Branch circuit with GFCI

[garrett1812]

I am working to install two 20A circuits to my garage. I have run a 12/3 wire from the electrical panel, and was planning to split this in the garage, with two GFCI outlets, each on one circuit, then feeding all other outlets off of their respective GFCIs from the load side. Not splitting the duplex outlets onto multiple circuits or anything fancy like that. I have been reading mixed things about if GFCIs will eprk on branch circuits, and the conclusions are not clear. Can someone please verify this would be the correct way to wire the garage?

Thanks.

 

[marklc]

They will nuisance trip sharing a neutral. You'll have to run individual circuits (12-2) to each.

 

[pattenp]

What's the point of using 12-3 to set up the circuits this way? Is the primary run of wire long and are you trying to save some money on the wire? Even so, I believe it's better to have run independent circuits.

 

[pattenp]

They will nuisance trip sharing a neutral. You'll have to run individual circuits (12-2) to each.

The way the outlets are wired in that diagram it should not be a problem.

 

[wes73]

If one side trips the breaker, the other side will trip as well. That could be a pain. Esp if you have a fridge or freezer plugged into either side and the other side forces a trip.

 

[pattenp]

If one side trips the breaker, the other side will trip as well. That could be a pain. Esp if you have a fridge or freezer plugged into either side and the other side forces a trip.

It's best to use single independent trip breakers with a handle tie to prevent this. The use of a double pole common trip breaker will cause both circuits to disconnect if there's a fault.

 

[garrett1812]

What's the point of using 12-3 to set up the circuits this way? Is the primary run of wire long and are you trying to save some money on the wire? Even so, I believe it's better to have run independent circuits.

To save cost and hassle of pulling a second wire. If it's an issue I will pull a second wire, but would prefer to avoid. I already had a good amount of 12/3 wire so that started it.

 

[garrett1812]

If one side trips the breaker, the other side will trip as well. That could be a pain. Esp if you have a fridge or freezer plugged into either side and the other side forces a trip.

I wasn't worried about one tripping the other, as that should be a rare occurrence. But now that you mention fridge or freezer that might be an issue. I could always run a new dedicated circuit if I am go to do that in the future.

 

[garrett1812]

They will nuisance trip sharing a neutral. You'll have to run individual circuits (12-2) to each.

The way the outlets are wired in that diagram it should not be a problem.

This is what I have been reading. Some way it's fine. Other think it will bean issue.

 

[sberry]

It wont trip a gfci, it will trip the breaker in a fault which is really rather rare and as long as it wouldn't be a sensitive issue wont matter.

 

[Fishplate]

It's best to use single independent trip breakers with a handle tie to prevent this. The use of a double pole common trip breaker will cause both circuits to disconnect if there's a fault.

What's the difference between a double pole breaker and two singles with a handle tie?

 

[Norcal]

I wasn't worried about one tripping the other, as that should be a rare occurrence. But now that you mention fridge or freezer that might be an issue. I could always run a new dedicated circuit if I am go to do that in the future.

Your refrigerator or freezer circuit will still be required to have GFCI protection in a garage.

 

[garrett1812]

It wont trip a gfci, it will trip the breaker in a fault which is really rather rare and as long as it wouldn't be a sensitive issue wont matter.

If that will be the only issue that will be okay for me. Most of my house is wired with branch circuits so I am used to it.

 

[Mustang51js]

Its fine using the 12/3. I do it for kitchens and bathrooms all the time and never had an issue. Just make sure to pigtail the nuetral from the feed

 

[pattenp]

What's the difference between a double pole breaker and two singles with a handle tie?

Double pole common trip, both poles will trip together on a fault. Two singles with a handle tie allows each breaker to trip independently of each other. The handle tie does not cause the breakers to trip together. The handle tie satisfies the code requirement of disconnecting both circuits together when servicing. The independent trip is allowed with multiwire circuits that only supply line to neutral loads. If serving line to line loads then the breaker needs to be a DP common trip.

 

[bczygan]

To save cost and hassle of pulling a second wire. If it's an issue I will pull a second wire, but would prefer to avoid. I already had a good amount of 12/3 wire so that started it.

If you have a good amount of 12/3, then just use it to run 2 separate circuits!!!

Bill

 

[sberry]

There is nothing wrong with mwbc, in some cases they are good and he has the ideal cable for it.

 

[garrett1812]

There is nothing wrong with mwbc, in some cases they are good and he has the ideal cable for it.

That's what I always thought. Just wanted to make sure my wiring method wasn't going to cause the random GFCI trips some talk about.

Thanks all for the feedback.

 

[sberry]

I keep a roll of 3 conductor for it and I was at a job a while back where a master did some work in a church. The handyman was a bit confused as sparky tied on to some existing circuits with 3 conductor and was trying top reduce some crowding in the panel and he is a speed demon anyway. Guy was going to change some breakers from 15 to 20,,, oh no. the guy tied it on to some 14. Nothing he did was unsafe if no one fugg with it. Only mistake he made was in a mess he tied both conductors to the same leg but it want really a deal breaker, a size heavier wire and not on recept circuits but fixed connected load of a few amps lights.

