Range hood experiences

[RearAdmiral]

My kitchen re-model has been complete for a bit. We have been slowly adding the finishing touches such as a chandelier, island lights, bar height stools. Something has been bugging me about my range hood though, it barely seems to move air. I am fairly convinced it is a problem with installation and not the unit itself.

Hood here: http://www.kitchenhoods.ca/shop/ran...-range-hood-with-mechanical-switches-715.html

It is a 600cfm fan so it should move some solid air. I am not expecting it to grab every bit of smoke, but most of the smoke / steam is not going up the hood. I think either a crappy damper was installed and/or it isn't opening right. I also think more than 1 damper was installed, which according to the installation materials shouldn't be done, but I feel like having the wimpy damper they include plus a roof damper shouldn't be a big problem vs a damper not functioning correctly. I also did test with a window open, but my house isn't that tight regardless. On the highest speed I have to practically have my hand 1-2 inches from the bottom of the hood to detect any air movement.

I believe the installation ducting is all good. 6" solid ducting with I believe 2 90 degree elbows. This should all work out with the math they give you for duct length.

I think I'm going to have to rip things apart a bit and see what's up with the dampers. Meanwhile I am curious about other folks experiences with range hoods, preferably with similarly sized fans / units(600cfm). I wish I could see a video of steaming / smoking cookware so I can know what sort of suckage to expect IRL.

 

[RearAdmiral]

Well for starters I was looking at the roof cap that was installed. I didn't measure it but there is no way the opening matches the area of a 6" duct(which is 28 and change inches). I don't think it was more than a 8x2 opening. Which is obviously way less than what is required / recommended by the manufacturer tips.

 

[zinfamous]

what is the distance from the surface of the range?

If your roof vent is less than the diameter of the ducting, then that will cause real flow issues, I think. As long as you have straight runs and few elbows, you shouldn't have problems otherwise. You probably have have an internal damper, right? Are you including that, with the external roof damper as the 2 dampers you are referring to? That should be normal. You shouldn't really feel much air being sucked up if you keep your hand near the filters, that is normal.

I recently installed a new hood myself, there is a thread here that I keep meaning to update with pics. It was a bit of a hassle and didn't exactly go perfectly, but it works well enough and I feel as though I learned a bit. Mine has 8 inch ducting and because I wanted to utilize an outlet that was already installed in the wall, the entire venting from the hood to the outside consists of 2 elbows attached to each other and out, around 30-45 degrees each, lol. So, far from perfect, not having a single straight run, but it is a short run, at least. my hood has 4 settings with the max at 1k CFM, and those 2 highest settings will occasionally cause some loud knocking inside the hood, which I think is the internal damper getting knocked back by the force of air getting trapped just as it exits, because there isn't really a straight run to move it efficiently. ...it is also rather susceptible the external wind conditions, heh.

But, it works. OK, it is still a disaster with butter burning in my cast iron pan, but I feel there is no real remedy for this problem. Before, I had a useless under-microwave blow-back everything in your face unit, and cabinets and walls and windows just perpetually coated with grease. I'd start cooking, and the entire house reeked. Now, smoke and odors can't be detected outside of the kitchen area. So, it's really working.

 

[RearAdmiral]

what is the distance from the surface of the range?

If your roof vent is less than the diameter of the ducting, then that will cause real flow issues, I think. As long as you have straight runs and few elbows, you shouldn't have problems otherwise. You probably have have an internal damper, right? Are you including that, with the external roof damper as the 2 dampers you are referring to? That should be normal. You shouldn't really feel much air being sucked up if you keep your hand near the filters, that is normal.

