flow switch powered by 120VAC

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You might be able to conjure up a situation where it is not so, but in general, there is no prohibition on 24VDC circuits being in the same conduit as 120VAC circuits.
 
Is the 24v circuit an Article 725 or 760 circuit?. If so, in general, it can't be in the same raceway.
 
Most flow switches that are NRTL have a Normally Open, Common, and Normally Closed set of contacts (Form C). If you're monitoring a flow switch, why not use the Normally Closed Contacts and make the circuit "fail safe" and save the money of cable and a relay?

Article 760 for "Fire Alarm Systems" and a DCS is not an NRTL fire alarm system, nor is it permitted by OSHA to be used as a fire alarm system, no matter what the applications. Having said that, 760.48 permits the mixing with 120 VAC circuits, stating:

(A) Class 1 with NPLFA Circuits. Class 1 and non?power limited fire alarm circuits shall be permitted to occupy the same cable, enclosure, or raceway without regard to whether the individual circuits are alternating current or direct current, provided all conductors are insulated for the maximum voltage of any conductor in the enclosure or raceway.​

The question now becomes what is the power supply?
 
DM2-Inc said:
Most flow switches that are NRTL have a Normally Open, Common, and Normally Closed set of contacts (Form C). If you're monitoring a flow switch, why not use the Normally Closed Contacts and make the circuit "fail safe" and save the money of cable and a relay?

Article 760 for "Fire Alarm Systems" and a DCS is not an NRTL fire alarm system, nor is it permitted by OSHA to be used as a fire alarm system, no matter what the applications. Having said that, 760.48 permits the mixing with 120 VAC circuits, stating:
(A) Class 1 with NPLFA Circuits. Class 1 and non?power limited fire alarm circuits shall be permitted to occupy the same cable, enclosure, or raceway without regard to whether the individual circuits are alternating current or direct current, provided all conductors are insulated for the maximum voltage of any conductor in the enclosure or raceway.​
The question now becomes what is the power supply?
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I don't think it is very common to have a non-power limited 24 volt fire alarm circuit. Power limited fire alarm conductors cannot be mixed with 120 volt conductors. 760.136(A).

I have no idea if this is a fire alarm flow switch, I just suggested Article 760 as one application that may prohibit the 24 volt circuit from being in the same conduit as the 120 volt circuit.
 
DM2-Inc said:
. . . Having said that, 760.48 permits the mixing with 120 VAC circuits, stating:
(A) Class 1 with NPLFA Circuits. Class 1 and non?power limited fire alarm circuits shall be permitted to occupy the same cable, enclosure, or raceway . . .​
Click to expand...

​

Non -Power Limited Fire Alarm systems and wiring are getting rare. Yeah, I'm retired, but didn't see a NPFL system for ages. If there is a fire alarm system and it is Fire Power Limited, then mixing the wiring with Class 1 circuits would not allowed.

I've seen plenty of water flows with dual switches and 120 running through one to an outside bell (took the place of a water gong outside the building). Irritated me when a 90 degree flex connector covered the other knock-out on the flow.
 
In the industrial world they're not rare at all. While the equipment may support the use of Power Limited Circuits, the wiring typically uses 600 volt insulation thereby allowing the circuit to be considered "Non-Power Limited"
 
DM2-Inc said:
In the industrial world they're not rare at all. While the equipment may support the use of Power Limited Circuits, the wiring typically uses 600 volt insulation thereby allowing the circuit to be considered "Non-Power Limited"
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Just having 600V insulation is not enough to allow mixing under the NEC.
The other factor is that all of the loads and devices in the circuit must NOT require a Class 2 or 3 power source as part of their listing, even though they may furnish a Class 2 power supply.
 
DM2-Inc said:
In the industrial world they're not rare at all. While the equipment may support the use of Power Limited Circuits, the wiring typically uses 600 volt insulation thereby allowing the circuit to be considered "Non-Power Limited"
Click to expand...
Can you cite the section in Article 760 that says that?
 
Flow switch not for fire alarm

Flow switch not for fire alarm

The flow switch isn't for a fire alarm circuit. It is just a 24V process control run through a normally closed contact on
a flow switch that also needs 120VAC power. Can I run the 120VAC and the 24VDC for the NC contact in the same conduit?
 
jssmit@monsanto.com said:
The flow switch isn't for a fire alarm circuit. It is just a 24V process control run through a normally closed contact on
a flow switch that also needs 120VAC power. Can I run the 120VAC and the 24VDC for the NC contact in the same conduit?
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Not if the 24 V conductors are part of a class 2 circuit.
 
don_resqcapt19 said:
Can you cite the section in Article 760 that says that?
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760.124 Circuit Marking. The equipment supplying PLFA circuits shall be durably marked where plainly visible to indicate each circuit that is a power-limited fire alarm circuit.
Informational Note: See 760.130(A), Exception No. 3, where a power-limited circuit​

760.130(A)
Exception No. 2: Conductors and multiconductor cables described in and installed in accordance with 760.49 and 760.53 shall be permitted.

Exception No. 3: Power-limited circuits shall be permitted to be reclassified and installed as non?power-limited circuits if the power-limited fire alarm circuit markings required by 760.124 are eliminated and the entire circuit is installed using the wiring methods and materials in accordance with Part II, Non?Power-Limited Fire Alarm Circuits.​
 
kwired said:
Not if the 24 V conductors are part of a class 2 circuit.
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Can you explain how one goes about defining if the circuit is class 2 or not?

This is something that I've never been able get my arms around. I've looked at Table 11(B) and If I understand this correctly (aside from the marking on the power supply), if the output of the power supply is above 8 Amps, it isn't a Class 2 power supply?
 
DM2-Inc said:
Can you explain how one goes about defining if the circuit is class 2 or not?

This is something that I've never been able get my arms around. I've looked at Table 11(B) and If I understand this correctly (aside from the marking on the power supply), if the output of the power supply is above 8 Amps, it isn't a Class 2 power supply?
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A lot of potential conditions in that chart - especially on right side where there are variables that can be entered, I think you can have a lot more then 8 amps in some instances - but also depends on voltage and power abilities of the source.
 
DM2-Inc said:
760.124 Circuit Marking. The equipment supplying PLFA circuits shall be durably marked where plainly visible to indicate each circuit that is a power-limited fire alarm circuit.
Informational Note: See 760.130(A), Exception No. 3, where a power-limited circuit​

760.130(A)
Exception No. 2: Conductors and multiconductor cables described in and installed in accordance with 760.49 and 760.53 shall be permitted.

Exception No. 3: Power-limited circuits shall be permitted to be reclassified and installed as non?power-limited circuits if the power-limited fire alarm circuit markings required by 760.124 are eliminated and the entire circuit is installed using the wiring methods and materials in accordance with Part II, Non?Power-Limited Fire Alarm Circuits.​
Click to expand...
Dan,
I don't see reclassification the same as just pulling the wire in the raceway with the power conductors. It also requires that you use nonpower limited devices on the reclassified circuits.
 
DM2-Inc said:
In the industrial world they're not rare at all. While the equipment may support the use of Power Limited Circuits, the wiring typically uses 600 volt insulation thereby allowing the circuit to be considered "Non-Power Limited"
Click to expand...

The insulation requirement in 300.3(C) has a note at the end, and typically you can't mix a power limited and non power limited. Class 1 yes, Class 2 and 3 no.
 
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