Hi my name is satoecho and I am trying to upgrade my kitchen counter plugin to GFCI outlet.
Here is the problem. I saw the wire was 12-3 so that 3 hot wire such as black, white and red and ground.
How do I wire red wire? I put black and white to LINE and also put ground to proper spot. But now red.
I wired red wire to LOAD. And it seems to be OK. Please help me out!!

How was the old outlet wired? Do you have only one black, one white and one red?

The red needs to be capped, it should not connect to this GFI device at all.

The red may be another circuit feed.

What did the red connect to before?

How were the wires attached to the old outlet?

Thank you very much for the help. The old receptacle, red and black wire were hooked on cupped screw side and white wire was on silver screw side. And ground wire was on bottom ground screw.. I just copy old wiring applied to GFCI receptacle but GFCI requires only 2 hot wire.
IF I didn't hook red wire and just capped, is there any problem? Right now I hooked red wire on LINE so circuit was kind of messed up but plugin tester lit correct. I don't know why??

Do you still have the old outlet. If so, look at the screws on the right side, the side the red and black were connected to. Is there a small metal strip connecting the screws?
Probably not, which means that the top half of the outlet was on one circuit and the bottom was on another.

If that is correct, you had what is called a split outlet. GFI outlets cannot be split like that. Put a wire nut on either the black or the red wire and connect the other to the line side of the GFI.

What if I didn't hook the red wire anywhere and capped, leave it alone, is there any problem?

You have not answered the question as to whether you have the old outlet and whether the connecting tab between the two screws had been removed. Doing that will confirm whether you had a split outlet.

If you do not have the old outlet, you most likely have other outlets in the kitchen, they will be wired the same. Remove one and confirm that the tab has been removed.

Thanks HKstroud's for the help. I really appreciate. Finally I figured it out. Connecting tab between red and black were removed. Is this called split outlet? Probably all outlets in kitchen are split outlet.

Yes, that makes everything logical. Just cap the red wire with a wire nut.

Thanks! Is there any problem if red wire leave it alone with cap on? Such as power leakage? As long as wire is capped its safe? If red wire hooked on LINE(GFCI) what is the possible risk? Burnt out? And also I put 20amp GFCI receptacle but the old outlet was 15 amp. Should I mutch?

Okay lets cover one initial problem in description for you.

The Red and Black conductors are ungrounded (Hot) conductors.

The White conductor is a grounded (Neutral or Return) conductor, not a hot conductor.

A split receptacle means that the top receptacle(s) is on its own circuit and the bottom is on an entirely different circuit. The Neutral wire is "Shared" between the two breakers.

If you look inside the main service panel, you should see two breakers tied together and labeled for the kitchen. The top breaker would be (most likely the Black conductor) and the lower breaker would be the Red conductor.

Without actually seeing the panel box, there are two possible solutions. Cap each red conductor in the circuit at each receptacle and remove the double breaker and replace it with a single 20 amp breaker. Also cap off the red conductor in the panel box.

The second way is to just cap off the red conductors at the outlets and leave the breaker in place. However, that does have you using both breakers where only one is needed.

Thanks DonF. Make sense. I saw the service panel and two breaker was tied together. Actually there 4 breakers (2 tied breakers) I will look into that. Kind of scarely working on service panels.

If you believe that working on a service panel is scary, then please do not go near the project.

Even though the main service panel most often has a Main Circuit Breaker, the only way to make absolutely certain all of the panel is dead is to pull the meter or if there is a disconnect switch in between the meter and service panel.

Trust me, if you do not know exactly what you are doing, you can very easily kill yourself.

Please call a licensed electrician. Any money spent that keeps you on this side of the grass is money well spent.