3-wire feed to sub-panel bonded to main panel

[ccurrins (Christopher Currins, CMI)]

I have a sub-panel (at left) with a 3-wire feed (H-H-N) from 100 amp breaker at bottom right of service panel, at right. The grounds and neutrals are Bonded at the sub-panel at ground/neutral bar behind all of the wiring at right of panel.

The two panels are bonded by metal conduit, as you can see between panels. When the panels are bonded can this be treated like one panel as far as keeping the grounded and grounding conductors bonded. Or does the “sub-panel” at left require isolating the neutral like any other sub-panel would, with the GEC’s bonded to panel?

House was built in 1986.

[Jim_Port]

The grounds and neutral mixed is wrong. They should have been separate.

[rmeier2 (Robert Meier)]

I agree with Jim also the FMC in this case cannot be used as an EGC.

250.118(5) Listed flexible metal conduit meeting all the following
conditions:
a. The conduit is terminated in listed fittings.
b. The circuit conductors contained in the conduit are
protected by overcurrent devices rated at 20 am-
peres or less.
c. The combined length of flexible metal conduit and
flexible metallic tubing and liquidtight flexible
metal conduit in the same ground-fault current
path does not exceed 1.8 m (6 ft).
d. If used to connect equipment where flexibility is nec-
essary to minimize the transmission of vibration from
equipment or to provide flexibility for equipment that
requires movement after installation, an equipment
grounding conductor shall be installed.

[Jim_Port]

Thanks Robert, I meant to add that part about the flex not being able to be used as the egc.

[ccurrins (Christopher Currins, CMI)]

@Jim_Port

The grounds and neutral mixed is wrong. They should have been separate.

Thanks Jim.

[ccurrins (Christopher Currins, CMI)]

@Robert_Meier

I agree with Jim also the FMC in this case cannot be used as an EGC.

So the RMC, short section of conduit in the middle, wouldn’t quality as an EGC?

[rmeier2 (Robert Meier)]

@ccurrins

So the RMC, short section of conduit in the middle, wouldn’t quality as an EGC?

It would but not for the feeder, the EGC for the feeder needs to be run with the feeder, either as a compliant metal raceway or as a conductor within the raceway.

[ccurrins (Christopher Currins, CMI)]

@Robert_Meier

It would but not for the feeder, the EGC for the feeder needs to be run with the feeder, either as a compliant metal raceway or as a conductor within the raceway.

Thanks again.