Tap Rule

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infinity said:
I think that I misread the setup the OP seems to indicate that he wants to feed the discos with SE cable. For tap conductors the conductors need to be in a raceway not a cable.
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Yep....but in all honesty fella its kinda been all over the spectrum....;)

I believe at this point he wants to feed two distribution panels located I assume at the AC unit locations as larry suggested, serve as the disconnection means and have those panels supply each AC unit.

Think that's where we are now...i think.

Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 
CurtLeeN said:
Gotcha! So what is the easiest calculation to make sure (1) #2 AL SE (existing) feeding 4 apt units will handle replacing a 15a Sp breaker (igniter) to 30a 2p breaker for the 5kw heat strip? Keep in mind there are only 2 - 20a Sp breakers feeding general lighting and plugs in a 520sq ft apt unit.
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Well CurtLeeN I may just be getting old or out of touch (both could be true) but how you describe the feeders run in this building seems wonky...but maybe that's just me.

Also knowing that 2 AWG AL is only good for 90 amps at 75C i would have to do a calc using 220.83(B) based on known info.

Here is an example of how to do that and determine your remaining load availability.
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Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 
CurtLeeN said:
That is correct but, sub-panels on a 100a breaker at the main 200a panel, So how do I calculate (7) 15a 240v units to figure how big of a SER cable I need?
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Well....where did the (2) pole 30A breakers with 5KW loads disappear in your equation?

Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 
LOL.....good grief...sorry 220.83(B) wont really apply to you because this is an apartment building....not sure what I was thinking...lol

So assuming you know the loads involved in the 200 amp panel and have calculated all that out, that said what is the nameplate values of the mini-split units they intend to install?



Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 
What I can say is if you are installing a 100A OCPD to the remote panel then install a cable that is rated for 100 A would be a simplistic approach.

However, to me just giving the breaker sizes doesn't help us calculate your loads. Sure we can take the 15A and 240V and come up with a VA but in reality what is the actual load of these units to be considered and have you actually done a calculation to determine if the service is adequate for the additional new loads.

Others will chime in I'm sure but even the feeder layout in this apartment building just seems strange.

Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 
You need the MCA of the units. That is the number you use for the calcs.

One minor thing: you will need a receptacle outlet within 25 feet of the units. Maybe it would be worth running a neutral with the feeder so you can get the 120 there vs finding it elsewhere?
 
electrofelon said:
You need the MCA of the units. That is the number you use for the calcs.

One minor thing: you will need a receptacle outlet within 25 feet of the units. Maybe it would be worth running a neutral with the feeder so you can get the 120 there vs finding it elsewhere?
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Great thought and I agree...sounds like a perfect time to simply run the SE-R and knock both out.

In terms of the calcs I also agree as to me he can just apply the rules in 220.82(C) for the units via the nameplate data (MCA) and sum them up and size accordingly. However, I still have the concern that the OP is not accounting what the available capacity is or at least a calculation to determine that.
 
just curious and forgive me, but what (or who's) meter is the existing line on? i'm assuming the house? and it seems no one wants to tell op how to load calc these units... I might of missed it...
scratch that last comment!
 
rambojoe said:
just curious and forgive me, but what (or who's) meter is the existing line on? i'm assuming the house? and it seems no one wants to tell op how to load calc these units... I might of missed it...
scratch that last comment!
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I though we did.....along with many other thoughts. In terms of his calc, i would think he needs to do a full calc on what's known in order to determine his available capacity to achieve what he wants to do.

We can't do his overall calculations based on adding the new loads because not enough of that info is present or at least if it was I also missed that.

Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 
I think Joe is asking "But, shouldn't each unit be supplied form its own apartment, or is the landlord paying for everyone's electricity?"

It sounds like each unit is not separately metered.
 
Kinda why my earlier remarks were that the set up seems wonky. Most certainly when described as a feeder loops from panel to panel as the OP stated.

Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 
I never ask "but shouldnt" because ive seen it all... nothing wrong with having mechanical consoladated- just curious. Its not the wiremans fault it may be wonky! However... ect ect. What you all already thought..
 
rambojoe said:
I never ask "but shouldnt" because ive seen it all... nothing wrong with having mechanical consoladated- just curious. Its not the wiremans fault it may be wonky! However... ect ect. What you all already thought..
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Oh no...I gotcha 100%

I think ultimately his calculation will take him to 220.50

220.50 Motors. Motor loads shall be calculated in accordance
with 430.24, 430.25, and 430.26 and with 440.6 for hermetic
refrigerant motor-compressors.

just trying to get him to do an actual load calc on the building first but maybe others agree he doesn't need to consider that.
 
Breakdown on Apt building

Breakdown on Apt building

The Apartment building has 15 apt units (downstairs and upstairs) and 1 Laundry room for everyone to share. The Owner has the apts all bills paid so therefore the Electric bill for the whole building is only (1) meter, Everything in the building is Gas. It has one Main breaker/breaker enclosure feeding a gutter on the backside of the Panel (located indoor), Out of the gutter has (4) #2 or possible #1 AL SE wire running up to the attic. Each AL SE feeds (4) apt units, The panel in each apartment only has (2) Single pole 20a breakers and a single pole 15a that feed the igniter on the blower unit in the ceiling. Since the HVAC company is installing mini-splits, then the gas AH will be changed with a Heat strip of 5kw....so the 15a will be replaced with a 2 pole 30a breaker. So I can use the sq ft X 3va to determine if the #2 AL SE will handle it, but then again with all 15 units on a 200a MB will also be a factor. I did the calculation and the 200a MB will be good but not sure about the #2 AL SE knowing that is feeds (4) apt units with that extra 5kw each. It will be helpful if anyone has a solution to this, Changing the #2 AL SE will be very difficult to change that the Owner is not willing to spend.
 
first question would be- are you comfortable with the integrity of all the existing? (because its not hokey- afew things are weird). second is tight wad property manegments suck. you can always persuade with words THEY use and understand like liability loss of blah blah.

in those kind of places i can only gaurantee my work from existing distribution to the units- then its less likely to be discontinued in the future from something else that wasn't right.

however,after your response, Im confident you'll hit the nail on the head because, for this forum, sight unseen does get a bit wonky sounding... even if its not.

I have always been a huge fan of rated gutters on the roof- on a bit of infrastructure (rigid styles and strut rails) tall enough to put all the discos in sight, in one damn spot- even if this existing feeder gets extended from a soffit somewhere. then just roof jacks, pipe it up, transition to your what ever and hit the units. ps.... roof guys love one penetration.... (insert dirty thought here)
 
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