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Skutt Envirovent II - is it supposed to be so LOUD?


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Just installed a new envirovent, seems to be working properly but it's really loud.
Like vacuum cleaner loud. A freebie noise measuring app on my phone put it between 76-82 decibels, 
and I can't imagine this thing running for the length of a firing, for me and for neighbors. 

A few questions for the collective:

  • Is noise a known issue for the envirovent II system, or is it possible I have a defective unit? 
  • If it is just the way it is, how do you handle the noise? Do you keep it running for the entire time? Has the noise discouraged you from using it? 

Thanks, all! 

Edited by kristinanoel
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  • kristinanoel changed the title to Skutt Envirovent II - is it supposed to be so LOUD?
24 minutes ago, kristinanoel said:

That sounds normal to me.  It's just a simple squirrel cage blower, so not the most advanced  blower technology. When they go bad the bearings wear out and they make a lot more noise than that. I couldn't hear it in the video, but if you're getting any additional noise from vibrations in the wall, you could put it on the floor on a piece of foam to isolate it more.

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Normal, huh? Shoot, I was afraid of that.

Curious if anyone who has and uses one of these has had complaints from neighbors about noise - it doesn't seem workable in a residential neighborhood with 50 foot wide lots. It's hard to believe they sell these things without a noise rating! Having that thing going for 8+ hours....

I'm considering replacing the fan with a quieter inline fan - anyone done this?
Have recommended products or warnings? 

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yeah, it's much more invasive than I would have thought!  it's already in the unattached garage, so it's as separate as can be expected. Nobody's working in the building, so the benefit was purely for the ware, not people breathing. 

If I can't replace the fan, I probably just won't use it. I was thinking it'd be good for evening out the temperature in the kiln and providing a better oxidation atmosphere, but there's no way I'd ask neighbors to put up with that noise for hours on end, not to mention that I'd never be able to fire early in the morning or late at night. I (stupidly) hadn't considered the noise factor. Not worth it. 

So bottom line -  anyone considering the envirovent, make sure you take the noise into consideration!

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2 hours ago, kristinanoel said:

I'm considering replacing the fan with a quieter inline fan - anyone done this?
Have recommended products or warnings? 

It can be done, but the design MUST limit the temperature of the air going through the fan. Here is a simple design that picks up as much air as the original and also draws air from above the kiln, virtually no noise, same draw from the kiln and the blower runs super cool but a lot of care was taken to dilute the kiln air with room air,, plus a goof proof vent above the kiln which ensures there is plenty of “cooler” dilution air.
Most of these fans purchased run a bit on the “starved” side meaning if allowed to they would pump more air, just the pickup side is rather small so they often run in a starved fashion. As a result, manufactures specify steel  fans that can survive 140 degree air anticipating that folks may or may not install these and set them up particularly well. Starving these fans tends to make them a bit noisier.

We measured and designed something to be equal or better than the original. This is not for everyone as making sure the fan stays cool is essential. Can this be done so virtually no noise is created? The answer would be yes with a good deal of design thought, experience and some goof proof way to ensure folks don’t inadvertently block things off and overheat the fan. This design would work nicely for a pickup above the kiln (hood) with a downdraft metered supplement added to it.

https://youtu.be/etpa2Pc9Hug

 

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Might be possible to attenuate the noise some - a baffle box for the unit itself; isolate the unit from the wall (sounding board) with squishy rubber or foam; isolate the unit from the resonator tube (heh, the metallic hose) with some rubber tape or somewhat; baffle box for the exhaust end - outside. The intake should be tight up against the kiln, hence fairly well baffled on that end, which leaves the unit itself, the hose, and exhaust...

Wrapping the hose might help somewhat as well.

I'd overlooked the ambient intake - a likely source of noise, that.

Edited by Hulk
ambient intake
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8 hours ago, Hulk said:

Might be possible to attenuate the noise some - a baffle box for the unit itself; i

@kristinanoel  Just an FYI - this motor has a separate cooling fan built into it (Notice the slots on the rear of the motor) so if you cover this with a box to reduce the noise you will need to let cooling air in and out of the box and motor else this motor will very likely overheat fairly quickly.

Edited by Bill Kielb
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18 hours ago, Bill Kielb said:

It can be done, but the design MUST limit the temperature of the air going through the fan.

If the existing motor is swapped for a inline fan with similar CFM but the rest of the system is used as-is, no further modifications would be necessary since the mixing is done at the collection cup under the kiln.

