gas ranges, vent hood and.. return air
#21
I hope to one day put a large® hood in with a decent exhaust fan.  I think 400+ CFM will be adequate, and it will be 400+ CFM more than we have now.

Typical (old school) design for commercial grease hood exhaust CFMs is 275 CFM per linear foot of hood.  Know that commercial hoods are generally 4' deep, whereas your residential hood is about 24", so there's that.  Also, there's a much greater expectation of grease-laden air in a commercial environment than residential.  400 CFM on a 36" wide residential hood that is 24" deep at most would be extremely adequate IMO/IME.

We probably both want to cook onions/peppers/garlic in a screamin' hot pan or steaks in a cast iron skillet and not wake up the next morning with an awful smell knocking you down, right?  

An inspector won't know about my installation.  Don't ask, don't tell...... I'm not putting in an ERV or make-up air fan/filtration system, either.  I would go crack the patio door in our bedroom (that has a screen slide on it) and/or open the screen porch door in the living room to allow make-up air.  My HVAC system is more than adequate to take care of a situation where there's gobs of raw air introduced into the house during a high-heat/grease/smoke cooking incident.

It's not like we'd use the fan twice a day, 7 days a week in high speed mode.  Speaking of mode, I would not install a fan that didn't have a speed controller, so keep that in mind.


Also... an ERV is not installed to provide make-up air into a building.  It's to recover energy from an exhaust air stream and pre-treat the outside air stream before it is dumped into the return duct of your air handler.  Make-up air systems are either filtered fans with heat in them or fully air-conditioned.  These can get pretty expensive.  A grease hood system for a typical restaurant is typically 6 figures today.  There's a lot of aluminum and stainless steel involved, welded carbon steel ductwork, fire suppression, controls, etc.
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#22
We have a 48" Vent-a-hood that I think is capable of 900 cfm and house has no provisions for make up air. Normally it's running far, far less than the max speeds. But when we do need to run it on max we just crack a window. No ill effects that I can tell. But house was built 30 years ago and might be pretty leaky by today's standards.
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#23
(10-13-2022, 07:54 AM)mound Wrote: lol. 
doesn't that also mean the bathroom fan lacks a damper? Shouldn't that only be able to push, not pull air?

A lot of the old fans didn't have dampers or if it did, it wasn't closing
Neil Summers Home Inspections




I came to a stop sign and a skanky tweaker chick in a tube top climbed out of the brush and propositioned me.  She looked like she didn't have any teeth so I counted that as a plus.


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#24
(10-13-2022, 01:20 PM)joe1086 Wrote: We have a 48" Vent-a-hood that I think is capable of 900 cfm and house has no provisions for make up air. Normally it's running far, far less than the max speeds. But when we do need to run it on max we just crack a window. No ill effects that I can tell. But house was built 30 years ago and might be pretty leaky by today's standards.

so you could use it as kind of a mini whole house fan in the cool evenings?  
Laugh
mark
Ignorance is bliss -- I'm very, very happy
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#25
So originally the building inspector told me "400CFM or greater you need makeup air".. I even double checked at that time and said "really 400 or greater, not just greater" and he said yes, 400 or more.  thus this whole discussion..

well that didn't sound right.. So many manufacturers offer a 400CFM model, seems to be a magic number, and when I looked up the actual building code, it says "any fan... in excess of 400CFM"

So I very politely asked the inspector to confirm, mentioned with all the manufacturers having a model at 400 and the code referencing "in excess of" that can't be a coincidence..  he wrote back "I'll double check" and a few days later "yes, you can buy a 400CFM unit and not require makeup air"

So that's what I'm going to do
Smile
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#26
When it is installed, run it to max speed and check all your other gas appliances to ensure you are not sucking flue gas into your home.
Blackhat

Bad experiences come from poor decisions. So do good stories. 


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#27
(10-13-2022, 12:51 PM)T.Hooks Wrote: Typical (old school) design for commercial grease hood exhaust CFMs is 275 CFM per linear foot of hood.  Know that commercial hoods are generally 4' deep, whereas your residential hood is about 24", so there's that.  Also, there's a much greater expectation of grease-laden air in a commercial environment than residential.  400 CFM on a 36" wide residential hood that is 24" deep at most would be extremely adequate IMO/IME.

