with a main disconnect. Each has 10 meter socket spaces and each socket has an individual breaker. Each meter space feeds a condo subpanel, with on meter space reserved for a landlord panel that just feeds outside lighting.

All appliances are gas within the condos.

Here electric and gas is payed by the renters.


In both cases article 220 dwelling occupancy load calcs are well below 100amps if not 60amps.
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It sounds like scenario two you are covered by the six disconnect rule since there is a main disconnect.

In terms of the minimum feeder I would talk with the authority having jurisdiction. Technically 100 amp is not required but I may venture a guess that the authority having jurisdiction mayu require it since they may read 225.39 differently. It does come into play if the conductors are outside the building.
 
Dennis Alwon said:
It sounds like scenario two you are covered by the six disconnect rule since there is a main disconnect.

In terms of the minimum feeder I would talk with the authority having jurisdiction. Technically 100 amp is not required but I may venture a guess that the authority having jurisdiction mayu require it since they may read 225.39 differently. It does come into play if the conductors are outside the building.
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The conductors are within the building fortunately, but how would definitions change if they were outside...

Ok I think I get, if the conductors are outside than they become in essence a service feeder?
 
mbrooke said:
The conductors are within the building fortunately, but how would definitions change if they were outside...

Ok I think I get, if the conductors are outside than they become in essence a service feeder?
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No art. 215 is for feeders but article 225 is for outdoor feeders so 225.39 does not apply
 
mbrooke said:
The conductors are within the building fortunately, but how would definitions change if they were outside...

Ok I think I get, if the conductors are outside than they become in essence a service feeder?
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a "service feeder" would be kin to a "bear elephant" or "kangaroo turtle"..
can't be both.
Therein lies the problem. If its a service Art 230 has a minimum size of 100 amp for a SF dwelling. If it's an outside Art 225 has a minimum in 225.39.
If it's an inside feeder, I see no minimum other than as required by Art 220,
 
mbrooke said:
But what qualifies as a service disconnecting means vs feeder disconnecting means? To me it has always been the main disconnect, ie the very first disconnect after the utility feed.


In the first scenario I take away that once the meter and disconnect is passed, that anything leaving the switch board is no longer considered a service and therefore 225.39 A, B, C, and D no longer apply. ...
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Service > Service Disconnecting Means | Feeder Disconnecting Means > Feeder.

I can't think of any scenario where a SDM is not also an FDM.

What matters here is whether 225.39 comes into play. If the FDM or any part of the feeder is outside, it does. An example is where all the apartment SDM's are outside. Also being the FDM's, 225.39 applies.

For the example you presented with main outside, switchboard inside, you will also have FDM(s) in the inside switchboard. As long as no part of the load circuit runs outside, 225.39 does not apply... but if any part does run outside, 225.39 does apply.
 
augie47 said:
a "service feeder" would be kin to a "bear elephant" or "kangaroo turtle"..
can't be both.
Therein lies the problem. If its a service Art 230 has a minimum size of 100 amp for a SF dwelling. If it's an outside Art 225 has a minimum in 225.39.
If it's an inside feeder, I see no minimum other than as required by Art 220,
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I will re-read each section for my understanding, but it sounds like a solid interpretation so far. :)
 
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