AC & DC in same conduit

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paumat

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I assume this is not allowed but an NEC article reference would be nice.

Large battery charger -- is it acceptable to place the charger's AC input conductor with charger's DC output conductor in same conduit?
 
paumat said:
I assume this is not allowed but an NEC article reference would be nice.

Large battery charger -- is it acceptable to place the charger's AC input conductor with charger's DC output conductor in same conduit?
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I don't think it matters any as long as the DC side is not a class 2 or 3 circuit.
 
I agree with Bob and will add that I doubt it would be a class 2 or 3 output unless it is a very small charger.

What do you see as a problem?
 
iwire said:
I agree with Bob and will add that I doubt it would be a class 2 or 3 output unless it is a very small charger.

What do you see as a problem?
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Wouldn't the AC conductor induce a voltage in the DC conductor. Perhaps this is one of those things that might be good practice but not necessarily covered by specific code requirements.
 
paumat said:
I assume this is not allowed but an NEC article reference would be nice.

Large battery charger -- is it acceptable to place the charger's AC input conductor with charger's DC output conductor in same conduit?
Click to expand...

IMHO good design practice says separate input from output. Some chargers have a nasty PWM current signal, so that PWM crap could couple into the AC line, and cause problems elsewhere in the facility. If it's a relativey clean DC voltage, then maybe there's no practical problem. I would further suggest that all wire in the conduit be rated for the highest voltage in the conduit.
 
kc8dxx said:
Some chargers have a nasty PWM current signal, so that PWM crap could couple into the AC line, and cause problems elsewhere in the facility. If it's a relativey clean DC voltage, then maybe there's no practical problem.
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Could you explain what PWM is, and what you're saying? I don't follow.
 
PWM is Pulse Width Modulated. The charger takes the incoming AC, and rectifies it into a DC bus. It then switches the dc connected to the battery on and off really fast. Really fast meaning anything between 1KHz and 100KHz. The amount of ON time vs OFF time causes an average voltage to appear, and the charger controls that voltage based on how much charge the battery has. The end result is that the charger varies the average dc voltage to the battery, so that it charges properly.

The battery is really good at absorbing low frequency signals. The switching transients, which happens when the dc changes from ON to OFF to ON, create very high frequency signals. These signals can couple to other wires in the area, which can cause problems with sensitive equipment in the area.

Most of the time this isn't an issue. But it can be. A battery charger can cause the same kinds of problems that a Variable Frequency Drive (VFD) can cause. The larger the current, the larger the potential noise problem.

It's cost effective, it's very popular, and it drives us amateur radio enthusiasts nuts.
 
PWM- is a way to get an approximation of DC from an AC signal using a set of diode bridges. Here is a write up to wet your appetite

http://en.wikipedia.org/wiki/Pulse_width_modulation
 
I see one major problem.The clamp on cables to that battery after it has reasonably been charged ,now have far more amperage available to feed backwords than we have conductors likely to handle this amperage should something short out on charger side.
 
Jim W in Tampa said:
I see one major problem.The clamp on cables to that battery after it has reasonably been charged ,now have far more amperage available to feed backwords than we have conductors likely to handle this amperage should something short out on charger side.
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How is this different than running branch circuits of different ratings in the same conduit?
 
iwire said:
How is this different than running branch circuits of different ratings in the same conduit?
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A lot since all your conductors would have over current protection.Think about them maybe #6 wires on that battery that has 500 amps available current.The limits of the battery are unknown and unfused.
 
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