Whip End Cords to Appliances

[bobinyelm]

Does one need to use BX armored cable between the wall box and hard-wired to the appliance, or is the heavy rubber covered appliance cord (I believe it's SJOOW Power Cord) sufficient to meet the latest codes?

I AM using BX in the air to my car lift (that could possibly be exposed to physical damage), but in the "corner" where my compressor will be located, I already have enough of the rubber covered cable to use as it was in the shop it was previously installed.

Since my installation will be inspected, I want to make sure I am in compliance.

Also, does the whip cord need to meet the power requirements of the APPLIANCE, or the BREAKER protection current of the circuit?

Obviously cords with plugs only need to meet the power requirement of the appliance, but since a whip cord is "hard wired," it does the same task as if it had a plug on the end, but it's directly wired to the heavier cable feeding the box itself, so it could be looked at that the whip is part of the building wiring and not the appliance wiring.

In other words, if I choose to power a 220v 30 amp and a 20a appliance off the same box wired with #6 cable, both connected to the box with flexible whip cables, it would seem illogical that both flexible cables should need to be rated at 50a (if plug-in devices, obviously not), but I no longer "guess" when it comes to codes.

Thanks!

BTW, the electrical guy at Home Depot (said he was a residential electrician at one point) had never heard of "BX Cable." Is that an old term no longer used? What is th correct term now (he said it's just called "armored cable").

 

[AntonLargiader]

BTW, the electrical guy at Home Depot (said he was a residential electrician at one point) had never heard of "BX Cable." Is that an old term no longer used? What is th correct term now (he said it's just called "armored cable").

These days it's MC, which has an actual ground wire in it. BX didn't. I think there were a few variations on the BX idea; from the old galvanized cloth-insulated stuff, to one that had a grounding trace inside the wrap, to modern MC. In my building here at work they just pulled a bunch of it for 200A services. The stuff is nearly 2" in diameter.

 

[wyliesdiesels]

Does one need to use BX armored cable between the wall box and hard-wired to the appliance, or is the heavy rubber covered appliance cord (I believe it's SJOOW Power Cord) sufficient to meet the latest codes?

I AM using BX in the air to my car lift (that could possibly be exposed to physical damage), but in the "corner" where my compressor will be located, I already have enough of the rubber covered cable to use as it was in the shop it was previously installed.

Since my installation will be inspected, I want to make sure I am in compliance.

Also, does the whip cord need to meet the power requirements of the APPLIANCE, or the BREAKER protection current of the circuit?

Obviously cords with plugs only need to meet the power requirement of the appliance, but since a whip cord is "hard wired," it does the same task as if it had a plug on the end, but it's directly wired to the heavier cable feeding the box itself, so it could be looked at that the whip is part of the building wiring and not the appliance wiring.

In other words, if I choose to power a 220v 30 amp and a 20a appliance off the same box wired with #6 cable, both connected to the box with flexible whip cables, it would seem illogical that both flexible cables should need to be rated at 50a (if plug-in devices, obviously not), but I no longer "guess" when it comes to codes.

Thanks!

BTW, the electrical guy at Home Depot (said he was a residential electrician at one point) had never heard of "BX Cable." Is that an old term no longer used? What is the correct term now (he said it's just called "armored cable").

First off what is the HP rating on the compressor?

30a and 20a rated equipment, unless its a motor, usually has to be connected to the same size breaker.

I would run a dedicated circuit for the compressor.

yes u can use rubber cord as long as it rated for the correct current.

If the compressor will be further than 50' of and not within sight of the panel then you will need a disconnect.

Yes BX is no longer made and was replaced by AC...

 

[AntonLargiader]

Actually Lowes still lists BX along with AC and MC, but it's mostly MC. Surprised me.

 

[wyliesdiesels]

These days it's MC, which has an actual ground wire in it. BX didn't. I think there were a few variations on the BX idea; from the old galvanized cloth-insulated stuff, to one that had a grounding trace inside the wrap, to modern MC. In my building here at work they just pulled a bunch of it for 200A services. The stuff is nearly 2" in diameter.

