Current on Air Conditioner Condenser Pipes, Induction?

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OpenCircuit

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A bit of a mystery here.

An A/C unit has 2.7 A of current on the condenser pipes that run from furnace to the outside unit.
1.8 A on the big, 0.9 A on the small one.

Happens whenever the gas furnace is running, even with AC off.

There is 2.7 A of imbalanced current on the circuit supplying the furnace (means I am clamping around entire cable which should not have a reading if current in and out was equal), and also 2.7 A on the circuit supplying the A/C unit (which has the breaker off).

There is 2.6 A on the EGC in j-box on the furnace, this EGC terminates at furnace enclosure/casing.

L has 8.9 A and N has 8.6 A when furnace is running. No current on gas pipes.

3 ft of heat tape is coiled around PLASTIC box and 2 ft of plastic drainage pipe. No shorts to ground on it.
No metal is touching the heat tape. It has an extension cord to a recep on the same circuit as furnace.

The moment I unplug the heat tape, no more amps on the condenser pipes... Goes down to 0.04 A

Trying to remove the current from the pipes where it's not supposed to be (no voltage to ground on the pipes).

Could there be a metal piece or pipe inside that plastic box the heat tape is coiled around, creating induced current that runs on the EGC onto the enclosure, and from there, takes a loop on the condenser pipes (possibly amplified by the internal coils on the AC)?

Any ideas about cause and cure?
 
Is the heat tape on a GFCI or GFPE as required?
What type of heat tape is it, constant wattage, or self regulating?
How old is the heat tape, does it have a braided shield?
I would make sure the heat tape meets current requirements if not replace it.
 
OpenCircuit said:
No metal is touching the heat tape. It has an extension cord to a recep on the same circuit as furnace.

... The moment I unplug the heat tape, no more amps on the condenser pipes... Goes down to 0.04 A
Click to expand...
It sounds like the furnace branch circuit with the receptacle may have the neutral tied to equipment ground somewhere, and the current from the heat tape is getting onto the EGCs. I would first pull that receptacle and verify that it's wired correctly. If so, then look at other places on the circuit where the N and ECG might be connected.
 
tom baker said:
Is the heat tape on a GFCI or GFPE as required?
What type of heat tape is it, constant wattage, or self regulating?
How old is the heat tape, does it have a braided shield?
I would make sure the heat tape meets current requirements if not replace it.
Click to expand...

The tape is like new, installed a year ago. However no gfci, wonder if there was one originally and someone took it off to avoid the tripping.Yes it has a grounded, braided shield. Constant wattage so they unplug it in the summer. No gfci on that circuit or recep or tape.. and that was next on my list...should be according to 427.22, Gfpe would probably be better for this, however it would show a fault on the heat tape itself. Nothing on ohm meter though.
 
synchro said:
It sounds like the furnace branch circuit with the receptacle may have the neutral tied to equipment ground somewhere, and the current from the heat tape is getting onto the EGCs. I would first pull that receptacle and verify that it's wired correctly. If so, then look at other places on the circuit where the N and ECG might be connected.
Click to expand...

Recep and boxes are fine though they may be a few more boxes to check in the basement.. or perhaps within the furnace
OL on ohm meter between ground and N or L on the heat tape. A faulty connection would at least show a value.
 
Heat tape before gfcis or gfpe was required was responsible for many fires. Where the taoe was crossed it would overhest and start a fire.
 
OpenCircuit said:
There is 2.7 A of imbalanced current on the circuit supplying the furnace (means I am clamping around entire cable which should not have a reading if current in and out was equal), ...

... There is 2.6 A on the EGC in j-box on the furnace, this EGC terminates at furnace enclosure/casing.

... L has 8.9 A and N has 8.6 A when furnace is running.

... The moment I unplug the heat tape, no more amps on the condenser pipes... Goes down to 0.04 A
Click to expand...
Was the place where you measured the L and N currents closer to the breaker panel or closer to the furnace than where you clamped around the cable to the furnace and measured the 2.7 A ? I'm asking just to clarify what you have.

So when the thermostat is turned down then this 2.7A current goes away, or do you have to turn off the furnace breaker to make it disappear?
 
You might try plugging in another load in place of the heat tape which draws at least an amp or so, and then see if you get the same behavior.
 
I suggest plugging an extension cord into a non-GFCI receptacle, preferably a lone one like the laundry, and make voltage comparisons. You might have current leakage at the compressor unit.

Who knows, you might even have a service neutral issue.
 
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