Kitchen Makeup Air - Adding A Powered Makeup Air Fan to Passive System

[u3b3rg33k]

Is it safe to assume that you have good capture efficiency/you're happy with the hood when you have a door/window open?

Agreed - however the 8" passive duct is already installed. Clearly I was given bad advise but it is what it is.

Regarding the shunt concept, the blower is remote and mounted on the roof exterior side. Thus the 10" duct and hood is under vacuum. The shunt would pull air from the attic space just like a roof mounted powered attic vent. The hood itself has a back draft damper at the hood itself. I assume you are thinking the ductwork has caught fire and the roof remote fan is not vacuuming the duct and therefore the flames from the duct fire go into the attic? To remedy this, the shunt could easily be ducted to a roof jack to blend in external air vs taking air from the attic space.

[/QUOTE]
you can't connect the occupied space to the attic, it's "naughty". if you did want to do it you'd need a fire damper, probably one rated for hood use, which would be $$$. most of code around things is keeping the fire contained. as soon as you put in what I think you're talking about, you've functionally defeated all the fire ratings of your walls, ceilings, etc.

that aside, what is the goal again of the attic duct? to reduce airflow from the hood? why not just slow the fan down?

The ship has sailed, its already in place, the kitchen is done, and we are not demoing the new kitchen to install an outdoor kitchen. Hey, I figured out if we never use it, it works great!

Rule of thumb on sizing hoods for gas units:
"To calculate the CFM for a gas stove, add the BTU ratings for all burners. Divide your total by 100 to figure the CFM you need." So in our case, all burners add to 128,000 btu so 1280 cfm would be the cfm recommended per this rule of thumb.

So we are in the right range. I guess we could have decided to cook on Sterno instead?

lol, not actually suggesting you use sterno. besides, you'd still need ventilation adequate for 130k BTU of sterno.

From the Wolf Ventilation Guide:

• CFM suggestions are based on the cooking appliance
  output.
• The chart below provides CFM suggestions
  specific to the Wolf cooking appliance and ventilation
  system used. To maximize airflow and performance,
  specify a blower to match or exceed the CFM listed.
• Additional CFM may be required for long duct runs (which we have)
• For the DF48850 dual fuel range and Pro Hood they recommend 1100 cfm.
• However, the 1100 cfm blower option is only for an in-line unit, not roof top. So no good.
• The remote roof top options are 900 (too small per Wolf), 1200, and 1500 cfm. Due to the long duct run, we chose the larger 1500 cfm.

I am still annoyed that the Wolf hood controller only reduces voltage to around 70V. Thus the minimum fan speed is 70/120 (58%).

So 1500 cfm *.58 = 870 cfm is the min which is still quite a bit. I would have thought the turn down would be broader range but no dice. Would have been nice for them to include the cfm range in their specs (min to max) vs just the max.

Still looking for clever, helpful, and minimally intrusive remediation options. I am following Denwood's science project.

[/quote]
here's nothing wrong with putting in a damper to further restrict airflow. you won't hurt the fan, assuming it's not cooled by exhaust airflow (most non-remote/built-in fans are cooled by the hot exhaust from the stove). power draw goes DOWN when you restrict centrifugal fan airflow (not as much as slowing it down, but substantially).

assuming you wanted remote control of a damper, grab a 10" duct damper, and put a Honeywell DCA on it. something like a MS7503A2030. 24VAC/DC powered, and 0/2-10V or 4-20mA control. configure it for fail open. then you can throttle the fan down as low as you'd like.

that won't help your 100% flow situation, but it'll reduce your airflow to whatever you need it to be for single burner operation.


another thing to figure out is how much air you're actually moving at full fan speed. might need to borrow a flow hood to measure that. then you can get an idea of what you need for a makeup fan, instead of shooting in the dark and missing. there IS a fan that will work with your 8" passive duct/hole without redoing the siding, assuming you are up for spending $ and have room for the fan itself.

 

[dave*99]

My guess is you already have enough leakage

The whole thread started because :

The range hood passive makeup air system is not flowing sufficient air. We can smell that the fireplace is back drafting when the hood is running. Also, the spring hinge closure on the garage door will not close the door automatically like normal when the hood is running. Obviously the house is now quite tight from all the renovation work we have done.

 

[u3b3rg33k]

@larry4406 , just came across this so with respect to ramping on the make up air I would use a Hubitat hub (nice way to integrate) and use some automation bits. This is a nice way to jump in to the automation world if that's something you're interested in.

1. Plug your range fan into a current sensing appliance module like this https://aeotec.com/products/aeotec-smart-switch-7/
2. Purchase a fan like the Terrabloom ECM 10" which can be controlled 0-10V and is rated at 1000 CFM using 126 watts (EC fan) : https://terra-bloom.com/products/te...nd-hydroponics-airflow-boosting-1065-cfm-150w
3. Attach a zWave 0-10V dimmer to the fan like this: https://www.fibaro.com/compatibility/qubino-flush-dimmer-0-10v-2/

This is a completely wireless solution that could be programmed however you like based on power detected from the main fan. About $200 in parts including the automation hub. This lets you ramp the make up fan depending on power use by your existing range fan.

