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Hood motor conduit in duct? #64906
04/21/06 04:07 PM
04/21/06 04:07 PM
Redsy  Offline OP
Joined: Mar 2001
Posts: 2,056
Bucks County PA
My first commercial range hood.
The exhaust blower discharge (domed) housing has a sleeve for the conduit supplying the motor, but the sleeve leads to the exhaust duct. Can the conduit be run in the exhaust duct? Otherwise a separate roof penetration (which I'd like to avoid) is necessary.

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Re: Hood motor conduit in duct? #64907
04/21/06 04:52 PM
04/21/06 04:52 PM
HotLine1  Offline

Joined: Apr 2002
Posts: 7,069
Brick, NJ USA
You need a hole. NO wiring can be within the hood, ducts, etc.

Re: Hood motor conduit in duct? #64908
04/21/06 05:06 PM
04/21/06 05:06 PM
Redsy  Offline OP
Joined: Mar 2001
Posts: 2,056
Bucks County PA
Thanks John!

I didn't think so, but I was wondering what good the sleeve would do. I guess the exhaust unit could be used for applications other than hoods.

Re: Hood motor conduit in duct? #64909
04/21/06 06:50 PM
04/21/06 06:50 PM
e57  Offline
Joined: May 2003
Posts: 2,876
That sleeve may be for the smoke detector sample tube, if it were used as a regular exaust/intake fan.

Mark Heller
"Well - I oughta....." -Jackie Gleason
Re: Hood motor conduit in duct? #64910
04/21/06 07:16 PM
04/21/06 07:16 PM
electure  Offline

Joined: Dec 2000
Posts: 4,279
Fullerton, CA USA
Often those "mushroom ventilators" are connected to a round duct the size of the actual opening in the bottom of the fan, or have no duct at all attached. This leaves the 3/4" EMT sized chase open below.

They are a big pain to wire with a roof penetration, but mostly because getting a LT flex into them requires some "stunts".

Re: Hood motor conduit in duct? #64911
04/21/06 07:27 PM
04/21/06 07:27 PM
renosteinke  Offline
Cat Servant
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
That pipe is a very useful chase, for running power to the motor, without getting in the way of the fan blades.

For it to work, the actual roof curb has to be somewhat larger than the ducting. Then, you can place the pipe so that it actually fits between the curb and the ducting.

You are generally required to have a space between the curb and the duct. Insul-wrapping the duct reduces, but does not eliminate, the spacing requirement.

My only problem is that the pipe is often too small for the wires you need to run, and you need to "re-engineer" it.

Re: Hood motor conduit in duct? #64912
04/23/06 03:24 PM
04/23/06 03:24 PM
fireguy  Offline
Joined: Feb 2006
Posts: 19
Baker City, OR 97814
Redsy, are you sure the exhaust fan is listed for use in a commercial kitchen? I do not recall a listed exhaust fan with a Sleeve leading to the exhaust duct. The listed up-blast fans I have seen have some kind sleeve/access point from the outside of the fan, leading to the motor. There should be a label, "This port for wiring access". There is usually a large port leading to the motor housing. That port is for cooling air to enter into the housing. There may be a label "This port for cooling air and is not to be used for wire entry".When you wire the fan, use water-tite or better, water-proof connections and conduit. Make sure there is enough wiring so the fan can be removed for service.

Wiring should not be run in the duct or chase. I have seen wiring run in the duct, a screwdriver used to poke a hole in the duct and the wire shoved through the jagged hole. If wiring is run in the chase, is it rated for the temperature? What happens if the wire makes contact with the outside of the duct? How are you going to seal the fire rated wall you just comprimised? If I see something like that on a job, I will contact the GC, and inspectors to voice my concerns. I will also make a note on my fire suppression system report.


Re: Hood motor conduit in duct? #64913
04/23/06 03:36 PM
04/23/06 03:36 PM
iwire  Offline
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Welcome fireguy.

Bob Badger
Construction & Maintenance Electrician
Re: Hood motor conduit in duct? #64914
04/23/06 07:14 PM
04/23/06 07:14 PM
Redsy  Offline OP
Joined: Mar 2001
Posts: 2,056
Bucks County PA
Actually the label in the compartment under the dome states clearly that if you don't use the sleeve, you SHOULD use the fan cooling inlet port to feed the motor.
I plan to poke up through the roof next to the unit and feed in through the cooling port.

Re: Hood motor conduit in duct? #64915
04/23/06 08:31 PM
04/23/06 08:31 PM
kencr  Offline
Joined: Jul 2004
Posts: 35
Southern, NJ USA
I have wired well over a hundred of the fans you describe. All of them have a switch mounted on the outside with a conduit running from the back of the switch box to the inside motor area, most times with SJ cord factory wired from the switch to the motor. If is mounted to a steel curb, I make a 7/8" hole and change the M/C cable over to carflex and to the switch box .. no metal curb ?? Pitch pocket is the only other way I go.
I have NEVER failed an inspection doing it either way.
MAKE sure to check the motor voltage hookup ..mine have been labled 120 volt ( like they should be for my installs ) only to be wired for 208-240 from the factory

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