My answer assumed that, but another look shows the OP did not say that.
Which question? The one regarding whether it's a duplex or a single receptacle? A 15 amp single receptacle is not permitted on a 20 amp circuit.
The OP's question.
Sure it will it clamps the voltage at the point it is installed so that surge will not appear on the down stream devices unless the surge originates down stream of the surge device.
A 15 amp single receptacle is not permitted to be the only outlet on a 20 amp circuit.
How would it clamp it before it sees it? It can't do anything before the spike or surge gets to the device, and it is not a time machine so everything on the line side of the device has already seen the spike or surge. The device eliminates or reduces the spike or surge and it no longer exists for the downstream equipment to see.
The surge recepts don't have "line" "load" terminals. The compoenents inside are inline with the receptacle. For the same reason when you plug in a surge strip, plugging it in does not protect anything but that strip.
Std recepts, but recepts with other components inside may not be able to do any more than rated. Surge recepts have inline components. Although I suspect a 15A rated surge recept can handle 20A, the internals are rated 15A. For that reason I don't think a 15A rated surge recept should be on a 20A BC.
Is it "in line" or is it just across the conductors kind of same way a whole house protector is, this just happens to be much closer to the point of use than a whole house protector is. If it is just across the conductors then a 2 gang box with one surge receptacle and normal receptacle in it would both have very similar protection simply because of close proximity where in situations where you had down stream receptacles with more distance between there might still be some protection but maybe not as near the same level of protection because of the distance between them.
When you plug in a surge power strip do you expect it to protect everything on the BC, all the way back to the pole it came from, and thus all BC's on that side of the center tap? They only protect the recepts of the surge strip.
I expect it to absorb surges at that point in the circuit. Just like a whole house panel absorbs surges at that point in the circuit. Further you get from the protective device the less effect it may have on where you are at. Now the whole house device at the service panel still pretty good at knocking off surges that come in on the service conductors and lessening those effects on everything downstream. If I had a surge power strip plugged into a duplex receptacle, I'd think it still offers some level of surge protection to the other receptacle of the duplex. All it usually is is MOV's between the H,N and G conductors and nothing that is in series with the supply conductors and load conductors. If it were in series how does it drain off the surge energy?