I'm doing a slightly simpler application very similar to your case. Power use by our induction cooktop in turn controls the range exhaust fan turning it on and off. Manual control can also be used: https://www.garagejournal.com/forum...nline-ecm-fan-turbocharge-yer-exhaust.491330/

Matt Risinger shot a vid you should watch on kitchen make up air!

and this is a very slick custom solution integrated to the hood:

and a test on the above system:

there's different takes on that style of makeup air. it's often called a "short circuit hood", because the makeup air goes right back out.

I'm a bit disappointed in their smoke test. my little 300CFM hood works great, too, if you don't have the gas on. turn on all the burners (save the one with the smoke grenade on it), and watch things be completely different. burning NG creates a massive updraft, that brings up combustion air and room air with it, and a short-circuit that works with a single smoke grenade can become virtually useless when you've got 100k of updraft, happily bypassing your hood, especially if the hood doesn't extend out past the front of the cooktop.


IIRC ASHRAE says at least 20% of the air needs to not be supplied by the hood intake, which means even if you're doing a short circuit hood like in the video, you need to let some of that supply air hit the room elsewhere. perhaps out up top around the soffit, or whatnot. you need to exchange some room air to keep the air clear.

 

[larry4406]

My guess is you already have enough leakage

No, no we don't.

If we did, we would not be back drafting down the fireplace flue reeking of soot and the spring hinge on the door to the garage would easily close like it automatically does when the hood is not running.

 

[larry4406]

Is it safe to assume that you have good capture efficiency/you're happy with the hood when you have a door/window open?

I would say yes,

"you can't connect the occupied space to the attic, it's "naughty". if you did want to do it you'd need a fire damper, probably one rated for hood use, which would be $$$. most of code around things is keeping the fire contained. as soon as you put in what I think you're talking about, you've functionally defeated all the fire ratings of your walls, ceilings, etc.

that aside, what is the goal again of the attic duct? to reduce airflow from the hood? why not just slow the fan down?"

At minimum, the fan controller drops voltage to 70V from 120V, 58%. So 58% of 1500 cfm = 870 cfm. The only lower flow is OFF. Off has been proven to not work well for venting.

The concept of the shunt was to have the remote roof top blower draw from two sources vs one. One being the kitchen hood and another a bleed. The bleed would be adjustable for tuning. By bleeding air into the duct (which is at vacuum) in a less restrictive manner, it would reduce the draw from the kitchen hood. By reducing the draw from the kitchen hood, it would pull less on the house, PERHAPS reducing it to a level that was closer to house leakage while still providing adequate cooking fume exhaustion while not back drafting the wood stove. The bleed air could come from a roof jack pulling external air (vs the attic as has been discussed) to address the duct fire concern.

"there's nothing wrong with putting in a damper to further restrict airflow. you won't hurt the fan, assuming it's not cooled by exhaust airflow (most non-remote/built-in fans are cooled by the hot exhaust from the stove). power draw goes DOWN when you restrict centrifugal fan airflow (not as much as slowing it down, but substantially)."

Here is the remote blower. Appears centrifugal to me. Not sure where I would put in a damper, perhaps in the attic just upstream of the pressure switch to ensure it still opens the anemic 8" passive makeup air system. Perhaps a slide type damper like a blast gate or??


"assuming you wanted remote control of a damper, grab a 10" duct damper, and put a Honeywell DCA on it. something like a MS7503A2030. 24VAC/DC powered, and 0/2-10V or 4-20mA control. configure it for fail open. then you can throttle the fan down as low as you'd like."

that won't help your 100% flow situation, but it'll reduce your airflow to whatever you need it to be for single burner operation."

How would I add a controller to the Honeywell DCA? Where would this mount? Really looking for a dumbed down fixed approach. Not a bunch of fiddly knob(s). "Hey wife, can you go adjust the DCA smells like whatever is burning" - this would not go well.

When hood is on, the person at the range can't really smell the soot from the woodstove as the smell blends in with whatever is cooking; however where my desk is, I certainly can as I am between the wood stove and the hood.

"another thing to figure out is how much air you're actually moving at full fan speed. might need to borrow a flow hood to measure that. then you can get an idea of what you need for a makeup fan, instead of shooting in the dark and missing."

Yes I would like to know what the hood actually does for CFM's in-situ at various speed positions with the elbows, length, etc. This has been discussed, (granted we are now into Page 2 of this thread...) but I want to know the desired test protocall before proceeding. Assuming I were to conduct this test do we do it with all doors and windows closed (Case 1), with all windows and doors opened (Case 2), block off fireplace flues while doors and windows are closed (Case 3), .....?

"there IS a fan that will work with your 8" passive duct/hole without redoing the siding, assuming you are up for spending $ and have room for the fan itself."

Please provide the link to the 8" fan you suggest. I have ability to mount the fan literally at the back side of the wall cap where air enters the passive duct assuming the fan is not gargantuine.

Remember, the passive system enters the kitchen ceiling thru a 14x14 filter (196 in^2) in a filter grille. I think my inlet filter grill is likely also a weak link. The link below suggests it can only flow 2.5 cfm/in^2 or 490 cfm (the link is for a return filter sizing so not sure if it is my case exactly).

Home | Louisiana Department of Conservation and Energy

The Department of Conservation and Energy is committed to remaining a national model for how energy development, conservation, and natural resource management work together to deliver meaningful outcomes. Through responsible stewardship, data-driven regulation, and a commitment to transparency...

www.dnr.louisiana.gov

Doing reverse math, the filter grille would need to change to 24x24 for 1500 cfm. Drywall and paint repair to change out the inlet unit is not the end of the world.

