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Wiring Dewhurst switch

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michael cole16/07/2016 17:06:34
163 forum posts

I have just bought a Dewhurst switch , with forward , off and reverse. It has 2 veritcal rows of 4 contacts each side. How is is wired up? It is for a old motor for a Britanic lathe


John Rudd16/07/2016 17:15:02
1368 forum posts
66 photos

A quick Google came up with this.....

Kiwi Bloke18/07/2016 09:06:19
408 forum posts
1 photos

Do yourself a favour, and use a push-button starter with no-volt release. It might save fingers, one day. You can easily add a reversing switch and panic-off buttons. However, if you insist on using the Dewhurst, the thing connects as follows. Terminals are numbered, left side, 1-4, from top to bottom, and, right side, 5-8, top to bottom. (1-2-5 means these terminals are all connected to each other.)

FORWARD: 1-2-5, 3-6-7, 4-8

OFF all disconnected

REVERSE 1-5-6, 2-3-7, 4-8

Assuming a capacitor-start, single phase motor, connect the supply to 1 and 3, RUN winding A1 to 7, A2 to 5, START winding Z1 or Z to 6, Z2 or AZ to 2. So the run winding is connected the same way to the supply in forward and reverse positions, but the start winding is reversed for direction change.

If it's not a single phase motor, ask again - these switches can cope with many types. Note that it's rated at 0.75 hp at 200-240V.

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