Bathroom light/exhaust fan

[ODDJOB]

I am going to replace a bathroom light with light/exhaust fan combo. There is no ground pulled on existing circuit. I know I should probably go all the way back to the panel and pull a new circuit in w/ground. That would be very time consuming if at all possible without removing drywall. Any recommendations?

[montytx]

IF you have a spot, (and I know this isnt code) but it works great, Is to drive a rod in near the bathroom and tie a ground wire in to it.

[dhill]

Do you have a circuit in your attic? If so, tie the ground into that one. The switch wire to the light probably has a ground wire with it, if it's romex, but it's probably cut. Check and see if the ground is connected inside the switch box. If so, run a pigtail at the light box off the cut ground.

[mdshunk]

IF you have a spot, (and I know this isnt code) but it works great, Is to drive a rod in near the bathroom and tie a ground wire in to it.

That's typical handyman advice that is quite hazardous. Let me explain why what Monty is suggesting is plain wrong and hazardous.

The ground wire on any fixture is the "return path" to the panel in the event that something associated with the fixture shorts out to one of the metal parts. When a deivce shorts to ground in a normally grounded circuit with a proper ground wire the whole way back to the panel, the current will flow in an infinate manner and trip the breaker almost immediately.

IF you drove a ground rod and grounded your device there, the EARTH is being used at the return path to the panel. If the device shorted out, the current would flow in the ground rod, through the earth, back in the main ground rod at the panel, and NEVER trip the breaker. WHY? The earth sucks as a conductor. Even the best ground rods have around 25 ohms resistance. There would be two ground rods in this instance (the one handyman proposes you add, and the other at the panel that's code required to be there). Not nearly enough fault current would flow out of the ground rod and through the earth to trip the breaker under a fault condition. The fan would remain ground faulted (and wasting tons of electricity). If you took the cover off to change the light bulb or something like that, you'd get a hell of a shock or even die.

Monty... there's a reason that your method is not code compliant. It is unsafe at best, and quite irresponsible.

[roger g]

Okay............ you made your point........... What's the answer to the original question?
Your explanation was good.......................maybe a little more diplomatic.


roger

[mdshunk]

Okay............ you made your point........... What's the answer to the original question?

There are two ways to install this fan with the required equipment grounding conductor. The first method, pull a new cable from the panel that does contain a ground. Second, pull a seperate ground wire. IF you pull a seperate ground wire, there are only three places where it may originate. 1) The grounding electrode (ground rod) for the service (not one you drove yourself) or the first 5 feet indoors of metal underground water piping if it is bonded to the service equipment, 2) the grounding electrode conductor (the wire from the ground rod to the panel) or 3) The ground bar in the panel in which this circuit originates. You can't "steal" a ground from a nearby grounded circuit and be in compliance. For reference, I've cited the code:

250.130 Equipment Grounding Conductor Connections.
(C) Nongrounding Receptacle Replacement or Branch
Circuit Extensions. The equipment grounding conductor
of a grounding-type receptacle or a branch-circuit extension
shall be permitted to be connected to any of the following:
(1) Any accessible point on the grounding electrode system
as described in 250.50
(2) Any accessible point on the grounding electrode conductor
(3) The equipment grounding terminal bar within the enclosure
where the branch circuit for the receptacle or
branch circuit originates
(4) For grounded systems, the grounded service conductor
within the service equipment enclosure
(5) For ungrounded systems, the grounding terminal bar
within the service equipment enclosure
FPN: See 406.3(D) for the use of a ground-fault circuitinterrupting
type of receptacle.
the equipment grounding conductors permitted by 250.118.

250.134 Equipment Fastened in Place or Connected by
Permanent Wiring Methods (Fixed) — Grounding. Unless
grounded by connection to the grounded circuit conductor
as permitted by 250.32, 250.140, and 250.142, non–
current-carrying metal parts of equipment, raceways, and
other enclosures, if grounded, shall be grounded by one of
the following methods.
(B) With Circuit Conductors. By an equipment grounding
conductor contained within the same raceway, cable, or
otherwise run with the circuit conductors.
Exception No. 1: As provided in 250.130(C), the equipment
grounding conductor shall be permitted to be run
separately from the circuit conductors.
Exception No. 2: For dc circuits, the equipment grounding
conductor shall be permitted to be run separately from the
circuit conductors.
FPN No. 1: See 250.102 and 250.168 for equipment bonding
jumper requirements.
FPN No. 2: See 400.7 for use of cords for fixed
equipment.