Short of the open window method, any solution is $$$.

 

[Denwood]

An 8" with a filter, (passive) is not going to be flowing much at all...so yes, I'd start with an 8" fan
You should swap out the 14x14 for a 24x24 for sure to lower the pressure drop. You can put a balancing damper anywhere in your 10" ducting..ideally closer to your hood so you can access it.

If you're thinking you'll want to control it via 0-10V and automation, get the Terrabloom 8" which comes with a manual controller as well. It only pulls 74 watts, so you can likely just power it from your hood to start (simple). That's as simple as it gets....but it's 600 CFM tops. That may be all you need (or less) to bring the house to positive pressure.

You can pick up an inexpensive wind vane anemometer from amazon to approximate CFM measurements. Readings with a simple device that this will vary a lot across a 10" or 8" duct, but it will give you a decent relative measurement if you are consistent with placement.

If you measure feet/min using the anemometer, you can use this handy link to approximate CFM : https://www.engineering.com/calculators/air-flow-conversion-calculator/

I have this inexpensive unit...it works fine: https://www.amazon.ca/gp/product/B08DHJFJYT/?tag=atomicindus04-20

I've been using a differential Magnahelic guage on the HRV project, and have found the method using the vane works (vane readings correlate with static pressure flow chart on HRV) but you need to be very consistent with where you place the vane when you're testing two ducts. Getting someone with a decent flow hood and knowledge on site would be money well spent.

If you want to experiment, just fire up an incense stick or similar and check air flow at your woodstoves etc. Go with your "Case 1". Any wood burning device using inside air for combustion is going to be very easy to back draft with your hood. So if you fire up your hood and "trial" makeup air fan, just check for back drafting at all your wood burning devices, open water heater etc. That's a no tools simple way to check. All windows/doors should closed for that type of testing, but don't block off or damper chimneys etc.

How is your hot water heated? If a tank with open flue, then you need to be extra careful on CO.

 

[yeldogt]

No, no we don't.

If we did, we would not be back drafting down the fireplace flue reeking of soot and the spring hinge on the door to the garage would easily close like it automatically does when the hood is not running.

I'm wondering what you have on the flue of the fireplace ?

Have three in the burbs and I don't have this problem -- do they have tight dampers ? I may play around and see how much down draft I get when they are open.

 

[larry4406]

I'm wondering what you have on the flue of the fireplace ?

Have three in the burbs and I don't have this problem -- do they have tight dampers ? I may play around and see how much down draft I get when they are open.

Both fireplaces had the traditional cast iron fireplace throat damper. Looks exactly like this.

These dampers have been the norm for eons in my area. Reach into the combustion box and open/close it using the serrated rack handle. Far from leak tight. My parents house here was built in late 1950's and has this style damper and my house built in 1987 also has this type.

The upstairs fireplace the damper has removed and modified to allow a stainless steel 6" liner continuous from the wood stove up to the new 6" chimney cap. The damper for the wood stove is the two adjustable air inlets (thimbles) on the gasketed door. Picture below shows the thimbles wide open at fire startup.

 

[larry4406]

An 8" with a filter, (passive) is not going to be flowing much at all...so yes, I'd start with an 8" fan
You should swap out the 14x14 for a 24x24 for sure to lower the pressure drop. You can put a balancing damper anywhere in your 10" ducting..ideally closer to your hood so you can access it.

If you're thinking you'll want to control it via 0-10V and automation, get the Terrabloom 8" which comes with a manual controller as well. It only pulls 74 watts, so you can likely just power it from your hood to start (simple). That's as simple as it gets....but it's 600 CFM tops. That may be all you need (or less) to bring the house to positive pressure.

You can pick up an inexpensive wind vane anemometer from amazon to approximate CFM measurements. Readings with a simple device that this will vary a lot across a 10" or 8" duct, but it will give you a decent relative measurement if you are consistent with placement.

If you measure feet/min using the anemometer, you can use this handy link to approximate CFM : https://www.engineering.com/calculators/air-flow-conversion-calculator/

I have this inexpensive unit...it works fine: https://www.amazon.ca/gp/product/B08DHJFJYT/?tag=atomicindus04-20

I've been using a differential Magnahelic guage on the HRV project, and have found the method using the vane works (vane readings correlate with static pressure flow chart on HRV) but you need to be very consistent with where you place the vane when you're testing two ducts. Getting someone with a decent flow hood and knowledge on site would be money well spent.

If you want to experiment, just fire up an incense stick or similar and check air flow at your woodstoves etc. Go with your "Case 1". Any wood burning device using inside air for combustion is going to be very easy to back draft with your hood. So if you fire up your hood and "trial" makeup air fan, just check for back drafting at all your wood burning devices, open water heater etc. That's a no tools simple way to check. All windows/doors should closed for that type of testing, but don't block off or damper chimneys etc.

How is your hot water heated? If a tank with open flue, then you need to be extra careful on CO.

Denwood - good info. Really want to come up with a slam duck solution vs experiment with buying and replacing things.

Water is heated via heat pump water heater.
House is heated via heat pump (kitchen floor now has electric resistance heat ceramic)
Electric dryer.

The fireplaces and new propane range are the only combustion appliances in the house.

 

[Denwood]

ok..and what do you have for fireplaces etc? Open, outside combustion air etc..

