Cut in/old work boxes in hospital rooms

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billybobjojo

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I was recently told that when using cut in boxes in hospital rooms that you have to leave the ears on your devices like receptacles when they are installed to help with more metal to metal contact even with self grounding receptacles.

It has been the practice when installing cut in boxes to clip the ears off so one can ensure the receptacles are set back far enough to make the face plate flush with the wall. I was informed that instead one is use a slightly raised or beveled cover for this application. Is this a true?
 
Seems like that defeats the reason for self grounding receptacles. The receptacles are still bonded with a wire. Most receptacles in flush installations don't have direct contact with the box. I don't see why a cut-in should be treated any differently.
 
raised beveled covers are suitable for grounding. straight sided square raised covers are not. If you use the square ones you need a pigtail bond. I think in hospital apps you need the redundant ground in all cases anyway?
 
billybobjojo said:
I was recently told that when using cut in boxes in hospital rooms that you have to leave the ears on your devices like receptacles when they are installed to help with more metal to metal contact even with self grounding receptacles.
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May not be a bad idea but, if it were in fact true, HG receptacles would not be manufactured with ears at all.

Roger
 
I think this is nonsense too. The reason they gave in addition to the ears making metal contact was because of an impedance test and voltage test for surface metal contact in patients rooms. They say it's not suppose to be more than 500 millivolts for existing and less for new installs for hospital certifications. So its not an NEC issue but some other practice. It's said that cut in boxes don't have as much conductivity as regular hard piped boxes in redundant grounding applications even though they are UL listed for these areas because the HCF cable connections to cut in boxes are just as good.

I still don't think the ears are going to make any difference in this, because if there is stray voltage or high resistance going on, there has to be other bonding issues in the room.
 
I personally see less chance of contact failure between the device yoke and the portion of the box with the threaded hole for the mounting screw than I see a assurance of good reliable contact between the device ears and the cut in box ears.

There should probably not be any insulating "screw keepers" between the contact points, but I can't recall not seeing a hospital grade receptacle that wasn't also self grounding type screw keepers.
 
kwired said:
There should probably not be any insulating "screw keepers" between the contact points, but I can't recall not seeing a hospital grade receptacle that wasn't also self grounding type screw keepers.
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If the device requires redundant grounding wouldn't it always need to be self-grounding?
 
infinity said:
If the device requires redundant grounding wouldn't it always need to be self-grounding?
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Isn't direct metal to metal contact with no insulating material between "self grounding". The accessory devices that assure screw to yoke contact are really there for flush box installations where maybe the box is not quite flush and the plaster ears are stopping the device from making direct contact with the box. Just my interpretation of how things work, feel free to disagree. I don't think the "self grounding" design is absolutely necessary by code if the device makes direct and secure metal to metal contact with the box.
 
kwired said:
but I can't recall not seeing a hospital grade receptacle that wasn't also self grounding type screw keepers.
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You won't but, if you do be sure to post a picture and the manufacturers name.

Roger
 
infinity said:
Sounds like another electrical urban legend not supported by code.
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This is from the NFPA 99 2005 edition


Grounding System Testing. The effectiveness of the
grounding system shall be determined by voltage measurements
and impedance measurements.
4.3.3.1.1.1 For new construction, (he effectiveness of the
grounding system shall be evaluated before acceptance.


4.3.3.1.1.4 Whenever the electrical system has been altered
or replaced, that portion of the system shall be tested.
4.3.3.1.2 Reference Point. The voltage and impedance measurements
shall be taken with respect to a reference point.


4.3.3.1.5.2 The voltage across the terminals (or between any
terminal and ground) or resistance-measuring instruments
used in occupied patient care areas shall not exceed 500 mV
ac or 1.4 dc or peak to peak.
4.3.3.1.6 Criteria for Acceptability for New Construction.
4.3.3.1.6.1 Voltage limit shall be 20 mv.
4.3.3.1.6.2 Impedance limit shall be 0.2 ohms for quiet ground
systems, and 0.1 ohms for all others.


Not sure if the 'ears' would really make a difference, but extra metal to metal contact for grounding and bonding is not going to hurt anything since there is a testing criteria that has to be followed and met for hospitals to maintain their certifications.
 
Correct me if I'm wrong but a self grounding device is only required to have metal to metal contact between the device and the mounting screw and the mounting screw and the metal enclosure. Metal to metal contact between the device and the box is not required. In fact a recessed box mounted in noncombustible wall material can have the box set back into the wall up to 1/4". That would eliminate the possibility of the yoke ever contacting the device.
 
infinity said:
Correct me if I'm wrong but a self grounding device is only required to have metal to metal contact between the device and the mounting screw and the mounting screw and the metal enclosure. Metal to metal contact between the device and the box is not required. In fact a recessed box mounted in noncombustible wall material can have the box set back into the wall up to 1/4". That would eliminate the possibility of the yoke ever contacting the device.
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I say you are correct. But I think the question here is if you don't have such a device in a patient care application are you in violation of the "redundant grounding" rules? But it is also been said that you may never find a hospital grade receptacle that does not have the self grounding feature.
 
kwired said:
I say you are correct. But I think the question here is if you don't have such a device in a patient care application are you in violation of the "redundant grounding" rules? But it is also been said that you may never find a hospital grade receptacle that does not have the self grounding feature.
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I dont think the original post was about the redundant grounding rules issue. Its more of an issue with the performance testing of the 500mv in existing and lower for new construction according to NFPA 99. I still think one should be able to passed the test even if the ears do not make the metal to metal contact, but I also know that the more bonding the better and less chance of failing the test in these critical areas. I always heard of 'rumors' of the dislike of cutin boxes in patient areas from hospital inspectors and certifiers. They actually want a person to spend unnecessary extra money and cut a wall open and hard pipe a receptacle and patch it later even though HCF cable works just fine. LOL .

I personally would not have any issue with using the beveled cover plates and making the ears touch the cut in box. Those covers are not that expensive and it sounds like a cheap insurance.
 
If the box is cut into a fire rated partition it cannot be supported solely by the drywall and must be attached to a framing member hence the need to cut the wall open.
 
infinity said:
If the box is cut into a fire rated partition it cannot be supported solely by the drywall and must be attached to a framing member hence the need to cut the wall open.
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It is not a 'fire rated wall' situation that they give for the reason. They like to apply NEC 2008 517.30(C)(3) to normal power systems even though it is for emergency wiring, . They want flex used only in prefabbed head board units and not for 'fishing' down a wall. 1 is for the mechanical protection and, 2, they feel the grounding is better with hard non flexible pipe.
Mainly to ensure the impedance testing and voltage testing criteria is met and kept. A lot of cut in boxes do get loose over time and start to pull away from the wall because of excessive uses. and they feel that with hard pipe its less chance of this happening.
 
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