Overload protection required for grinders?

overkill94

Member
Location
California
Did an inspection on a 1 1/2 HP grinder at a manufacturing company. While it would seem that something like this would not require overload protection, I'm having a hard time finding an exception in the NEC. It's cord-connected and has an on/off switch, so someone could turn it on and leave it on. Thoughts?
 

suemarkp

Senior Member
Location
Kent, WA
Occupation
Engineer
Why are you inspecting a cord-and-plug connected grinder?
Was it a 15A 120V cord cap?
Is this a product they are making or a tool they bought?
What is wrong with someone leaving it on?

I would think it has internal thermal protection.
 

overkill94

Member
Location
California
The code requires any equipment operating at higher than 50 Volts to be inspected (though that's not always enforced). [edit - should have specified that I'm a compliance engineer, not a building inspector]

Yes, normal 15 Amp, 120 Volt cord cap.

Tool they've had for a long time - what makes me even more wary is that they have similar grinders on site without separate overload protection which have a UL sticker (although it says UL 439B which seemingly no longer exists)

The fact that someone could leave it on exempts it from intermittent duty IMO. Pedal-operated and push-to-run equipment does not require an overload since the operator would have to be physically using the machine and would notice if an overload was occurring.

The motor does not state that it is thermally protected.
 

broadgage

Senior Member
Location
London, England
If it comes with a cord and plug, then IMHO it is an appliance that simply requires plugging in to any standard outlet.

It may be a requirement, and is certainly prudent to inspect such equipment, but IMO such inspection should normally be confined to looking for damage such as a frayed cord or broken/missing gaurd, rather the querying the original design.
 

suemarkp

Senior Member
Location
Kent, WA
Occupation
Engineer
The code requires any equipment operating at higher than 50 Volts to be inspected (though that's not always enforced). [edit - should have specified that I'm a compliance engineer, not a building inspector]
What NEC code article would that be requiring things over 50V to be inspected? I don't think this is an NEC issue. If there was a microwave oven in a break area or a 120V desk lamp, would you be inspecting that too?

Perhaps what you're doing is similar to what we have here in WA and many other states where all electrical utilization equipment must be NRTL listed. For us, if it has a UL sticker, we're done. If not, we're supposed to hire a firm to give the item its blessing.

Or maybe this is a "safety check" like broadgage mentioned (e.g. frayed cords, missing guards, etc). I find many of those rules to be subjective or impractical. Example - a table saw may come with a combination splitter/guard with anti kickback pawls. For half the cuts I make, it must be removed because it will not work on blind or angled cuts. Putting in on and off is wasted time, so I took it off and never put it back on. A stickler to the rules would want that guard put on the saw while it is sitting there.
 

overkill94

Member
Location
California
What NEC code article would that be requiring things over 50V to be inspected? I don't think this is an NEC issue. If there was a microwave oven in a break area or a 120V desk lamp, would you be inspecting that too?

Perhaps what you're doing is similar to what we have here in WA and many other states where all electrical utilization equipment must be NRTL listed. For us, if it has a UL sticker, we're done. If not, we're supposed to hire a firm to give the item its blessing.

Or maybe this is a "safety check" like broadgage mentioned (e.g. frayed cords, missing guards, etc). I find many of those rules to be subjective or impractical. Example - a table saw may come with a combination splitter/guard with anti kickback pawls. For half the cuts I make, it must be removed because it will not work on blind or angled cuts. Putting in on and off is wasted time, so I took it off and never put it back on. A stickler to the rules would want that guard put on the saw while it is sitting there.
Yeah, I work for an NRTL and this grinder is not UL listed.

Would a grinder not be considered "industrial equipment"? It does shape metal which is one of the types mentioned in the back of NFPA 79.
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
Yeah, I work for an NRTL and this grinder is not UL listed.

Would a grinder not be considered "industrial equipment"? It does shape metal which is one of the types mentioned in the back of NFPA 79.
Doesn't NFPA 79 cover Industrial 'Machinery'? I don't believe the scope covers hand held portable tools.
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Did an inspection on a 1 1/2 HP grinder at a manufacturing company. While it would seem that something like this would not require overload protection, I'm having a hard time finding an exception in the NEC. It's cord-connected and has an on/off switch, so someone could turn it on and leave it on. Thoughts?
It's indirect, but it's there.

422.62 Appliances Consisting of Motors and Other Loads.
(B) Additional Nameplate Markings. Appliances, other
than those factory-equipped with cords and attachment
plugs and with nameplates in compliance with 422.60
, shall
be marked in accordance with 422.62(B)(1) or (B)(2).