If you have an HRV/ERV have you checked the intake/exhaust filters?

 

[u3b3rg33k]

I would say yes,

"you can't connect the occupied space to the attic, it's "naughty". if you did want to do it you'd need a fire damper, probably one rated for hood use, which would be $$$. most of code around things is keeping the fire contained. as soon as you put in what I think you're talking about, you've functionally defeated all the fire ratings of your walls, ceilings, etc.

that aside, what is the goal again of the attic duct? to reduce airflow from the hood? why not just slow the fan down?"

At minimum, the fan controller drops voltage to 70V from 120V, 58%. So 58% of 1500 cfm = 870 cfm. The only lower flow is OFF. Off has been proven to not work well for venting.

The concept of the shunt was to have the remote roof top blower draw from two sources vs one. One being the kitchen hood and another a bleed. The bleed would be adjustable for tuning. By bleeding air into the duct (which is at vacuum) in a less restrictive manner, it would reduce the draw from the kitchen hood. By reducing the draw from the kitchen hood, it would pull less on the house, PERHAPS reducing it to a level that was closer to house leakage while still providing adequate cooking fume exhaustion while not back drafting the wood stove. The bleed air could come from a roof jack pulling external air (vs the attic as has been discussed) to address the duct fire concern.

"there's nothing wrong with putting in a damper to further restrict airflow. you won't hurt the fan, assuming it's not cooled by exhaust airflow (most non-remote/built-in fans are cooled by the hot exhaust from the stove). power draw goes DOWN when you restrict centrifugal fan airflow (not as much as slowing it down, but substantially)."

Here is the remote blower. Appears centrifugal to me. Not sure where I would put in a damper, perhaps in the attic just upstream of the pressure switch to ensure it still opens the anemic 8" passive makeup air system. Perhaps a slide type damper like a blast gate or??


"assuming you wanted remote control of a damper, grab a 10" duct damper, and put a Honeywell DCA on it. something like a MS7503A2030. 24VAC/DC powered, and 0/2-10V or 4-20mA control. configure it for fail open. then you can throttle the fan down as low as you'd like."

that won't help your 100% flow situation, but it'll reduce your airflow to whatever you need it to be for single burner operation."

How would I add a controller to the Honeywell DCA? Where would this mount? Really looking for a dumbed down fixed approach. Not a bunch of fiddly knob(s). "Hey wife, can you go adjust the DCA smells like whatever is burning" - this would not go well.

When hood is on, the person at the range can't really smell the soot from the woodstove as the smell blends in with whatever is cooking; however where my desk is, I certainly can as I am between the wood stove and the hood.

"another thing to figure out is how much air you're actually moving at full fan speed. might need to borrow a flow hood to measure that. then you can get an idea of what you need for a makeup fan, instead of shooting in the dark and missing."

Yes I would like to know what the hood actually does for CFM's in-situ at various speed positions with the elbows, length, etc. This has been discussed, (granted we are now into Page 2 of this thread...) but I want to know the desired test protocall before proceeding. Assuming I were to conduct this test do we do it with all doors and windows closed (Case 1), with all windows and doors opened (Case 2), block off fireplace flues while doors and windows are closed (Case 3), .....?

"there IS a fan that will work with your 8" passive duct/hole without redoing the siding, assuming you are up for spending $ and have room for the fan itself."

Please provide the link to the 8" fan you suggest. I have ability to mount the fan literally at the back side of the wall cap where air enters the passive duct assuming the fan is not gargantuine.

Remember, the passive system enters the kitchen ceiling thru a 14x14 filter (196 in^2) in a filter grille. I think my inlet filter grill is likely also a weak link. The link below suggests it can only flow 2.5 cfm/in^2 or 490 cfm (the link is for a return filter sizing so not sure if it is my case exactly).

Home | Louisiana Department of Conservation and Energy

The Department of Conservation and Energy is committed to remaining a national model for how energy development, conservation, and natural resource management work together to deliver meaningful outcomes. Through responsible stewardship, data-driven regulation, and a commitment to transparency...

www.dnr.louisiana.gov

Doing reverse math, the filter grille would need to change to 24x24 for 1500 cfm. Drywall and paint repair to change out the inlet unit is not the end of the world.

Short of the open window method, any solution is $$$.

this is getting visually messy so I won't do in-line comments.

1. the fan you have pictured appears to be a reverse curve fan - those are typically pretty decent at static pressure, vs axial/forward curve (furnace blower), motor appears to be on the 'outside'. a prime candidate for controlling airflow via damper.

2. a damper would go in-line with your exhaust fan. likely wherever you'd put your "T" for the bypass duct. pre-made inline dampers aren't hard to come by.

3. there are pressure activated, variable speed, automatic MAUs, like this one:

HVACQuick - AirScape Residential Make-up Air Unit

https://www.hvacquick.com/catalog_files/AirScape_MAU_Brochure.pdf

how much air it'll pull through your 8" passive inlet depends on how long the 8"ducting is, how many bends, etc. will it fit is a question, too. you don't have to make your own controls or "right size" it. definitely something worth considering.

4. here's a fan that can move 1800CFM through a 5" duct. available in single or 3ø (speed controllable).

