Please help new business owner with this calc

[olly]

Wondering if any one can help a new small business guy with this brain buster.
Please see the attached drawing.

All of the 15a and 20a existing circuits are VERY rarely used with the exception of one for a motorized gate. The others are pretty much never used.

I have always been taught to size the conductors / VD to the load being used

Each compactor pulls 28a full load current 120/240 single phase

Will the inspector want to see a calculation from a engineer? If I can do it would someone please explain roughly how?

You all are greatly appreciated! Teaching the young guys.

 

[petersonra]

The guy that applies for the permit can do the load calculations per article 220.

If you are a licensed electrician or some other person in the electrical field, you would know this. In general, we are not allowed to answer DIY type questions on the board.

 

[charlie b]

Bob, I don't think this is a DIY situation. Olly has posted well over 100 times on this forum I glanced through his posts, and believe he has shown enough evidence for me to allow this thread to continue.

But to Olly, it would help if you could send me a private message addressing Bob's concern. Are you in fact an electrician, and are your questions related to your job?

 

[Another C10]

If I can do it would someone please explain roughly how?

Even though I've been in the Industry for over 3 decades doesn't mean I should know this, being said .. from my understanding on motors one should add 125% to accommodate the starting surge so, my guess would be 28 A x 125 = 35 A , which seems like a lot for a compactor.

your Image for review, without giving information that could endanger yourself.

 

[Another C10]

Wondering if any one can help a new small business guy with this brain buster.
Please see the attached drawing.

I would consider right off the bat, have the proper licensed individual upgrade the main panel to a 200 A if possible, the little 125 A is going to be pushed pretty hard to perform.

 

[olly]

Bob, I don't think this is a DIY situation. Olly has posted well over 100 times on this forum I glanced through his posts, and believe he has shown enough evidence for me to allow this thread to continue.

But to Olly, it would help if you could send me a private message addressing Bob's concern. Are you in fact an electrician, and are your questions related to your job?

The guy that applies for the permit can do the load calculations per article 220.

If you are a licensed electrician or some other person in the electrical field, you would know this. In general, we are not allowed to answer DIY type questions on the board.

I am really going to bite my my tongue here. There are a few things I would really like to say to you. I am a Master Electrician, Journeyman Lineman, and have four years of controls / relay logic experience. I have worked on touched every thing from 24V to 7620V. Sure the question probably read like a DIY guy and I probably should have listed my calculation out and shown the work I have put in. I guess I'll get to that.

 

[ramsy]

See drawing for 120/240v service

If compactors may run together (28A x 2 + 10A gate) x 1.25 for 100% Motor Loads = 78A
#2cu runs just under 3%vd in 300ft feeder raceway

If compactors are interlocked not to run together (28A + 10A gate) x 1.25 for Motors = 45A
#4cu runs ~2.5%vd in 300ft feeder raceway

 

[hbiss]

I am a Master Electrician

Well, that's what happens when you don't say who you are. Those who recently signed up to this board are required to provide their occupation. Those of us, like you who have been here for a long time can (should) provide that information in their profile along with where they are from and the Code cycle they are on. All that will appear under their avatar- see mine to the right.

-Hal

 

[olly]

Well, that's what happens when you don't say who you are. Those who recently signed up to this board are required to provide their occupation. Those of us, like you who have been here for a long time can (should) provide that information in their profile along with where they are from and the Code cycle they are on. All that will appear under their avatar- see mine to the right.

-Hal

How do you edit the bio? I see where you can change your avatar. Does anyone know?

 

[olly]

How do you edit the bio? I see where you can change your avatar. Does anyone know?

Well, that's what happens when you don't say who you are. Those who recently signed up to this board are required to provide their occupation. Those of us, like you who have been here for a long time can (should) provide that information in their profile along with where they are from and the Code cycle they are on. All that will appear under their avatar- see mine to the right.

-Hal

Nevermind, I found it and thanks for the heads up.

 

[olly]

If compactors may run together (28A x 2 + 10A gate) x 1.25 for 100% Motor Loads = 78A
#2cu runs just under 3%vd in 300ft feeder raceway

If compactors are interlocked not to run together (28A + 10A gate) x 1.25 for Motors = 45A
#4cu runs ~2.5%vd in 300ft feeder raceway

I really appreciate your reply. I will have to figure out how to interlock so they don't run together. I believe if I do it that way I would only need one circuit to hit each disconnect? is that correct?

 

[Another C10]

If it were me I'd run ( 3- #1 Cu w #3 Gr ) or if shaving the fat 3 - #2 w #4 for the 300' 1-1/2 PVC to your 100 Amp Sub Panel.

 

[petersonra]

I am really going to bite my my tongue here. There are a few things I would really like to say to you. I am a Master Electrician, Journeyman Lineman, and have four years of controls / relay logic experience. I have worked on touched every thing from 24V to 7620V. Sure the question probably read like a DIY guy and I probably should have listed my calculation out and shown the work I have put in. I guess I'll get to that.

I seem to have taken the title of your post and lack.of other information and jumped to a bad conclusion. My apologies.

 

[ramsy]

I really appreciate your reply. I will have to figure out how to interlock so they don't run together. I believe if I do it that way I would only need one circuit to hit each disconnect? is that correct?

One circuit can hit sub-panel with interlock kit at trash compactors, serving as disconnect for both.

 

[ramsy]

If it were me I'd run ( 3- #1 Cu w #3 Gr ) or if shaving the fat 3 - #2 w #4 for the 300' 1-1/2 PVC to your 100 Amp Sub Panel.

Op said he was taught to size per voltage drop.

#6cu might work if the gate motor is <= 2A.
If compactors are interlocked (28A + 2A gate) x 1.25 for Motors = 35A
#6cu runs ~3%vd in 300ft feeder raceway

 

[ramsy]

I really appreciate your reply. I will have to figure out how to interlock so they don't run together. I believe if I do it that way I would only need one circuit to hit each disconnect? is that correct?

Residential interlock kits are cheep, not idiot proof. Maintenance / operators may remove them and blow feeder breakers.
Industrial interlocks, preferred for this application, cost a lot more. Perhaps more than any cable savings you might gain from the interlock.

 

[mikeames]

To get max VD of 7.2v or 3% of 240 at the compactors, assuming no other loads and that they will run together.
2/0 For the feeder

2 X 12.9 X 70A X 300ft
-------------------------------- = 4.070 VD
133,100 CMills = 2/0


7.2 Volts
- 4.07 volts
-----------------
3.13 Max VD on branch circuits feeding each compactor


2 X 12.9 X 35A X 75ft
-------------------------------- = 21,637 Cmills = #6
3.13 Volts

 

[olly]

Residential interlock kits are cheep, not idiot proof. Maintenance / operators may remove them and blow feeder breakers.
Industrial interlocks, preferred for this application, cost a lot more. Perhaps more than any cable savings you might gain from the interlock.

Ramsy, by chance do you have a link or a model # or name of an interlock that you would recommend for this application? Industrial or residential?

 

[ramsy]

If your supplier can't help, you must call around and find one who can