Protect attic ventilator fan motor?

ritelec

Senior Member
Location
Jersey
Hello. I've installed a few attic ventilators and have also replaced several attic ventilator motors that have burnt out in the past. I've never given it much thought as they are thermally protected however I read an article last year about an AC contractor I use to do work for. Turns out, he (his company) installed a new attic ventilator for a customer, 10 years later it caught fire and he was being sued by the old costumer for setting his house on fire.
Does anyone here put another fuse on it or just hook them up and walk away?
If I were to put it on a fuse how much larger than the motor fla would you think it needs to be, 125% to 150%?
Thank you.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
From what I see attic ventilator fans are a big source of fires because they are usually out of sight and never maintained. True, you would think that the thermal protection means something but apparently in some cases not.

I'm not sure a fuse would do anything given that a stalled shaded pole motor doesn't draw much more than when it is running.

-Hal
 

ceb58

Senior Member
Location
Raeford, NC
Hello. I've installed a few attic ventilators and have also replaced several attic ventilator motors that have burnt out in the past. I've never given it much thought as they are thermally protected however I read an article last year about an AC contractor I use to do work for. Turns out, he (his company) installed a new attic ventilator for a customer, 10 years later it caught fire and he was being sued by the old costumer for setting his house on fire.
Does anyone here put another fuse on it or just hook them up and walk away?
If I were to put it on a fuse how much larger than the motor fla would you think it needs to be, 125% to 150%?
Thank you.
10 years later I would let my insurance company handle it.
 

Buck Parrish

Senior Member
Location
NC & IN
I too have seen some catch on fire.
I set the temp at near the highest rating it can go. In NC an attic can stay pretty hot. Even with the fan running.
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
We have one big new house that these motors keep burning out on.
I have replaced the same motors 2X over the last 6 years, the roof gets lots of south facing sun, and its just a really hot attic.
We ended up running dedicated circuit to the fans just to be sure it was not voltage drop, 2 years later motors burnt out again.
I did some reading up on attic fans and they also require 'make up' air.
If a lot of stuff is stored in the attic or the intake vents are blocked it could make the motor burn out quicker.
I'd love to find a more commercial grade motor that is rated for lots of heat and dust, that will fit.
 

mikeames

Senior Member
Location
Germantown MD
Occupation
Teacher - Master Electrician - 2017 NEC
Not sure how not having make up air would shorten the life of the motor. If a fan moves no air the the load and current decreases. Those motors don't have cooling fins either so Its hardly for cooling.
 

retirede

Senior Member
Location
Illinois
Not sure how not having make up air would shorten the life of the motor. If a fan moves no air the the load and current decreases. Those motors don't have cooling fins either so Its hardly for cooling.
No makeup air means the attic gets incredibly hot. It’s the makeup air that cools the attic - the whole reason for having the fan.
 

drcampbell

Senior Member
Location
The Motor City, Michigan USA
Occupation
Engineer
... Those motors don't have cooling fins either so Its hardly for cooling.
"Air over" motors rarely have cooling fins. They still rely on air flowing over the motor to keep its temperature within limits.

... Probably hot enough to smoke it.
Apparently, hot enough to ignite ten years' worth of dust & dander accumulation.

Attic fans are just a bad idea. Out of sight, out of mind, never maintained. No performance monitoring. Never installed behind a filter, despite the dusty environment. And in a properly-designed attic, with adequate passive ventilation and a radiant barrier, they just aren't needed.
 

ritelec

Senior Member
Location
Jersey
Besides keeping it clean How would you maintain it?

I’m in a dilemma installing one for a friend.

I have to cut in a bunch of eave vents ( eaves are plaster and metal lathe. Not looking forward to it.

The roof. I have a choice between cutting in ONE attic ventilator or 13 passive vents.

I’d rather do the passive vents but.not comfortable with 13 roof penetrations


Decisions decisions
 

ritelec

Senior Member
Location
Jersey
4 or 5, maybe 6 - 3 or 4" round hockey pucks. One centered in the soffit on each of the 4-6 six sides of the house.



GAF... also been checking out other brands and other calculations but as on now it looks like this may be the way to go.


2625 sq' attic space


says it needs 630 sq" nfa in and 630 sq" nfa out.

translates into 13 - 16x8 metal soffit vents at 65 sq" nfa (at 65 = 845, not sure why the calculator has that)

11 (not 13) SSB960 roof vents at 60 sq" nfa ( = 660 sq" nfa)

or one ERV6 ventilator fan 1500 cfm for 2800 sq '
 
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