Two timers don't work. RPLS740B and SA170

I had a SA170 timer which would quickly use up its back up batteries. I tried to replace it with the RPLS740B. The 740B would come on, I would start programming it and in about 45 seconds the unit would go dead. No reaction to any of the buttons. I'd turn off the breaker for a few minutes and then return to on. The 740b would light up, I'd start programming and in 45 seconds it would die again. I'm sure that I'm wiring correctly as the SA170 would work, it would just die after 6 months or so when the batteries were dead. Seems like the line power to the timer itself was not working.

So my guess is the there is something wrong with the wiring that's got something to do with the neutral. But I can't figure out what. Any ideas?

 

Welcome to the forums!

Are you connected to a neutral? Are you sure it is really a neutral and not just a switch loop? If you only have 2 wires in the box (not including the ground) you only have a switch loop and the switch will not work.

 

Yes I've got neutral (white) in the box. Several of them in fact going to a common wire nut. Besides those whites, I've got 3 blacks which I believe are the load (outside lights). 1 red which I believe is the line coming from the breaker box. I've got several bare copper [wires] are all wire nutted together.

 

It is very unusual for power to be fed into a multi-gang electrical box on the only red wire in that box and fed out on multiple black wires. You need to use an analog (preferably) multimeter to determine which wire the 120V panel feed is on.

 

I agree. You need to take some readings with a meter. You might have a multi-wire circuit with a red wire present which could mean to put 240 volts to the timer.

 

Thanks for the ideas. I did think about seeing if the red was connected correctly in the breaker box. But if I took a multi meter and measured voltages between pairs, what should I expect to see?

 

From any hot wire to ground/neutral you should get 120 volts.
From any hot wire to another hot wire on the opposite phase you should get 240 volts.
IF you have two hots on the same phase you will get zero volts. You will know its hot because you already measured it to ground.
Neutral to ground, zero volts.
If you have a colored wire (not ground or white/neutral) and you get zero volts to ground/neutral, that is likely a switch leg going to your lights.

 

Two possibilities with a three-conductor cable in a switch outlet-box : the Red conductor is a "return" switched conductor , or it's one of the two "live" conductors of a three-conductor cable supplying two Branch-Circuits to two seperate loads.

Please determine the # of cables terminating in the box, and the type of cables , either two or three conductor cables.

Also describe the devices that are connected to the conductors , and how they are connected--- Thanks!!

 

Well we have figured it out. Thanks to the suggestions for measuring. Bottom line was that the red wire was not the correct line wire. In the picture you might be able to see that coming out of the same wire sheath as the red are two blacks that were wire nutted together.

After we disconnected the two blacks, only one of them showed line voltage. I'm guessing that enough current was being induced into the red wire from the 2 black wires that were nutted together and with the red wire in the same sheath. So in use, the voltage was not enough to power the timers, but I guess enough to light the lights in the load.

I was also fooled earlier as I did measure the voltage in the red wire at 120. But with no load on it, the induced voltage made it look hot and when I cut the breaker naturally the black wire went off and so did the red. I'm just surprised that the lights in the load had enough power to glow. I am guessing that the contractor needed some wire to complete the run and only needed one line wire, but had some left over stuff with two blacks and one red. He wired it up and the SA170 kind of worked, so he moved on.

 

Glad you got it solved, and thanks for letting us know.

I blew your image up to nearly double the original size, and I didn't see any cable that has two blacks and one red wire in it. Not that I expected to - that's even rarer than having a red wire be the hot feed to multiple black wires. Like nonexistent.

What I did see was one piece of conduit with at least two 2-conductor cables and one 3-conductor cable in it. Is that conduit a protective sleeve or does it run from a second electrical box?

 

I had an ipad glitch so I hope that you don't get this post twice.

So, if you look at the conduit that feeds in from the top, you can see that there is a cable on the right side. If you look closely at that cable, reading from right to left, you will see; bare, white, red and then black. From what I can see and remember, right behind the black wire is another black wire. You might be right that the second black is actually from another cable, but since things are working, I'm not going back to break open the box.

The cable and conduit under discussion must come from an electrical box somewhere (in a wall somewhere). Because there is no red wire any where in the breaker box where all circuit breakers are.

 

The question is whether the piece of conduit is a protective sleeve or one end of a conduit run that's continuous from another electrical box.

Type NM cable should not be installed in continuous conduit, in order to avoid having it exposed to heat which it is not built to withstand. It can be, and should be, protected by a sleeve of conduit - a piece which is open at the other end - where it needs to be protected from physical damage. Only individual conductors should be installed in continuous conduit.

If you cannot see the other end of that piece of conduit, and see that it is the open, then the assumption is that it is one end of a continuous section.

Separately, when more than three current-carrying conductors are installed in a single raceway, the conductors must be derated. Just counting the conductors in the visible cables, and assuming that the loads on the two hot wires in the 3-conductor cable will always be balanced, there are six current-carrying conductors in that conduit. Those conductors may need to be larger to safely supply their connected loads.