# Solved: Over the Stove Fan Leak



## silverado4

When I boil Water On My Stove, I get dripping from my exhaust fan over the stove and counterop. This fan is mounted in my Range Hood. It is a BUF-03R From Fujioh. I Purchased it from Kraftmaid and it fits in the cabinet over the stove, it's a range hood made for the stove. When it rains, it doesn't leak, so I know it not from the rain. The vent goes through the ceiling into the attic and through the roof to vent. I live in a cold climate, this may help, Don't guess, I need to know before my fan rusts, it is only 4 months old. Seems like just when the wife boil things it happens, so it's condensation being caused somehow, I guess. Thanks
Silverado. HELP! Thanks


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## Guyzer

I would venture a guess that the exhaust pipe going to the outside isn't insulated. When it's cold and the warm moist air hits it that's when the water collects and eventually drips down.... condensation. If you didn't have this problem during the summer that's most likely the issue. You could solve it by insulating the entire thing if you can get at it.
Psssstttt... the air is being exhausted and not blocked in any way.......... I hope.


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## silverado4

Wimpy369 said:


> I would venture a guess that the exhaust pipe going to the outside isn't insulated. When it's cold and the warm moist air hits it that's when the water collects and eventually drips down.... condensation. If you didn't have this problem during the summer that's most likely the issue. You could solve it by insulating the entire thing if you can get at it.
> Psssstttt... the air is being exhausted and not blocked in any way.......... I hope.


That's a good point about the air being blocked, I'm going to wait for a good day, turn on the fan on high, go on the roof, and feel for some air, the fan is strong, so I should feel some air coming out the roof vent, this way I can get piece of mind and look at the vent also for leaks, that bothered me also. When the fan was installed, I watched the damper open, it opened smoothly, I think this would have had trouble if the vent were blocked, but I'll check anyway. Thanks.. What a head-ache this is... I don't remember anything in the summer, just about late September.


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## Rockn

Condensation is most lkely the problem like mentioned before. Steem will rise until it gets too cold and will fall again in the form of water. Unless the air going out of the vent wan stay warmer than the surrounding air it will drip back in the form of water. Insulating the pipe may help like suggested earlier.


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## silverado4

Rockn said:


> Condensation is most lkely the problem like mentioned before. Steem will rise until it gets too cold and will fall again in the form of water. Unless the air going out of the vent wan stay warmer than the surrounding air it will drip back in the form of water. Insulating the pipe may help like suggested earlier.


I have the guy that connected the vent to the fan coming over within the next couple of days to look at it, he is going to wrap it up in insulation. I went on the roof, everything looks ok. I had my wife turn on the fan, It exhausts real good. I turned on the fan today, not boiling anything, just heat from the kitchen, and it had a steady flow of water coming out of the fan. I can't believe the vent is that cold. it's about 50 here today. It's about 4-4 1/2 feet long in the attic. It's easy to get at. I can't, too big, I would come through my ceiling. If this doesn't work, I don't know what to do, I thought maybe the damper wasn't opening, that's why I went on the roof to make sure. I'll keep you posted. Still can't believe the heat from the house would make the water drip....
Thanks for your help. Silverado


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## JohnWill

Believe it! A surface that's significantly colder than the air passing through it will cause considerable condensation.


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## Guyzer

silverado4 said:


> Still can't believe the heat from the house would make the water drip....
> Thanks for your help. Silverado


It could be that you have excess moisture in your house as well. Do you have a humidifier running or something else that could be causing this? It's just strange you never had the problem with the old fan.


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## JohnWill

The old fan may have been piped where the condensation was running down inside the wall somewhere.


