exhaust fan trips GFI...

I have a triple box in my bathroom that contains 2 switches (lite & ceiling exhaust fan), and a duplex outlet w/ GFI. Occasionally when turning the fan off, it trips the GFI.
Is is normal for some A/C motor devices to do this, and should I just re-wire things so that the fan switch is "after" the GFI? I had assumed that all devices in a bathroom should be GFI'd.
I've tried grounding/ungrounding at the fan box end; even tried a new fan motor - still often trips the GFI when you turn the fan off.
Any advice is much appreciated.
thanks, JohnB
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
johnnyzero wrote:

I had eggsackly the same problem maybe 20 years ago when our home was brand new.
I believe it's because the moist air being drawn up into the fan unit when someone showers can cause enough leakage to ground (it only takes a few milliamps y'know.) to trip a GFCI.
Fortunately the wiring to the bathroom was arranged so that I could replace the GFCI breaker in the service panel with a regular type, and the standard outlet in the bathroom with a GFCI one, and from that outlet feed the adjacent bathroom's outlet. Thus the fans (and lights) were no longer on a GFCI circuit, but both bathroom's outlets were GFCI protected.
The only other circuit on the breaker I changed went to an outlet mounted on an outside wall (For our deck) and I replaced that outlet with a GFCI one also.
Problem solved, and the original fan motors still work fine all these years later. <G>
Jeff
--
Jeffry Wisnia

(W1BSV + Brass Rat \'57 EE)
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks for the info, Jeff. Actually I don't think it could be moisture causing it - on my last go-round I was testing it with the clng box completely open & dry. It seems to happen when you turn off the fan by flipping the switch *fast*, regardless of the moisture conditions in the b/r. That led me to believe that the switch might be the problem (burnt contacts?), so a couple months ago I tried replacing that - no go.
Oh well - I'm gonna pull that wall box apart and double-check my wiring. I guess I can always just re-wire things so that the fan isn't GFI'd.
thanks again, JohnB
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks for the info, Jeff. Actually I don't think it could be moisture causing it - on my last go-round I was testing it with the clng box completely open & dry. It seems to happen when you turn off the fan by flipping the switch *fast*, regardless of the moisture conditions in the b/r. That led me to believe that the switch might be the problem (burnt contacts?), so a couple months ago I tried replacing that - no go.
Oh well - I'm gonna pull that wall box apart and double-check my wiring. I guess I can always just re-wire things so that the fan isn't GFI'd.
thanks again, JohnB
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks for the info, Jeff. Actually I don't think it could be moisture causing it - on my last go-round I was testing it with the clng box completely open & dry. It seems to happen when you turn off the fan by flipping the switch *fast*, regardless of the moisture conditions in the b/r. That led me to believe that the switch might be the problem (burnt contacts?), so a couple months ago I tried replacing that - no go.
Oh well - I'm gonna pull that wall box apart and double-check my wiring. I guess I can always just re-wire things so that the fan isn't GFI'd.
thanks again, JohnB
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
johnnyzero wrote:

It's the motor inductance causing the trip. When the circuit is switched open, there is a sharp voltage spike created by the motor.
Some GFI's are more tolerant of this kind of thing. Swap out the GFI for another brand as a quick test.
MOV arrestors applied at the motor *may* help.
Jim
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
johnnyzero wrote:

Well since the GFCI is electronic and fans are electrically noisy, it could be a problem with the GFCI. You can get a higher quality fan/motor, or higher quality GFCI. Its probably easier to get a better quality fan/motor, but easier to replace the GFCI so I'd start there. If it turns out not to fix it, send me the GFCI, the one in my bathroom makes very quiet, tinny and odd noises continuously.
--
Thank you,



"Then said I, Wisdom [is] better than strength: nevertheless the poor
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Bathroom exhaust fan motors are shaded pole and are not electrically noisy. Sounds like the guy that suggested it may be an inductive kick back may be right.
Al
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Big Al wrote:

You don't consider inductive 'kick back' noise?
--
Thank you,



"Then said I, Wisdom [is] better than strength: nevertheless the poor
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Regardless of what may be causing the problem, the NEC requires GFCI protection of the fan only if it is installed directly over the tub

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.