This was put in the electrical course, is all of this true?

“The NEC requires a distinct separation of low voltage wiring and high voltage wiring, so you cannot have any part of the low voltage wires or the transformer itself inside the electrical panel.”

the course is telling me that no low voltage wires are allowed in the service panel?? that sounds crazy to me idk…

Consider this… What do you suppose occurs if the Low voltage system becomes energized in some way from the (ANY higher) voltage system?
(Note: standard residential systems ARE NOT considered HIGH VOLTAGE although they are a HIGHER VOLTAGE!).
I recommend you go back through the course until you fully understand WHY it is not allowed.


By low voltage they really mean Class 2 wiring like you would see powered from a doorbell transformer or the controls on a boiler, AC unit, etc.


Robert has it.

Basically, you don’t want high voltage running across wires and components design for low voltage only. Think about what the consequences could be if you sent 110 volts down your thermostat wire.


Thanks for doing his homework for him!!

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Not everything, I said “think about what the consequences could be…”

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Aside from the safety concerns, there is the functional aspect. Low voltage wiring can pick up inductive voltages and currents causing device/system malfunctions.

If I remember correctly under 80V was the top voltage for low voltage wiring definition. The landline telephone ringer voltage, not operating voltage was about that.

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The Difference Between High Voltage and Low Voltage | Bay Power.

Not just the service panel, but there must also be separation along branch circuits, service entrance cables and service conductors.

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Brian do you have some examples of this? From an NEC perspective in general cables of any type can be run together without separation.

Without a doubt one of the best comedic lines ever uttered in a movie!

I lost my last search but found this similar information. Please review and correct me as needed.

Also, I believe it was NACHI training which stated communication cabling could not share electrical drop masts etc.

Security Wiring Cable Separation..

Thanks Brian, yes service entrance conductors and other communications cables typically require 2’ of separation per the utility company rules. You are correct that the nec does not permit the communications wiring on a service mast.

Since this thread is about Class 2 wiring Class 2 cables can be run with power cables. For example a thermostat cable can be run through the same hole in a wood stud with NM cable.

Not sure if its even applicable anymore but back in the day alarm wires were not run in cables they were individual conductors usually twisted together. As far as interference from the alarm system and power system wiring running in proximity to each other I dont know that with 2022 technology if that’s even an issue anymore.


Many years ago I had an electrical inspector chide me for running thermostat wire in a conduit with NM. I assume that is treated different than bored holes then Robert?

Was the conduit just a sleeve for the two cables?

It was rigid pvc conduit where I had run NM cable across a garage to an electric garage heater. I ran the thermostat wires for the heater through the same sonduit with the NM. I guess I would consider it a sleeve, as both the NM and thermostat wire were cable assemblies, and not individual conductors, if that’s what you mean.

Yes that would be the same as running the cables through the same hole in a stud. The key word here is cables. Power and Class 2 cables can be run together. If you pulled individual conductors in then separation would be required.

I often hear electricians say that they pulled in 600 volt wire in the raceway for both the power and the stat. That is not permitted because class 2 individual conductors have separation restrictions.


There may be differences in other countries, but the standard American voltage for POTS phone service has always been -48 DC while the phone is ringing; and between -3 and -12 volts while the phone is off the hook. (Positive ground).