I recently installed a new hood myself, there is a thread here that I keep meaning to update with pics. It was a bit of a hassle and didn't exactly go perfectly, but it works well enough and I feel as though I learned a bit. Mine has 8 inch ducting and because I wanted to utilize an outlet that was already installed in the wall, the entire venting from the hood to the outside consists of 2 elbows attached to each other and out, around 30-45 degrees each, lol. So, far from perfect, not having a single straight run, but it is a short run, at least. my hood has 4 settings with the max at 1k CFM, and those 2 highest settings will occasionally cause some loud knocking inside the hood, which I think is the internal damper getting knocked back by the force of air getting trapped just as it exits, because there isn't really a straight run to move it efficiently. ...it is also rather susceptible the external wind conditions, heh.

But, it works. OK, it is still a disaster with butter burning in my cast iron pan, but I feel there is no real remedy for this problem. Before, I had a useless under-microwave blow-back everything in your face unit, and cabinets and walls and windows just perpetually coated with grease. I'd start cooking, and the entire house reeked. Now, smoke and odors can't be detected outside of the kitchen area. So, it's really working.

I find it pretty interested that even with your 1k CFM hood you still don't feel the air moving too much. I believe I am including the damper on the roof cap and the damper inside the hood itself, the one the manufacturer includes. The distance from the surface of the range is within spec, but I don't know off the top of my head. I just know it is about where it should be. Maybe I'll get out and measure the roof cap when I get home since it'll be nice out.

 

[zinfamous]

I find it pretty interested that even with your 1k CFM hood you still don't feel the air moving too much. I believe I am including the damper on the roof cap and the damper inside the hood itself, the one the manufacturer includes. The distance from the surface of the range is within spec, but I don't know off the top of my head. I just know it is about where it should be. Maybe I'll get out and measure the roof cap when I get home since it'll be nice out.

Well, that air being pulled into the fan is being pulled into ~29" x ~24" surface area. You're not going to feel a lot of force across that space, especially considering the business end of the fan is generating the force on the other side. It really doesn't need to be that strong over your range, anyway, because smoke and steam will naturally rise into that space and it takes very little pressure to pull it into that pocket of air that directs it into the fan and through your ducting.

....now the story on the other side of your system is vastly different. Because my duct exits just above and outside the same wall, I was able to hang out on the ladder to mess around with the wall cap and do whatever adjustments were needed while it was on, and to diagnose some problems. On the lowest setting--300 cfm, I think--my fan is nearly silent and you certainly can't feel any air movement under the baffles, but it effectively draws out steam from a large pot of boiling water. But put your face next to the 8" exit vent cap that I have and it is almost enough to blow you off the ladder if it surprises you. Forcing that air into a vastly smaller space is what generates the necessary pressure to get it out of your kitchen efficiently.

The bottom of my hood sits at about 28" from the surface of the range, so within the 27-~33" recommended spec. I wanted it an inch or two higher, but that really is the only place that I could mount it, because of the very short run that I have and because it allowed me to perfectly fit my chimney soffet into the existing ceiling soffet with little trouble (OK, well that ended up not being true, as it seems that shaving off an ~1/8 inch of wood to make that fit, was more trouble than I expected--I just wasn't using the proper tools at first )

That's a good looking hood, by the way. I was originally looking for that type of chimney design, but couldn't find one with the angled baffle filters like I wanted, and the standard 30" dimension like yours. I actually only need ~600cfm anyway, so the higher speeds I got with mine were really just a bonus that I don't necessarily need most of the time, but were only available on the model that fit my needs, and still came under planned budget. And in retrospect, that chimney never would have worked for because only when I started putting things together, did I realize that the outlet vent in the wall was about a foot off from the exit vent on the hood, and the run was much, much shorter than I imagined in my head.

This is mine, and I used a single full-width SS soffet to cover the run into the ceiling soffet and through the wall.

 

[RearAdmiral]

Well, that air being pulled into the fan is being pulled into ~29" x ~24" surface area. You're not going to feel a lot of force across that space, especially considering the business end of the fan is generating the force on the other side. It really doesn't need to be that strong over your range, anyway, because smoke and steam will naturally rise into that space and it takes very little pressure to pull it into that pocket of air that directs it into the fan and through your ducting.