MC is different than BX or AC which is what replaced BX.

And then theres FMC aka greenfield which is just the conduit and has no factory conductors.

Code no longer allows the use of the BX or AC jacket as an EGC...

 

[wyliesdiesels]

Actually Lowes still lists BX along with AC and MC, but it's mostly MC. Surprised me.

The charts at Lowes and Home depot are frequently discovered to be wrong. No one manufacturers BX anymore so that chart is old or incorrect if recently printed.

 

[Norcal]

"BX" is trade slang for AC cable, MC cable is the most common one seen in the box stores. MC and AC cables are covered under seperate NEC articles.

 

[bobinyelm]

First off what is the HP rating on the compressor?

30a and 20a rated equipment, unless its a motor, usually has to be connected to the same size breaker.

I would run a dedicated circuit for the compressor.

yes u can use rubber cord as long as it rated for the correct current.

If the compressor will be further than 50' of and not within sight of the panel then you will need a disconnect.

Yes BX is no longer made and was replaced by AC...

Actually, I am running dedicated circuits for the welder and the compressor, but asked a theoretical question to try to understand code better.

The compressor is a 5hp motor that says it takes 20a, but to breaker it at 30a, so I am running #10 and a 30a breaker. It is about 10ft from the panel.

My car lift uses a 3hp labeled motor is rated at 17amps (marked on the motor) and I ran a 30a circuit to it w/ #10 ga wire to the wall box (it's about 15ft from the main panel).

On the wire gauge for the 4ft of AC armored whip cable to the car lift from the box, does it have to be 10ga (sized for the hard wall-wiring, and the breaker), or can it be 12ga based on the 17a motor current?

I know motor start-up currents exceed the running current, but many corded appliances (with plugs) size the wire for the running current rather than the momentary start-up current.

I found a provision where circuit protection cannot exceed 150% of the running current of the appliance. In the case of my car lift, the running current (marked on the motor) is 17 amps (150% of 17a is about 25a), so would I be unlawful in supplying it with a 30a circuit? Do I need to replace the 30a breaker with a 25a breaker retaining the #10 wiring to stay within the 150% rule?

 

[bobinyelm]

Yes, what I called BX DOES have an internal ground wire, so I guess it's NOT BX-just the old term I incorrectly used as the HD employee implied.

 

[wyliesdiesels]

Actually, I am running dedicated circuits for the welder and the compressor, but asked a theoretical question to try to understand code better.

The compressor is a 5hp motor that says it takes 20a, but to breaker it at 30a, so I am running #10 and a 30a breaker. It is about 10ft from the panel.

My car lift uses a 3hp labeled motor is rated at 17amps (marked on the motor) and I ran a 30a circuit to it w/ #10 ga wire to the wall box (it's about 15ft from the main panel).

On the wire gauge for the 4ft of AC armored whip cable to the car lift from the box, does it have to be 10ga (sized for the hard wall-wiring, and the breaker), or can it be 12ga based on the 17a motor current?

I know motor start-up currents exceed the running current, but many corded appliances (with plugs) size the wire for the running current rather than the momentary start-up current.

I found a provision where circuit protection cannot exceed 150% of the running current of the appliance. In the case of my car lift, the running current (marked on the motor) is 17 amps (150% of 17a is about 25a), so would I be unlawful in supplying it with a 30a circuit? Do I need to replace the 30a breaker with a 25a breaker retaining the #10 wiring to stay within the 150% rule?

Motor circuits are different than appliance circuits so u cant compare the 2.

For a true 5HP motor it will need 35a rated wire which is 125% of NEC FLC table current. This means #10 THWN or #8/2 NM-b. Breaker can be max 70a. This compressor will need to be hardwired as NEMA outlets arent rated for more than 3HP.

For the lift, what does the manufacturer call for? The manufacturer's directions need to be followed to be in compliance with code. Many lift directions say to use 25a breaker. For a true 3HP motor u will need 21a rated wired so either #12 THWN or #10/2 NM-b.

Now i say "true" because many manufacturers exaggerate their motor's HP ratings.

 

[bobinyelm]

Motor circuits are different than appliance circuits so u cant compare the 2.