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## silverado4

Here is an update and picture, the pipe has a slight bend when it goes from the fan to the attic. Could the exhaust hit the bend, causing the condensation? Also, the roof is about 4 - 4 1/2 feet from my ceiling to the roof, the cold still could come in from the outside through the vent even if it was insulated, will the insulation still help to keep it warm. It gets pretty cold here in Michigan, an 4 1/2 feet isn't too far from the fan to the roof. Maybe the attic isn't the problem, maybe the cold is coming from the outside to the vent. I'm getting a head-ache. This is getting worse the more I think about it. The vent on the roof of course is an open vent. We went to Lowes and told the rep. who sold us the fan about the problem, she said, you know what, I have the same problem. She is going to contact Kraftmaid, who supplied the fan to see what they say, but in the mean time, I still am going to insulate the vent, I know that won't hurt, from the ceiling to the roof. Only thing I used up one roof vent for this. I never had a fan before, so I can't tell you of any past experience, sorry. Thanks for all you help, keep thinking, it helps me a great deal. The fan is on the right, and the exhaust is on the left side. There is a damper inside of this duct that opens and shuts when the fan is on.


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## Guyzer

Neither the fan or the bend will be the problem. You have proved that by going on the roof and checking it's flow. The damper is there to stop the outside air from coming in... kind of a check valve. It's a condensation issue plain and simple. Once you insulate the pipe your problem should be resolved. Don't leave any bare metal showing. If it isn't solved then I would suspect the pipe itself is to short and the transition between warm and cold isn't sufficient. There is something you might try to assist after you have the insulation on it. After you have finished your cooking and have removed all the pots from the stove let the fan run an extra 5 minutes to dry the inside of the pipe off so you don't get a buildup. 

I installed a bathroom fan ( 90cfm if I remember ) in an older house once and used the " flex " type exhaust hose that came pre-insulated. I ran the hose about 20' to a vent that I had installed on the side of the house. When taking a shower there is of course quite a bit of steam generated and it never gave me a problem and it didn't matter if it was 80 above or 30 below. ( we lived in Manitoba at the time ) We had a habit of running it for an extra 5 or 10 mins. just to " clear " (dry ) it out and avoid any build-up.


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## silverado4

Good point on leaving the fan running a few minutes.
Heres a good one. My wife just went to the stove now, and there is water on the counter, nothing was boiled, or used, it was just from during the night. I hope there isn't ice settleing in there somewhere. Crazy isn't it, I wanted this fan especially for this stove, and look what it got me into. Thanks for your input.


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## Guyzer

If you have moisture dripping from it after sitting overnight it's definitely a condensation issue caused by warm air hitting the cold.
From the sound of it you have warm air escaping via the pipe when the fan isn't on. Is the flapper closing tightly to seal it off?


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## Guyzer

I have no idea how your house is built so I'm just winging it. What I would have done was vented the fan with 4" pre-insulated flex hose from the fan to the side of the house. They come in about 25' lengths. For the vent on the outside of the house I would have used a dryer exhaust vent to connect my hose to and I would have it exhausting just above the ceiling line. I also made sure I had as much of the flex pipe covered with the attic insulation. In a cold climate you can never have enough insulation. That's what I did for my bathroom fan. Here's a couple of real quick drawings to help you get the idea. You might want to consider it if it isn't to late.


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## silverado4

Wimpy369 said:


> I have no idea how your house is built so I'm just winging it. What I would have done was vented the fan with 4" pre-insulated flex hose from the fan to the side of the house. They come in about 25' lengths. For the vent on the outside of the house I would have used a dryer exhaust vent to connect my hose to and I would have it exhausting just above the ceiling line. I also made sure I had as much of the flex pipe covered with the attic insulation. In a cold climate you can never have enough insulation. That's what I did for my bathroom fan. Here's a couple of real quick drawings to help you get the idea. You might want to consider it if it isn't to late.


Here is what the we did:
1. There was a 6" duct in the attic, not installed to the roof vent already. Once used by the previous owner I found out for a microwave. He had the exhaust going into the attic for a little while, then he exhausted it into the kitchen through the microwave.
2. We took the previously 6" round vent, put it to a roof vent on about a 20-25 deg angle to the roof vent from the stove fan and added the additional duct to the exhaust fan.
3. The installer (a friend) called around, he is a metal worker by trade, said his friends said the vent should be straight, he was going to cut a hole in the roof and make it straight today. This was going to be too close to my "Peak" of my house. I really didn't want that.
4. So we are deciding to insulate first to see what happens in about 1/2 hour of so from now. I will give you feed back within the next couple of days if the insulation works.
I asked him if they made an "in-line" damper that he could put at the roof vent to close when not in use so the cold would not come in. He didn't know, but would look at home depot. I don't give that any chance.
The worst case on this whole thing, (I talked to my cabinet installer, my cabinets are only 6 months old from kraftmaid), is I have him take out this range hood (bonnet) and fan, put in a couple of cabinets, and range hood that exhausts to the kitchen and call it quits.....
Thanks for all your help with this, it's greatly appreciated.