....now the story on the other side of your system is vastly different. Because my duct exits just above and outside the same wall, I was able to hang out on the ladder to mess around with the wall cap and do whatever adjustments were needed while it was on, and to diagnose some problems. On the lowest setting--300 cfm, I think--my fan is nearly silent and you certainly can't feel any air movement under the baffles, but it effectively draws out steam from a large pot of boiling water. But put your face next to the 8" exit vent cap that I have and it is almost enough to blow you off the ladder if it surprises you. Forcing that air into a vastly smaller space is what generates the necessary pressure to get it out of your kitchen efficiently.

The bottom of my hood sits at about 28" from the surface of the range, so within the 27-~33" recommended spec. I wanted it an inch or two higher, but that really is the only place that I could mount it, because of the very short run that I have and because it allowed me to perfectly fit my chimney soffet into the existing ceiling soffet with little trouble (OK, well that ended up not being true, as it seems that shaving off an ~1/8 inch of wood to make that fit, was more trouble than I expected--I just wasn't using the proper tools at first )

That's a good looking hood, by the way. I was originally looking for that type of chimney design, but couldn't find one with the angled baffle filters like I wanted, and the standard 30" dimension like yours. I actually only need ~600cfm anyway, so the higher speeds I got with mine were really just a bonus that I don't necessarily need most of the time, but were only available on the model that fit my needs, and still came under planned budget. And in retrospect, that chimney never would have worked for because only when I started putting things together, did I realize that the outlet vent in the wall was about a foot off from the exit vent on the hood, and the run was much, much shorter than I imagined in my head.

This is mine, and I used a single full-width SS soffet to cover the run into the ceiling soffet and through the wall.

If the steam / smoke rises into the hood it is captured fairly effectively. It seems that a lot of it can escape forward of the hood though. I went onto the roof and had my wife turn on the fan and it indeed blows out a lot of air as you mentioned. So the dampers aren't stuck and everything is working I think but the cap may still be a little small. I can't find any identifying markings / models #s on it but the closest example I can find may be for a 500cfm model. So a fair bit underrated if that is true.

Perhaps if you have time you can show a pot of boiling water on a front burner with the fan on? I'll have to do the same. Though last night I made some burgers in a cast iron pan and the hood seemed to capture most of it.

 

[zinfamous]

I'll see what I can do. That does involve setting up some online hosting account thingy, which I have been loathe to do for various reasons (laziness, mostly ) ever since bbddzz went down.

But it does sound like your remote blower, if really rated at 500cfm, is too weak. I think they need to be a good bit more powerful than internal blowers, especially if placed at a fair distance from the hood. In my mind, with modern gas ranges, it seems that the minimum high-speed rating you would want is probably 600 cfm for an internal blower. I forget the exact calculation, but the recommendation is to total up your maximum BTU output (or "heat energy?" I have no idea how this is calculated with non-gas ranges), then you multiply by some 0.1 factor, or something, to get your blower cfm requirement (which is an estimate for maximum need, because you are assuming all burners on at high heat at once--which probably is a rare scenario, anyway).

For me, it's 54k BTU, adding up the max BTU of all of my burners which, I think, translates to 540cfm or thereabout for the blower. It's a factor of 10, obviously. My range isn't all that fancy. It's a GE that I got on sale at Lowe's last year for about $450.

 

[RearAdmiral]

You can make me a private youtube vid The fan doesn't have a remote blower though, it is a 600cfm blower in the hood. I just meant the roof cap may only be rated for venting 500cfm, my mistake for the confusion. My range is only electric even, it puts out some decent heat I think but it is nothing crazy. The hood should be well within spec to handle it all.

 

[zinfamous]

Ah, I see. I'd wager it is the stepdown in duct size that you mentioned, and is trapping exhaust air at that point and possibly causing some blowback out of the hood. It's weird that it can't handle steam that effectively and allows it to float over and away from the hood like that.