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6 hours ago, kristinanoel said:

Thanks for all of the great advice - my new plan is to find a suitable inline fan motor to swap out, keeping the rest of the apparatus, the collection cup and hose, and see if that is a better solution. 

If you swap for an in-line fan and use the same kiln pickup, the existing mixing box is usually very undersized to let the proper amount of air through the fan. In-line fans are self cooled, you could try an in-line fan rated for dryer booster service to deal with the starved condition, but these are often rated in the 200 Cfm rangę, so nosie and overkill become your issues. This type of fan can be enclosed for noise, but it must cool itself with enough exhaust air. 

When we actually MEASURE the air that can make it through the commercial units its  generally on the order of 1/10 th the fan rating. No surprise since the pickup area is usually  a fraction of the 4” diameter it would need for full flow.. The mixing manifolds on the commercial units are generally too small and therefore do not allow much  room air to enter. This is fine with an externally cooled motor, but an in-line fan needs this to cool itself. Not an issue as long as you pay attention to temperature of the units and folks often find a goof proof easy way to let more room air in. I have seen folks simply install a 4” open T fitting above the kiln  and still get enough suction at the kiln connection to perform as originally designed.

Edited by Bill Kielb
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Am feelin' compelled to reiterate...

Material the motor/fan assembly is connected to can act as a sounding board.

The ducts can act as resonator tubes.

A large portion of the noise may be emanating from the intakes and exhaust.

My kiln vent is fairly quiet, however, the secondary system (overhead, for heat and any escaping fumes) is rather loud; I have some ideas for reducing the noise.

Any road, please do post an update with your findings/results OP!

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6 hours ago, Bill Kielb said:

If you swap for an in-line fan and use the same kiln pickup, the existing mixing box is usually very undersized to let the proper amount of air through the fan.

The can handle two kilns, so yes on one kiln they are starved. They work, though. Thousands of these out there functioning as intended...

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38 minutes ago, neilestrick said:

The can handle two kilns, so yes on one kiln they are starved. They work, though. Thousands of these out there functioning as intended...

Yeah, measured on a two kiln setup, they end up starved. They work, just not able to move near their design air because of the high losses on the suction side. This is fine for their design, since all the production motors are externally cooled just generally not good for a fan that cools itself such as an in-line fan.  If you hook up a 100 cfm in-line fan, it will not discharge 100 cfm drawing through a few 1” holes. The dual Orton setup was measured at 14 cfm total discharge on a  100 + cfm rated fan. The inlet size was 3 - 1” holes on each kiln so six 1” holes or about 4.5 square inches. A 4” diameter pipe is about 12.5 square inches so no surprise, a big restriction.  In their defense, they don’t need anymore since airflow through the kiln is way less given a 1/4” diameter hole or two into the kiln.

They are starved because of the inlet restriction, which is fine for their use and design. Not necessarily for a quiet in-line fan that gets cooling by the air through it though.

Edited by Bill Kielb
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One more question - I want to fire before I'll be able to try and upgrade my setup, but no way I'm running that thing all day!

But...now I've got these holes drilled into my kiln lid and floor.
Would you take any steps to mitigate that, like putting a kiln shelf or stilts over the holes? Or just leave it be?

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9 minutes ago, kristinanoel said:

One more question - I want to fire before I'll be able to try and upgrade my setup, but no way I'm running that thing all day!

But...now I've got these holes drilled into my kiln lid and floor.
Would you take any steps to mitigate that, like putting a kiln shelf or stilts over the holes? Or just leave it be?

The holes won't affect the firing.

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I have a shelf that is broken in half on one inch stilts above the holes in my kiln.     The outlet vent is about 50 feet away from one of my neighbors.   No complaints but they have a house full of kids so they probably don't even hear it.   I live at the edge of my town,  fields every where,   at night I can here the  the semi's on the highway that is a half of mile away.   Tanker airplanes warming up  from the airbase that is five miles from where I live.  Try wearing some earplugs  when you work in the studio while firing.   I have had my envirovent for twelve years and barely notice it anymore,  it has turned into white noise.     Denice

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On 5/16/2021 at 10:26 AM, Hulk said:

The intake should be tight up against the kiln, hence fairly well baffled on that end, which leaves the unit itself, the hose, and exhaust...

There's definitely something to this. The semi-rigid ducting acts a bit like a sounding board. I use rubber duct, Blo-R-Vac Flexible Duct Hose from McMaster-Carr,  and it's definitely quieter than the metal stuff. It's rated to 250F and doesn't corrode. I run both of my kiln vent during classes and they aren't overbearing. You can hear them, but they're no worse than the fans we run to keep us cool during the summer.

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