422.60 Nameplate.
(A) Nameplate Marking. Each electrical appliance shall
be provided with a nameplate giving the identifying name
and the rating in volts and amperes, or in volts and watts. If
the appliance is to be used on a specific frequency or frequencies,
it shall be so marked.
Where motor overload protection external to the appliance
is required
, the appliance shall be so marked.

So if it is connected with a cord and cap, they do not have to mark it WITH something that says it is thermally protected, they only need to mark it IF the overload protection must be external.

Your grinder has a plug, it has no marking saying it needs an overload relay, so it does NOT need external overload protection.
 

overkill94

Member
Location
California
Thanks Jraef, but the small print in 422.60 says to refer to 422.11 for overcurrent protection requirements and in that section it states:

(G) Motor-Operated Appliances.
Motors of motor-operated appliances shall be provided with overload protection in accordance with Part III of Article 430.
 

rlundsrud

Senior Member
Location
chicago, il, USA
internal thermal protection

internal thermal protection

I cannot site a reference for this, it is strictly IMO. I thought single phase (120v) motors came with internal overloads. I only mention this as I am certain some of the wiser members of this forum can educate me one way or the other. But I can honestly say I have never seen a 120v motor that didn't have internal thermal protection. I would like some feedback on this.

Bob
 

ActionDave

Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
wire pulling grunt
I cannot site a reference for this, it is strictly IMO. I thought single phase (120v) motors came with internal overloads. I only mention this as I am certain some of the wiser members of this forum can educate me one way or the other. But I can honestly say I have never seen a 120v motor that didn't have internal thermal protection. I would like some feedback on this.

Bob
I agree with you. I am sure somewhere out there is a 120V motor with no internal protection but the ones I deal with on any given day have it or are impedance protected.
 

overkill94

Member
Location
California
This one was dual rated at 115/230 V and the nameplate did not specify that it was thermally protected. I re-read NEC 430 III and it says that even cord-connected equipment with motors 1 HP or above require overload protection.
 

rlundsrud

Senior Member
Location
chicago, il, USA
You said it was cord connected, did it come from the manufacturer this way and is it UL listed? If it is, I can't envision any scenario where it wouldn't have thermal protection. If you are still uncertain, contact the manufacturer. I frankly would be shocked (no pun intended) if it wasn't.

Bob
 

suemarkp

Senior Member
Location
Kent, WA
Occupation
Engineer
This one was dual rated at 115/230 V and the nameplate did not specify that it was thermally protected. I re-read NEC 430 III and it says that even cord-connected equipment with motors 1 HP or above require overload protection.
But there are multiple solutions for overloads, one being internal thermal protection [430.32(A1)(1) - (4)].

Also, is this really a continuous use application? It sounds like it could be intermittent use, as "tool heads" is one of the uses listed under intermittent use [430.22(E)]. If this is intermittent duty, the motor shall be permitted to be protected against overload by the branch-circuit short-circuit and ground-fault protective device, provided the protective device rating or setting does not exceed that specified in Table 430.52 [430.33]. I'd argue that you can't use a grinder continuously under load. Turning it on and walking away is not under load. You need to press the work into the grinder wheel to load it up. No one there, no load.

Also, is this really a 1.5 HP motor? That sounds a bit large for a 120V 15A cord and circuit. Is there a FLA rating on the motor nameplate?

These NRTL certifications really burn me up. We have equipment that is 30 to 50 years old (e.g. drill presses and various tools) that is working fine and not killed anyone yet. But it is not listed so now it needs to be evaluated and stickered if it is relocated (technically, it needs to be evaluated even if it doesn't move, but its the inspection process for the new circuit that triggers it). At the time it was built, the rules were different (both in content and labeling). Certifying some of these things can be expensive or a pain to comply with. Sometimes, its just easier to buy a new listed unit than mess with the old ones. Seems wasteful to declare these old simple things as unsafe and toss them away.
 

overkill94

Member
Location
California
But there are multiple solutions for overloads, one being internal thermal protection [430.32(A1)(1) - (4)].

Also, is this really a continuous use application? It sounds like it could be intermittent use, as "tool heads" is one of the uses listed under intermittent use [430.22(E)]. If this is intermittent duty, the motor shall be permitted to be protected against overload by the branch-circuit short-circuit and ground-fault protective device, provided the protective device rating or setting does not exceed that specified in Table 430.52 [430.33]. I'd argue that you can't use a grinder continuously under load. Turning it on and walking away is not under load. You need to press the work into the grinder wheel to load it up. No one there, no load.

Also, is this really a 1.5 HP motor? That sounds a bit large for a 120V 15A cord and circuit. Is there a FLA rating on the motor nameplate?

