bathroom fan working well?

mmmeSeptember 6, 2008

My new Panasonic bathroom fan is soooo wonderfully quiet, I often forget to turn it off. But does it work?

Our bathroom is 8x10, and the fan is mounted right in the shower space. Even with the bathroom door cracked slightly, the mirror and windows fog over completely. 10 mins later, with the fan still running, they are still more than 50% fogged up. I'm talking about a 5-8 min shower, with the temp nowhere near the hottest setting. So I'm a little surprised by this.

I've noticed that even with the windows and door wide open, the windows fog up a little bit.

Shouldn't a new fan do a better job than that? Or do I have unrealistic expectations?

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"Or do I have unrealistic expectations?"

No, but your trouble is probably not indicative of the brand of fan you chose. Panasonic is arguably the best, and was certainly a pioneer in quiet bath fans. Your trouble is most likely from an inadequately sized fan, poor placement or both.

What model fan do you have, what size is your bathroom (ceiling ht. too) and where is the fan plaed?

    Bookmark   September 6, 2008 at 5:23PM
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With the fan running, if you take a square of toilet paper and hold it a few inches from the grill, is the draw of the fan enough to pull the paper tight to the grill?

With the door open...and closed?

Where does the fan duct terminate? Roof? Through an exterior wall? Can you get to the outlet and feel if much air is coming out?

Do you know about how long the run of duct is? Is it flex duct or rigid metal? Can you approximate a guess as to how many 90-degree bends there are in the duct?

Do you know the model of your fan?

No, your bath should not be fogging up like it is.


    Bookmark   September 7, 2008 at 12:16AM
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Aha! Thanks, Mongo and antss, for confirming that my fan is not working well. (Like I said, I wasn't sure if my expectations were too high.)

Now I just need to know what I'm looking for so that I can speak intelligently to the electrician about this.

This is a brand new fan, brand new installation, new construction. So there were no pre-existing conditions to work around, and I expect it was done properly. I just need to know what properly is, so that I can confirm this.

Ceiling height is 8', and the fan is located smack dab in the middle of the ceiling above the shower. Like I said before, IN the shower. I don't think location is the problem.

I can see that the fan terminates through the exterior wall, right where the shower is located. (I don't know why it doesn't go through the roof, as the bathroom is on the second floor. Would that have been better?) . So my guess is that there is one 90-degree bend, and the length is 3-4 feet tops.

I cannot reach the terminus to feel if air is coming out, but I can see that the flap stays open when the fan is running. Also, when the fan is running, a square of TP is drawn tight to the grill (from 1-2" away), with the door open.

SEEMS like all should be fine. But why, then, is the bathroom fogging so much?

The fan is a Panasonic but I don't know the model number. Is there a model-to-bathroom-size correspondence? Also don't know about flex/rigid duct. Which is better?

Thanks a lot for all of your advice.

    Bookmark   September 7, 2008 at 4:57PM
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What is your shower enclosure arrangement? Is there an air flow path from the fan out into the room or is the shower enclosure floor to ceiling?
My fans are outside the shower enclosure. The shower doors fog some inside but the rest of the bath stays clear.
The fan model number should be inside on the fan housing. If it has a light, the number may be partly hidden by the light mounting base.
The Panasonic fan model numbers indicate the CFM. 05 in the model number = 50 cfm, 08 = 80, and 11 = 110 CFM.
Here is a formula from a web site. At 8x10x8 high, you need 85 CFM minimum.
[(Length * Width * Height) * 8] / 60 = Minimum CFM required.

    Bookmark   September 7, 2008 at 9:10PM
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Thanks for the formula. I am learning a lot in this thread!

I tried to find the model number, but I can't figure out how to remove the plastic cover. There are no visible screws or brackets. How do you get the dang thing off? I'm afraid if I yank on it too much it will break.

Looked on the panasonic web site trying to find instructions, but no luck. It's a little annoying that the electrician did not leave the info sheet that must have come with the fan. How the heck am I supposed to change the light bulb, if nothing else??

I'm also mystified because the fan/lights I see on the panasonic web site all seem to have a nightlight option, but mine doesn't offer that option (or at least, I have no switch to operate that feature). I can't believe I am being driven crazy by a bathroom fan.

    Bookmark   September 7, 2008 at 10:44PM
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My Panasonic (older than yours, but I don't think they change much) has the face held in by a couple of metal arms. Just pull the whole face down gently. It should come down about 4 inches, at which point it'll be obvious how you unclip the face.

Better installations use rigid ducting, as opposed to flex.

Have you looked to see that the flaps on the outside hood are opening properly? A couple of them could be stuck, impeding airflow.

    Bookmark   September 8, 2008 at 7:55AM
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There is also a flap inside where the fan attaches to the duct. This flap is almost always taped shut during shipping. My Panasonic had a reducer over that so it was difficult to see the tape. If the installer didn't take this tape off, it would impede the air flow.

    Bookmark   September 9, 2008 at 6:31AM
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Before remodeling our bathroom, our old fan was noisy and did not work well. When we went up in the attic while installing a new one, we discovered a layer of insulation right on top of where the fan vented.

    Bookmark   September 9, 2008 at 9:02AM
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Okay, here's another twist:

When I pull down the face (thanks for the instructions), I see the model number: FV-LP003. Unfortunately, Panasonic doesn't list anything with this model number on their web site. When I google it, I get nothing. ????

Now what?

    Bookmark   September 10, 2008 at 2:46PM
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That is the model number of the light module. The fan model number is on a label on the inside wall of the black housing. It is hard to see because it is at an angle.

    Bookmark   September 10, 2008 at 9:10PM
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Yes, I discovered that after calling Panasonic this morning. I had to remove the light housing in order to find/read the fan model number. They don't make it easy.

And guess what? This is the answer to my problem. The fan is 80 cfm, but the size of my bathroom requires a 110.

But the good news is that I sure did learn a lot about bathroom fans while figuring this out! Thanks to all for all the help.

    Bookmark   September 11, 2008 at 7:46PM
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Thank you all. It is nearly 2 years later, but I have spent hours trying to find a replacement bulb for this same model. I did not know how to find the model number and learned a lot about cfm. Now I will begin my search for a proper bulb. Thanks again to all of you.

    Bookmark   June 9, 2010 at 3:20PM
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