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non fusable disco question #36105 03/28/04 01:48 PM
Joined: Feb 2004
Posts: 17
S
seattleman Offline OP
Member
What applications would you use a non fusable disco.

Are these used for all loads except motor loads where separate overload protection is required?

For example a FourPak of heavy duty welders.

Any other examples where nonfusable disco's are commonly used? And could a fusuable disco be used for any load that currently uses a nonfusable disco.

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Re: non fusable disco question #36106 03/28/04 02:02 PM
Joined: Jan 2003
Posts: 4,391
I
iwire Offline
Moderator
Welcome seattleman.

You can use a non-fusible disconnect on any load that the correct overcurrent protection is already installed.

Say a HVAC unit that has the correct overcurrent protection at the panel, why spend extra money on a fusible switch and fuses, this can be a lot of money when it is a large 600 volt rated switch and fuses.

You may use a fusible switch any place that a non-fusible switch is presently installed and you can even get "non-fuse" 'fuses' for the switch.

These are UL listed devices to make a fusible switch non fused.

Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: non fusable disco question #36107 03/28/04 03:02 PM
Joined: Feb 2004
Posts: 17
S
seattleman Offline OP
Member
thanks Bob

I just looked back a square d catalog. one of the few that actually lists prices. And i see that a fusable 600v 100amp is $792 versus a nonfusable at $522. Thats a good savings.-thanks

Re: non fusable disco question #36108 03/28/04 08:20 PM
Joined: Mar 2002
Posts: 582
R
Ron Offline
Member
One additional note to Bob's.
A non-fusible disconnect generally has a withstand value (capability to resist explosion during a fault) of 5k and sometimes 10k, depending on the manufacturer. A fusible disc., with fuses, has a withstand/AIC generally of the fuse AIC rating.
So just check fault current available before selecting.


Ron
Re: non fusable disco question #36109 03/28/04 10:57 PM
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Posts: 171
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Merlin Offline
Member
seattleman

We use many non-fusible disco's at the quarry where I work. We use them as a disconnect between every motor and starter. All of our fuses are located with with the starters in one cabinet. Therefore we have seperate disconnects that we can lock out to work on that piece of equipment. It seems to work good.

It also makes it simple to reverse rotation on a motor ( 3 phase ) without exposing yourself to a great danger.

Re: non fusable disco question #36110 03/29/04 05:07 AM
Joined: Jan 2003
Posts: 4,391
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iwire Offline
Moderator
Thank you Ron, that is an important aspect to consider, I am glad you pointed that out. [Linked Image]

Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: non fusable disco question #36111 03/29/04 09:52 PM
Joined: Mar 2002
Posts: 582
R
Ron Offline
Member
The withstand rating is the reason I end up having to have non-fusable discos replaced after they have been installed by well meaning folks.


Ron

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