Motor Circuit Sizing Question

[Tim Ganz]

I need to setup a motor circuit for what is now a 30 HP motor and will be a 40 HP soon.

I am using a 100-C55 Allen Bradley contactor and the E300 overload that goes with it.

I have been trying to size my wire with several different online motor calculator with mixed results and I keep coming up with # 4 AWG which is too large to fit in the E300 or the 100-C55 terminals.

The motor is only about 15 feet from the contactor and other calculators have come up with # 6 which would work better for the whole situation.

Any Insight would be helpful.

 

[TConnolly]

What voltage?

The following is based on a 460 to 480V feeder. If you have anything else then disregard.

A 40HP motor on 460V has an FLA of 52A. According to my Ugly's reference book you need a #6 wire for a 40HP motor and the Overload is set at 59.8A.

I think I'd use a larger starter. I know the AB book says its OK for 40HP, but where the AC₃ rating is 55A I would prefer a little heavier starter. Especially if it is an IEC starter, I'd probably choose a -72. But that is just me

 

[James Mcquade]

Tim,

i'm not tryng to slam you, but at what point in time are you going to study up on electrical circuits and design?

i ask because i seem to be seeing a lot of design questions here that you should already know.

we have asked you to buy several code books so you can study and learn.

online calculators give you results based on their interpetation of the code book. which version?

temperature, the number of conductors, voltage drop, and even the fact that wiring smaller that a certain size must be rated at the 60 degree rating, termination ratings, all play a factor in wire size.

another factor that has not been mentioned, how many times will this motor be started / stopped in an hour?
if its three or more, i advise toy to go to a larger contactor. the contactor you specified is not a NEMA motor starter and will not hold up.

regards,
james

 

[Tim Ganz]

Tim,

i'm not tryng to slam you, but at what point in time are you going to study up on electrical circuits and design?

i ask because i seem to be seeing a lot of design questions here that you should already know.

we have asked you to buy several code books so you can study and learn.

online calculators give you results based on their interpetation of the code book. which version?

temperature, the number of conductors, voltage drop, and even the fact that wiring smaller that a certain size must be rated at the 60 degree rating, termination ratings, all play a factor in wire size.

another factor that has not been mentioned, how many times will this motor be started / stopped in an hour?
if its three or more, i advise toy to go to a larger contactor. the contactor you specified is not a NEMA motor starter and will not hold up.

regards,
james

James I hate to slam you but.

With all due respect what makes you think I don't have code books? Because I do likely more than you do. News flash NEC code books clarify very little when you talking about industrial machinery the NFPA machinery directives are a little better in that regard.

I have not been doing this long so I like to get second opinions and check my work and not do anything incorrectly.

Many questions I have can not be answered with a code book at all and even for those that can I still value the feedback of experienced people in this field and the last I checked that's what forums were for.

If you don't want to answer a question I post then don't bother. I won't miss you as most of your replys have been wrong, Off base or just a rant.

 

[Tim Ganz]

What voltage?

The following is based on a 460 to 480V feeder. If you have anything else then disregard.

A 40HP motor on 460V has an FLA of 52A. According to my Ugly's reference book you need a #6 wire for a 40HP motor and the Overload is set at 59.8A.

I think I'd use a larger starter. I know the AB book says its OK for 40HP, but where the AC₃ rating is 55A I would prefer a little heavier starter. Especially if it is an IEC starter, I'd probably choose a -72. But that is just me

TConnolly the voltage is 480 3 phase. Sorry I left that out. With my Ugly's book I too came up with # 6 but I also understand that because it's a motor that runs all the time and very seldom does it start / stop that I need to apply 125% rating to the wire size which puts me into # 4.

AB has some expansion lugs for a larger size like # 4 for the contactor I have but they are not available and this job has to happen this week.

I agree with you I would like to have the contactor itself 1 larger size but I am having to use an E300 overload and that's the largest contact they direct mount for at the moment and I don't have room in the small local panel to fit the overload DIN rail mounted separate from the contactor.

I was hoping with a distance of less than 15 feet and a Max ambient of 100 F I could get away with # 6?

 

[jraef]

I need to setup a motor circuit for what is now a 30 HP motor and will be a 40 HP soon.

I am using a 100-C55 Allen Bradley contactor and the E300 overload that goes with it.

I have been trying to size my wire with several different online motor calculator with mixed results and I keep coming up with # 4 AWG which is too large to fit in the E300 or the 100-C55 terminals.

The motor is only about 15 feet from the contactor and other calculators have come up with # 6 which would work better for the whole situation.

Any Insight would be helpful.

The 100-C55 has power terminals that accept #14 through #4AWG conductors. Those same terminals are extended through the E300 OL relay, assuming you have the 193-ESM-I-60A-C55, which is rated 60A. If you have selected the 30A E300 unit for some reason, i.e. you are in Canada and using 600V so the 30HP motor is under 30.0 FLA for instance, that might explain why the terminals are too small...

 

[TConnolly]

What voltage?
A 40HP motor on 460V has an FLA of 52A. According to my Ugly's reference book you need a #6 wire for a 40HP motor and the Overload is set at 59.8A.