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## kilowatt1

I think the biggest problem you have is that the proper termination cap has not been provided for the exhaust vent. In addition to the backdraft damper on the hood vent itself, you also need a damper to prevent air from entering the exhaust pipe above the roof line or where the exhaust terminates to the outside. In fact, the International Residential Code requires a backdraft damper for BOTH the duct and the exhaust hood itself. An approved termination cap will also help to prevent any frost that may form from dripping back into the duct work. I also see in the picture you posted that regular duct tape was used on the connections. I suggest that you have your installer replace this with foil backed tape which will last longer and provide a better seal. (regular duct tape will tend to dry out and deteriorate over a period of time).


Good luck.

Kilowatt


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## silverado4

kilowatt1 said:


> I think the biggest problem you have is that the proper termination cap has not been provided for the exhaust vent. In addition to the backdraft damper on the hood vent itself, you also need a damper to prevent air from entering the exhaust pipe above the roof line or where the exhaust terminates to the outside. In fact, the International Residential Code requires a backdraft damper for BOTH the duct and the exhaust hood itself. An approved termination cap will also help to prevent any frost that may form from dripping back into the duct work. I also see in the picture you posted that regular duct tape was used on the connections. I suggest that you have your installer replace this with foil backed tape which will last longer and provide a better seal. (regular duct tape will tend to dry out and deteriorate over a period of time).
> 
> Good luck.
> 
> Kilowatt


He said he could not find this type of damper at Home Depot or Lowes, I suggested it to him to put a damper on the roof to keep the cold from coming back in the pipe, see my updates below on insulation. Thanks for your input. Silverado


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## silverado4

Well, here is my latest on my vent problem. The vent has had and operation. The insulation has been put on it from the ceiling to the roof line. (see pictures). If this doesn't work within the next two weeks, he will re-route the pipe to exit out the side of the house. He looked at the vent, and it will be too close to the peak of the house to put a new roof vent in, good, I didn't want that, all I need is a roof leak in the future for new problems. Check out the angle, is that ok?


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## hewee

I see from the picture that not all the seams are even sealed. Plus duct tape is used. It will get old and come all apart from the heat. Best to check all the seams and get the foil tape because it is better and will not rot from the heat like the duct tape. 
Plus your want to seal the opening in the ceiling. Not just wood like it is now. You need to sheetrock and tape it to bring it up to code. You can then have the wood over top of the rocked ceiling that is sealed. 
I would see if you can look up into the fan to make sure the damper is down or close when the fan is off and when the fan is on that it opens all the way. It should move freely.
Look at all seams and seal them good with the foil tap. I marked the picture to show the ones I can see so you know there are places I can't see. But they should all be sealed.


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## silverado4

If we decide to go to the side of the house, I will get the foil tape, I will get it before I put the range hood cover back on also.
You make it a big job, I may take it down and put a microwave in after that last answer...
Thanks for your support in all this.... It's been an ordeal..
Silverado.


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## hewee

Opps missed this page. You got to gave a damper. Darn it is the code and the damper should be down at the fan. From the picture you have a damper under that duct at the bottom or there should be one there. Look at the paper work. The damper is right overtop of the fan. 
http://www.repairclinic.com/0100_10.asp 
Move your mouse over the damper and your see the type of damper you have. 
Look at how bad this duct was put in.
http://www.nachi.org/gallery/details.php?image_id=91&sessionid=760eb6104329a09ccec6a1ee832f9115
Should have had screwed the ducts together. Also metal straps to how and support it. Then see how old the duct tape looks and it is coming apart because it rots.
I do not think you have to seal your duct the way you did because your trouble is something else. Then I would find out the right way to seal in because you don't want it to get worse because it builds up Condensation more because of the way you wraped it up.


