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How to choose the right KT7 Bus Bar Power Wiring system

Question: There are several different types of bus bar systems available. How do I know which system to choose for my assembly? If I have an old bus bar system, what is the current replacement recommendation? What if I need to add a unit to an existing system?

Common Applications

The most common application of compact bus bar is in a multiple motor starter control panel. A multi-motor control panel could utilize a series of KTA7 or KTC7 motor controllers, either alone or with a contactor to make a Type E/F starter (CL7/CK7). Compact busbars allow power wiring of multiple units without running individual wires to each controller. The KTA7 or KTC7 would be used to protect motor loads, while KTU7 would be used to protect non-motor loads (transformer or heater).

Busbar Replacement on an Existing Assembly

When the panel assembly is using KTA7 or KTC7 exclusively, the KT7-32-DB busbars should be used. In 2011, Sprecher & Schuh discontinued the old "fork" stab KT7-25-DB in favor of the molded single stab KT7-32-DB models. For an older existing panel that needs a busbar replacement, the KT7-32-DB and KT7-25-DB cannot be mixed on the same power run as the connections are not satisfactory. All of the old KT7-25-DB on the same assembly run should be replaced with the KT7-32-DB of the same size for the best replacement fit.

Old KT7-25-DB Compact Busbar with "Fork" terminals

KT7-32-DB Molded Compact Busbar with single stab terminals

Mixed Applications

In mixed applications, when KTA7 or KTC7 and KTU7 are being used in the same run, the KTU7-D-DB compact bus bar can be used to connect both the KTA7 and KTU7. This is possible because the KTU7 busbars have a built-in creepage distance of 2" as required by UL. KT7-32-DB compact bus bar will not work with KTU7, but KTU7-D-DB works well with both KTA7 and KTU7.

If availability of replacement compact bus bar is an issue, then there are other alternatives to consider.

• If the total connected load (current of a group) is not more than 30 Amps, the devices may be daisy-chain wired since the line terminals are #10 AWG (good for 30 amps).
• If there are several KTA7 and only one or two KTU7 then you might consider using a second KT7-32-A3E supply block attached to the KT7 compact busbar to feed just the KTU7 from the compact busbar via wire.
• If the above suggestions do not apply to the specific application, and KT7-32-DB is NOT an option, then you must consider using a power distribution block.

Older existing panel system that need to be updated to replacement motor control units or to meet a new UL requirement should be analyzed for replacement options and/or engineered cost savings.