SERVICE SIDE BONDING OF MYERS HUBS

[florida-sparkey]

Hello and thank you!
I am installing an auxiliary gutter that has two parallel risers with each containing 4- 250KCM AL wires (3P 400A service)
Each RMC will be threaded into a myers hub.

Question. Is a bonding jumper required? I will cut my own holes and a myers hub does not rely on a "standard locknut" 250.92(B) or so I think. Clearly I may be wrong.

If needed This becomes the bonding jumper question.
I planned on bonding each riser with an individual #4 CU jumper wire per 250.102(2) using a meg bushing
I will install a ground block solidly bolted to gutter and bond the 2 neutrals and 2 bonding jumpers (if required) here for service side bonding.

I am totally confused as to what table 250.120(C)(1) note 2 is saying.
Can someone tell me in English because 10 rereads did not clear it up for me. Do I need to change the size of the bond wire or change it to #2 AL to meet the notes requirement?

 

[augie47]

As just mentioned in this thread:
http://forums.mikeholt.com/showthread.php?t=191538&highlight=myers

Myers hubs with no bonding jumper are not listed for service bonding.
A #4 bonding jumper is sufficient for 250 AL if you bond each conduit individually.
If you are running one jumper to bond both conduits then you need to base the jumper size on the sum of the phase conductors or, in your case, 500 kcmil (2 X 250) which would require a #2 Cu

 

[florida-sparkey]

As just mentioned in this thread:
http://forums.mikeholt.com/showthread.php?t=191538&highlight=myers

Myers hubs with no bonding jumper are not listed for service bonding.
A #4 bonding jumper is sufficient for 250 AL if you bond each conduit individually.
If you are running one jumper to bond both conduits then you need to base the jumper size on the sum of the phase conductors or, in your case, 500 kcmil (2 X 250) which would require a #2 Cu

Thank you, I did not see the other thread.
What about the reading of the note? Any idea?

 

[texie]

As augie mentioned, there are "regular" type Meyers hubs that are suitable for "normal" grounding and do not meet the requirements of 250.92. These are UL Product Category DWTT in the UL White Book. To comply with 250.92 you need to use a grounding hub listed as UL Product Code KDER.

As to the Table 250.102(C)(1), Note 2 question this only applies over 1100 kcmil CU/1750 AL. This is fixed in the 2017 edition. This has to do with the way the math works when the sizes are over 1100 CU/1750 AL. Otherwise just use the table values, IE if using a separate jumper for each raceway containing a 250 kcmil AL ungrounded conductor you would need a #4 CU jumper.

 

[texie]

Sorry, did not mean to be redundant on the Meyers hub types, but I did not realize augie had already referred to my comments on this subject in the other post.