For a true 5HP motor it will need 35a rated wire which is 125% of NEC FLC table current. This means #10 THWN or #8/2 NM-b. Breaker can be max 70a. This compressor will need to be hardwired.

For the lift, what does the manufacturer call for? The manufacturer's directions need to be followed to be in compliance with code. Many lift directions say to use 25a breaker. For 3HP motor u will need 21a rated wired so either #12 THWN or #10/2 NM-b.

Unfortunately, it's seems difficult to know "true" hp anymore. I see really SMALL motors labeled 5hp, and some much larger ones (same RPM) rated 5hp. The 30a I quoted was in the brochure that came w/ the motor (my used compressor came with an 80 pound monster motor rated at 5hp, and I am replacing it w/ a brand new lighter motor still rated 5hp)*

So you are saying I should use a 70a breaker for the compressor circuit? Doesn't 70a circuit require more than the #8 wire you mention, or is a compressor circuit like a welder circuit where you can downsize the wire because the draw (Duty Cycle) is intermittent??

You say the compressor has to be hard wired, so I would need to mount the tank rigidly to the floor with concrete anchors and run hard conduit from the wall to it? So I cannot use a flexible whip-cord to power it in other words, even properly rated wire gauge?

I am using #10 nmc for the lift, so I am OK there, but the instructions said to protect it with a MAX 30a breaker. It didn't specify a minimum breaker. If the 150% rule is not applicable, I CAN use a 30a breaker I guess? You didn't mention hard-wiring to the lift. Is that because it's 3hp and not 5hp? So I CAN use CA flexible armored cable to it rather than the hard conduit you say I need for the compressor?

*I called the compressor maker (Ingersol Rand) who said the newer 5hp motor I got would require a smaller pulley than my old 5hp due to the motor's "case size" (rather than the rated hp) to turn the compressor at 900rpm vs the 1350rpm it originally turned at w/ the factory motor. It will supply 12 cfm at 155psi w/ the new motor vs 17 cfm at 155psi w/ the old motor he said. That leads me to believe the true hp of the new motor is less than a true 5hp?

 

[wyliesdiesels]

Unfortunately, it's seems difficult to know "true" hp anymore. I see really SMALL motors labeled 5hp, and some much larger ones (same RPM) rated 5hp. The 30a I quoted was in the brochure that came w/ the motor (my used compressor came with an 80 pound monster motor rated at 5hp, and I am replacing it w/ a brand new lighter motor still rated 5hp)*

So you are saying I should use a 70a breaker for the compressor circuit? Doesn't 70a circuit require more than the #8 wire you mention, or is a compressor circuit like a welder circuit where you can downsize the wire because the draw (Duty Cycle) is intermittent??

You say the compressor has to be hard wired, so I would need to mount the tank rigidly to the floor with concrete anchors and run hard conduit from the wall to it? So I cannot use a flexible whip-cord to power it in other words, even properly rated wire gauge?

I am using #10 nmc for the lift, so I am OK there, but the instructions said to protect it with a MAX 30a breaker. It didn't specify a minimum breaker. If the 150% rule is not applicable, I CAN use a 30a breaker I guess? You didn't mention hard-wiring to the lift. Is that because it's 3hp and not 5hp? So I CAN use CA flexible armored cable to it rather than the hard conduit you say I need for the compressor?

*I called the compressor maker (Ingersol Rand) who said the newer 5hp motor I got would require a smaller pulley than my old 5hp due to the motor's "case size" (rather than the rated hp) to turn the compressor at 900rpm vs the 1350rpm it originally turned at w/ the factory motor. It will supply 12 cfm at 155psi w/ the new motor vs 17 cfm at 155psi w/ the old motor he said. That leads me to believe the true hp of the new motor is less than a true 5hp?

The way to verify HP is by checking the FLA on the nameplate.

And it seems only parts of my comments are being read.

I never said to use a 70a breaker for the compressor. I said the MAX size breaker u can use is a 70a breaker. For a 5HP motor u could try a 30a and see if it doesnt trip.

