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double throw disco #36275
04/03/04 02:19 AM
04/03/04 02:19 AM
S
seattleman  Offline OP
Member
Joined: Feb 2004
Posts: 17
Seattle, WA, USA
Has anyone used a double throw safety switch. Just wondering what applications this had been used for.

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Re: double throw disco #36276
04/03/04 04:03 AM
04/03/04 04:03 AM
P
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
I would have thought one of the most common uses would be to select different power sources, e.g. utility power or generator.

Re: double throw disco #36277
04/03/04 06:43 AM
04/03/04 06:43 AM
electure  Offline

Member
Joined: Dec 2000
Posts: 4,263
Fullerton, CA USA
Manual transfer switch, as Paul says.

Re: double throw disco #36278
04/03/04 08:32 AM
04/03/04 08:32 AM
M
Matt M  Offline
Member
Joined: Mar 2001
Posts: 93
Laporte, MN, USA
We use them all over the place in the factory that I work at to reverse 3-phase motors. Matt

Re: double throw disco #36279
04/04/04 09:25 AM
04/04/04 09:25 AM
N
nesparky  Offline
Member
Joined: Jun 2001
Posts: 642
omaha,ne
Another use is to select which load gets power when the same source runs one OR another load.


ed
Re: double throw disco #36280
04/04/04 03:05 PM
04/04/04 03:05 PM
B
Bjarney  Offline
Moderator
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
Note that nowadays there are two styles of ‘double-throw’ XOP switches. See http://ecatalog.squared.com/catalog/173/html/sections/03/17303014.html
A newer style has two sets of movable blades and two sets of fixed jaws. Older is one set of movable blades and two sets of fixed jaws. (Note upper vs. lower photos.)

[I believe Cutler-Hammer has a similar variation.]

Re: double throw disco #36281
04/04/04 04:51 PM
04/04/04 04:51 PM
N
NJwirenut  Offline
Member
Joined: Sep 2001
Posts: 806
Bergen County, NJ
AFAIK, the 2 different variations in construction are a result of fusible or non-fusible design.

The extra length needed for 2 sets of fuses requires 2 separate interlocked switch mechanisms, while a non-fused switch can be made with a single set of blades.

Re: double throw disco #36282
04/04/04 09:37 PM
04/04/04 09:37 PM
B
Bjarney  Offline
Moderator
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
NJ, that is a good point. I installed one fusible double-throw switch in a service-entrance application in the 1970s to accommodate a standby genset. One set of fuses was normally hot through the utility feed [with the switch open.] At the time there was an NEC exception that clearly allowed the practice.

By job completion, a prominent label warned of the condition, and a piece of clear acrylic secured with non-metallic machine screws covered the {utility-powered} set of fuses.

Re: double throw disco #36283
04/04/04 10:03 PM
04/04/04 10:03 PM
B
Bjarney  Offline
Moderator
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
Two C-H double-throw switch versions [one set of movable blades versus two] are illustrated on page 26 of www.eatonelectrical.com/unsecure/cms1/TB00800001E.PDF {Aaak! 5MB file}
[Linked Image]
Note also the two applications on page 24 fig. 8-7 — “two sources” versus “two loads”.
[Linked Image]




[This message has been edited by Bjarney (edited 04-05-2004).]

Re: double throw disco #36284
04/05/04 01:18 AM
04/05/04 01:18 AM
K
kody wilson  Offline
Member
Joined: Mar 2004
Posts: 11
vancouver wa. 98664
should it be called a three posion insted of a "double trough"?


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