 

[justsam]

GFCI's only care about what is on their load side, not the line side feeding them. On the load side hot and neutral currents must be within 5 mA of one another.

 

[joel63]

Its fine using the 12/3. I do it for kitchens and bathrooms all the time and never had an issue. Just make sure to pigtail the nuetral from the feed

I'm not sure by what do you mean by pigtail the neutral from the feed.


Also why?

Just asking.

Thanks.

 

[rburke65]

In your diagram you have one neutral from the neutral bar....he is suggesting running two. One to each set of outlets.

 

[pattenp]

I'm not sure by what do you mean by pigtail the neutral from the feed.


Also why?

Just asking.

Thanks.

In your diagram you have one neutral from the neutral bar....he is suggesting running two. One to each set of outlets.

He doesn't need to run a second neutral from the neutral bar. The two neutrals are connected together using one wire from the neutral bar pigtailed to the line sides of the two gfci outlets just as it's done in the diagram.

 

[benjamintmiller]

If you insist on running a multi-wire branch circuit, you do need to take power factor into consideration for any equipment you plug in.

Some loads, such as induction motors, typically have a low power factor. If you put such a load on one leg and put a load with a high power factor on the other leg (such as a heat gun), you could overload the neutral.

Kitchens are (were) often wired with MWBCs because nearly all loads they see are simple resistive loads with near-unity power factor, thus not a problem. With the advent of AFCIs, they aren't MWBCs around here anymore.

If you do choose to go forward, it is vitally important, and required by code, that you pigtail every receptacle. If you don't do that and one becomes open (for maintenance or similar), you could find 220V across a device intended for 110V.

 

[alfredeneuman]

It's best to use single independent trip breakers with a handle tie to prevent this. The use of a double pole common trip breaker will cause both circuits to disconnect if there's a fault.

The handle tie will cause both circuits to disconnect also if there's a fault. (At least it should if the handle tie is installed correctly)
What's your point?

 

[pattenp]

The handle tie will cause both circuits to disconnect also if there's a fault. (At least it should if the handle tie is installed correctly)
What's your point?

I don't believe so.

My point is by using two singles with a handle tie on a MWBC is if a fault occurs on one circuit it doesn't kill both circuits. That's why a common trip DP breaker is called a "common" trip because both sides trip.

This is an excerpt form EC&M http://ecmweb.com/content/common-misunderstandings-overcurrent-protection

Misunderstanding No. 4: Handle ties provide the same operation as internal common trip.

Handle ties provide an acceptable method of linking operating handles of several single-pole circuit breakers together so they'll switch the tied circuit breakers together. Although good reasons exist for using handle ties, such as in multiwire branch circuits, the method in which a handle tie functions is often not well understood. And in some cases, application of handle ties may lead to unnecessary hazards.

It's important to understand the difference between the handle tie feature and the common trip feature. Handle ties fasten the handles of two or more single-pole circuit breakers together. With handle ties installed, all of the poles are switched on and off together. However, if one pole trips because of an overload or short circuit, the handle tie doesn't cause the connected poles to trip. The condition can leave one pole tripped and the other tied poles energized.

 

[alfredeneuman]

Thanks, I guess that they're just not all that dependable

 

[pattenp]

Thanks, I guess that they're just not all that dependable

Handle ties on two singles should never be used as a substitute where a DP common trip is required.

 

[alfredeneuman]

I don't ever use handle ties myself

 

[garrett1812]

If you do choose to go forward, it is vitally important, and required by code, that you pigtail every receptacle. If you don't do that and one becomes open (for maintenance or similar), you could find 220V across a device intended for 110V.

This assumes maintenance is done with the breaker still on?

 

[pattenp]

What code requires receptacles to be pigtailed?

Never mind, this was in reference to MWBC. The neutral only needs to be pigtailed.

 

[dave*99]

If you insist on running a multi-wire branch circuit, you do need to take power factor into consideration for any equipment you plug in.

Some loads, such as induction motors, typically have a low power factor. If you put such a load on one leg and put a load with a high power factor on the other leg (such as a heat gun), you could overload the neutral.

Kitchens are (were) often wired with MWBCs because nearly all loads they see are simple resistive loads with near-unity power factor, thus not a problem. With the advent of AFCIs, they aren't MWBCs around here anymore.

If you do choose to go forward, it is vitally important, and required by code, that you pigtail every receptacle. If you don't do that and one becomes open (for maintenance or similar), you could find 220V across a device intended for 110V.

You are correct that outlets on a MWBC must be pigtailed. And this does apply to the (2) GFCI's at their line side as shown in the OP's diagram. The receptacles on the load side of the GFCI's will not need to be pigtailed. The risk of 240 VAC appearing across a receptacle due to an open neutral is not there after the GFCI's in this diagram. YMMV