2 different circuits to same switch

[Designer69]

I have an existing 3 way switch that needs to control 25 fluorescent troffers. I can't put all in one circuit.

can I replace this switch with a double pole single throw and run 2 circuits to it?

It's a business office environment, is this how this is normally done?

Thank You

 

[Designer69]

Actually I think you need a power relay in the ceiling to do this. Right?

 

[Designer69]

Lastly, what is more commonly done in these instances, power relay or just add new 3 way switches?

 

[LarryFine]

I would definitely use a contactor with as many poles as circuits. Don't forget to use the contactor's inductive rating, not its resistive.

If you want the contactor to last forever, wire two contact sets in series for each circuit. I.e., a 4-pole contactor for two circuits.

 

[Designer69]

If you want the contactor to last forever, wire two contact sets in series for each circuit. I.e., a 4-pole contactor for two circuits.

Thank You. Does that allow less stress per each contact?

 

[LarryFine]

Thank You. Does that allow less stress per each contact?

Yes. Contacts in series behave like a single set opening twice as fast and as far, extinguishing any arcing faster, reducing contact pitting. Series contacts handle high current better that parallel contacts.

 

[drcampbell]

You could replace it with a double-pole single throw (or triple-pole single throw) switch and supply it with a multi-wire branch circuit.
Is it essential that they all be controlled by a single switch? You can't use more than one switch? (or more than one pair of three-way switches?)

The usual practice is to connect no more than about a dozen troffers to a single switch, however many don't exceed a single circuit's capacity.

 

[topgone]

Yes. Contacts in series behave like a single set opening twice as fast and as far, extinguishing any arcing faster, reducing contact pitting. Series contacts handle high current better that parallel contacts.

Methinks the other way is going to be better--> having contacts arranged in parallel to share the load. Arcing is a function of current, voltage and gap of contacts. For the same voltage and contact separation, arc extinguishing would be the same so you'd rather tweak the value of the current to prevent excessive pitting on contacts!

Unless yours is a DC circuit, it helps to provide a longer arc gap to extinguish the arc faster, as in connecting the contacts in series, IMO.

 

[ramsy]

I have an existing 3 way switch that needs to control 25 fluorescent troffers. I can't put all in one circuit.

can I replace this switch with a double pole single throw and run 2 circuits to it?

It's a business office environment, is this how this is normally done?

Thank You

Who can't install 1600 Watts, or 100-Linear LED lamps on 1 circuit?

@ 277vac ~6 x 1.25 = ~7 Amps continuous
@ 208vac 1Ø ~8 x 1.25 = ~10 Amps continuous
@ 120vac ~13 x 1.25 = ~17 Amps continuous

My State energy code requires high-efficiency for replacement, or new lighting. 4ft linear, 16watt-LED lamps are UL listed for T8 ballasts, and so competitively priced, there's little price difference between 32watt T8 lamps.

 

[LarryFine]

My State energy code requires high-efficiency for replacement, or new lighting. 4ft linear, 16watt-LED lamps are UL listed for T8 ballasts, and so competitively priced, there's little price difference between 32watt T8 lamps.

I would never opt for leaving a ballast in the circuit when upgrading to LEDs. It's a waste of much of the energy you're trying to save.

It's like putting LED turn signal bulbs on a bike (where power is limited) and then adding load resistors instead of replacing the flasher.

Maybe that's just me.

 

[ramsy]

This 20A 3-way toggle switch for $5.28 works without relays.

 

[LarryFine]

Who can't install 1600 Watts, or 100-Linear LED lamps on 1 circuit?

He said fluorescent, so I'm going with that.

I found a few F32-T8 4-tube ballasts with 120v line current between 1.32a and 1.66a. Let's use 1.5 as an average. The Op's 25 lights would use (25 x 1.5) 37.5a on 120v. Even half of that is more than 80% of one 20a circuit. I take that to mean three circuits with 8, 8, and 9 lights for 12, 12, and 13.5a, respectively.

 

[ramsy]

I would never opt for leaving a ballast in the circuit when upgrading to LEDs. It's a waste of much of the energy you're trying to save..

