GFI on main service

[deltawhy]

Hello, I have an installation at 600V that requires ground fault protection (RCD) on the main service disconnect. I have designed it with fuses, but obviously fuses have no RCD. As a GFI breaker at this size would be very expensive, has anyone heard of a stand-alone zero sequence transformer and interrupting circuit? (Yes, essentially a breaker without the thermal/mag trip).

Thanks for your time

 

[jraef]

Sure. There are stand-alone GFRs (Ground Fault Relay) with a GFCT that can be used to operate a shunt trip or contactor coil. So if you got a Molded Case Switch (a.k.a. Non-Automatic Circuit Breaker) and installed a Shunt Trip, there you go. Done all the time. Some disconnect switches also have trip coil options available, you may want to check into that too.

Most of the major mfrs sell them, do a search using the term "Ground Fault Relay", GFCI is something different.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376

 

[deltawhy]

Thanks for that quick response jraef.
I have found a GFR with a neutral cond. C/T. Considering the GFR is still just a signalling device, I still require an external interrupting device (moulded case switch). With this setup I still require OCP by means of fuses upstream. Seems to me this setup will be overcomplicated and cost more than just buying switchboard with a GFI MCCB. Thoughts?

Thanks for your time,

 

[jghrist]

As you noted, you still need a molded case switch to interrupt the current, which needs to be rated to interrupt full fault current. It would appear to be cheaper to add a phase trip unit or relay and eliminate the fuses. You would have to compare the cost with a GFI MCCB.

 

[jraef]

Do you have a disconnect ahead of the fuses? I would hope so. Did you check to see if there is a shunt trip coil available for that disconnect?

The decision to use fuses or circuit breakers is one that elicits a lot of debate, but in general if you used fuses for current limiting and/or very high interrupt capacity, you may not be able to replace them with an MCCB. There's more to it than just the ability to shunt trip it.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376

 

[deltawhy]

jraef - a shunt trip is not available on any disconnect I have seen. Have you seen auto disconnects with shunt trip capabilities that have sufficient interrupting capacities?
.. and yes I have the disconnect on the supply side of the fuses. Always good practice to be replacing fuses on live conditions.

Thanks,

 

[jraef]

Siemens HCP switches have shunt trips available, others must as well.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376

 

[VTer]

Google Bolted Pressure Contact Switches. Eaton's version is the Pringle switch.

"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic — and this we know it is, for certain — then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". – Nikola Tesla

 

[DRWeig]

Had Siemens stuff at a mega-hospital I worked for, bolted pressure switches with shunt trip devices. We used 'em for ground fault protection and load shedding on emergency power startup. Good stuff.

Good on ya,

Goober Dave

 

[busbar]

Another provider is

http://www.boltswitch.com