Fuji Electric FDC-050A-7W Turbo Blower

The FDC-050A-7W Direct Drive Turbo Blower is a high-quality cast aluminum blower with a maximum flow rate of 1860 CFM and a maximum pressure of 18.5 in. H2O. This is a 3-phase unit capable of operating under a wide range of input voltages and is UL-certified and RoHS compliant.

ringcompressors.com

I'm not suggesting you actually get that fan. just that the 8" duct, while limiting, is not a deal breaker. the next size down is 1100CFM and 5" inlet.

5. i bet your efficiency guy knows how to test properly. he can likely get you actual flow numbers (with doors closed and passive vent open) and full flow numbers (door/window open and fan on max)

6. can you get a motor data plate picture? or a link to the spec sheet? if you can get a frame number, it could be swapped for a 3ø motor. doing a speed pot on a small VFD is easy - vfds have 10V supplies on them for exactly that purpose. then you get full control over the fan, not 70% or whatever.

 

[PoorUB]

I'm not sure I understand this statement---- 80-100 CFM? The OP has a hood that runs 750 to 1500 CFM. A very large HRV would be needed to get to those levels. And force feeding a smaller unit will get more air through it, but heat recovery will be severely diminished. What am I missing?

But now we are back to square one with the original unsolved problem. Unconditioned makeup air. My comment about scalability was based on the limited capacity of the HRV.

The bottom line is moving 750-1500 CFM of air our of the house with a range hood creates significant issues in replacing that air without compromising the air temperature and humidity of the conditioned space.

I did confirm that the Terrabloom EC fan's speed can be controlled by the Qubino 0-10V dimmer. The fans come with a pigtail plug so it's pretty much plug n play. I've sent a few tech emails to see if the AC Infinity EC fans can be controlled this way as well.

I'm working on a little science experiment here, but hoping to ramp these AC Infinity EC fans via that 0-10V dimmer to unbalance the HRV (intake) with exhaust fan use in the kitchen. Bench testing now.

I would not bother with an HRV. What is the purpose? You need ten times the air a typical residential HRV can handle so it will be so imbalanced it does nothing. Plus and HRV needs exhaust air to condition the make up air, that doesn't happen in this situation. An HRV just adds more to the exhuast side of the problem.
I would dump make up air from outside directly into the kitchen, as close to the range as possible. That way you don't mess up the heating or cooling in the rest of the home. Trouble is if you get severe cold, you will have winter air dumping into the room. Same with the other extreme, dumping 100F 95% humidity air right into the kitchen.

The perfect answer would be a variable speed make up air with heat and air conditioning, but how many thousands do you want to spend? You will need 7.5 tons of cooling for that 1500 CFM in heat of the summer. Not sure of the heat load for winter, maybe 150K BTU.

 

[Denwood]

If you bothered reading the posts, I have suggested only controlling a high capacity makeup air fan via 0-10V and automation as the OP wanted an easy way to ramp to his exhaust hood.

And for the the third time in this thread, I will also say that differential makeup via the HRV is for my use case with a much smaller hood fan. However, the automation methods I am using can be applied to a makeup air system. An unbalanced HRV still runs air through the core (you’re not turning off exhaust, jus tramping intake) and although less efficient, will still transfer thermal energy. Also, automating it means it is only unbalanced during hood use. I have a fully instrumented unit on my bench with four temp sensors and a magnahelic differential gauge attached and I can assure you that unbalancing 100CFM is trivial. 100CFM is more than enough for our use case.

Now back to the issue for the OP. You have a passive 8” vent, with a 14x14 filter in place and no fan. Your two basically open chimneys are a much easier path currently for makeup air. So getting a powered fan in there will for sure address the issue. Also keep in mind that putting a monster fan in the makeup system may be quite loud…so you’ll need to plan for this with acoustic lining, duct mufflers etc. 1000 CFM via an 8” duct will mean air velocity of about 3000 ft/min.

Not sure on cost, but FanTech has a complete makeup air system, including a controller that varies the EC fan speed based on pressure: https://shop.fantech.net/en-US/muas--750--makeup--air--system/p111416

 

[Denwood]

For 8" duct: https://shop.fantech.net/en-US/muas--750--makeup--air--system/p111416

For 10" duct: https://shop.fantech.net/en-US/muas--1200--makeup--air--system/p111242

This vid goes over the variable speed response via 0-10V control:

 

[Denwood]

sorry about the repeat posts..I'm out of edits for the day

and this one goes over setup...it's quiet a nice plug and play setup.

 

[yeldogt]

Obviously powered is going to bring in more air. I use the CCB system -- small company in TX. They make a switch and damper system set w/ plug in transformer. I just add in a relay that gives me a second contact to the dehumidifier. When the hood start and trips the switch -- the dampers open and the fan on the dehumidifier is energized. The 8" damper on the inside air intake to the dehumidifier closes.

I have a 10" intake on the side of the building -- just inside it has a "Y" / 8" and 6". The 8" has the damper and the 6" as well. Both run to the intakes of the dehumidifier. It has both 6" and 8" connections. The 6" is tied to the dehumidifier fresh air controller.


It all sounds complex -- but basically it is set up so the dehumidifier can cycle dehumidified air from the lowest part of the house to the HVAC system. The controller is set to bring in fresh air through the dehumidifier from the outside on a timed basis or if I want extra -- say when we have a party. It opens that 6" duct while keeping the inside intake open. When the hood is on all the air is coming from outside (the 6' closes and so does the 8" on the inside intake) ... in the summer or in times of high humidity the humidifier will sense this as the air comes in and dehumidify the incoming air.

