# Wiring a RTU for a Walk-in Freezer help plz



## jtomara37 (Jan 31, 2008)

I live in New Hampshire USA. 

I am working on supplying the feed for a RTU for a walk-in freezer.
The unit is 3 phase 
The Max overcurrent protection for the unit is 30 Amps.
the length of the run is approximately 100ft
The job is at a restaurant

This is my plan:

1. The Panel is 120/240V 3 phase panel
2. The panel will have a 3-pole 30amp breaker
3. Will come out of the panel with 10-4 MC or Flex with THHN (black, red, blue, green) for about 25ft to a 6x6 metal j-box near the outside wall basement of the restaurant
4. From the 6x6" j-box will run a short stub 3/4" conduit to a 3/4" emt compression connector which will be screwed into the 3/4" LB on the outside wall of the restaurant.
5. From the 3/4" LB I will run along the outside wall of the restuarant with 3/4" EMT and compression connectors to a WP (weather proof) 3 phase Knife switch which will be mounted on the side of the RTU.

Questions:

1. What is the required size of the equipment (green) ground wire
2. Is the 6x6 j-box needed or could I get away with a 4x11/16" j-box
3. Is the 3 phase circuit required to be UNbroken to the unit or is it ok to splice within the junction box
4. Is the color code (black, red, blue, green) correct for this type of 3 phase application
5. Do electrical supply houses sell 10-4 MC with ground or would I have to use flex and fish the wires through it myself
6. When is it required to use a bonding bushing, would this application require it
7. Would a 3 phase knife switch be acceptable in this application or would I be required to put a 3 pole 30amp breaker disconnect on the unit instead of a knife switch

 NOT going to do this>> but hypothetically if I were to run a white(neutral) wire would this require that I de-rate my 3 #10 tthn wires? Only 3 current carrying conductors are allowed in a conduit right? Is a neutral wire concidered a current carrying conductor? 

Thanks in Advance for all the comments, suggestions and support.

Jerry


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## ATS (Jun 28, 2005)

Not meaning to pick a fight here but you say you're an electrician. These are very elementary questions you are asking. You may want to call in someone on this one. No offense intended.


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## Speedy Petey (Sep 30, 2003)

I have to candidly state as well, ALL eight questions are ones that ANY seasoned, or at least qualified, electrician would most certainly know.
Three phase is no place to mess around and learn as you go.


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## Speedy Petey (Sep 30, 2003)

I'll do this though.

1) 250.122

2) 314.16

3) ? - There is nothing prohibiting splicing.

4) The NEC does not care.

5) Call them and ask. 10/4MC would sure be easier.

6) 250.4(A)(5), 250.122

7) What does the unit say? Max circuit breaker; max fuse; or max fuse/circuit breaker?

8) _"Only 3 current carrying conductors are allowed in a conduit right?".._ Since when? 
310.15(B)(2), 240.4(D)


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## mickeyco (May 13, 2006)

Had this pic, seemed like a good place to use it.

.


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## jtomara37 (Jan 31, 2008)

Sorry I'm used to only residential wiring. The only commercial work sadly was bending conduit for 2 yrs. This is the first time I've sought suggestions on a website regarding my trade.

I tried to focus on simplifying the details with only 1 unit without having to give all the details to over confuse the subject which only resulted in me screwing up my questions and made me sound retarded.

This is what I had in my head when writing the questions:

There are 2 units a freezer and cooler rtu.
MAX ocpd for freezer is 30amp (3p)
MAX ocpd for cooler is 15amp (3p)
there is obvioulsy going to be a 30A 3 pole breaker for freezer and a 15A 3 pole breaker for cooler
There will be another 120v circuit as well for lighting for the freezer and cooler along with heat tape for the drainage as well.
I assumed just 1 #10 ground would be acceptable for all these.
Factory installed on the freezer unit is a defrost timer, power terminates on the contactor and factory 2 legs are jumped off the contacter to the defrost timer (obviously {240v room t-stat & 240v lsvalve) there is wiring beteen the defrost timer and 2 evap heaters which run approx 8A each which will not be running at the same time as the condensor which only has RLA of 11 even if they were running at the same time which they may for a short time that only equates to 27A which the 30A breaker is sufficient. Although it is planned for this type of wiring it concerns me a little that if the condensor is pulling 30A because of malfunction it would not be good since it only has RLA of 11. I guess if soemthing is wrong with it and it pulls that much prob won't matter anyway would need to be replaced.