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## hewee

Do a search on hood fans and how to install them. I have put in 1,500 or more into new homes and then fiinished up with the duct that that goes from the fan to the duct coming tru the ceiling. 
If you want a really good one then it will cost more because you do not want the fan blade type. Plus they are not as loud as a fan blade of you get the the turbine type that will also more more air.


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## silverado4

hewee said:


> Do a search on hood fans and how to install them. I have put in 1,500 or more into new homes and then fiinished up with the duct that that goes from the fan to the duct coming tru the ceiling.
> If you want a really good one then it will cost more because you do not want the fan blade type. Plus they are not as loud as a fan blade of you get the the turbine type that will also more more air.


Here is a drawing of my fan, it appears to me to be a turbine, that's why I got it. I wanted a stronger fan. My old microwave fan wasn't very strong, never pulled anything up, and it exhasted into the kitchen through the top of the microwave. The installer, remember he is a friend, and a metal worker, a teacher of this at school, said he screwed the sheet metal together, and he said that he taped up the insulation good and tight, with commerical duct tape. I have to leave it go at at that. My wife is boiling cabage tonight with corn beef, this will be a good test, somehow, I think it will still leak, but we'll see. He does have another game plan to go to the side of the house. The Damper is at the base of the unit at the fan, it opens and closes when the fan is turned on. I watched it after the first duct was in to make sure it cleared the duct.


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## hewee

Well you can see where I marked it where is is not taped. Duct tape does work and is what had been used for years but as it get old it will rot from the heat so the foil tape is better. 
I can not see from the picture if there is a damper but you say you have so that is good.. 
But if you at a outside wall then going right out that wall would be best and your know the air will get blowed out. 
You say you got a stronger fan but how far does it have to blow the air to get to the other end at the ceiling?
Like all your cooking tonight your get lots of steam but if it does not get sucked up and out of the top at the roof then your have all that water from the steam setting inside the duct and run back down and you now what that does because that is why you posted. 
I can see a good reason for not having the microwave where the range hood because I never like it as much as a range hood. They are still vernt the same or all the ones I have put in are but they don't take as much out of the room as a range hood.


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## silverado4

Well after our cooking last night with boiling, nothing leaked, but it could be just a coincidence. Here's my thinking on the whole thing. I thought that cold air was coming down the roof vent, hitting the cold vent in the attic turning into ice crystals, then when warm air hits it, it melted, came back in the house throught the fan. Just maybe now that the vent is warmer due to the insulation, it wont create the ice crystals, thus, no water. Do you buy that?
I'm going to look on line to see if they make an in line damper to fit inside the roof vent from the attic side, then the vent go into that. There's got to be something like that.
Ever heard of anything like that? I just want something to stop the cold from coming in.


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## Guyzer

silverado4 said:


> Do you buy that?


Yes


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## silverado4

Wimpy369 said:


> Yes


Ok, do you know of a site I can look at, I went to home depot, of couse they didn't have anything like that, they only have standard things.
Yes,,,, That didn't help me...


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## hewee

Well it does not get as cold around here but yes I say what you said could be true but I would also if it is true then why is it not code that for insulation to be on the ducts so that does not happen.


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## Guyzer

silverado4 said:


> Ok, do you know of a site I can look at, I went to home depot, of couse they didn't have anything like that, they only have standard things.
> Yes,,,, That didn't help me...


When I said yes I was answering your question about why you didn't have a water drip after you insulated it. You said " do you buy that " to which I replied " yes ".

As far as a damper goes I don't know of anything specific that would do the trick. What I would do is speak to a heating + cooling shop ( ie: furnace sales & serv ) to see if they know of something. If something is available I'm sure they would know.

Just curious but hows it been today? Any water dripping even though you haven't used it? ( I remember you mentioned you had that problem )

PS: I'm by no means an expert. I just know what I did with the bathroom fan and it worked for me.