 

[PoorUB]

If you bothered reading the posts, I have suggested only controlling a high capacity makeup air fan via 0-10V and automation as the OP wanted an easy way to ramp to his exhaust hood.

And for the the third time in this thread, I will also say that differential makeup via the HRV is for my use case with a much smaller hood fan. However, the automation methods I am using can be applied to a makeup air system. An unbalanced HRV still runs air through the core (you’re not turning off exhaust, jus tramping intake) and although less efficient, will still transfer thermal energy. Also, automating it means it is only unbalanced during hood use. I have a fully instrumented unit on my bench with four temp sensors and a magnahelic differential gauge attached and I can assure you that unbalancing 100CFM is trivial. 100CFM is more than enough for our use case.

I have read the posts, my reply was not for you directly. I just wanted people to understand in the OP's situation an HRV will be worthless. If you want 50-100 CFM, sure, you will gain a bit with an unbalanced HRV, but not when you need and extra 1500 CFM.

 

[mike93lx]

I assume a large bank of scuba tanks in the basement connected to solenoids isn't practical?

Good luck with a solution. It's been interesting reading posts about this. Makeup air for a hood is nothing I've ever had to worry about, but hope to at some point.

 

[larry4406]

I assume a large bank of scuba tanks in the basement connected to solenoids isn't practical?

Good luck with a solution. It's been interesting reading posts about this. Makeup air for a hood is nothing I've ever had to worry about, but hope to at some point.

Mike - yes this thread has been interesting for me as well. Lots of good insight from folks and well some not so much.

My gut has me leaning towards the packaged Fan Tech solution with heat pack option. I had watched the 3-part series on YouTube previously (Denwood linked to parts 1 and 3). This would be attic mounted.

I can easily remove the existing 8” motorized damper and block off the 8” passive line without drywall and insulation repairs. This would let me retain the existing 14x14x14 ceiling plenum box and attach it to the 10” outlet of the FanTech unit and remove the 14x14 pleated filter since the Fan Tech has its own filter. Thus the tempered air would enter the kitchen ceiling via the 14x14 grille.

I would use an appropriate roof cap for the inlet air to the Fan Tech system with adequate separation between intake and exhaust.

 

[Denwood]

Fantech definitely has it sorted out. I just ordered a 14x14x4 prefilter box for my setup from HVACquick.com, so far so good. They push the Fantech bits and have nice web based configuration tools to build a system.

I also just found out the Qubino 0-10V zWave dimmer is EU only for zWave frequency. Therefore, controlling an EC fan here in NA this way is not as easy as I was hoping. I may still give it a go with an EU spec hub as this way make up air or HRV fans could potentially respond to more than just a kitchen fan. #dog_on_a_bone Going with automation also makes it easier to toggle "boost" mode as you could ramp fans for example when a bathroom light is turned on, and turn off the same way.

 

[yeldogt]

Fantech definitely has it sorted out. I just ordered a 14x14x4 prefilter box for my setup from HVACquick.com, so far so good. They push the Fantech bits and have nice web based configuration tools to build a system.

I also just found out the Qubino 0-10V zWave dimmer is EU only for zWave frequency. Therefore, controlling an EC fan here in NA this way is not as easy as I was hoping. I may still give it a go with an EU spec hub as this way make up air or HRV fans could potentially respond to more than just a kitchen fan. #dog_on_a_bone Going with automation also makes it easier to toggle "boost" mode as you could ramp fans for example when a bathroom light is turned on, and turn off the same way.

The filter boxes are nice .... I normally upside them. Most of the whole house dehumidifiers use nonstandard filters so the filter boxes make replacement easier both from getting the filter and switching it out ...

 

[yeldogt]

Mike - yes this thread has been interesting for me as well. Lots of good insight from folks and well some not so much.

My gut has me leaning towards the packaged Fan Tech solution with heat pack option. I had watched the 3-part series on YouTube previously (Denwood linked to parts 1 and 3). This would be attic mounted.

I can easily remove the existing 8” motorized damper and block off the 8” passive line without drywall and insulation repairs. This would let me retain the existing 14x14x14 ceiling plenum box and attach it to the 10” outlet of the FanTech unit and remove the 14x14 pleated filter since the Fan Tech has its own filter. Thus the tempered air would enter the kitchen ceiling via the 14x14 grille.

I would use an appropriate roof cap for the inlet air to the Fan Tech system with adequate separation between intake and exhaust.

What would be interesting. To understand when the problem starts to occur ... A smoke test would show you this as you upped the speed and sampled at the fireplaces

 

[danski0224]

I am still annoyed that the Wolf hood controller only reduces voltage to around 70V. Thus the minimum fan speed is 70/120 (58%).

I would guess that there is a limitation of how low the voltage can go, without damaging the motor.

The motor would likely need to be a variable speed (ECM) to reliably be slowed down further. Or some other, more expensive option than what's provided for a "regular motor".

 

[jar944]

Good luck with a solution. It's been interesting reading posts about this. Makeup air for a hood is nothing I've ever had to worry about, but hope to at some point.

X2

I was lazy (and cheap) so I kept it to 400cfm. After watching this unfold, I'm really glad I did.

 

[u3b3rg33k]

I would guess that there is a limitation of how low the voltage can go, without damaging the motor.

