dryer vent through chimney?

[CheckItOut]

Electric dryer is vented into a un-used brick chimney. Entrance point into the chimney is about 3' up from the bottom. Chimney is about 12' high.

Other than having a hard time cleaning the lint out, is this not allowed?

[Bain]

I've seen that about half a dozen times. The clothes dryer has to discharge to the exterior of the house, not into what is essentially a brick catch-basin.

Bust 'em on it.

[msteger]

I would call it out as well. Also, what was the total length of the dryer vent run? Max is 25', then subtract 5' for every 90 deg angle and 2.5' for each 45 deg angle. Seems it would have been much simpler and easier to clean by running it out the side of the home with a proper cover and using metal ducting.

[Neal Lewis]

Originally posted by msteger

Max is 25', then subtract 5' for every 90 deg angle and 2.5' for each 45 deg angle.

Matt, the installation instructions for my dryer allows a maximum of 65 feet. No mention of 45 degree bends.

Where do you get the 25 feet from?

[Brandon Whitmore]

Where do you get the 25 feet from

I just got home from my softball games and don't want to look it up. I am guessing he got this from the IRC -- 25' sounds about right. I believe there is an allowance to comply with the manufacturers installation instructions if you know who the manufacturer of the dyrer will be.

I did not look this up and am relying on memory only.

[Bain]

The 25' rule with appropriate reductions for bends dates back at least as far as 1992 CABO.

[Darren]

Neal;

Go to (NJ) chapter 15

M1502.6 give you the 25 feet max.

However, the exception states:

Where the make and model of the clothes dryer to be installed is known and the manufacturer's installation instructions for the dryer are provided to the building official, the maximum length of the exhaust dust, including any transition duct, shall be permitted to be in accordance with the dryer manufacturer's installation instruction.

I don't see any manufacturer adding 40 feet to their exhaust, but hey, you never know.

[Neal Lewis]

As a matter of fact, the chart in the installation manual tells me, with four 90 degree bends, the maximum is still 28 feet.

Well, I did pay extra for this fancy Neptune front loader, so hey, ya never know...

Edit-Just looked up an installation manual for a GE dryer. The maximum allowed is 90 feet without bends.

[Mike Lamb]

I, too, find that most manufacturer's instructions allow way more than the 25' that the IRC dictates. From IRC 2000:

IRC 2000

SECTION M1501

CLOTHES DRYERS EXHAUST

M1501.1 General.

Dryer exhaust systems shall be independent of all other systems, shall convey the moisture to the outdoors and shall terminate on the outside of the building. Exhaust duct terminations shall be in accordance with the dryer manufacturer’s installation instructions. Screens shall not be installed at the duct termination. Exhaust ducts shall not be connected with sheet–metal screws or fastening means which extend into the duct. Exhaust ducts shall be equipped with a backdraft damper. Exhaust ducts shall be constructed of minimum 0.016–inch–thick (0.406 mm) rigid metal ducts, having smooth interior surfaces with joints running in the direction of air flow. Flexible transition ducts used to connect the dryer to the exhaust duct system shall be limited to single lengths, not to exceed 8 feet (2438 mm) in length and shall be listed and labeled in accordance with UL 2158A. Transition ducts shall not be concealed within construction.

M1501.2 Exhaust duct size.

The minimum diameter of the exhaust duct shall be as recommended by the manufacturer and shall be at least the diameter of the appliance outlet.

M1501.3 Length limitation.

The maximum length of a clothes dryer exhaust duct shall not exceed 25 feet (7620 mm) from the dryer location to the wall or roof termination. The maximum length of the duct shall be reduced 2.5 feet (762 mm) for each 45–degree (0.79 rad) bend and 5 feet (1524 mm) for each 90–degree (1.6 rad) bend. The maximum length of the exhaust duct does not include the transition duct.

Exception:

Where the make and model of the clothes dryer to be installed is known and the manufacturer’s installation instructions for such dryer are provided to the building official, the maximum length of the exhaust duct, including any transition duct, shall be permitted to be in accordance with the dryer manufacturer’s installation instructions.

[Phillip]

Here is the dryer vent from todays inspection

Image Insert:

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Going out the roof

[msteger]

Yeah, the IRC is where I got the 25' max length. I use that as my standard; I had never heard that some manufacturers allow for a bit more.

The longer it is, the higher risk of big time lint clog-up and fire hazard. Also, the more clogging of lint that is in there, the less air flow and more energy needed to dry the clothes.