GFCI and Timer working

yazkNovember 2, 2013

Hi Everyone.

I am installing an outdoor lamp, which now needs to be protected by a GFCI outlet. The good news is I have GFCI outlet already in our utility room that I can use.
However, I want the outdoor lamp to be controlled by a timer switch (such as the Honeywell Econoswitch RPLS740B).

It will be wired Supply -> GFCI -> Timer Switch -> Lamp.

What I don't know is whether the GFCI protection will still work if it's through a Timer switch.
Also the Timer is only rated for lighting circuits at max 15A, so is there a possibility the Timer might blow before the GFCI trips?

I did think about wiring it with the Timer switch before the GFCI outlet, but then the outlet wont be able to be used if the Timer isn't "on".


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Ron Natalie

Hopefully your "utility" room isn't the laundry room in actuality. The GFCI doesn't care what's after it provided it doesn't have a ground fault in it. The timer should work fine if wired correctly (this timer uses an internal battery and hence doesn't draw any power from the circuit other than for the connected load. It does not require a neutral).

    Bookmark   November 2, 2013 at 9:40AM
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Your mix of questions is mixing "apples and oranges" as the cliche goes.
- The timer is rated at 15 amps, so if you have more than 15 amps load it will probably heat up and fail. If you are lucky it will just quit working and leave the circuit open (lights off).
- GFCI's are designed to find circuit faults, not overvoltage or high amperage conditions. They are not like a fuse or breaker that reacts simply to amperage draw.
- GFCI's can be rated at either 15 amps or 20 amps. Most provide a wiring diagram that gives you a choice between protecting only the GFCI outlet and protecting all outlets downstream of the GFCI. If you wire it to protect all downstream outlets it will also protect your timer at the end of the circuit.

Is this a 20 amp or a 15 amp circuit? If you wire the GFCI in the middle to protect the timer, the GFCI must be able to handle the full circuit amperage.


    Bookmark   November 2, 2013 at 5:53PM
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ronnatalie, Bruce,

Thanks for taking the time to help me with this.

No my utility room doesn't house my washer/dryer, but it does have my furnace. Out of curiosity, why would it being a laundry room make any difference?

This timer does actually have a neutral and no battery - that's one of the reasons for choosing it as we have it in another location and it works great.

I understand how GFCI's work and that it's not to detect an overload, but my (badly worded) question was whether by putting the timer switch between the GFCI and outdoor lamp would diminish the effectiveness of the GFCI in any way.

The more I'm thinking about it I may just put a GFCI on the outdoor circuit after the Timer switch.


    Bookmark   November 4, 2013 at 4:57PM
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Ron Natalie

The circuit in the laundry room is not allowed to serve other outlets, that's the only reason I asked (there are a few such circuits in the house, notably the kitchen, laundry, and bathrooms).

The GFCI is not going to be affected (either by spurious tripping nor is it going to be hampered) by a properly installed timer.

    Bookmark   November 5, 2013 at 6:36AM
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