Installing dryer exhaust vents

[mk162]

Who would handle this type of thing?  I checked with a couple of our HVAC customers and they didn't have an idea.

The basic idea we are looking for is to install vents on each end of the oven with a blower motor to pull hot air and exhaust fumes through the roof.  I could do it myself, but I really don't want to.

We've got the vent boxes made, we just need to mount them to the dryer and hook up the ductwork and punch it through the roof.

[im_mcguire]

I need to do this as well, but what I am being told is in California, maybe all over the country, you have to get a permit to put a hole in the roof. Can anyone here confirm that? I'm sorry to detail, but this has been a issue for us in not being able to run WBDC properly.

[ZooCity]

We are ducted at front and back of dryer to our main exhaust run (shop wide system pulled by a restaurant style vent fan).  System is separate form the main exhaust stack.  I'd recommend putting in a light air system for this like ours.  If you're HVAC person isn't crazy expensive they can duct it to many other places in the shop where it could be beneficial- over the washout, heat press areas, compressor room, etc.

Intake vent has no fan assist.  I think it's purpose is to grab heat and any fumes escaping, not really sure actually.

Outtake vent fan has a furnace style blower to assist.  Got it from M&R on Rich Hoffman's recommendation.  Works pretty good.   Doesn't really matter what you use here just keep the motor outboard of the duct. 

I recommend two things that our setup does not have (yet):

• Put a filter before your outtake boost fan.  Our gets absolutely fuzzed to death and requires more and harder cleaning than if it had a filter before it. Something like the filter/booster fan setup on an M&R sprint's main stack would be ideal.  You can probably buy that assembly from M&R if you ask.  It would definitely cost more than building it up yourself but would be an easy solution.
• Zone off your outtake exhaust area with some silicone sheeting or metal sheet.  We haven't done this yet but it seems obvious that it will be a great help.

Last off, if it's heat that your are mainly trying to exhaust you should consider building at least 4' of cool down zone at the outtake.  I have a large sheet metal hood that I had my guy make for this but it's been one of those many projects that hasn't been focused on.  If you insulated what would essentially be a last cool down chamber and exhausted it very well you could grab a lot of the heat that radiates off those garments.  Radiant heat from the garments is our largest heat issue here.   It's hard to quickly capture radiant heat, you need more time and space than an 18" section of vent.

[screenxpress]

Not sure if you were looking for normal venting or a hood vent.  What I did was get 2 sheets of stiff insulation from a local HVAC company and built a hood that extends outside the dryer by about 2 inches.  The hood sits on 2 parallel 2 x 4s (front and back) that have several short blocks attached to allow air to pass through the supports to the vent hole cut into the top.  I have a bathroom vent to pull the air as it floats up from the inlet and outlet (and sides to a smaller degree) and pulls it up and outside.  The non-flex tubing line is from the dryer vent itself and is not helped by an external fan.  The dryer vent has an internal fan that blows exhaust air out.

I did have to extend the crank for heating element height so it would poke thru the hood.  I sealed the cracks and corners with HVAC aluminum insulation tape.  Checking with a temp gun, it dropped the temps on the back wall by about 25 degrees and overall made a big difference in shop heat.  As you can see, my venting is thru the wall, not up.

Think of it as a loose fitting dryer condom.

[tonypep]

Nice clean job. Although its often necessary the less bends the more efficient. Since we built this facility from the ground up we were very fortunate to vent straight up

[mk162]

We had the boxes fabricated.  We were going to install both the front and rear vent boxes to a single duct in the middle above the oven with a booster fan to pull the heat out.

I only wanted 1 hole in the corrugated roof and so far I am not having any luck finding someone to do that.  Our current oven is vented through the roof, but that was an existing 10-12" vent that leaks like a motherfreaker every year so we have to go up and reseal it at least once a year.

I just want maybe an 8-10" duct to help pull the heat out in the summer and any time we run discharge or some poly shirts.

I was planning on installing a filter on each end to keep the blower very clean.

[GKitson]

There is a time for DIY and a time to consult a pro.

If you do the duct/exhaust works yourself you can pretty much assume you did it wrong.

If you oversize you will over-exhaust and cause increased energy cost by increasing the amount of required make-up air.

If you under-exhaust you will, especially with WB, cause curing issues.

The burner size and internal exhaust fans are mathematically calculated for certain criteria.

IF you mess with that you are not getting the value you paid for in terms of dryer efficiency.

A qualified HVAC contractor will configure the duct/exhaust to maintain the promised efficiency and comply with local fire and building codes. 

Do it once, do it right and sell the HVAC guy some hot/cool shirts.  After all you don;t wnat him printing shirts do you 

My 2 cents....

[mk162]

Greg, the dryer itself is vented, and it's done properly.  I'm not worried about that at all.  I am mainly worried about the heat and fume spillout at the ends of the dryer.  I would think I would have to put a jet engine exhaust on there to mess with the curing of the dryer itself.

I just remembered I have a friend that runs a commercial mechanical company, I am checking with him.  I might have him go through the dryer exhaust as well just to make sure it's good.

[mk162]

To dredge this back up.  We finally had this completed over the winter, so we didn't run them at all.  Now that it's warming up we are finally using them.

I had an HVAC guy look at the specs of what is available commercially for the oven and rework it for us.  It came to about $2700 installed for everything.  I am adding insulation to the hoods and the ducts to help more of the hot air get out without radiating the heat back into the shop. 

It has a 1200 cfm fan, hooked to a speed controller.  We run it on low.  Our cure times are exactly the same, so we aren't pulling anything from the oven..or at least very little.  The main ducts are 12" that split to 10" to the hoods themselves.  You can feel a little bit of airflow over your hand if you stick them up inside the ducts.

The most important part though is that it's made an insane difference at the side of the oven.  It's actually comfortable there now.  It was money very well spent.

[Sbrem]

we've always used a sheet metal shop to fabricate what we need.

Steve

[mk162]

I had some built, but the HVAC guy said they were too small.  We took them from 12x12x54 to 18x18x54.  The extra volume helps spread out how the air pulls and pulls some from further down the belt.

The custom roof curb was a thing of beauty though.  It's a shame it's on the roof and not somewhere I can look at it all the time.