Kitchen venting overkill?

[blown383]

I'm currently remodeling my kitchen and trying to figure out the ducting size and fan size I should be using.

The kitchen is 10x10 with 9 foot high ceilings. We have a 36" Wolf range that puts out about 114,000 BTUs. I plan on using the charbroiler once in a while. The Viking chimney range hood I have has a 10" opening that will go straight up into the ceiling and through the roof.

I estimate the duct run will be will about 15 feet. I found a good deal locally on 2 different Fantech inline fans. a 10" that pushes 1,200cfm or a 12" that does 2,000 cfm.

My question should I go with the 10" fan and 10" ducting all the way through?

Or use the 12" fan on the 10" ducting with 2 reducers.

What's the most efficient setup?

-B

 

[bored350]

Will you be able to varry the fan speed? I'm not an HVAC guy but I have cooked and consequently burned my share of food in my lifetime. On those rare oops moments, I can't recall anyone saying "wow, I have too much exhaust fan, the smoke and smell cleared out too quickly". This is a case where I can't see bigger not being better if ducted properly.

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[acer66]

perfect timing since I am also trying to figure that out too and as long as the specs say that you can run the 12” on a 10” duct I would go with the bigger one.

 

[Firebrick43]

The problem with fans that big is make up air. You can have the biggest fan on earth but it will only move as much as its supplied.

 

[blown383]

LOL! You have a very good point! the fan's speed will be controlled via a knob on the range hood.

-B

Will you be able to varry the fan speed? I'm not an HVAC guy but I have cooked and consequently burned my share of food in my lifetime. On those rare oops moments, I can't recall anyone saying "wow, I have too much exhaust fan, the smoke and smell cleared out too quickly". This is a case where I can't see bigger not being better if ducted properly.

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[blown383]

I can simply open a window and that'll solve the problem pretty quickly.

-B

The problem with fans that big is make up air. You can have the biggest fan on earth but it will only move as much as its supplied.

 

[acer66]

The problem with fans that big is make up air. You can have the biggest fan on earth but it will only move as much as its supplied.

Good point, I think it was in FHB where they said they had a hood fan drag ashes out of the fire place because the chimney was where the make up air was coming from.

 

[Firebrick43]

Good point, I think it was in FHB where they said they had a hood fan drag ashes out of the fire place because the chimney was where the make up air was coming from.

Absolutely. Could even air thru water traps in the drains bringing sewer smells or or thru water heater / furnace chimneys causing carbon monoxide issues.

A window is a solution but are you going to use it if it's cold out? Will your wife open it when your not home or some one who buys the house after you?? It really needs to be automatic for safety of everyone.

 

[SARG]

Just to mention an experience I had in the past ..... if you run the piping through the unheated (single story house) space above your ceiling and you live where it gets chilly ......... and the vent pipe is metal ..... you will create a source of condensation.
I thought I had a roof leak it was so significant.

 

[yeldogt]

What does Wolf suggest? When you say "charboiler" are you speaking of a grill on top or the flame broiler in the oven?

Also -- do they recommend the chimney style with that set up ? Typically a range is against a wall and the chimney for open cooktop?

1200cfm -- is a lot -- it's typically 10" and will do a larger than 36" stove. The key is the hood -- you need a hood that will capture the full range -- especially if it has a shelf on the wall behind the range.

I have three homes -- two with 48" ranges (Viking and DCS) the third with a 60" Lacanche -- the DCS has a grill ... it has a matching DCS hood that's a bit bigger to make sure it captures the smoke. While you need enough power -- the hood design is equally important.

All of mine have 1200 CFM blowers --- Fantech are great (I use them all the time for bath and makeup air) ,... but not all are rated for stove hoods ... and you must be able to access them. Also -- if it's inspected ... make up air is required.

If it's got the grill -- you will need the 1200cfm. 2000 is going to need a huge intake ... and a huge exhaust vent on the roof.

 

[reader2580]

I had an HVAC company put in an exhaust line for my range hood. They put in a 10" line in the space between the top of my wall cabinets and the ceiling. They insulated the outside of the metal duct and ran the duct out the wall instead of the roof. They prefer not to go out the roof as it just adds another potential leak point and I agree.

I had to come up with a way to cover the previously open section between the wall cabinets and the ceiling. What I did makes it look like it was always enclosed.

 

[Jim greengo]

I always just use the charcoal filters in range hoods myself,I hate making extra holes.
More places for bugs and other stuff to get in through.

 

[TurnipTruck]

I have one of the 52” GE Monogram hoods good for 1200 cfm, and cannot imagine ever needing that much flow. Lowest speed is too much. The hood depressured the house more than the blower door when we got the house energy rated. Do not go for the 2000cfm.
I think the in-line fan you mentioned is not rated for kitchen use, only bathrooms.

