Don - I thought I'd throw this at you since you are a wealth of information about the minute details of the code.
In the Mike Holt forum it was stated: "Also bonding is required around reducing washers if the metal raceway is used as an EGC per 250.118".......which led to "Reducing washers to not allow the low impedance path as required in 250.4(A)(3)."
My question: Where is the documentation, code recital, UL or other Standard that supports such a claim?
I have read in Mike Holt's 'Ground & Bonding' and in Soares ' Book on Grounding' that "reducing washers are not suitable for bonding and should always be bonded around"
HOWEVER - neither of these books cite or footnote a study, report, document, or standard that reducing washers do not meet a 'low impedance' criteria.
The reason I bring this up is that both of these books usually refer to studies, standards or the code, etc. in supporting such a statement......AND - how would an inspector be able to support such a requirement to the electrician in the field with 'Soares says so in his book'.?
I know some devices/materials are not tested by UL and as such automatically do not satisfy a standard - but I don't know where to look further to satisfy this curiosity I have around this reducing washer issue.
Thank you for any information you may be able to provide on this subject.
Dana1028, Exactly the point, UL does not list them for grounding purposes, never did, at least for a long time. Article 250 supports bonding around all weak points, and that is why they also must be bonded around, which is the 2nd point.
Soares quotes an IEEE testing procedure, and that is acceptable not only for enforcement with USBC standards, but NFPA documents as well. It was not enforced around here for a long time, but did finally catch up with us.
Re: Bonding Around Reducing Washers#84819 05/07/0307:20 PM05/07/0307:20 PM
Dana, I'm not aware of any specific document that says reducing washers are not suitable for grounding, but I'm also not aware of any document that says they are suitable. I'd require bonding based on 250.4(A)(5) and if the contractor doesn't agree, then he can provide me with a document from a NRTL that says they have been tested and found suitable for grounding. don
Re: Bonding Around Reducing Washers#84822 05/09/0306:16 AM05/09/0306:16 AM
Reminded once again that the NEC provides MINIMUM acceptable requirements. Why the hesitancy to install a bushing that will ENSURE electrical continuity, due to it's listing. (See 250.96 (A)) The potential arcing due to a loosely connected grounding path creates a fire and/or electrocution hazard in the event of a fault. Do it to it.
[This message has been edited by Redsy (edited 05-09-2003).]
Re: Bonding Around Reducing Washers#84823 05/09/0309:32 AM05/09/0309:32 AM
All reducing washers are subjected to a Resistance Test and a Current Test by UL. These tests are in the test standard UL 514B, and also in UL 467. All reducing washers currently Listed by UL have been subjected to these tests. Creighton.
Re: Bonding Around Reducing Washers#84824 05/09/0312:15 PM05/09/0312:15 PM
Thanks Creighton. How do they insure contact with the enclosure? Is the installer required, by 250.95(A), to remove the enclosure paint before installing the reducing washers? I really can't imagine reducing washers providing the required low impedance fault clearing path, but if the NRTL says they do, I guess we'll have to accept them. If they are not listed to provide contact through the paint, I would require that the paint be removed. I would expect it would be cheaper to install a grounding bushing, than to remove the paint. Don