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## silverado4

Oh, I see about the Yes, I didn't know where the Yes applied to, I thought it was for the damper, sorry. Glad you agreed on the way I thought about the way I thought about the ice formation. No water dripping today It's warm today for Nov in Michigan about 60, very unusual. I bought a charcoal filter today a home depot. I put it in, and the fan kind of suck it up a little. I modified it by drilling 4 holed in the metal grille, and putting a thin wire across to hold down the charcoal filter. All the fan came with was a metal grille. That won't stop grease from going up. It's really a bad design. Looking on line, It said a charcoal filter can be used. I didn't want the charcoal filter to be sucked up into the fan, then I would have another problem.


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## Guyzer

silverado4 said:


> Oh, I see about the Yes, I didn't know where the Yes applied to, I thought it was for the damper, sorry. Glad you agreed on the way I thought about the way I thought about the ice formation. No water dripping today It's warm today for Nov in Michigan about 60, very unusual.


That might be why you didn't have any condensation dripping. It sounds kind of warm. What were the outside temps like when you noticed the moisture?


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## silverado4

They were colder a few days ago before Thanksgiving, That's why I'd wait a couple of weeks or so and see what happens. The guy that put the insulation on, said if it didn't work, we'll tackle it again. He is a sheet metal teacher, and he made the duct you saw over the output of the fan because of the space I had in the range hood. I'm going to talk to him before we start anything else and see if he can make me a "damper" to fit at the end of the 6" vent just before the roof vent that will slide on, or in the duct which he can screw into it, then put it back into the roof vent. He works with other metal workers at the school so between them maybe they can put their head together and make one. It sounds simple. I'll keep you posted. Thanks for hanging in there.


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## silverado4

Look what I found, this may be the answer, let me know what you think. I could have this installed ner the roof vent.
http://www.ec-securehost.com/positiveenergyconservationprod./VENTILATION.html#PEB


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## Guyzer

Which item is it exactly that you are looking at?


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## silverado4

Wimpy369 said:


> Which item is it exactly that you are looking at?


The Butterfly, I'm glad to see you are always on. That helps. I should say, I'll order the 6" one


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## Guyzer

When I look at the pic I'm trying to figure out how it would close by itself as I don't see any springs or weights. If I use my imagination it would lead me in the direction of a weighted system that would make it close when not forced open by the fan. I theory it should help, it sure wouldn't do any harm, but the short length of your pipe ( 4' ) could be an issue. I didn't look at the sites info close enough but is there a phone # you could call just to run those things past them?
edit: they do have a toll free #. Give em a call. Run your whole problem past them and see what they say. You might be on to something.


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## silverado4

I sent them an e-mail already, I'm just waiting for a reply. If it's a 6", and it's length is 6" long, I think it should be ok, heh, I don't have anything now...
I'll wait for an answer from them and let you know.


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## silverado4

I received a response from the company that makes the butterfly damper, I wanted to make sure that this particular damper will open when my fan is on:

*Hi Jack,

Yes, the damper does open when the fan is on, and closes by itself when the fan is off. This would keep the cold air from coming in through the exterior vent. Another option would be to replace your exterior vent with one of our dampered vents. Both the 6" butterfly, and the 6" roof vent are stock items. You would not need both. Both should open when the fan is on low.*

At least I know they are in stock, I'm just making sure that he used a 6" duct, before I order it. My wife works the installer at the same school and she is finding out today or tomorrow. I will order it then and go from there. I wonder if it will open if the fan is on low?, it should...


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## silverado4

Well, I've ordered the damper, it's a 6" damper she wrote back again and told me the size. I'll have it put right at the roof vent on the inside of the roof. So now I wait. What a saga this has turned out to be. I've learned a lot from this, to much if you ask me. I'll be prepared if anyone ever asks me about a exhaust duct that's for sure. When it gets installed, all get back here and let you know that its in, should be here in about a week to 10 days. Ah, a break.
Silverado out for now..... unless it leaks.


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## hewee

For it to open if you have that damper up top by the roof you better hope that the fan blows good so it can open the damper up. It should but having it down by the fan it get more force from the fan then having it at the other end by the roof.


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## Guyzer

hewee said:


> For it to open if you have that damper up top by the roof you better hope that the fan blows good so it can open the damper up. It should but having it down by the fan it get more force from the fan then having it at the other end by the roof.


