I am installing a new Intermatic Timer -model T-1975 to replace an existing timer that no longer works. The wiring instructions state- This time switch can be wired to control two circuits as Single Pole Double Throw, or to control one circuit as Single Pole Single Throw. Either Normally Open (NO) or Normally Closed (NC). To wire Time Switch as desired, see wiring diagram above. I'm no good at wiring diagrams.
The timer has 4 terminals, instead of the 3 on my previous unit, so I can't just copy the wiring. The timer is used only for a single yard light. The 4 terminals are labelled NO,NC,Common, and Clock. It looks like I run the supply line to the Common and Clock terminals. Then do I run one wire from the light to the clock, and the other to NO OR the NC terminal? Is this a normally open circuit?
Power in black shoud go to your clock neutral in should go to your common. switch leg out to light black should go to NO and the white neutral again should go the the common.
Hope this helps
Wg
When I wired the unit as per your instructions, and turned power back on- nothing happens? Previous unit ticked like a clock. This unit doesn't tick and when I trip the manual override, the light doesn't come on. Do I assume the unit is defective or ??
Supply (hot, maybe black) goes to CLOCK and supply neutral (maybe white) goes to COM. The light should connect between clock and N.O.
Assuming this is the wiring diagram:
http://www.intermatic.com/techsup/t1975.pdf
I vote for neither of the above two answers.
The diagram shows that the COM is the connection that is switched. So it seems you should attach the supply line hot wire to the COM, and the supply line neutral wire (i.e., grounded wire) to the CLOCK. Then the load hot connects to NO or NC, and the load neutral connects to the CLOCK.
Otherwise, you're going to switch the neutral.
It sure would have been nice if they would have labeled those two supply wires. It doesn't seem very intuitive to attach the hot wire to the COM terminal.
I'm OK with the supply lines- black to clock and white to COM. And that is the identical wiring diagram on my unit- thanks. But when you say the light should connect between the clock and NO, I'm lost. Neutral (white) from light goes to COM and black goes??
Appreciate your help.
Tom
Now I'm getting worried. If I try any of the options suggested and the suggestions are wrong- is there a chance I'll fry my new unit, or worse?
Is the worse that can happen is I'll trip the breaker?
Thanks
Tom
Wait to see if somebody concurs with my opinion.
The thing that is throwing everyone it the fact that the word common is most often associated with neutral or ground.
When I posted my reply I was going by memory. After looking at the wiring diagram that HandyRon provided for us, the following wiring is correct.
The black of power connects to the common. The white of power connects to the clock. The white of the light connects to the clock. The black of the light connects to the NO.
Sorry, my memory didn't serve me well in my first post.
John is right that you can not install a switch on a grounded or neutral wire.
My opologies
Wg
Looking again, I'll agree with John and WG, that the hot (maybe black) should go to COM and both Neutrals (maybe white) to CLOCK and the remaining wire to the light goes to ......... N.O. If there is a severe mix up, the circuit breaker should trip due to a short.
John's point is that we shouldn't open and close (switch) the neutral conductor, the hot is what should be switched. Although they both will functionally work, switching the hot is the correct way.
The unit is functioning properly now. It's amazing how what sometimes seems to be a 10 minute job can develop into a real head-scratcher. Thanks for the advice- couldn't have done it without you.
Tom
Tags: wiring, intermatic, timer, wiring diagram, supply line, between clock, black goes, black should, clock white, Common Clock, connect between