300.3 Conductors.
(B) Conductors of the Same Circuit. All conductors of
the same circuit and, where used, the grounded conductor
and all equipment grounding conductors and bonding conductors
shall be contained within the same raceway, auxiliary
gutter, cable tray, cablebus assembly, trench, cable, or
cord, unless otherwise permitted in accordance with
300.3(B)(1) through (4).

(2) Grounding and Bonding Conductors. Equipment
grounding conductors shall be permitted to be installed outside
a raceway or cable assembly where in accordance with
the provisions of 250.130(C) for certain existing installations
or in accordance with 250.134(B), Exception No. 2,
for dc circuits. Equipment bonding conductors shall be permitted
to be installed on the outside of raceways in accordance
with 250.102(E).

[roger g]

Interesting. I would have thought I could have pulled it from a grounded circuit nearby.
Good to know. Thanks.


roger

[ODDJOB]

So, I have to go back to the panel for my ground. There being a existing fixture there and this being and upgrade wouldn't grandfather the new fixture in some way would it.

[Sparks]

MD, I've done this myself (ran a grounding conductor independent of circuit conductors) a number of times in old houses but I've only used this article once for a job that was inspected. The article specifically pertains to receptacles or branch circuit extensions. Neither applies here. I'm not sure that this would be allowed for simply swapping out a fan/light fixture. Obviously the installation would be safe, but I would wonder if what you are suggesting would be code compliant given the explicit terminolgy used. Any thoughts on this? Have you yourself done this and passed an inspection?

[mdshunk]

The article specifically pertains to receptacles or branch circuit extensions. Neither applies here. I'm not sure that this would be allowed for simply swapping out a fan/light fixture. Obviously the installation would be safe, but I would wonder if what you are suggesting would be code compliant given the explicit terminolgy used. Any thoughts on this? Have you yourself done this and passed an inspection?

250.134 is for "equipment fastened in place", which is what this fan is. It specifically gives you the "right" to run a seperate ground. I might have muddied the waters by also posting 250.130(C), but I did so to demonstrate the places where this seperate ground is to terminate.

Furthermore, these fan/light combos are UL White Book listed as "luminaires", so they fall under §410.18, which also gives you the ability to run a seperate ground in exception #1. Here's that section:

410.18 Exposed Luminaire (Fixture) Parts.
(A) Exposed Conductive Parts. Exposed metal parts shall
be grounded or insulated from ground and other conducting
surfaces or be inaccessible to unqualified personnel. Lamp
tie wires, mounting screws, clips, and decorative bands on
glass spaced at least 38 mm (11⁄2 in.) from lamp terminals
shall not be required to be grounded.
(B) Made of Insulating Material. Luminaires (fixtures)
directly wired or attached to outlets supplied by a wiring
method that does not provide a ready means for grounding
shall be made of insulating material and shall have no exposed
conductive parts.
Exception No. 1: Replacement luminaires (fixtures) shall
be permitted to connect an equipment grounding conductor
from the outlet in compliance with 250.130(C). The luminaire
(fixture) shall then be grounded in accordance with
410.18(A).

Good one, Sparks. You made my head hurt looking that stuff up. You had me doubting myself for a while.

[mdshunk]

Interesting. I would have thought I could have pulled it from a grounded circuit nearby.
Good to know. Thanks.


roger

I see that you are in Canada. The CEC is different from the NEC in that respect. I do know that the CEC permits you to get a ground from any nearby metal water line (the NEC does not). I'm not sure if the CEC permits you to grab a ground also from a nearby grounded circuit or not. I have my hands full with the NEC, and I don't really follow the CEC. Sooner or later they'll be the same. They're coming closer and closer each code cycle.

[Sparks]

Hey MD, Thanks alot. I never read the exception cited in 410.18. I was always a little unclear on the issue due to the wording used. In fact many still are, this was just discussed recently on Holts forum and it's apparent that some are still completely unaware of this possibility altogether. You cleared it up for me by posting the articles, thanks, good to have ya here!

[giddonah]

good to have ya here!Amen.

[Bakerdog]

So if you don't have a ground wire, what happens when the fixture shorts out? Doesn't the breaker still get tripped?


Oddjob, are there any other grounded circuits nearby? If so, you might be able to use that for your power source (assuming that the light/fan fixture wouldn't exceed capacity for that circuit?).

[mdshunk]

So if you don't have a ground wire, what happens when the fixture shorts out? Doesn't the breaker still get tripped?


Good question. There are two typs of shorts. Hot to neutral shorts, and hot to metal chassis shorts. In the hot to neutral short, the breaker will trip. In the hot to metal chassis short, since there is no ground wire, the metal of the fan will remain energized, laying in wait for some unsuspecting person to touch it.