eleectric drier venting code questions

I was in a basement today and saw this:
Two electric driers side by side. Each had the standard metal vent pipe coming out of the driers going to a common T and then the same diameter pipe running maybe 20 feet, an elbow, another 8 feet, and elbow, and then outside.
Doesn't this sound like an awful long run of vent pipe? And shouldn't it be a larger diameter pipe where the 2 pipes are venting togethert? And shouldn't there be t y' where the 2 driers meet? And shouldn't that T be a 4 * 4* larger than 4 (I will guess 7)?
Its a condo association and one member has told me that their set up is fine as is and was done by licensed plumber...
TIA
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oreo123 wrote:

It all depends on what the dryer makers specs the dryers for. As for the "T" I am not sure that is a good idea, but frankly I don't know, I have never had two dryers. Size and length is spelled out by the manufacturer and included on the install manual.
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A condo , just call the building inspector, He will know.
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Hack plumber... Since when did plumbers become licenced HVAC techs? Just curious, since that falls under OUR codes not theirs....under the V part.
And its in the code book for duct work..since its a duct. Clearly states that they cant share a common..
Section 504.1 Dryer Exhaust systems shall be independent of all other systems and shall convey the moisture and and producs of combustion to the outside of the building or dwelling.

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in message

Thanks! I now have something with a code number on it. I spoke to a friend who is retired plumber and he was positive that one couldn't put 2 driers on the same pipe. He said it was mositure related and one could blow mositure into the other unit.
I do remember reading somewhere that every elbow reduced the run by something like 5 feet. So with 2 elbows this is just w-a-y off.
I am just a property manager who sees things that seem to amaze me weekly.
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On 11/29/2004 7:10 PM US(ET), Steve@carolinabreezehvac took fingers to keys, and typed the following:

confirms that the dryer venting is either right or wrong, and the OP does not mention whether the dryer vent has a booster fan installed to handle the extra length of the venting ducts, but I am having a problem with the section that you cited as a reference about multiple dryers venting into the same system. "Dryer exhaust systems shall be independent of all other systems..." To me, 'all other systems' means any system 'not a dryer system', such as exhausts for furnaces, boilers, etc, but maybe my reading comprehension is different than yours. How do laundromats handle the exhaust of multiple dryers running all at once? Does each dryer have a separate vent to the outside, or are they all piped into one main vent to the outside?
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Laundromats have a sep section of the Mechanical code. A Condo does not fit into that section.
When you have living space, such as in a condo, or apartment building, each dryer must have an independent vent.
504.7 deals with commercial clothes dryers, and they are required to have fan motors installed that run all the time , if the business is open, and /or designed, and installed so that if ONE unit comes on, the fan will run as long as any unit in any combination is running. they also must be type 2 dryer units.
The fan motors also have to be outside the airstream.
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Does not meet code in our area. Call the city's residentail building inspector. In out area each dryer needs it's own vent. Also the vent needs to be less than 25 feet. Adding elbows shortens the total run even more. Greg
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And for runs over 25' in duct length a booster fan is needed such as the one made bt FanTech.

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