The motor would likely need to be a variable speed (ECM) to reliably be slowed down further. Or some other, more expensive option than what's provided for a "regular motor".

speed control via dropping voltage increases slip in the windings. you stay at 60Hz, you just drop torque off a cliff. this is how PSC fans work in furnaces. if you take the fan wheel off, all the speeds give you the same RPM. it's a terrible way to control a motor if you care about efficiency, but if you don't, it works fine for fans.

a 3ø induction motor on a VFD is vastly more efficient, and a PM-ECM motor a bit more efficient still. economies of scale make the latter the go-to choice for new stuff.

 

[dave*99]

It’s not likely the motor speed has a linear relation to voltage. 58% of voltage probably doesn’t equate to 58% of speed.

Or for that matter 58% of airflow.
Does this matter? Not really but predicting airflow this way may be inaccurate.

 

[larry4406]

I made the assumption that CFM was linear to voltage and thus the 58% proration discussed. However it is close based on the fan curve for a similar blower the Wolf Tech provided me (See Post 34).

Regardless, Wolf should include specifications showing the min and max CFM of their units so the available "turn down" is known. Stating the max and saying its adjustable is lacking in full disclosure.

Imagine seeing a 150 mph speedometer in your new car and the normal accelerator. Life is good! Only later do you discover that the minimum speed is 87 mph!

At the day job, many of the customers spec Zephyr hoods. The specs on those give the min and max CFM's.

 

[larry4406]

Deleted. Duplicate post.

 

[danski0224]

I made the assumption that CFM was linear to voltage and thus the 58% proration discussed. However it is close based on the fan curve for a similar blower the Wolf Tech provided me (See Post 34).

Regardless, Wolf should include specifications showing the min and max CFM of their units so the available "turn down" is known. Stating the max and saying its adjustable is lacking in full disclosure.

Imagine seeing a 150 mph speedometer in your new car and the normal accelerator. Life is good! Only later do you discover that the minimum speed is 87 mph!

At the day job, many of the customers spec Zephyr hoods. The specs on those give the min and max CFM's.

No, Wolf should provide full design assistance with their products to ensure proper installation and that they are working as designed...

 

[mike93lx]

No, Wolf should provide full design assistance with their products to ensure proper installation and that they are working as designed...

Then they would have to charge a premium price

 

[Denwood]

X2

I was lazy (and cheap) so I kept it to 400cfm. After watching this unfold, I'm really glad I did.

Actually, at just 160 CFM (measured at the hood) our kitchen exhaust fan is pulling my house to negative .03 WG differential pressure compared to outside. If I also turn on the two small exhaust fans for the 2 bathrooms, that drops to .04 WG. The threshold (recommend anyway) is .025 WG before back drafting CO from say a water heater becomes a concern. Running the EC kitchen hood fan at its typical setting (just 100 CFM does the trick), we're just at the threshold. This is a heavily retrofitted 100 year old home, so a new home built with attention to air sealing would be worse. Our furnace and on-demand water heater are direct vent, so use outside combustion air. This means a back draft CO situation would be unlikely. We do have a high efficiency fireplace (using outside combustion air), but back drafting when loading (door open) can be an issue if exhaust fans are running.

In other words, even with a much lower CFM hood, makeup air is a consideration in a tighter home. With all the attention of late to interior air quality and ventilated/tight homes, I would not be surprised for a second if that make-up air code requirement gets dialled back below 400 CFM sooner than later.

If you do need a very high CFM hood, Fantech does have a nicely engineered kit with a hood liner (a bit pricey in my book though) EC hood remote fan, code approved duct silencer, and a matching makeup air kit (that ramps via an EC makeup air fan) with optional pre-heater and filtration for incoming air. They would be my pick for a well engineered setup off the shelf.

For our kitchen, I will likely swap out the gutted hood I'm using in favour of an insert just based on the larger intake/filter area.

 

[jar944]

Actually, at just 160 CFM (measured at the hood) our kitchen exhaust fan is pulling my house to negative .03 WG differential pressure compared to outside. If I also turn on the two small exhaust fans for the 2 bathrooms, that drops to .04 WG. The threshold (recommend anyway) is .025 WG before back drafting CO from say a water heater becomes a concern. Running the EC kitchen hood fan at its typical setting (just 100 CFM does the trick), we're just at the threshold. This is a heavily retrofitted 100 year old home, so a new home built with attention to air sealing would be worse. Our furnace and on-demand water heater are direct vent, so use outside combustion air. This means a back draft CO situation would be unlikely. We do have a high efficiency fireplace (using outside combustion air), but back drafting when loading (door open) can be an issue if exhaust fans are running.

In other words, even with a much lower CFM hood, makeup air is a consideration in a tighter home. With all the attention of late to interior air quality and ventilated/tight homes, I would not be surprised for a second if that make-up air code requirement gets dialled back below 400 CFM sooner than later.

Fortunately or unfortunately in my case my house leaks, likely a lot. Not that surprising for late 2000s construction. Air sealing the attic is in on my list, but way down the list. Air sealing everything else is about impossible without significant remodeling.

 

[yeldogt]

Actually, at just 160 CFM (measured at the hood) our kitchen exhaust fan is pulling my house to negative .03 WG differential pressure compared to outside. If I also turn on the two small exhaust fans for the 2 bathrooms, that drops to .04 WG. The threshold (recommend anyway) is .025 WG before back drafting CO from say a water heater becomes a concern. Running the EC kitchen hood fan at its typical setting (just 100 CFM does the trick), we're just at the threshold. This is a heavily retrofitted 100 year old home, so a new home built with attention to air sealing would be worse. Our furnace and on-demand water heater are direct vent, so use outside combustion air. This means a back draft CO situation would be unlikely. We do have a high efficiency fireplace (using outside combustion air), but back drafting when loading (door open) can be an issue if exhaust fans are running.

