Recently a friend and professional manufactured home installer purchased a new clothes dryer for his home. Looking over the installation instructions he uncovered a few very interesting requirements specific to installing clothes dryer in a manufactured home. Given that these are safety related issues, we felt we should share with all of you. In every case, review the installation instructions that are provided with the dryer being installed.
The manufactured home installation instructions and Complete Installation Checklist (see earlier post) speaks to dryer vent installation. So as the professional installer, we could be held responsible for improper dryer exhaust duct installation that occurred as a part of our installation of the home. Unfortunately, the Model Installation Standards (24 CFR 3285) don’t offer much guidance or information to follow, so we need to get familiar with the appliance producers instructions. As always, make sure any appliance being installed is “listed” for use in a manufactured home.
I reviewed about six different dryer instructions and they all are pretty similar. Below I am listing some of the concerns that I suspect a lot of professional installers are not aware.
- Secure the exhaust vent to a non-combustible portion of the “mobile” home structure.
So, I would read that as attachment of the exhaust vent to vinyl skirting is not permitted. I cannot think of a “noncombustible” potion of any home so I am not sure of any other options here. But a few of the instructions were slightly different and only stated that the vent be attached to the structure of the home. That is fine if the duct goes through the wall, but pretty tough if the duct goes through the floor.
- Metal exhaust duct system
In most cases, the dryer manufacturer requires 4” ridged metal ducts. Flexible metal ducts are only permitted if ridged ducts can’t be used. Flexible metal is NOT Mylar-foil type vents!!! Make sure the vent piping is UL listed for Clothes Dryer Exhaust Ducts.
Sheet metal screws are not permitted to be used to join the duct piping together. The screws penetrating into the duct will catch lint and create a very hazardous situation.
The dryer exhaust may NEVER terminate under the home. Always run the exhaust outside of the crawlspace.
Ducts that are crushed or misshapen should never be used. Minimize the number of elbows and keep the ductwork as short as possible. The dryer instructions provide charts limiting the length and elbows for safe, proper operation.
- Electrical Connections
A four-wire connection is required for manufactured homes. Always remember to remove the ground strap and toss it away. Keep in mind, in a manufactured home, the ground and neutral circuits are separated. Removal of the ground (or bonding) strap, keeps them that way.
- Make up air
When I first read this requirement, I assumed that make up air was only for to gas dryers. Nope! In order for the dryer to properly exhaust, the appliance producers are calling for a way to introduce air into the home to make up for the air being discharged through the ducts. Negative air pressure inside the home could result and make the dryer work harder than needed.
I fully understand that this is well beyond the control of manufactured home installers, BUT…if you ever have interior air pressure or air quality issues inside a home, allowing for make-up air to the dryer might be part of your answer. Pilot lights going out, back-drafting of fireplaces and furnaces, mold, mildew or condensation are other symptoms.
Ok, that is enough for now….just be sure to take a few moments the next time you install a dryer exhaust duct and make sure you are familiar with all the requirements.