Line filter question

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sw_ross

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I changed out a time switch that controls a contactor which controls outside lighting.

I used the intermatic ST01 which is a astronomic time switch.

I program the time switch and set on/off events.
When I turn it on and manually turn the lights on the clock zeros out to 12am.
It’s done it several times. Even if the lights aren’t hooked up to the contactor.
When I read about troubleshooting in the paperwork it describes the problem and says to install a line filter.

Can someone give me the cliff notes on line filters please? I’ve never worked with them.

The circuit is 20 amp. The outside lights are all LED.

Thanks
 
Is it possible you have line (black) and load (red) mixed, or the timer's neutral not connected?
 
sw_ross said:
When I read about troubleshooting in the paperwork it describes the problem and says to install a line filter.
Click to expand...

Yes, I see that. Another design screw up that they expect us to fix. So just install a line filter. Where? (Accross the contactor coil I suppose.) Any hint as to what that might be? Why don't they make it available as an accessory?

Nope, I'm sick of it. I would return it and get something else that works.

-Hal
 
sw_ross said:
I changed out a time switch that controls a contactor which controls outside lighting.

I used the intermatic ST01 which is a astronomic time switch.

I program the time switch and set on/off events.
When I turn it on and manually turn the lights on the clock zeros out to 12am.
It’s done it several times. Even if the lights aren’t hooked up to the contactor.
When I read about troubleshooting in the paperwork it describes the problem and says to install a line filter.

Can someone give me the cliff notes on line filters please? I’ve never worked with them.

The circuit is 20 amp. The outside lights are all LED.

Thanks
Click to expand...
If there are connected HID lights, I could see the starting current causing the voltage to drop taking out the power to the contactor just long enough to reset the clock. Then a filter might be just enough to keep the clock powered and/or limit the starting currents to the lights enough to keep the voltage up.

But with no lights connected that should not happen. And do you have HID lights or newer LED's? Shouldn't happen with LED's.

I suspect something else is wrong. Are you sure there isn't another contactor or something in the circuit?

And why doesn't the time clock have a backup battery? If it does, this shouldn't happen. Again, maybe another problem?
 
LarryFine said:
Is it possible you have line (black) and load (red) mixed, or the timer's neutral not connected?
Click to expand...
The ST01 doesn’t use a neutral. Line in, load out, and ground.

The thing that is really confusing is that this is a hotel/motel setup that was put together about 3 years ago.
There are 6 rows of units. Each row contains about 30 rooms.
Every row is setup the same way. All the outside lights are on contactors. The other 5 rows all work fine. This particular row has had issues since day one apparently.
They’ve had the original contractor change out the time clock 2 or 3 times, didn’t fix it.
They asked me to try a different timer switch so I used the Intermatic ST01, which I’ve used a lot.
I actually installed 3 others for the same outfit yesterday in a different complex and all worked fine.
I think this is the first time I’ve used it to control a contactor.

In the paperwork under troubleshooting it says that if the clock reverts back to 12am that it is sensing a contactor or motor load, and it suggests installing a line filter.

The service is 3-phase.
This particular panel is a single phase 208/120 panel.
After I eat lunch I think I’m going to move the single pole breaker (that is the control circuit) from L1 to L2 and see if there’s any change.

It has to have something to do with operating the coil. I don’t have lights even hooked up to the contactor and it still does it.
I even tried a different contactor and it does the same thing.
 
steve66 said:
If there are connected HID lights, I could see the starting current causing the voltage to drop taking out the power to the contactor just long enough to reset the clock. Then a filter might be just enough to keep the clock powered and/or limit the starting currents to the lights enough to keep the voltage up.

But with no lights connected that should not happen. And do you have HID lights or newer LED's? Shouldn't happen with LED's.

I suspect something else is wrong. Are you sure there isn't another contactor or something in the circuit?

And why doesn't the time clock have a backup battery? If it does, this shouldn't happen. Again, maybe another problem?
Click to expand...
It does have a battery backup. I’m thinking it’s a “issue” indicator that is designed in, based on the troubleshooting suggestions.
 
synchro said:
I suggest putting this device from Intermatic, which I suspect is an RC snubber, across the contactor's coil:


There may be some ringing from switching the coil's inductance that's causing the problem.
Click to expand...

Well look at that, they actually do have one!

No, it's not "sensing" the coil, rather the inductive kick from the contactor coil is messing up the timer circuitry. In short, it's not designed for an inductive load.

Get that snubber and put it across the contactor coil screws. Should take care of the problem.

-Hal
 
LarryFine said:
Those are usually only suitable for incandescent loads. I suggest another model, one rated for inductive loads.
Click to expand...

I would agree with you Larry except the instruction sheet implies it can be used with a contactor but it may require a line filter. It's rated for up to a 1hp/120V motor load.

Timer resets to 12:00. Timer is installed in conjunction with a contactor or motor load. Install a line filter.
Click to expand...

Flicker Index said:
A device called RC snubber, placed across the contacts work great to mitigate this issue, however it does have a side effect of stray voltage being present on the load end if it was to be open circuited. Installing it in the timer would likely fix your issue, but it wouldn't be up to code.
Click to expand...

Well, no. It would be placed across the coil of the contactor, not across the contacts of the timer. You would use one across switch contacts if you were wanting to suppress arcing and contact damage when they open. Although the same cause, here you want to suppress the back EMF when the voltage is removed from the coil at the coil. It's that over-voltage pulse that is disrupting the timer circuitry and making it reset.

-Hal
 
I’m ordering the filter that was linked by Synchro in post #6. I will report back when I test it out.

Thanks for the feedback!
 
hbiss said:
Well, no. It would be placed across the coil of the contactor, not across the contacts of the timer. You would use one across switch contacts if you were wanting to suppress arcing and contact damage when they open. Although the same cause, here you want to suppress the back EMF when the voltage is removed from the coil at the coil. It's that over-voltage pulse that is disrupting the timer circuitry and making it reset.

-Hal
Click to expand...

Either works. See http://www.bpesolutions.com/bpemanuals/Snubber.pdf
Sometimes fans have issues with causing GFCI nuisance trips when they're switched off. Sometimes placing it across the switch is more practical and it works just as well. The problem occurs when energy stored in coil has nowhere to go. By having it across the switch, or across the coil, it gives a place for stored energy to dissipate more gradually and avoid the problem.
 
Using ground+hot to power the timer isn't allowed any more, and would immediately trip a GFCI or a duel function AFCI. So the situation here is that the timer circuitry gets it power from being in series with the load. When the contacts open, the magnetic field in the contactor coil collapses generating a high voltage spike which is added to the power that the timer circuitry is using. So this is not your normal switch/contactor circuit because of the electronics in parrallel with the switch contacts.

I agree that placing a snubber across the timer would probably work, but IMO the better option in this case is placing it at the source which is the contactor coil. Besides, physically the easier location is at the contactor rather than stuffing it into a wall box.

-Hal
 
Hey all I am dealing with a similar issue EI500C 120V timer / contactor issue and that intermatic link is bad now.
I was thinking of putting together my own snubber and found this thread.

Did that intermatic part work and is there a link to it?
Thanks
 
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