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Use Thread Forming Screws...no chips...better grip.

If there is any movement of the cable, a 1-hole lug may become loose (and then hot) or short to another phase or ground. Movement can be caused by tension of heavy cable & vibration, magnitizim during a short circuit, or just someone pulling on the cable. NEMA has developed a standard. (2) 1/2"...

If there is a short on B-Phase, any available current will pass through the B-Phase of your contactor. If the avaible current is above 4500A, the contactor will fail.

Overcurrent Protection is to protect the Conductors & the Devices they feed during normal operation. In this case, this is the job of your circuit breaker. Your Conductors & your Overcurrent Protection Device (your breaker) have specific short circuit ratings. The short circuit rating is the...

To a UL 891 Switchboard manufacturer, 100% can mean a few different things. 1. Sized and spaced per the manufacturers temperature test results: Most of the current flows along the skin of a bus bar. Therefore you might get a greater current carrying capacity with a lower density, large surface...

To a UL 891 Switchboard manufacturer, 100% can mean a few different things. 1. Sized and spaced per the manufacturers temperature test results: Most of the current flows along the skin of a bus bar. Therefore you might get a greater current carrying capacity with a lower density, large surface...

Re UL 891: There is no more Suppliment B. 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.

Typical switchgear is a bolted frame construction. For the most part, a heaver gauge material will not prevent twisting. Gear must be level and square for drawout breakers to opperate properly. Proper installation is everything. An option is to order switchgear with a seismic rating...

Waross, you are correct in you assessment....The 8" dimension is not to be taken into consideration. At 800A per sq in, you will need 20" of .25 cu to carry the 4000A. (the 8" dimension can be anything)

Per UL891 Table 23 & 24: less than 3000A: 1000A per sq. in. 3000A - 6000A: 800A per sq. in This is what we typicaly use in our switchboards. Some city codes require 800A per sq. in. everywhere. Your .25 x 8.0 bar will need to be 20" (or double up so that you have 20" or more of .25 cu)

From a Switchboard/gear perspective: If the Breaker has a Non Interchangeable Trip....We size our cable/bus to the trip (AT). If the Breaker has an Interchangeable Trip, we size our cable/bus to the frame (AF). Also for a Fuse Holder or a Fused Switch, we'll size to the frame (or the maximum...

I thought the same thing at first....mixing IEC & UL. But my search came up with this chinese site that plainly refers to IP4LX. It makes mention to IEC 529 but clearly does not mimic it. I've attached the chinese site...

I have a customer inquiry from Argentina who is asking for a IP4LX enclosure. My googles have come up with only chinese web sites. I've translated the page, but I am still not clear. Can someone please define IP4LX for me. Thanks!

This is a common situation on breaker & switches. Torque & loctite or completly remove the unused set screw.

All Enclosure manufactures sell Type 4 & 12 Freestanding enclosures. But they have no means of securing the enclosure to the floor. No instructions. No kit. UL50 says "Floor supported enclosures are not required to be provided with a mounting means." I called Hoffman. They had no instruction...

See UL 891 Supplement B. It has a chart for between 42K & 100K, Max 4000A. Example:800A-4000A, 65,000 @ 480V, bars edge-edge, min. 1" bar to bar, min. 5" center to center, 21" between supports. Example:800A-4000A, 65,000 @ 480V, bars face-face, min. 4" bar to bar, min. 6" center to center...

UL891 (Switchboards) contains defined minimum bus ampacities, bus spacing, & bus arrangements. 891 also defines minimum support & bracing requirements based upon the necessary short circuit requirements. Basically, UL891 is an engineering guideline for building safe equipment that will meet NEC...

Switchboards are built to engineering guidlines set out in UL 891. Switchgear is built to UL 1558.

UL 891 says "Part of the bus material may be removed for slots or holes (wether used or not) if the remaining material at any cross section along the bus bar has at least 70 percent of the required ampacity and the remaining metal in any 6 inch length of bus is at least 93 percent of the metal...

We are using 2002. Is there a way to join two line segments? Thanks!