In other words, even with a much lower CFM hood, makeup air is a consideration in a tighter home. With all the attention of late to interior air quality and ventilated/tight homes, I would not be surprised for a second if that make-up air code requirement gets dialled back below 400 CFM sooner than later.

If you do need a very high CFM hood, Fantech does have a nicely engineered kit with a hood liner (a bit pricey in my book though) EC hood remote fan, code approved duct silencer, and a matching makeup air kit (that ramps via an EC makeup air fan) with optional pre-heater and filtration for incoming air. They would be my pick for a well engineered setup off the shelf.

For our kitchen, I will likely swap out the gutted hood I'm using in favour of an insert just based on the larger intake/filter area.

Got me thinking .... what's the square foot of the space?

I may be looking at this the wrong way ?

 

[jar944]

Got me thinking .... what's the square foot of the space?

I may be looking at this the wrong way ?

I'd guess sqft of the envelope would be a better indication than just sqft.

 

[Denwood]

Jar/Yeld we're at about 2500 sq/ft including the basement, 8 ft ceiling average. As we've reno'd and air sealed with spray foam etc. the house has become too tight so the 30 CFM panasonic ERV is no longer doing the job. My goal on the HRV project is about 60 CFM continuous for normal exchange to keep CO2 levels under 800 PPM.

Although my setup is a lot different than Larry's ( @larry4406 ), we still have occasional smoke puffing back through the fireplace on loading, and as I've now measured...ya, we're about .02-.03 negative WG with the hood fan running. Open a door and pressure diff drops to zero in 10-15 seconds.

 

[yeldogt]

Jar/Yeld we're at about 2500 sq/ft including the basement, 8 ft ceiling average. As we've reno'd and air sealed with spray foam etc. the house has become too tight so the 30 CFM panasonic ERV is no longer doing the job. My goal on the HRV project is about 60 CFM continuous for normal exchange to keep CO2 levels under 800 PPM.

Although my setup is a lot different than Larry's ( @larry4406 ), we still have occasional smoke puffing back through the fireplace on loading, and as I've now measured...ya, we're about .02-.03 negative WG with the hood fan running. Open a door and pressure diff drops to zero in 10-15 seconds.

What are you using to measure the differential .... do you have a gauge on the HRV/ ERV?

I am dealing with more sf and in some cases much higher ceilings.

 

[Denwood]

I'm using an old school magnahelic diff gauge for the house readings. High side tube ran outside (low/no wind during test), low inside the house. It's shown here on the mod'd HRV (fresh door ports) as I baseline flow vs pressure.

And ya, I need a stand for it...ha. It needs to be plumb/level for accuracy.

 

[larry4406]

Got me thinking .... what's the square foot of the space?

I may be looking at this the wrong way ?

I'd guess sqft of the envelope would be a better indication than just sqft.

That is kind of where my head is at as well.

Suppose one uses best practices to construct a perimeter wall and ceiling to attic. WRB, sheathing, fire stopped, caulk sealed framing, foamed windows, windows flashed, band boards foamed, attic penetrations caulk sealed, etc. There is some leakage/SF of that system (wall and ceiling) regardless of how well you tried using normal methods.

So with this logic, if the SF of the envelope is small, then the aggregate leakage is small. Conversely a McMansion by virtue of its acres of wall and ceiling areas, will have a radically larger total leakage even though the leakage/SF is the same.

So the cracker box house with the mega hood (mine) has back draft issues while the McMansion with the same mega hood could care less even though both benefit from the same best practices.

 

[dave*99]

That is kind of where my head is at as well.

Suppose one uses best practices to construct a perimeter wall and ceiling to attic. WRB, sheathing, fire stopped, caulk sealed framing, foamed windows, windows flashed, band boards foamed, attic penetrations caulk sealed, etc. There is some leakage/SF of that system (wall and ceiling) regardless of how well you tried using normal methods.

So with this logic, if the SF of the envelope is small, then the aggregate leakage is small. Conversely a McMansion by virtue of its acres of wall and ceiling areas, will have a radically larger total leakage even though the leakage/SF is the same.

So the cracker box house with the mega hood (mine) has back draft issues while the McMansion with the same mega hood could care less even though both benefit from the same best practices.

The 2018 IECC specifies a maximum air leakage rate of 3 ACH in the NJ Climate Zones.

Air Changes per Hour:

• The number of times the full volume of air in the house flows out and is replaced with outdoor air flowing in during a one hour period.
• Calculated by measuring the leakage rate (in cubic feet per minute - CFM) in the house with a blower door, converting it to cubic feet per hour, and dividing it by the house volume (in cubic feet).
• ACH = (CFM x 60) / Volume

 

[dave*99]

Here is the reference.

Air Leakage | NJ Energy Code

The NJ Energy Code requires comprehensive air sealing to minimize heat loss, including a documented inspection and blower door test.

njenergycode.com

Do the math for your volume. A big house will leak enough - but still be required to have makeup air if the hood is over 400 CFM.
Go figure.....