Legal to use 600v disconnect in place of 300v ?

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milemaker13

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Suburbs of Chicago
There is a cnc tech here today. He is installing a fused disconnect switch to our machine. The machine is running 208v 3 ph. It takes 45 amp fuses. The tech wants to install a 60 amp 600 v disconnect.

Is this legal? Safe? Proper?

I want him to instead install a 60 amp 300 v disconnect switch that I have on hand.

He doesn't understand voltage (208 vs. 480) and insists this is the correct box because that is what the manufacture sold him. The machine is multi-volt from 208-480.
 
The voltage rating on the disconnect (and fuses) is "maximum". A 600 v disconnect is permissible on any voltage below 600.
(I believe some manufacturer's Heavy Duty disconnects are only available in 600v)
 
milemaker13 said:
There is a cnc tech here today. He is installing a fused disconnect switch to our machine. The machine is running 208v 3 ph. It takes 45 amp fuses. The tech wants to install a 60 amp 600 v disconnect.

Is this legal? Safe? Proper?

I want him to instead install a 60 amp 300 v disconnect switch that I have on hand.

He doesn't understand voltage (208 vs. 480) and insists this is the correct box because that is what the manufacture sold him. The machine is multi-volt from 208-480.
Click to expand...

Not only is it OK, sometimes you must use a 600V disconnect. When you need a high AIC rating on a service disconnect, a 600V disconnect may be specified to a 208 volt system for example. Higher voltage is fine, it is lower voltage that can be an issue. Regardless of the voltage, it is the amperage that melts the fuse element. The voltage rating is there to prevent jumping across the gap basically and negating the open.
 
You have to be very careful though, because if you have a 208V system and install a 600V disconnect, it can put almost 400 extra volts on the system when the disconnect is open under fluxing shunt conditions, such as if the retroencabulator of the motor is spinning backwards.







Nah... just kidding...:angel:
 
Jraef said:
You have to be very careful though, because if you have a 208V system and install a 600V disconnect, it can put almost 400 extra volts on the system when the disconnect is open under fluxing shunt conditions, such as if the retroencabulator of the motor is spinning backwards.







Nah... just kidding...:angel:
Click to expand...

well duh! we ALL know that :D:D:D
 
Jraef said:
You have to be very careful though, because if you have a 208V system and install a 600V disconnect, it can put almost 400 extra volts on the system when the disconnect is open under fluxing shunt conditions, such as if the retroencabulator of the motor is spinning backwards.
Click to expand...

I am pretty sure it is the when the neoencabulator spins backwards, doesn't the retroencabulator just increase the capacitation?:D
 
Strathead said:
I am pretty sure it is the when the neoencabulator spins backwards, doesn't the retroencabulator just increase the capacitation?:D
Click to expand...
I've got a GE turboencabulator (which predates the retroencabulator) so should I be concerned about increased levels of side fumbling? I believe the retroencabulator design added hydrocoptic marzelvanes to combat this issue.

I believe there's room in the budget for an upgrade for the sake of performance. There should be a few years of service life left as the sinusoidal depleneration is still within spec. I'm just wondering if I should push for replacement now, rather than wait a few years?
 
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