My HVAC system is more than adequate to take care of a situation where there's gobs of raw air introduced into the house during a high-heat/grease/smoke cooking incident.

Also... an ERV is not installed to provide make-up air into a building.  It's to recover energy from an exhaust air stream and pre-treat the outside air stream before it is dumped into the return duct of your air handler.  Make-up air systems are either filtered fans with heat in them or fully air-conditioned.  These can get pretty expensive.  A grease hood system for a typical restaurant is typically 6 figures today.  There's a lot of aluminum and stainless steel involved, welded carbon steel ductwork, fire suppression, controls, etc.

I'm sure you mean well, but let's look at some issues with your advice:

1. Extrapolating a commercial spec to a residence is fraught with problems.  Very few resi hoods are 24" deep.  Those that are, are usually custom affairs with +600 cfm and designers associated with them.    Commercial is also regulated by the Fire Marshall / Code that isn't involved at your house.   Saying that 400cfm is extremely adequate is just plain bad advice in many cases.

It may be adequate is some instances, but in many it won't be.  Like..............when I have a long duct run with several 90deg bends and flex pipe.  Or a 6 burner professional type rangetop.  Or a 4 burner with a BBQ.   Or any type of downdraft that's got any amount of duct run.  Or a capture area that's a bit too far away.

2.  Your HVAC may be able to cope with the heat/cooling load of an open door , but most people don;t live in a mild / temperate climate with low humidity.   Meaning their systems (if properly sized) are not going to cope with a sudden surge of frigid air or swamp like humidity.  Even if they did , the room(s) where the MUA enters will be very uncomfortable in the short term.

3.  ERVs bread and butter is not MUA for hoods, but there's no reason they can't be employed.   And there's no reason your MUA system can't be dumped directly into your HVAC system either.    Yes, this stuff is expensive.  The best approach is to stay at /under 400cfm.  That often requires wanting less though-  and we know how much dreamers and remodelers like that.
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#28
(10-17-2022, 05:45 PM)Cabinet Monkey Wrote: I'm sure you mean well, but let's look at some issues with your advice:

1. Extrapolating a commercial spec to a residence is fraught with problems.  Very few resi hoods are 24" deep.  Those that are, are usually custom affairs with +600 cfm and designers associated with them.    Commercial is also regulated by the Fire Marshall / Code that isn't involved at your house.   Saying that 400cfm is extremely adequate is just plain bad advice in many cases.

It may be adequate is some instances, but in many it won't be.  Like..............when I have a long duct run with several 90deg bends and flex pipe.  Or a 6 burner professional type rangetop.  Or a 4 burner with a BBQ.   Or any type of downdraft that's got any amount of duct run.  Or a capture area that's a bit too far away.

2.  Your HVAC may be able to cope with the heat/cooling load of an open door , but most people don;t live in a mild / temperate climate with low humidity.   Meaning their systems (if properly sized) are not going to cope with a sudden surge of frigid air or swamp like humidity.  Even if they did , the room(s) where the MUA enters will be very uncomfortable in the short term.

3.  ERVs bread and butter is not MUA for hoods, but there's no reason they can't be employed.   And there's no reason your MUA system can't be dumped directly into your HVAC system either.    Yes, this stuff is expensive.  The best approach is to stay at /under 400cfm.  That often requires wanting less though-  and we know how much dreamers and remodelers like that.


Well I'm glad you addressed all of that.

Would you come up with a generic residential kitchen hood design that will work and solve all the issues you bring to light?
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#29
In my last house I installed air make-up with an automatic damper that would open when the hood was at 400cfm or the higher 600cfm.
It ducted through through a filter before entering the cold air return. That might not be code where I was (SW Ohio), or where you are, but I had no issues with it and it worked well.
Ray
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#30
(10-19-2022, 09:29 AM)T.Hooks Wrote: Well I'm glad you addressed all of that.

Would you come up with a generic residential kitchen hood design that will work and solve all the issues you bring to light?

If you’d like to engage us, we’d be happy to design something that meets all your needs.

 We can even have it fabricated for you if off the shelf options don’t please you. 

Be warned , the whole affair will cost more than you’re spending on all your appliances combined.
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