Furnace acting as EGC

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resistance

resistance

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WA
Seen a gas furnace that seems to be acting as the equipment grounding conductor for a near by electrical box--using MC cable. Seems the furnace housing was bonded by the gas pipe entering the equipment (Note: The only thing I found that could be bonding the unit is the gas pipe it self). Can someone give me a quick code (besides 110.3) against this install.

Thank you!!
 
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I'm guessing that people are having a hard time visualizing what you're trying to describe. Maybe you can add some more detail to the description.
 
resistance said:
Seen a gas furnace that seems to be acting as the equipment grounding conductor for a near by electrical box--using MC cable. Seems the furnace housing was bonded by the gas pipe entering the equipment (Note: The only thing I found that could be bonding the unit is the gas pipe it self). Can someone give me a quick code (besides 110.3) against this install.

Thank you!!
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Break out your code book. Is it acting as a grounding electric conductor or simply bonded per 250.104 (2) (B). Study "grounding" VS "bonding"
 
From the HVAC guy:

Only thing that would be done at the furnace is to connect the ground to the ground screw inside of the junction box in the furnace. Metal ductwork/plenums could technically be isolated by the use of non-metal flexible duct connectors..... Is something wrong with the furnace, or someone got lit up by it?
 
This may not be any help but when working in PECO's gas dept, the procedure was to bond the gas pipe to the water system and jumper a bond across the water meter.

As per the "Gas National Fuel Code" 1988, 3.14 Electrical Bonding and Grounding, (sorry this is all I have), section a: states Each above ground portion of a gas piping system............shall be eletrically continous and bonded to any grounding electrode, as defined by the NEC, ANSI/NFPA 70.
section b: "Gas Piping shall not be used as a grounding electrode.
 
My guess would be that objectionable current (250.6) is present at the appliance due to normally operating current using the bonded metal parts of the furnace branch circuit and the bonded metal gas piping. In short, a paralleled return path to the source is present.
 
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