Bus Bracing for Low Voltage Switchgear
Bus Bracing for Low Voltage Switchgear
(OP)
Please advise if there are any specific guidelines for bracing/supports for 480V 50kA Switchgear. There seams to be a table/chart available from UL891 Supplement B for Switchboards but haven't come across anything for Switchgear.
Also, have not been able to actually "find" the Supplement B that many refer to, even when searching on the UL web site. They only list Supplement A???
Also, have not been able to actually "find" the Supplement B that many refer to, even when searching on the UL web site. They only list Supplement A???





RE: Bus Bracing for Low Voltage Switchgear
"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic — and this we know it is, for certain — then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". – Nikola Tesla
RE: Bus Bracing for Low Voltage Switchgear
Rafiq Bulsara
http://www.srengineersct.com
RE: Bus Bracing for Low Voltage Switchgear
Yes, 891 is for Switchboards and 1558 is for Switchgear Assemblies.
It appears that UL provide charts (in Supplement B that I can't find on the UL web site)for mfgr's to build switchboards but to build swgr, one has to follow testing guidelines to prove it can withstand the levels it maybe subjected to. Therefore, there are no charts for swgr bus supports and bracing. If someone has a different information on this, please advise.
I know that there are companies out there that will modify existing bus systems for a higher IC rating and I wonder what they use for guidelines/calculations to warrant what they do.
RE: Bus Bracing for Low Voltage Switchgear
See Annex G (at the very end of the 891 file). Annex G covers 4000A maximum & up to 100,000 RMS.
1558 Switchgear: Supports & bracing must be per individual testing. Once that testing has been done, we can design per the spacings in our UL File.
RE: Bus Bracing for Low Voltage Switchgear
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RE: Bus Bracing for Low Voltage Switchgear
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RE: Bus Bracing for Low Voltage Switchgear
Barry, the company I work for utilizes a arc-flash study along with a design program. The placement is dependant upon final kA rating.
RE: Bus Bracing for Low Voltage Switchgear
"Those who can't do, teach But those who can't teach, inspect!"
Inspectors here are referred to as an "AHJ", Authority Having Jurisdiction. It means the are the demigod of their own little world. There is an appeal process, but you are loathe to use it if you are not prepared to be challenged on everything. Most inspectors are retired (or failed) contractors, not engineers. This one was a retired engineer, but he was not an EE, I think he was an ME, maybe even a CE.