Also i never said anything about running conduit to it. What i said was that u cant use a NEMA outlet since they are only rated upto 3HP. Hardwired means no outlet and plug. so yes u can use flexible cord or MC with stranded wire which is advisable because of vibration.

And again i never said anything about using conduit for either the compressor or lift. The lift could use a nema 6-30p and r because the motor is rated 3HP.

Please read a little more careful next time.

 

[bobinyelm]

The way to verify HP is by checking the FLA on the nameplate.

And it seems only parts of my comments are being read.

I never said to use a 70a breaker for the compressor. I said the MAX size breaker u can use is a 70a breaker. For a 5HP motor u could try a 30a and see if it doesnt trip.

Also i never said anything about running conduit to it. What i said was that u cant use a NEMA outlet since they are only rated upto 3HP. Hardwired means no outlet and plug. so yes u can use flexible cord or MC with stranded wire which is advisable because of vibration.

And again i never said anything about using conduit for either the compressor or lift. The lift could use a nema 6-30p and r because the motor is rated 3HP.

Please read a little more careful next time.

First off, I apologize profusely for misunderstanding what you said. I obviously upset you and I had no intent to do so, believe me.

I am not an electrician, so if I misunderstood, please chalk it up to my ignorance of proper terminology.

I guess I misunderstood what you meant by "hard-wired," since I had no intent of using an outlet and plug on either unit, and I was permanently wiring them to their wall boxes. I guess you thought I was going to install plugs on the flexible cables.

I planned on wiring to wall boxes using either rubber insulated or AC armored cable terminating by direct wiring into the boxes through cable clamps at the boxes, which I understood to be termed "whip cables" from someone else's post (no receptacle except for my 50a welder circuit). If you mentioned NEMA outlets, I missed that comment. But interesting I COULD use a plug-and-receptacle for the lift (which is bolted to the floor) based on hp rating.

You mentioned 70a right after mentioning #8 NMC or #10 THNN so I drew an unwarranted conclusion that the two were connected, thinking maybe it was like wiring for welders where I read you can use #10 wire for a 50a welder running 20% duty cycle IF the outlet is marked "For Welder Use Only." (I am using #6 cu on my 50a welder circuit, however, but it will terminate in a 50a wall socket). Again, bad conclusion on my part of what you were syaing.

As I mentioned the brochure that came w/ the new compressor motor mentioned a 30a breaker so I will try that first since I wired with #10 NMC already. I thought the compressor motor mentioned 20a current, but I looked again, and it says 22 amps. I photo'd the motor's label (below).

I didn't see a "FLA" rating unless that is "A" in FLA is the running current in amps. The Frame Size didn't reproduce well in the photo below-it's a "56Y."

Again, I am just trying to learn through questions, and if I re-state what I read, it's because I am trying to figure out if I read/understood the statement correctly (it could always be a typo, too), not that I am "questioning" or trying to put words in anyone's mouth. I figure by re-stating, if I got it wrong, the poster will correct me (as you did).

Again, my apologies for upsetting you with my poor comprehension of your intent. It was not that I was reading only part of your reply, but rather I was only understanding part of it. My fault.

 

[wyliesdiesels]

U didnt upset me one bit. I do this for a living and deal with misunderstandings and lack of knowledge on the subject weekly. So dont think u did upset me.

The funny thing is u didnt repeat what i said but rather added to it because you were assuming. not a good idea. better to ask "what do u mean by hardwiring?"

As far as the 70a ampacity mismatch with the motor circuit and #10 wire, the NEC allows that for motor circuits. This is because the breaker doesnt protect the wire or the motor from overcurrents. This is the job of the integrated overload(red reset on end of motor) or motor starter overload relay if so equipped. The breakers only purpose on a motor circuit is to protect against short circuits and ground faults. Sometimes due to in-rush startup currents inherent to motors, the breaker needs to be sized larger than usual to prevent nuisance tripping.

So yes u can have a 70a breaker protecting #10 THWN or #8/x NM-b wire.

as for the motor nameplate, it doesnt say FLA but instead just simply says amps which is the running current. 22a is about right for a 5HP motor. The NEC lists a max FLC of 28a for a 5HP motor and 17a for a 3HP.....

