try this site ( I have no affiliation). It gives grill dimensions for each one as well as opening size. Hope this helps. edited to add: You have to click on the link for each fan to see the specs for both the grill and opening. Here is a link that might be useful: compare fans This post was edited by olychick on Mon, Apr 8, 13 at 19:43

I second the post above. Read the manual very very carefully. We had a wood burner installed by a fireplace company and I reviewed their work after reading the manual and found many mistakes. The insulation has to be done right and there are usually requiements for cement board around the perimeter of the firebox (on the inside wall) and on the top of the hearth if it is raised. You also have requirements for spacing between firebox and any combustable framing. And many venting requirements. You should also check your local building code for fire protection which is generally discussed in the fireplace install manuals but your local code may have additional install requirements. We needed firestops installed inside the chase between each floor and any penetrations for flues through those firestops had to be filled with non cobustable insuation (rock wool). Just remember that the appliance you are installing can kill you if not done properly. I would also put a CO detector in the room the fireplace is in.

I thought new motor was defective so I exchanged it and I'm still dealing with same issue. I also have plenty of ventilation with my full ridge vent as the original fan worked phenomenal before it quit on me. I remember before how the original fan would suck a cracked door open, it had that much force. But with this new motor, I can barely feel anything. I'll open only one window to check air flow, but feel nothing. The luvers open up on the ceiling panel when fan is on, so I know fan is at least trying to do what it's supposed to. I just don't understand the situation. If a motor is turning the shaft/blades, why no air being pulled in from the outside?

The timer switch is just RATED to 20amps, I doubt very much the fan draws that much, in fact your load always needs to be well below the rating of all the associated items like switches etc - so in essence, it's probably fine to be wired from the GFCI if it's possible. Most codes require GFCIs on the outlets in bathrooms and I thought some did lights, too. The risk is the proximity to moisture - say a kid directed water upwards that hit the fan - or if you have a hand held shower head, you accidentally spray it, or the shower head splits, etc. A GFCI breaker on the switchboard's the easiest way to fix it, and you'll have the benefit of additional safety on the rest of the circuit. Well worth it, I say. In Australia, all new homes or major electrical work, requires the installation of a whole-house safety switch or GFCI, it's not a breaker as such so it can interrupt the active to any circuit in the house if it detects a leak to earth, ironically, in your case, they don't usually require (and it's not usually done) protection of the lighting circuits. Put another way, you won't be risking your life or others' lives by putting a switch in, but you might save one, down the line.