 

[blown383]

Here's the fan and it's okay for exhaust hood useage.

http://www.fantech.net/products/fan...-with-ac-motors/fkd/fkd-12-xl-mixed-flow-fan/

I have one of the 52” GE Monogram hoods good for 1200 cfm, and cannot imagine ever needing that much flow. Lowest speed is too much. The hood depressured the house more than the blower door when we got the house energy rated. Do not go for the 2000cfm.
I think the in-line fan you mentioned is not rated for kitchen use, only bathrooms.

 

[blown383]

Wow...I learn something new every day! I didn't think it was possible for the fan to pull sewage fumes past the p-traps. If the windows are closed the only other area that's open for ventilation is the gas fed chimney.

The water heater is in the garage and vented through the roof with double doors separating the living room, so I don't see a carbon monoxide issue in that area.

The house didn't have a vent hood and I've been cooking indoors with the windows closed for the last 10 years with no issues. LOL!

-B

Absolutely. Could even air thru water traps in the drains bringing sewer smells or or thru water heater / furnace chimneys causing carbon monoxide issues.

A window is a solution but are you going to use it if it's cold out? Will your wife open it when your not home or some one who buys the house after you?? It really needs to be automatic for safety of everyone.

 

[blown383]

Wolf suggests a 36" hood with a minimum of 900cfm and 10" ducting. So maybe the 1,200 cfm with a 300cfm buffer is sufficient?

-B

What does Wolf suggest? When you say "charboiler" are you speaking of a grill on top or the flame broiler in the oven?

Also -- do they recommend the chimney style with that set up ? Typically a range is against a wall and the chimney for open cooktop?

1200cfm -- is a lot -- it's typically 10" and will do a larger than 36" stove. The key is the hood -- you need a hood that will capture the full range -- especially if it has a shelf on the wall behind the range.

I have three homes -- two with 48" ranges (Viking and DCS) the third with a 60" Lacanche -- the DCS has a grill ... it has a matching DCS hood that's a bit bigger to make sure it captures the smoke. While you need enough power -- the hood design is equally important.

All of mine have 1200 CFM blowers --- Fantech are great (I use them all the time for bath and makeup air) ,... but not all are rated for stove hoods ... and you must be able to access them. Also -- if it's inspected ... make up air is required.

If it's got the grill -- you will need the 1200cfm. 2000 is going to need a huge intake ... and a huge exhaust vent on the roof.

 

[yeldogt]

Again -- does it have a grill on top? not a griddle ... a grill? for steaks etc.

The grill trumps everything -- you need 1200cfm for the gas grill. Electric -- like a Jennair I think is 900. I can't remember -- but my memory is it's 8" not 6" (had one in a house a while back).

If it's only burners on top -- 36" can be six or five -- you don't need as much. Also -- you have to match the hood to the output. It sounds like the hood can take 1200cfm since it's got the 10" opening. You can't try and pull 2000cfm though a 1200 hood -- silly.

Again -- I have done many of these ..make sure the hood design is best. The typical type -- with large open area work best ..... some of the shallow types just can't capture the smoke.

 

[larry4406]

New construction guy here.

We provide a makeup air system whenever a hood exceeds 400 cfm. Power from the hood energizes a 24VAC transformer which then opens a damper in a 6” line which comes from an exterior wall cap with screen (no flapper) which then connects to a filter grille in the kitchen ceiling. We insulate this duct.

Our inspectors want this inlet within 15’ of the appliance being served.

 

[blown383]

Yes it has a grill in the middle. This is the range hood I have: https://www.vikingrange.com/consume...ds/36--wide-18--high-chimney-wall-hood---vcwh

Thanks for clearing things up! 10" inline motor and 10" ducting it is!

-B

Again -- does it have a grill on top? not a griddle ... a grill? for steaks etc.

The grill trumps everything -- you need 1200cfm for the gas grill. Electric -- like a Jennair I think is 900. I can't remember -- but my memory is it's 8" not 6" (had one in a house a while back).

If it's only burners on top -- 36" can be six or five -- you don't need as much. Also -- you have to match the hood to the output. It sounds like the hood can take 1200cfm since it's got the 10" opening. You can't try and pull 2000cfm though a 1200 hood -- silly.

Again -- I have done many of these ..make sure the hood design is best. The typical type -- with large open area work best ..... some of the shallow types just can't capture the smoke.

 

[MikeinNorthWales]

Please don't overlook the importance of make-up air, as noted by others. If your house is tight, the fan will pull air from SOMEWHERE. It must. If this is reno or construction, now is the time. It isn't just an inspection requirement. It's physics. You won't get the performance from the fan without proper make-up air.

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[danski0224]

New construction guy here.

We provide a makeup air system whenever a hood exceeds 400 cfm. Power from the hood energizes a 24VAC transformer which then opens a damper in a 6” line which comes from an exterior wall cap with screen (no flapper) which then connects to a filter grille in the kitchen ceiling. We insulate this duct.