Yes, I'm curious how much energy a T8 electronic ballast can waist on a 16watt LED lamp, but I suspect much less than magnetic ballasts.

The only direct-wire LED's I've seen on store shelves, which bypass ballasts, are not listed by NRTL's. I was told by a UL rep, listed LED's that bypass ballasts can be special ordered for a price, and require conspicuous labeling & special hardware assembly kits in the field.

The same UL rep told me, if I choose to install the un-listed ballast bypass LED version on store shelvs, neither my GL policy nor building property insurance covers it, and given the chance he would personally see to my prosecution for installing un-listed equipment.

 

[ramsy]

The bottom of this spec sheet for a 12W LED shows an electronic-ballast performance of 12.5W, using a Low Ballast Factor 0.77

1250 Watts @ 120vac = 13A continuous LED, if the right Low Ballast Factor fixture is ordered with the lamps.

12W LED products may not be on store shelves, but this ballasted LED is UL listed with published list of compatible ballasts.

Some high factor ballasts are burning 22 Watts on that 12watt LED lamp, so getting 100 of those listed LED lamps on 1 circuit would require some careful planning.

Also, if electronic ballasts makes the neutral a CCC regardless, LED lamps may make both the neutral current and xfmr noise a bit worse.

 

[infinity]

I have an existing 3 way switch that needs to control 25 fluorescent troffers. I can't put all in one circuit.

can I replace this switch with a double pole single throw and run 2 circuits to it?

It's a business office environment, is this how this is normally done?

Thank You

If you use a multi-pole switch for two circuits it needs to be listed for multi-circuit use.

404.8(C) Multipole Snap Switches. A multipole, general-use
snap switch shall not be permitted to be fed from more than
a single circuit unless it is listed and marked as a two-
circuit or three-circuit switch.

 

[infinity]

You mean listed for multi-circuit use....

Yes, I made the correction.

 

[steve66]

I would never opt for leaving a ballast in the circuit when upgrading to LEDs. It's a waste of much of the energy you're trying to save.

It's like putting LED turn signal bulbs on a bike (where power is limited) and then adding load resistors instead of replacing the flasher.

Maybe that's just me.

I don't know about the bikes, but I totally agree on not leaving the ballast. Using the LED T8 replacement lamps is a waste - better to just leave it fluorescent.

Electric-Light may have been anti-led, but he is right about not using this type of retrofit.

For me, the minimum retrofit to make it anything worth while has to replace the ballast with a driver, it has to replace the lamps with LED boards, and it has to replace the fixture optics including the reflector and lens.

Anymore, its probably just as cheap to just replace the entire fixture.

 

[drktmplr12]

I don't know about the bikes, but I totally agree on not leaving the ballast. Using the LED T8 replacement lamps is a waste - better to just leave it fluorescent.

Electric-Light may have been anti-led, but he is right about not using this type of retrofit.

For me, the minimum retrofit to make it anything worth while has to replace the ballast with a driver, it has to replace the lamps with LED boards, and it has to replace the fixture optics including the reflector and lens.

Anymore, its probably just as cheap to just replace the entire fixture.

cost of LED fixtures has been dropping for some time now. the payback period on retrofits should be around 5 years. if businesses are sitting on cash that's a no brainer.

doesn't take into consideration savings on maintenance. not sure if additional harmonics are an issue going from ballasts to drivers.

 

[kwired]

I have an existing 3 way switch that needs to control 25 fluorescent troffers. I can't put all in one circuit.

can I replace this switch with a double pole single throw and run 2 circuits to it?

It's a business office environment, is this how this is normally done?

Thank You

It would have to be a MWBC, which technically is a single circuit. You do lose the three way features of course.

 

[drcampbell]

If you use a multi-pole switch for two circuits it needs to be listed for multi-circuit use.

404.8(C) Multipole Snap Switches. A multipole, general-use snap switch shall not be permitted to be fed from more than a single circuit unless it is listed and marked as a two-circuit or three-circuit switch.

Would this be true of a 240-volt device on a 240-volt split-phase single-phase residential circuit, such as a baseboard heater? Two wires only; no white wire -- would that be considered one circuit or two?

Would you be so kind as to provide two citations, one for an approved switch and one not?