Grounding Of Hot Air Ductwork ?
 

Hello:

Checked the hot air ductwork from a forced hot air furnace, and find that it
is not grounded.

Probably because there is a non-metallic "flex-joint" between the furnace
and the main outgoing duct.

What does the Code say regarding this ?

Should I just run a ground wire between the furnace shell (which is
grounded, probably via the
the AC power ground) and the Duct ?

This should work well, I guess, as most furnaces that don't have a
non-metallic joint are probably being grounded, in effect, in this manner.

What about the electrical Code, though ?

B.

"Robert11" wrote in message
...
Hello:

Checked the hot air ductwork from a forced hot air furnace, and find that
it is not grounded.

Probably because there is a non-metallic "flex-joint" between the furnace
and the main outgoing duct.

What does the Code say regarding this ?

Our code, states that you dont use ductwork as a ground, ever.
And really, since you would have to bond each joint to be effective, its not
worth the time to.

Should I just run a ground wire between the furnace shell (which is
grounded, probably via the
the AC power ground) and the Duct ?

No.
Why do you want to ground the ductwork?


This should work well, I guess, as most furnaces that don't have a
non-metallic joint are probably being grounded, in effect, in this manner.

What about the electrical Code, though ?

B.

If you just need something to fill your time, I bet some local charity
would love to have you volunteer. I know of no reason for you to
ground your ducts.

Stretch

"Robert11" wrote in message
...
Hello:

Checked the hot air ductwork from a forced hot air furnace, and find that
it
is not grounded.

Probably because there is a non-metallic "flex-joint" between the furnace
and the main outgoing duct.

What does the Code say regarding this ?

Should I just run a ground wire between the furnace shell (which is
grounded, probably via the
the AC power ground) and the Duct ?

This should work well, I guess, as most furnaces that don't have a
non-metallic joint are probably being grounded, in effect, in this manner.

What about the electrical Code, though ?

B.

I just took a quick look at the 2002 NEC section 250. and the phrase that I
found over and over was "may become energized"

Practically I have not seen duct work grounded except for a project that I
can not talk about. That not residential and it was more than 10 years ago.
There was not a piece of metal in the whole building that was not grounded
more than once. Door frames were grounded once on the inside and once on the
outside. We installed 250 MCM bare copper on the duct connections near the
air handlers. I protested that the connection would eventually break the
ductwork do to the ductwork moving and the copper would not. I was over
ruled by the EE. He just graduated so consider the source.

"Robert11" wrote in message
...
: Hello:
:
: Checked the hot air ductwork from a forced hot air furnace, and
find that it
: is not grounded.
:
: Probably because there is a non-metallic "flex-joint" between
the furnace
: and the main outgoing duct.
:
: What does the Code say regarding this ?
:
: Should I just run a ground wire between the furnace shell
(which is
: grounded, probably via the
: the AC power ground) and the Duct ?
:
: This should work well, I guess, as most furnaces that don't
have a
: non-metallic joint are probably being grounded, in effect, in
this manner.
:
: What about the electrical Code, though ?
:
: B.

NEC, far as I know, doesn't require you to ground that in most
cases. The requirement for grounding is for anything that has
electricity somehow connected to it, that could cause the frame
etc. to become live.
Ductwork normally isn't going to have anytyhing electrical
connected to it unless a remotly located humidifier or such is
being added.

If there were a requirement to ground the ductwork, you'd be
seeing wired connections between pieces and even to the registers
themselves, as metal touching metal can NOT be considered a
functional connection for safety purposes. So, no, it's not
necessary to ground it.

That assumes, of course, that there has been no electrical device
or equpment added IN the ductwork at some location - then there
might, not will be, a need for grounding it in some very few
cases.

HTH,
Pop

According to Carolina Breeze HVAC :

"Robert11" wrote in message
...
Hello:

Checked the hot air ductwork from a forced hot air furnace, and find that
it is not grounded.

Probably because there is a non-metallic "flex-joint" between the furnace
and the main outgoing duct.

What does the Code say regarding this ?

Our code, states that you dont use ductwork as a ground, ever.

The code says that you must not use ductwork as a _grounding conductor_.

That's different than _grounding_ ductwork.

I suppose it's up to debate.

Both US and Canadian codes require "grounding of major metal components of
structures".

Both US and Canadian codes require that you ground plumbing and steel
building frames. [But in _neither_ case can you use plumbing or
steel structure as a grounding conductor for other things.]