Our inspectors want this inlet within 15’ of the appliance being served.

Pretty sure there are CFM limits to non-powered makeup air. For some reason, 300 CFM sticks in my mind, but probably wrong.

In any event, a 6" hole in the wall isn't going to relieve much, probably less than 100 CFM.

A 1200 CFM exhaust fan will need a powered intake fan, and it should supply a little more so the kitchen area is under positive pressure. Ideally, the hood will have a connection for makeup and exhaust air.

 

[blown383]

Thank you for bringing this up. How far from the range should the outlet of the makeup air system be?

-B

Please don't overlook the importance of make-up air, as noted by others. If your house is tight, the fan will pull air from SOMEWHERE. It must. If this is reno or construction, now is the time. It isn't just an inspection requirement. It's physics. You won't get the performance from the fan without proper make-up air.

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[larry4406]

Thank you for bringing this up. How far from the range should the outlet of the makeup air system be?

-B

Not sure what Code requires but the County I was building in (Montgomery County MD) required that the make up air grille be within 15’ of the appliance being served.

Thus we had filter grilles in the kitchen ceiling with the filter pointed towards the interior of the home in direction of flow.

 

[Radix2]

One other thing - check the electrical specs on the hood fan controls to make sure they can handle the current required by the fan you choose.

 

[yeldogt]

The make-up air requirement is a moving target ... if you notice it's not mentioned in any of the literature for the hoods.

I pipe mine (make up) through the dehumidifier system I always install -- two dump into the HVAC system -- the other is a split into the house with a filter and the HVAC.

I use a sail switch that designed for a hood -- can take any build up. It also does not switch on the damper immediately. I use an 8" damper to an 8" vent that I also use for the fresh air system. I rarely have the unit on high -- so the times that it's really pulling I crack a window. The problem with having an open vent in the kitchen is there is no way to temper the incoming air -- it's very cold in the winter around me. The heated units are 10,000 watts.

 

[blown383]

Thank you for the reminder! The hood's panel is good for 15 amps, the inline fan pulls 4.7 amps at full tilt so I think we're good. The strangest thing is that the power outlet for the hood where the fan plugs in has no ground. It's just a 2 prong outlet. So I figure if I find a cord that's 2 prong and good for 15 amps I should be good.

-B

One other thing - check the electrical specs on the hood fan controls to make sure they can handle the current required by the fan you choose.

 

[u3b3rg33k]

There's basically two ways to do kitchen exhaust - lots of "CFM", or lots of CFM (and make up air to provide that CFM).

but if your goal is to keep fumes and noise down, get the biggest, deepest hood you can get. CFM is secondary to capture efficiency, as a hood that doesn't come out to the front of the range will require massively more airflow to effectively capture smoke and gas fumes than a hood that is actually over the area you're cooking in.

I have a hood rated for 400cfm that extends about halfway out over my range, and it's hooked up to a 6" duct, that exits out a 4" dryer style vent. it's horribly inadequate. and yet, it's so much better than nothing I can't tell you how happy I am to have it there and functional, even while I hate everything about its capture efficiency (I like to cook on hot cast iron on the front burners).

and yes, I leave a small basement window open just enough to allow some air in for my natural draft appliances and my range hood. I can still tell that opening a window in another room makes a HUGE difference in performance.

 

[yeldogt]

Thank you for the reminder! The hood's panel is good for 15 amps, the inline fan pulls 4.7 amps at full tilt so I think we're good. The strangest thing is that the power outlet for the hood where the fan plugs in has no ground. It's just a 2 prong outlet. So I figure if I find a cord that's 2 prong and good for 15 amps I should be good.

-B

Manufacturers typically don't make the electrical -- except the established hood makers like Newtone/ Broan -- and even they source out the motors.

The controls on the hood are designed for a particular set up ...make sure that hood is not set up for the fan assembly to be siting on top ... that's typically the case with a simple plug set up. You have to make sure the speed control is compatible with the motor so it will adjust the speed.

Both the DCS and the Viking I have use Broan duel squirrel cage blowers -- I don't know what my lacanche has inside the Best brand hood insert.

 

[Falcon67]

FWIW - echo on makeup air. We have a max 400 CFM hood and I crack the window over the sink anyway. We tightened up the house a couple of years back and now running the vent hood and both bath fans makes for a home brew blower door test LOL.

 

[hausfxr]

It sounds like you've settled on the in-line fan, but if budget is not the primary issue, I recommend you get a roof or sidewall mount unit. The reason is that you can get a variable speed unit designed specifically for stoves, and you also will be putting the fan noise as far away from the stove as possible. If you do want 900 CFM, that's a lot of air (=energy) exhaust and that amount of air will be noisier over your grill - even remote fans create air friction noise.

On the makeup air, I'd recommend you get a powered damper and consider putting the grill behind your stove. I've done this in my own home, and it seems to work well with no noticeable cold air drafts.