Quick Q- occupancy sensor in parallel with timer?

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Netpog

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Boston, Massachusetts, USA
Intermatics says: Don't put voltage on a photocontrol's load side!

Intermatics says: Don't put voltage on a photocontrol's load side!

kwired said:
... If you shunt across that occupancy sensor with the time control - you have no voltage across it [snip]
Click to expand...

Absolutely correct. But if you try this with a sensor that takes a neutral, you will be putting unexpectedly-high voltage between the load-side and the neutral.

Intermatics tech support tells me not to put line voltage on the load (red) conductor of their photo controls, regardless of whether the line (black) conductor is open, or is also at line voltage. The guy was emphatic.

I had wanted to parallel the photo control with a generic toggle switch, but I can get the same result. My solution: I'll put a SPDT switch on the load side of the photo control. (E.g. the P&S 1221 or 1225.) In the "manual override" position, line voltage goes to the load, but the photo control's load is open. In the "auto" position, vice versa.

This leaves the photo control 'live' 7x24, squandering a watt or two, but that also means there won't be any confusion or upset resulting from lights turning on every time the photo control goes live and has to warm up. (If these guys are green-freak enough to be disturbed by the watt-or-two wasted, they can instead have an astronomic timer running off a small battery, like Intermatics' EI600. If I'm smart, they'll never be aware of the wasted energy.)
 
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greenspark1

Senior Member
Location
New England
Netpog said:
Absolutely correct. But if you try this with a sensor that takes a neutral, you will be putting unexpectedly-high voltage between the load-side and the neutral.

Intermatics tech support tells me not to put line voltage on the load (red) conductor of their photo controls, regardless of whether the line (black) conductor is open, or is also at line voltage. The guy was emphatic.
...
Click to expand...

Good to know Intermatic isn't a fan.

Yes this is a good solution for a logical AND function- both the photocell and switch need to be closed to work.

The tricky part is if you need a logical OR function- lights on when either the photocell or the switch. Or a more likely situation of a time clock where you need a manual override.
 
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Netpog

Member
Location
Boston, Massachusetts, USA
greenspark1 said:
[...] this is a good solution for a logical AND function- both the photocell and switch need to be closed to work.

The tricky part is if you need a logical OR function- lights on when either the photocell or the switch. Or a more likely situation of a time clock where you need a manual override.
Click to expand...

My switch actually DOES deliver the "OR" function, with lights-on via switch or photocell:

The switch I'm using is double-throw. The light is on when the photocontrol closes, if the switch is in it's usual position (connecting the load to the photo control), OR the light comes on, anytime, when that switch is thrown the other way (connecting the load to line). The switch also has a central "off" position, so you can have "AND" logic if you want it.

Now, how to do this with a time clock, rather than a switch? I guess you'd need a SPDT-switching time-clock. Otherwise you can always use controllers, or relays, or a dedicated CPU. (I mean: how much logic do you WANT?)
 
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Netpog

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Boston, Massachusetts, USA
Oh, yes, of course! A 3-way switch would work just FINE. I like the Legrand/Pass & Seymour SPDT "controllers" (e.g. 1221) because I like having an "off" position, as well as "auto dusk-dawn" and "manual on".

But I wasn't thinking: not everyone wants the absolute "off" position, in which case the 3-way is a cheaper/easier/smaller device. So I'm glad you mentioned that.

If anyone else goes for a SPDT controller-style switch, double-check that you're getting maintained-contact switches, avoiding the otherwise-identical momentary-contact versions! (Which will come in handy for something else, someday, I know it will.)
 
kwired

kwired

Electron manager
Location
NE Nebraska
Netpog said:
Absolutely correct. But if you try this with a sensor that takes a neutral, you will be putting unexpectedly-high voltage between the load-side and the neutral.

Intermatics tech support tells me not to put line voltage on the load (red) conductor of their photo controls, regardless of whether the line (black) conductor is open, or is also at line voltage. The guy was emphatic.
Click to expand...

:huh:

I could understand some solid state device not playing well but one that uses a dry contact as the main output device shouldn't matter.

Load side of switch is 120 volts to neutral either way (on a typical 120 volt application) - don't see where this unexpected high voltage you mention would come from. You ever seen a schematic for how a typical photo controller works? All that is between the black and red lead is a dry contact, why should any other components care if the 120 volts goes through that switch or an external switch?
 
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Netpog

Member
Location
Boston, Massachusetts, USA
I hear you, Mr K. I'm just reporting what the man at Intermatic told me. And I don't pretend to know what's inside their photo controls.

I do read this, in the install instructions: "Note that multi-voltage models self-adjust for the voltage. Models rated for 120-277 volts will not work on 120-volts once used on 208-277 volts."

So maybe they've internal fuses of some sort? Of course, this doesn't explain why I can't apply 120v to the load side of their 120v-only photo controllers.
 
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greenspark1

Senior Member
Location
New England
Netpog said:
If anyone else goes for a SPDT controller-style switch, double-check that you're getting maintained-contact switches, avoiding the otherwise-identical momentary-contact versions! (Which will come in handy for something else, someday, I know it will.)
Click to expand...

Yea the momentary contact versions seem to be better sellers and easy to accidentally order. Not sure what people use them for, besides fancy lighting control systems.
That Leviton 1221 SPDT looks like a good choice, thanks.
 
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