Is not ductwork just as major a component of a structure as, say, plumbing
is? In fact, there's a lot more of it, and much bigger contact area.

[And the code especially notes duct bonding in some circumstances.]

Isn't the consequences of a hot-to-ductwork fault just as potentially
lethal as, say, a hot-to-plumbing fault?

I'm fully aware, as most other people would be, that duct-to-duct
electrical conductivity wouldn't be perfect. But, at least having
the majority of it having a least nominal connectivity is better'n nothing.

I suspect that officially, it _should_ be grounded, but given that
most ducting is more or less effectively grounded anyway, the incidence
of problems _at present_ is sufficiently low that inspectors and code
isn't getting anal about bonding between components.

In other words, it's certainly legal to do, may not be _necessary_ in
practise, but it won't hurt, and whether the OP wants to do it is up
to their own risk avoidance preferences.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

According to :
On Mon, 15 Aug 2005 19:51:58 -0000, (Chris
Lewis) wrote:

That's different than _grounding_ ductwork.

I suppose it's up to debate.

The code says metal likely to be energized should be bonded but that
is allowed to be bonded by the EGC of the circuit likely to energize
it so the ground in the humidifier circuit would do it.

Or, obviously, the furnace ground.

This obviously begs the question as to whether it's continuous
throughout the ductwork (as per the OP's original posting), but I don't
see evidence of inspectors being anal over it (see previous posting).
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

Do you have a particular reason for wanting duct work grounded?






"Robert11" wrote in message
...
Hello:

Checked the hot air ductwork from a forced hot air furnace, and find that
it
is not grounded.

Probably because there is a non-metallic "flex-joint" between the furnace
and the main outgoing duct.

What does the Code say regarding this ?

Should I just run a ground wire between the furnace shell (which is
grounded, probably via the
the AC power ground) and the Duct ?

This should work well, I guess, as most furnaces that don't have a
non-metallic joint are probably being grounded, in effect, in this manner.

What about the electrical Code, though ?

B.

Hi,

Thanks to all for the info and thoughts on.

Had a new hot air furnace put in, and the circuit board was fried by a
recent lightning storm,
with a very nearby hit.

It was suggested that it would minimize the possibility of it happening
again if all the hot air
ducting were grounded.

Guess the thought was that the transient voltage spike might have used the
ductwork, in some manner ?

Actually, it seems to me that it can't hurt, and "possibly" a good idea, but
who really knows if it would actually help any ?

Bob
--------------

"Anthony Berlin" wrote in message
. ..
Do you have a particular reason for wanting duct work grounded?






"Robert11" wrote in message
...
Hello:

Checked the hot air ductwork from a forced hot air furnace, and find that
it
is not grounded.

Probably because there is a non-metallic "flex-joint" between the furnace
and the main outgoing duct.

What does the Code say regarding this ?

Should I just run a ground wire between the furnace shell (which is
grounded, probably via the
the AC power ground) and the Duct ?

This should work well, I guess, as most furnaces that don't have a
non-metallic joint are probably being grounded, in effect, in this
manner.

What about the electrical Code, though ?

B.

It sounds like someone was looking hard for an excuse to blame for the fried
board, and maybe pick up a little paying work at the same time. The most
common cause for the board to be fried is a "voltage spike" coming through
the power lines, caused by the lightning.

"Robert11" wrote in message
...
Hi,

Thanks to all for the info and thoughts on.

Had a new hot air furnace put in, and the circuit board was fried by a
recent lightning storm,
with a very nearby hit.

It was suggested that it would minimize the possibility of it happening
again if all the hot air
ducting were grounded.

Guess the thought was that the transient voltage spike might have used the
ductwork, in some manner ?

Actually, it seems to me that it can't hurt, and "possibly" a good idea,
but
who really knows if it would actually help any ?

Bob
--------------

"Anthony Berlin" wrote in message
. ..
Do you have a particular reason for wanting duct work grounded?






"Robert11" wrote in message
...
Hello:

Checked the hot air ductwork from a forced hot air furnace, and find
that
it
is not grounded.

Probably because there is a non-metallic "flex-joint" between the
furnace
and the main outgoing duct.

What does the Code say regarding this ?

Should I just run a ground wire between the furnace shell (which is
grounded, probably via the
the AC power ground) and the Duct ?

This should work well, I guess, as most furnaces that don't have a
non-metallic joint are probably being grounded, in effect, in this
manner.

What about the electrical Code, though ?

B.