So 3 legs for freezer, 3 legs for cooler 1 leg for 120v circuit 1 neutral and 1 EGC that leaves us with delta phase wiring (I believe its called) which would make the neutral figured as a current carrying conductor for de-rating purposes there are 8 ccc wires to de-rate.. I planned on using #12 wire for the cooler even though the ocpd max is 15A and #12 for the lighting/heat tape wire as well.

As for the J-box that is why I originally wanted a 6x6 cause there will be 8 #10s, and 10 #12s spliced together might just go with 4x 11/16th and if needed use a extension box. Ground a figured obviously be at least #10 in accordance with the 30A breaker... Splicing I wasnt sure of cause I had never seen it broken or splice any time I had to trouble shoot a unit which has not been that often.

Of course I plan on using a weather proof suitable for outside knife switch for the units. At one point I was concidering using a lug panel... seems to me I've heard somewhere there needs to be a outlet near the unit to service it.. that could be something in another state.

The whole question about 10-4 MC was a mistype totally. I meant 10-3 which obviously has a ground as well which makes 4 wires.. On this same job I have to make up this twist lock plug and pick up some S/O cord and cord counts all the wires so 12-4 s/o would be black,red,white,green.. I must have confused my question that way. It was a dumb quesiton but I really just wanted to know if supply houses normally carry 10-3 or higher MC cable since I had never had a reason to ask them before. I know it is made I've seen it before.

I know that the "high" leg of the delta phase requires a orange wire. that is the most I know. That stuck in my head. which to determine is the high leg I do not know or if it even matters.. and the other can be whatever color to my understanding (red, black etc)

I apologize is my knowledge and experience is not that of your expectations seeing how most of you seem to be seasoned tradesmen I'm sure your frustrated by it. My downfall here has only been my distain for looking in the code book and being lazy. Thought I might save some time and aggrevation and maybe some suggestions tip. Certainly didnt expect the response of look and find it in the code book yourself. Sorry for wasting your time.


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## Speedy Petey (Sep 30, 2003)

jtomara37 said:


> Certainly didnt expect the response of look and find it in the code book yourself.


Why not? Isn't that what we (as electricians) do?


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## Magnettica (Dec 19, 2006)

Nothing wrong with coming here seeking help. It's just that when you use your first post to ask about how to do a job, or a how to price it, I think we all wonder if you're actually an electrician or a homeowner looking to cut one of us (electricians) out of the picture. We seem to get thus scenario almost daily on cold winter nights.

I believe you are an electrician and I do believe that you are clueless about this installation and are genuinely asking for our help. There is alot to learn when it comes to three phase-type electrical systems. For instance, you say the service you are working with is 120/240. Are you sure? And what is the rooftop unit nameplate voltage requirement?


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## Magnettica (Dec 19, 2006)

> Of course I plan on using a weather proof suitable for outside knife switch for the units. At one point I was concidering using a lug panel... seems to me I've heard somewhere there needs to be a outlet near the unit to service it.. that could be something in another state.



NEC article 210.63

You need to have a receptacle within 25' of any HVAC equipment (residential, commercial, industrial), and it needs to be on the same level as the heating/ cooling equipment.


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## mickeyco (May 13, 2006)

Magnettica said:


> NEC article 210.63
> 
> You need to have a receptacle within 25' of any HVAC equipment (residential, commercial, industrial), and it needs to be on the same level as the heating/ cooling equipment.


I could have illustrated why this is a few weeks ago, my fingers are almost all healed now and I didn't take pictures.


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## Magnettica (Dec 19, 2006)

mickeyco said:


> I could have illustrated why this is a few weeks ago, my fingers are almost all healed now and I didn't take pictures.



It's a nice requirement and serves a purpose, but what tradesmen who'll one day be servicing the equipment doesn't have cordless tools?


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## mickeyco (May 13, 2006)

It wasn't an HVAC service guy, it was the waterproofing baboons with a hammer drill to lazy to get an extention cord but happened to have an alligator clip setup handy (everythings in conduit out here).