 

[bobinyelm]

OK, I repeated what I THOUGHT I was reading, hoping you would correct any misunderstanding on my part. I guess I could have phrased it with a question mark so it wouldn't have appeared I was putting words in your mouth, or questioning your information.

I did assume, though. I was assuming you understood I was directly wiring it w/ no plugs/receptacles (since I didn't mention them, and since both items will be "fixed" in place).

I appreciate you taking the time helping to educate me (and others on the forum) enough to get my installation (and others) through inspection.

So if my compressor trips its 30a breaker, it's nice to know that I CAN upsize the breaker without having to pull a new cable, though hopefully I can go with a modest up-size). When I read about special welder circuits, I didn't realize such rules can apply to motor circuits as well (I guess maybe only for fixed, "dedicated" motor circuits so labeled?)

If I am ever questioned by anyone on that, is there a place or search-term I should look for documentation? Obviously I will leave the 30a breaker in place for the inspection (the circuit won't be energized until after the inspection, so I won't at that point know of it will hold or not of course), but somewhere down the line it would be handy to know.

I hesitate to ask my inspector that question since he made it clear he wasn't there to educate-only inspect, and I respect his right to draw a line between the two.

Would such a provision apply for most circuits using motors (like a dedicated air conditioner compressor)? The reason I ask is that I have an RV where in very hot weather, the A/C will sometimes trip its breaker unless I direct a small fan onto the panel, yet the measured constant running draw (using two separate clamp meters) show is below the installed circuit breaker and also the capacity of the installed wiring?

In the case of the RV, once the return (recirculated) air cools off, the current draw is about 15% lower than when hot (I have observed this mostly in AZ where ambient temperatures have exceeded 115 degrees F and it can take hours (in hot sun) to get the interior temperature to 80 deg), and the problem disappears as pressures in the system drop off, allowing the compressor to draw less current.

 

[wyliesdiesels]

OK, I repeated what I THOUGHT I was reading, hoping you would correct any misunderstanding on my part. I guess I could have phrased it with a question mark so it wouldn't have appeared I was putting words in your mouth, or questioning your information.

I did assume, though. I was assuming you understood I was directly wiring it w/ no plugs/receptacles (since I didn't mention them, and since both items will be "fixed" in place).

I appreciate you taking the time helping to educate me (and others on the forum) enough to get my installation (and others) through inspection.

So if my compressor trips its 30a breaker, it's nice to know that I CAN upsize the breaker without having to pull a new cable, though hopefully I can go with a modest up-size). When I read about special welder circuits, I didn't realize such rules can apply to motor circuits as well (I guess maybe only for fixed, "dedicated" motor circuits so labeled?)

If I am ever questioned by anyone on that, is there a place or search-term I should look for documentation? Obviously I will leave the 30a breaker in place for the inspection (the circuit won't be energized until after the inspection, so I won't at that point know of it will hold or not of course), but somewhere down the line it would be handy to know.

I hesitate to ask my inspector that question since he made it clear he wasn't there to educate-only inspect, and I respect his right to draw a line between the two.

Would such a provision apply for most circuits using motors (like a dedicated air conditioner compressor)? The reason I ask is that I have an RV where in very hot weather, the A/C will sometimes trip its breaker unless I direct a small fan onto the panel, yet the measured constant running draw (using two separate clamp meters) show is below the installed circuit breaker and also the capacity of the installed wiring?

In the case of the RV, once the return (recirculated) air cools off, the current draw is about 15% lower than when hot (I have observed this mostly in AZ where ambient temperatures have exceeded 115 degrees F and it can take hours (in hot sun) to get the interior temperature to 80 deg), and the problem disappears as pressures in the system drop off, allowing the compressor to draw less current.

Welder circuits have different sizing parameters than motor circuits. Different animals, different articles in the NEC. Same goes for air conditioning compressors the only difference being that manufacturers already did the calcs and listed them on the nameplate.

As for the AC issue in the RV, it sounds like it may be low on refrigerant. I would have it serviced before you take it out into the heat again.