GFCI type main breaker??

Toros

Senior Member
Location
Tujunga, CA
Hi,
My friend's house, an apartment unit in multiunit complex in Italy has sub panel in the unit that has main breaker with GFI. (Not Main lug only)
Is it a good engineering???
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Electrician
Hi,
My friend's house, an apartment unit in multiunit complex in Italy has sub panel in the unit that has main breaker with GFI. (Not Main lug only)
Is it a good engineering???
I think they are called RTD or something like that.
Probably cheaper than buying all the GFCI stuff that we have to install!:rant:
 

ATSman

ATSman
Location
San Francisco
Occupation
Self Employed
Hi,
My friend's house, an apartment unit in multiunit complex in Italy has sub panel in the unit that has main breaker with GFI. (Not Main lug only)
Is it a good engineering???
From your wording it sounds like the sub panel main breaker has GF protection only, not the feeder breakers. (Not sure what you mean by Not Main Lug Only means.) Not good engineering but the cheap and dirty way out because if there is a GF on one feeder circuit it can and most likely will trip out the whole house; no coordination to isolate the fault. The expensive way is for all feeder bkrs to have GFI so only that circuit is lost whenever a GF occurs in the unit.
The GF trip setting on the main breaker (current & time) is set to protect against a fault on the load side of the main breaker (inside the sub panel.) But experience shows that on larger systems the magnitude of the fault current can and will pass right through the 20A branch panel breaker to the building main breaker. That is why for continuity of service, feeder GF protection is so important. In most cases it is a race and the 20A breaker AND main breaker both trip! :eek:
One other note here, the GFI in a residential setting is designed to protect people from shock and structure fires. The GF schemes in commercial and industrial applications are mainly there to protect against equipment damage, although some people may differ on this subject. :D
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
RCD, not RTD. It means "Residual Current Device", formerly known as an RCCB (Residual Current Circuit Breaker) but, it may or may not have actually had the regular kind of CB trips, they don't necessarily have to. If it is actually a full on circuit breaker, then it is called an RCBO. Either way, it is not a GFCI in the same sense that we use that term, their rules are very different. GFCI is a specific term reserved for use here in North America in describing a PERSONNEL protection system that will trip at between 4 and 6mA of ground current. This is also referred to as a Class A Ground Fault Circuit Protector. That is NOT what they will have on their main CB, it would likely never hold in. And RCD is allowed to trip at 30mA, maybe even up to 100mA depending on the system. By our rules, you would be long dead. But you cannot directly equate EU distribution system requirements to ours, they have some very different issues and rules.

The closest thing we have to that is "Equipment Ground Fault" protection, also called "GFP". There are several sub-classes within that as well, too detailed to go into, but you can read about them all here.
 
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