This all assumes you have chosen the correct branch circuit protection. Do not size the wire to the load. Size the wire to the branch circuit protection and make the branch circuit protection the correct size and type for the load.

 

[Tim Ganz]

The 100-C55 has power terminals that accept #14 through #4AWG conductors. Those same terminals are extended through the E300 OL relay, assuming you have the 193-ESM-I-60A-C55, which is rated 60A. If you have selected the 30A E300 unit for some reason, i.e. you are in Canada and using 600V so the 30HP motor is under 30.0 FLA for instance, that might explain why the terminals are too small...

It's the 60 amp E300 and #4 DLO cable will barely fit and will not fit with a ferrule on it.

I tried to purchase 100-CT43 to make it work but none in stock in the U.S> and a 4 week lead time which seemed weird but something about them being made in Denmark.

Cable has to be DLO because of the tight space it's in as the control cabinet is built into the frame of the machine.

 

[Tim Ganz]

This all assumes you have chosen the correct branch circuit protection. Do not size the wire to the load. Size the wire to the branch circuit protection and make the branch circuit protection the correct size and type for the load.

It has a 100 service and disconnect for the main in the control cabinet and now this will be the only motor. The only other load is a small Point Io rack and a small hydraulic pump motor and a few 24 Volt DC power supplies.

100 amp disconnect is class J fused.

 

[jraef]

Ahhh, DLO cable, that explains it.

You can't use DLO cable on contactors at all. The terminals are not rated for K stranding, a requirement per the NEC now. A-B has some power distribution blocks that accept K stranded wire like DLO, then you can run regular stranded wire from there to the starter.

 

[jraef]

Missed the edit deadline:

NEC, Article 110.14, second paragraph:

Connectors and terminals for conductors more finely
stranded than Class B and Class C stranding as shown in
Chapter 9, Table 10, shall be identified for the specific
conductor class or classes.

This is interpreted by inspectors, NEMA and UL as meaning, unless it SPECIFICALLY says you can use finely stranded wire, you cannot. The people selling this wire by telling you how extra flexible it is, should also be telling their customers about the restrictions on using it, but they usually don't.

A-B 1492-PDE blocks are rated for fine stranded wire, one of the only mechanical connections that are. Most of the time you have to use a special crimp-on connector.

 

[Jeff23spl]

What voltage?

A 40HP motor on 460V has an FLA of 52A. According to my Ugly's reference book you need a #6 wire for a 40HP motor and the Overload is set at 59.8A.

Are you increasing the FLA setting for the motor Servicde Factor with electronic overload?
I may have missed something but it was my believing that new design already include the SF of standard motor so in normal conditions, you just have to set it for motor FLA.
The E300 spec says it will trip at 120% of ajustement. To me fla+15%+20% = 135% Is it safe to run a motor at 135% of it's fla for a while ?

For the cable size, it really depend on cable type. You shoud use the amp chart of the used wire according to amperage needed. Our rules up north is normally 125% of the load so a cable that could accept 65amps (52x125%) As stated, cable need to comply with the terminal connected to it also.

 

[Tim Ganz]

Missed the edit deadline:

NEC, Article 110.14, second paragraph:
This is interpreted by inspectors, NEMA and UL as meaning, unless it SPECIFICALLY says you can use finely stranded wire, you cannot. The people selling this wire by telling you how extra flexible it is, should also be telling their customers about the restrictions on using it, but they usually don't.

A-B 1492-PDE blocks are rated for fine stranded wire, one of the only mechanical connections that are. Most of the time you have to use a special crimp-on connector.

Jraef

If a Ferrule would fit on the DLO cable would that then make it Legal /Code /Ok to use directly to the contactor?

 

[Tim Ganz]

Ahhh, DLO cable, that explains it.

You can't use DLO cable on contactors at all. The terminals are not rated for K stranding, a requirement per the NEC now. A-B has some power distribution blocks that accept K stranded wire like DLO, then you can run regular stranded wire from there to the starter.

Being the same AWG though I would think the DLO would fit even if it's not a legal use case. Is there a size difference between THHN and DLO of the same AWG? Insulation is thicker I know but wire itself won't fit with a ferrule.

 

[jraef]

Being the same AWG though I would think the DLO would fit even if it's not a legal use case. Is there a size difference between THHN and DLO of the same AWG? Insulation is thicker I know but wire itself won't fit with a ferrule.

Wire gauge is technically about the outer diameter of the wire itself, but in a compressed state (because it's really about the cross sectional area). So adding a ferrule increases the outer diameter by the thickness of, and deformities in, the ferrule itself, which means if you are at the limits of a terminal size range, adding a ferrule may or may not work. The ferrules you use must ALSO be specifically recognized for use with high strand classes of wire and are not the same as those used for Classes B and C, plus they must be crimped with a tool specifically listed for them, because the pressure necessary to form a solid mass in the high strand count is higher.

If you are stuck with not being able to increase the contactor size or add a listed terminal block, I have heard there are "pin adapters" for use with DLO that crimp to the end (again, special crimps) and have a short piece of Class B wire coming out. I don';t know who makes them though.