Please correct me if i am wrong, if an OCPD is larger than 1000a and used for main emergency panel, then this ocpd is recommended to be LSIG but it shall not be GFCI, accordingly it will trip the ground fault after 1000a only....am i right ?
NECESSITY OF LSIG 700.6(D)
- Thread starter m sleem
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There are often restrictions about using an automatic trip on a Ground Fault on emergency circuits, however sounding an alarm is allowed so it is common to specify LSIA trip functions.
common breaker terminology
L = long time trip function
S = short time trip function
I = instantaneous trip function
G =ground fault trip function (not to be confused with GFCI)
A = ground fault alarm, without tripping
common breaker terminology
L = long time trip function
S = short time trip function
I = instantaneous trip function
G =ground fault trip function (not to be confused with GFCI)
A = ground fault alarm, without tripping
ron
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You've listed 700.6(D) correctly. Ground fault alarm is appropriate.
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- San Francisco Bay Area, CA, USA
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- Electrical Engineer
GFCI is different from “Ground Fault” as used in reference to a large breaker. Ground fault in this case is Ground Fault Protection of Equipment or GFPE (some just say GFP). When referring to an electronic trip breaker with LSIG, the G in this case means GFPE, never GFCI. Don’t conflate the two.
GFCI is required to trip at 5mA of differential current (between 4mA and 6mA) to protect humans that come in contact. GFPE is a percentage of the main breaker rating, the L, and is often set at 30%. So as an example on a 1,000A breaker, it will be 300A, which would fry a human. Hence, totally different concepts.
GFCI is required to trip at 5mA of differential current (between 4mA and 6mA) to protect humans that come in contact. GFPE is a percentage of the main breaker rating, the L, and is often set at 30%. So as an example on a 1,000A breaker, it will be 300A, which would fry a human. Hence, totally different concepts.
Thanks, but what will cause such fault, if it's not a short circuit, also LSIG doesn't mandate 4 pole breaker.
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- San Francisco Bay Area, CA, USA
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There are two main types of “short circuit”; line-to-line, and line-to-ground, or “ground fault”. Within either type, you might have a high impedance/resistance in the connection, in which case the LEVEL of current flow is reduced by that resistance and might be below the trip threshold of the Instantaneous trip sensing. But the L and S trips will take time, which might be dangerous for a ground fault. So the GFPE sensor is not a time based sensing, it is just looking at whether all of the current going out is also coming back on another phase. If not, the assumption is that it is going to ground somewhere and the trip is activated. The GFPE trip threshold however must also allow for unbalanced current coming back on the neutral, if any.
GFCI does basically the same thing, but at a much much lower threshold of current and the neutral is monitored along with the hot lines, because neutral current is part of the circuit in most single phase applications. You will rarely see GFCI on three phase systems but if so, it is a 4 wire system where the neutral is monitored too.
Who said anything about 4 pole?
So, it could be a ground fault either at the outgoings or inside the panel it self,
But, seems the non emergency main breakers will not be redundant, also having LSIG at all breakers is a cost.
Thanks for your good explanation.
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