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Homeowner Forum / Construction / October 2005Dryer vent: booster fan vs larger duct
I'm installing a 22' long x 4" smoothwalled aluminum dryer vent with six 90 degree elbows for a client. The dryer will be full size, vent terminates close to grade in West facing wall at dead end of 20' long space between houses 6' apart, 2.5 stories high, prevailing winds from the west. The Canadian Mortgage & Housing Corporation recommends adding an inline booster fan if duct is longer than recommended, and standard length from http://repair2000.com/dryer.html is given as follows: The International Mechanical Code article 504.6 stipulates the requirements for Domestic clothes dryer ducts. In brief, the maximum length of duct permitted is 25 ft. This maximum length should be reduced by 2.5 ft for each 45-degree bend and 5 ft. for each 90-degree bend. The duct should be a minimum nominal size of 4 inches in diameter and shall have a smooth interior finish. I've priced inline fan as $311.00 CAN + tax = 357.65, + two hours labour to buy & install, say total $410.00. Is there any chance that increasing size of duct from 4 to 5" would reduce static pressure enough to skip fan installation, or would it be necessary regardless of duct size given length of run + 6 elbows? The next part of the code dictates that if you know the appliance to be installed, you can meet the requirements of the dryer. The dryer I just installed allowed 35' with 4 elbows.... I had to show the inspector the specs for the dryer. Shannon Pate > I'm installing a 22' long x 4" smoothwalled aluminum dryer vent with six > 90 degree elbows for a client. [quoted text clipped - 20 lines] > static pressure enough to skip fan installation, or would it be necessary > regardless of duct size given length of run + 6 elbows? Thanks very much Shannon. The one you bought would acutally serve his length of run, do you remember the make & model? Peter > The next part of the code dictates that if you know the appliance to be > installed, you can meet the requirements of the dryer. [quoted text clipped - 29 lines] >> reduce static pressure enough to skip fan installation, or would it be >> necessary regardless of duct size given length of run + 6 elbows? Kenmore Elite HE4t Get ready to shell out about $1000 for it... Shannon > Thanks very much Shannon. > The one you bought would acutally serve his length of run, do you remember [quoted text clipped - 35 lines] >>> reduce static pressure enough to skip fan installation, or would it be >>> necessary regardless of duct size given length of run + 6 elbows? OP- IMO either put in the booster fan or desgn / build in a provision for easy retrofit when (if) the system under performs. Let the client in on the decision ; give him the pros & cons Maybe they're willing to accept the risk of under performance to save the $'s.....maybe they would rather have a "sure thing"? cheers Bob That "underperformance" could result in a fire. The ICC isn't really concerned that your clothes are dry. But they would like to keep you from perishing in a fire. The OP should install the booster fan as set forth in the building code, or they should install a dryer that can perform with the stated length of run. Shannon Pate > OP- > [quoted text clipped - 8 lines] > cheers > Bob > The next part of the code dictates that if you know the appliance to be > installed, you can meet the requirements of the dryer. [quoted text clipped - 4 lines] > > Shannon Pate Even thought the code allows this, I wouldn't do it. What happens 15 years from now when the third owner moves in and owns a cheapo dryer that doesn't push an adequate volume of air? His house burns down. Always consider the worst case when building residential. Someone else will own the house at some point in time, and safety-specific items that make sense to the present owner will surely be forgotten as the ownership changes over the years. Err on the side of caution. Install the booster fan. S. >> I'm installing a 22' long x 4" smoothwalled aluminum dryer vent with six >> 90 degree elbows for a client. [quoted text clipped - 20 lines] >> reduce static pressure enough to skip fan installation, or would it be >> necessary regardless of duct size given length of run + 6 elbows? When you put brakes on your car, do you think how they'll perform for the next owner? I build MY house for me...not the next owner. Shannon Pate >> The next part of the code dictates that if you know the appliance to be >> installed, you can meet the requirements of the dryer. [quoted text clipped - 39 lines] >>> reduce static pressure enough to skip fan installation, or would it be >>> necessary regardless of duct size given length of run + 6 elbows? A little different here, Shannon. Though I agree that you should build the house for you, concealing something that could very easily be a hazard is irresponsible. Once it is built, It will quickly be forgotten about, and would be a fire hazard for a smaller, less powerful dryer that didn't meet the extraordinary specifications of the super dryer. Worrying about the performance of brakes for the next owner of my car is a poor analogy of this situation. S. > When you put brakes on your car, do you think how they'll perform for the > next owner? [quoted text clipped - 47 lines] >>>> reduce static pressure enough to skip fan installation, or would it be >>>> necessary regardless of duct size given length of run + 6 elbows? - Peter Shepherd - > I've priced inline fan as $311.00 CAN + tax = 357.65, + two hours labour to > buy & install, say total $410.00. - Nehmo - Even at the current exchange rate of CAD = 0.851354 USD, that sounds a little high. But I've never bought one, so what do I know? http://snipurl.com/i911  Signature)|||(__Nehmo__)|||( I too was expecting more in the order of $200 for fan. I got this first price from one of the cheaper manufacturers in town, may-be they've gone to the Dark Side. Will call around to compare. >- Peter Shepherd - >> I've priced inline fan as $311.00 CAN + tax = 357.65, + two hours [quoted text clipped - 5 lines] > little high. But I've never bought one, so what do I know? > http://snipurl.com/i911 Shannon- I didn't mean violate the code provisions. I meant sneaking by at the code minimum would potentially give a poorly performing system. Just because it meets the code doesn't mean it works great. A short run thru an exterior wall is the way to go. If this is not possible then the better installation would dictate a booster fan. The question I have is why a booster fan is so much? cheers Bob > Shannon- > [quoted text clipped - 9 lines] > > The question I have is why a booster fan is so much? Its an inline squirel cage fan... those are made in much lower volumes than standard squirrel cage fans.. (the cheaper propeller fans dont produce enough static pressure to be useful as boosters). Phil Scott > cheers > Bob After emailing Fantech for local distributors, I've found their DBF110 with pressure switch for $221.76 CAN + 15% tax = 255.02, though prices varied over $120 depending on which distributor I called. I'm assuming that using 30" pcs of aluminum duct with seams upwards & all joints taped with foil tape will be enough to keep ceiling dry. Instructions for one fan said to use steel band clamps for some joints, not sure if they meant all. Thanks for all replies to date. Peter >> Shannon- >> [quoted text clipped - 14 lines] >> cheers >> Bob |
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