In your part of the country where the climate is milder it would work but up in the cold country you want to stop the air as far away from the fan as possible.


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## hewee

I understand that Wimpy but you have to have to force from the fan to lift that damper up still and remamber you also have the damper down just above the fan. It really does not take much force to open and once they are open they stay open easy till the fan gets trurned off and the they drop back down to close.
So you want to check that it opens both dampers at the low fan speed and if so you know any faster speed will also open it.


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## Guyzer

hewee are you telling me people actually use a fan on low speed. I gotta tell my wife that, maybe she won't burn the food so much. Everything is always done in overdrive including the burners.


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## paisanol69

silverado4 said:


> I received a response from the company that makes the butterfly damper, I wanted to make sure that this particular damper will open when my fan is on:
> 
> *Hi Jack,
> 
> Yes, the damper does open when the fan is on, and closes by itself when the fan is off. This would keep the cold air from coming in through the exterior vent. Another option would be to replace your exterior vent with one of our dampered vents. Both the 6" butterfly, and the 6" roof vent are stock items. You would not need both. Both should open when the fan is on low.[/B]
> 
> At least I know they are in stock, I'm just making sure that he used a 6" duct, before I order it. My wife works the installer at the same school and she is finding out today or tomorrow. I will order it then and go from there. I wonder if it will open if the fan is on low?, it should...*


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## hewee

Wimpy369 said:


> hewee are you telling me people actually use a fan on low speed. I gotta tell my wife that, maybe she won't burn the food so much. Everything is always done in overdrive including the burners.


Some people do and can. But not all fans like the one we had here that is just on and off. But it is a good fan and is not loud like most hood fans. Also it is a big 8" fan. Even with having the great fan all is not so good because there is no range hood. It is just in the cabinet so if your using the front burner lots of the heat and that goes up above the cabinet even with having a good fan that the hood would help get if there was one.


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## silverado4

hewee said:


> Some people do and can. But not all fans like the one we had here that is just on and off. But it is a good fan and is not loud like most hood fans. Also it is a big 8" fan. Even with having the great fan all is not so good because there is no range hood. It is just in the cabinet so if your using the front burner lots of the heat and that goes up above the cabinet even with having a good fan that the hood would help get if there was one.


Ok, I'm back,
It's been a few days, it's been cold here in Michigan. We had that snow storm that came through. In fact we had a good snow last night. It's been in the 20's for the last say 3-4 days. As you know my vent to the roof has been insulated since my leaking problem. Well I'm glad to report, knock on wood, that, do you believe this, there has "NOT" been any water. We tried everything from boiling water, to just the heat from the stove, or just the heat from the house. He had the fan on HI, Low, Med, etc. Trying to get it to drip. nothing yet. I did however receive my damper in via ups. The damper is very light and closes on foam. It is split in half, which I like, less weight to open. I think if I don't get any dripping, I'll have this installed on a warmer day near the roof vent. My fan on my range hood when it's on low, pulls a paper and holds it agains the grille. I'm sure it will open this damper on low. I'm not worried about that. I will let you know how things go. I agree with the previous reply, I think the damper must be near the roof to keep cold out.


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## Guyzer

Good to hear.


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## silverado4

Thanks...


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## hewee

Hope all goes well.


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## silverado4

hewee said:


> Hope all goes well.


I Thought I would drop all of you a quick line. Well it's been some time now, and it's been real cold here in Michigan, and there hasn't been a "DROP" of water leaking over my stove through my fan. Can you believe that? It was the insulation around my vent that was needed. Boy do I have something to pass down. I would have never believed it was just insulation. I still have the damper that I will put in when it gets warmer in the spring, but for now, Its solved. So for this end, it's over and out for Silverado. And thanks for your help....


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## JohnWill

The damper will probably save you some energy when the vent is not running, so I would not forget to install it when you get the chance.


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## silverado4

Nope, I won't forget to install the damper, take care, have a nice holiday.


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## silverado4

Well, It's Jan 25, 2007 and there still isn't a leak. The temp is 17. The damper is not in, but will be in when it gets warmer. What a relief, and what a headache that was. Thanks again for your help. I still can't believe it was just the insulation, but it was.


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