These NRTL certifications really burn me up. We have equipment that is 30 to 50 years old (e.g. drill presses and various tools) that is working fine and not killed anyone yet. But it is not listed so now it needs to be evaluated and stickered if it is relocated (technically, it needs to be evaluated even if it doesn't move, but its the inspection process for the new circuit that triggers it). At the time it was built, the rules were different (both in content and labeling). Certifying some of these things can be expensive or a pain to comply with. Sometimes, its just easier to buy a new listed unit than mess with the old ones. Seems wasteful to declare these old simple things as unsafe and toss them away.
I think you found the exception right there - I was under the impression that you couldn't consider a machine intermittent duty if it wasn't push-to-run or any other situation where the operator HAD to be present; didn't realize that the words "under load" were part of the definition. Sounds like this equipment doesn't need overload protection after all.

I feel your pain about the NRTL certifications, I actually feel bad when I have to write up reports with a laundry list of discrepancies on equipment that has functioned perfectly for years. My guess is it's all about liability so if something does go wrong there needs to be somebody to blame. Plus, otherwise I would be unemployed!
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
It's indirect, but it's there.

422.62 Appliances Consisting of Motors and Other Loads.
(B) Additional Nameplate Markings. Appliances, other
than those factory-equipped with cords and attachment
plugs and with nameplates in compliance with 422.60
, shall
be marked in accordance with 422.62(B)(1) or (B)(2).

422.60 Nameplate.
(A) Nameplate Marking. Each electrical appliance shall
be provided with a nameplate giving the identifying name
and the rating in volts and amperes, or in volts and watts. If
the appliance is to be used on a specific frequency or frequencies,
it shall be so marked.
Where motor overload protection external to the appliance
is required
, the appliance shall be so marked.

So if it is connected with a cord and cap, they do not have to mark it WITH something that says it is thermally protected, they only need to mark it IF the overload protection must be external.

Your grinder has a plug, it has no marking saying it needs an overload relay, so it does NOT need external overload protection.
Thanks Jraef, but the small print in 422.60 says to refer to 422.11 for overcurrent protection requirements and in that section it states:

(G) Motor-Operated Appliances.
Motors of motor-operated appliances shall be provided with overload protection in accordance with Part III of Article 430.
I think you had missed my point on this.

Yes, the motor needs to have OL proection, as you point out is in the fine print of 422.60 and 422.11. What I was meaning was, if it has a cord, they are NOT required to say that it DOES have internal OL protection, they are only required to say that it DOESN'T. So if it does not say anything on it, and it has a plug-in cord, that means it does NOT need an external OL relay. It's a little bit of pretzel logic to be sure, but IMHO you erred in writing them up for not having an OL.
 

jxofaltrds

Senior Member
Location
Mike P. Columbus Ohio
Occupation
ESI
Did an inspection on a 1 1/2 HP grinder at a manufacturing company. While it would seem that something like this would not require overload protection, I'm having a hard time finding an exception in the NEC. It's cord-connected and has an on/off switch, so someone could turn it on and leave it on. Thoughts?
Yes they could turn it on and leave.

III. Motor and Branch-Circuit Overload Protection
430.31 General. Part III specifies overload devices intended
to protect motors, motor-control apparatus, and motor branchcircuit
conductors against excessive heating due to motor
overloads and failure to start.

430.42 Motors on General-Purpose Branch Circuits.
Overload protection for motors used on general-purpose
branch circuits as permitted in Article 210 shall be provided
as specified in 430.42(A), (B), (C), or (D).

(B) Over 1 Horsepower. Motors of ratings larger than
specified in 430.53(A) shall be permitted to be connected to
general-purpose branch circuits only where each motor is protected
by overload protection selected to protect the motor as
specified in 430.32. Both the controller and the motor overload
device shall be approved for group installation with the
short-circuit and ground-fault protective device selected in accordance
with 430.53.

(C) Cord-and-Plug-Connected. Where a motor is connected
to a branch circuit by means of an attachment plug and
a receptacle or a cord connector, and individual overload protection
is omitted as provided in 430.42(A), the rating of the
attachment plug and receptacle or cord connector shall not
exceed 15 amperes at 125 volts or 250 volts. Where individual
overload protection is required as provided in 430.42(B) for a
motor or motor-operated appliance that is attached to the
branch circuit through an attachment plug and a receptacle or
a cord connector, the overload device shall be an integral part
of the motor or of the appliance. The rating of the attachment
plug and receptacle or the cord connector shall determine the
rating of the circuit to which the motor may be connected, as
provided in 210.21(B).
 
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