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## Celtic (May 23, 2007)

jtomara37 said:


> My downfall here has only been my distain for looking in the code book and being lazy.
> 
> Certainly didnt expect the response of look and find it in the code book yourself.
> 
> ...



Just how long do you plan on being lazy?
You were given numerous code articles as reference...all you had to do was open a book...if it was spoon feed to you anymore, we would be doing the job for you as well (and if you continue being lazy, that possibility is more of a reality than fantasy).

You are not wasting OUR time - you are wasting your employers time and the customers time - all of which is being paid for by someone other than you.


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## ATS (Jun 28, 2005)

Magnettica said:


> It's a nice requirement and serves a purpose, but what tradesmen who'll one day be servicing the equipment doesn't have cordless tools?


I'll answer that. Recovery equipment for the refrigerant as well as a vacuum pump come to mind. These are high current users, haven't seen any cordless yet but granted it would be nice. As for the op, it sounds like you are a HVAC mechanic wanting to be a sparky. I'm just being honest here, sounds like you need a bit more education before you tackle this project. Just because you can troubleshoot a walk-in doesn't make you a competent electrician. This takes many years to accomplish and reading the code is just a small but necessary part of the process. You had to expect the responses you got, c'mon.


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## 220/221 (Sep 29, 2007)

> Thought I might save some time and aggrevation and maybe some suggestions tip. Certainly didnt expect the response of look and find it in the code book yourself. Sorry for wasting your time.


 
Don't apologize to those clowns. It's called using your tools. Instead of trying to look everything up and decipher it yourself, you asked for help. Some guys just have issues and they deal with them by being internet bullys.

Go do the job. It obviously aint rocket science cause I can do it. The best way to learn is by doing.


For that short of a run, I'd just use conduit,flex/thhn instead of buying a roll of #10.

I'd put a wp jb ouside and run your flex into the back. It would be an easier installation.


I'd also use a pullout syle disco and save some money.


#10 conductors no matter what size breaker require #10 ground. I just learned that a few years ago after pulling #12 grounds for all my life :whistling

You can splice all you want but the fewer, the better and TIGHTEN those nuts.


Mark your hi leg and make sure your phasing is correct. 3 phase motors phased incorrectly will run backwards.


Mark the panel and circuit numbers on the disconnects for furure reference.


The compressor will start up if wired incorrectly but will be really noisy and I assume will eventually be damaged from running backwards.

Don't fall off the ladder.


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## Magnettica (Dec 19, 2006)

And don't stand in water when tying-in at the panel.


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## Speedy Petey (Sep 30, 2003)

jtomara, why don't you and 220/221 exchange addresses so he can bring his 1984 code book over and help you. :laughing:


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## Celtic (May 23, 2007)

220/221 said:


> Don't apologize to those clowns. It's called using your tools. Instead of trying to look everything up and decipher it yourself, you asked for help. Some guys just have issues and they deal with them by being internet bullys.
> 
> 
> #10 conductors no matter what size breaker require #10 ground. I just learned that a few years ago after pulling #12 grounds for all my life :whistling


:blink:

WE are the clowns and you just found out that a #10 goes with a #10 ...after doing this all your life?

But don't lose sleep over it...after all:


220/221 said:


> ____________________________________________
> Just because it's within code doesn't make it safe.
> 
> Just because it's against code doesn't make it unsafe.


Speaking of tools.... a hammer is a tool....if you can't hammer a nail in straight, you might not want to call yourself a carpenter. 

Like wise, the NEC is a tool....if you're too lazy to read it.....

So just how did you have this epiphany on the EGC?
Did you:
a) look it up and decipher it all on your own after doing it wrong all your life
b) have one these bullys spoon feed you the proper method and supply you with the code reference:stupid:


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## 220/221 (Sep 29, 2007)

:laughing: Is that all you got Petey? 

Get your clown posse together and see if you can come up with something a little more substantial.






> So just how did you have this epiphany on the EGC?


An inspector pointed it out to me, douchebag.


Any more questions???, because I'm an open book.


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## Celtic (May 23, 2007)

220/221 said:


> An inspector pointed it out to me, douchebag.


And WE are the alleged bullys??? :blink:



220/221 said:


> Any more questions???, because I'm an open book.


Yea...why are you such a tool?
:laughing:


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