If I remember (which I almost never due), I'll try to set up something this evening, because I wanted to update my other thread with pics anyway. --my own hood project isn't technically finished, either, but it's mostly cosmetic and whether or not I just accept the unpredictable functioning of the max blower speed.

 

[RearAdmiral]

Ah, I see. I'd wager it is the stepdown in duct size that you mentioned, and is trapping exhaust air at that point and possibly causing some blowback out of the hood. It's weird that it can't handle steam that effectively and allows it to float over and away from the hood like that.

If I remember (which I almost never due), I'll try to set up something this evening, because I wanted to update my other thread with pics anyway. --my own hood project isn't technically finished, either, but it's mostly cosmetic and whether or not I just accept the unpredictable functioning of the max blower speed.

I'll try to get some measurements and a vid tonight.

 

[RearAdmiral]

Video from "turbo boil" burner

Video from other front burner

 

[zinfamous]

hmm, seems more effective on the 2nd burner, strangely.

But my first thought is that is LOUD for 600cfm. like, really freaking LOUD. I do believe that is one of the issues when you step down the ducting diameter. Hmm, I guess I should try and make my own video....

 

[zinfamous]

Whoo hoo! I uploaded a video!

So I mostly left it running at 600cfm as a comparison to what you have going. Mine has 4 settings, and 600 is the second to lowest, of "L" button that I will push on and off. One difference that I notice is that the steam generally defaults to going into my hood anyway, only a little bit trickles off to the left side in a section of the video, with the blower off. The one time so far that I tossed butter in a scorching hot cast iron pan, over a chop, the smoke was going everywhere, all over that side on the same burner, and at full, 1k cfm. nothing could be done.

at 2min, I turn it to max, 1k CFM. You'll notice that goddamn knocking noise, which I think is the internal damper knocking back and forth? This is what I tell myself. In an earlier video that I did not upload, the knocking didn't happen at 1k CFM. It is quite random, but also seems to be determined by how long air has been blasting through the ducts. The noises, like the floor creaking (which it does) seem louder to me in this video than they are, so the fan sounds a bit louder than it does in the room (to me, anyway), but it still sounds a lot quieter than yours? Minus the knocking, I think my 1k CFM setting is about the same as your max (600?) setting.

...the kitchen is a WIP. no backplash yet, as I'm ordering some accent tiles from some fancy tile place in Canada, I think, and it's right right there at the range because I need to move the horribly deep fridge to the other side of the room. Need to tile up the walls, replace the counters, rip up the godawful vinyl tile on the floor that is covering NAKED OAK. ...why the fuck anyone did that is beyond me. sigh....

 

[RearAdmiral]

Yes I think it is more effective on the right burner. The centrifugal fan seems to pull air from the right side so that makes sense. Another issue I see is that compared to yours, I have several inches of control panel before the baffles start so the baffles are basically at the very rear of the front burners.

I do not think my ducting is reduced, only a small roof cap if anything, unless it is reduced as it attaches to the roof cap.

It's not quite as loud as it seems in the vid. Pretty easy to have a normal conversation. Maybe it is just the best it can do with that panel in the way.

 

[zinfamous]

Is the roof cap properly protected from backflow, with the shield angled down and along the roof line? It's just very weird to me that with the blower off, the steam seems to be going everywhere it can away from your baffles.

and yeah, I was thinking that the audio is just louder in the videos compared to real life overall. ...something to do with being "older" and not hearing as well these days.

 

[RearAdmiral]

Is the roof cap properly protected from backflow, with the shield angled down and along the roof line? It's just very weird to me that with the blower off, the steam seems to be going everywhere it can away from your baffles.

and yeah, I was thinking that the audio is just louder in the videos compared to real life overall. ...something to do with being "older" and not hearing as well these days.

Yea the shield is angled as I think you mean, meaning the flap follows the roof downward. I don't know about it being protected from backflow otherwise. I'm trying to get in touch with my contractor and I'm going to shoot an email off to the hood company to get their input.