Standing in line at a convenience store last night, I overheard the following conversation between the man in front of me and the woman behind me, apparently coworkers.

Woman: How's it going?
Man: Not good. I still have to go back up there tonight. We're doing a shutdown.
Woman: Tonight? Complete shutdown?
Man: Critical bus panel that feeds the fourth floor.

I was laughing at myself, wondering what the heck a critical bus panel was, and thinking that everything reminds me of Y2K. Then, when I went out to my car, I saw the man get behind the wheel of an Avista Utilities truck (local power company). Now I really want to know what a critical bus panel is.

-- (RUOK@yesiam.com), December 23, 1999

Answers

A bus panel is a electrical "bus" (usually a metal strip) that supplies a defined voltage for something. There could be one or many, different voltages from which electricity is drawn when that specific voltage is needed.

It should not be much of a problem to replace the bus (metal strip) with power (usually from one of many oputputs of a transformer and/or power supply

In your house you have two voltage busses from which you get your power, 110-120 for normal outlets which power most of your appliances and 220-240 volts which powers your clothes dryer, stove and possibly heater and water heater. If you look in your circuit breaker box you will see the power "bus" (metal strip) which runs down the row of circuit breakers (usually on both sides) and a second "bus" (metal strip) to which your larger circuit breakers are attached. The larger ones of course are for the higher voltage for your real electrical power hogs *grin* (the ones that cost you the most money because they use the most voltage). Your (electric) oven pulls so much current that you could light your house for a month with the electricity you use for cooking a Thanksgiving dinner.

In a commercial building there will be the need for more than the two power settings. Repairing or replacing a "power bus" is basicaly a no brainer and takes more elbow grease then technical intellect.

-- Cherri (sams@brigadoon.com), December 23, 1999.

Best guess: either a power distribution unit or other power routing unit (line conditioner?). The "bus" is just like the bus in a computer. It provides a link between all circuits and the main feed (for a computer, all devices and the CPU). If, like many systems, it has an embedded chip that monitors loads on various phases and circuits, and provides some balancing between them, it may need to be tested. Thus: critical (serves the important circuits on the floor: a server room, comm closet etc); bus (central junction for all these circuits, plus maybe other functions like load balancing); panel (control panel for said unit, provides some manual control for monitoring circuit and phase load, and possibly control over local circuit breakers as well). If any aspect of this system uses a RTC, and fails to make the rollover smoothly, it could cause a fault condition which the unit would not recognize. In such a case, the unit would trip all circuits (cut them off) until reset and checked by the power company. Hope this helps.

Jes' Thinkin'...

-- Little Pig (littlepig@brickhouse.com), December 23, 1999.

Thanks, Cherri and Little Pig, for your responses. If I'm understanding you correctly: The critical bus panel being discussed would be what regulates electrical distribution to the afore-mentioned 4th floor. They would be shutting down in order to repair or replace the panel, which may or may not be Y2K-related. In either case, the repair/replacement would not be complicated. If this summary reflects a misunderstanding of your reply, please feel free to correct.

-- (RUOK@yesiam.com), December 23, 1999.

Bus maintenance is normal for commercial buildings. Many insurance policies require infrared video scan of main power distribution panels (where the buses are)on a regular basis. This reveals minor problems before they become major problems (hopefully).

A warm or hot area in a panel can be caused by a failing breaker, or a poor elect. connection.

These inspections are always done during off hours. You had better totally power the panel down if you intend to start replacing components or checking connections.

These big panels can be very dangerous, those big circuit breakers have been known to explode.

-- Tryntohelp (beenthere@donethat.com), December 23, 1999.