What is the source of makeup air when you run the hood?

Try opening a kitchen window slight when running the hood and crating smoke during cooking.

Let the hood tun for a few minutes after smoke stops also.

400 CFM is not all that large for dealing with wok smoke.

I would also suggest you turn the fan on for a few minutes before you begin cooking. This will allow the fan to pick up the loose air and get the currents flowing thru it. In todays tight home construction you may have to crack a window to allow more airflow.

Good luck !

I know it might be awkward, but if you are stir frying on the front burners, try using a back burner instead. Sometimes it is just a matter of the hood not extending out from the wall far enough.

Thanks for the prompt responses. I'm thinking of replacing with a 900cfm hood but if the problem is related to needing incoming make-up fresh air to make it work, then I may be back to the same problem. As tom99 stated, homes these days are very tight and I dont see many people leaving their windows open when cooking in winter. So, how does everyone deal with cooking smells? Compared to other homes I've been in with same cooking styles, ours is a lot worse. I just feel something is not right with our setup.

I am no expert, but 4" flexible duct does not sound like enough ducting for 400 cfm to me.

The fact that your hood draws better when you open a window is a sure indication that you need make-up air. Adding more CFMs means that you will need more MUA. No hood can operate efficiently if it is starved for air. Check the building codes in your jurisdiction - if you get cold winters and use any combustion appliances like furnaces, water heater, fireplace, or wood stove, MUA is a safety issue, not just an operational one for your vent hood.

You can NOT have flex duct !! Whoa...that is completely totally out of code . Whoever did it and inspected is irresponsible.

We stir fry with our wok all the time and have a built in deep fat fryer as well. We have 54 " wide 1400 cfm at 33 " above a gas Caldera. We have no odors at all. We have no make up air as we are in an 1890 home...leaks a plenty :)

First your entire set up needs replacing from the guts out...proper duct and higher CFM. Then you need to make sure and turn it on 5 min before you start to cook. You also need to have air circulation as mentioned if your home is so tight that you are not drawing. You also need to make sure and run it for 5 -10 min after use. The HOGS generated while cooking need to go all the way out...not settle in the duct. Heat/Odors/Grease/Steam. These are your culprits. Good Luck . I hope you have some strong words with your contractor/HVAC/appliance person/inspector..whoever is responsible for your current set up. c

Thanks for all the inputs. Its flexible metal duct, not the PVC type but point taken. Any recommendation for a good 900+ cfm hood? Most that I've seen are $2K and above. Its ridiculous that just the hood enclosure itself is $1-2K, then on top of that, it costs another $1K+ for the blowers. I did think of ERV/HRV but as one poster mentioned, its not cheap and will need new ducts installed, drywall work etc. I've been to homes without a HRV which exhausts cooking smell fairly well but they also have a much bigger commercial range hood. Time to go shopping, I guess.

I think before you replace your hood with something more powerful you should try increasing the duct size. According to the manual with my vent hood the minimum duct size for 300 -450 CFM is 6 inches. You probably know this by now but I copied the info below from the do's and don'ts section of the manual for my vent. I'm sure it applies to all vents.
My blower is a bit more powerful than yours and the ducting is 8 inches. The best part of my new vent is that it does eliminate all smells. I do not have make up air. I live in an area with old winters but have not needed to open any windows. I hope you can resolve your venting issues without too much trouble .
This is the info that I copied:
"Do not use flexible or corrugated duct. This type of duct will restrict airflow and reduce performance. Only use smooth, galvanized, metal duct. Observe local codes regarding special duct requirements and placement of duct against combustibles. Make the duct run as short and as straight as possible with as few turns as possible. Avoid sharp-angled turns. Instead, use smooth, gradual turns such as adjustable elbows or 45 degree angled turns. For duct runs over 20 feet, increase the duct diameter by one inch for every ten feet of duct. A 90 degree elbow is equal to 5 feet of duct. Using Vent-A-Hood roof jacks or wall louvers (back page) will ensure proper efficiency. Airflow must not be restricted at the end of the duct run. Do not use screen wire or spring-loaded doors on wall louvers or roof jacks."

I have 10" duct..I planned for a year before I bought my set up. It was NOT expensive at all. I will link to the company. They make a wonderful product. We have used it hard for over 6 years and it looks and works as it did the day it was installed. I have a very long run and several turns..thus the need for high cfm. as well as the way we cook. My cabs have never had the first bit of oil/grease residue on them. I wipe down the top and sides of my wooden hood area about 1x every few months and it never has anything on it but dust...old house :)

As badger said the size of your duct and the smoothness of the product will make a lot of difference and then add in the higher cfm and you should be good to go. Please post anymore questions..I couldn't have done without all the stuff I read here and on other sites when I was planning. c

you will find a wealth of info on their site about everything you ever wanted to know...they have liners as well as hoods.

Here is a link that might be useful: Tradewind liner

Trailrunner--how do you clean your hood? Easy, difficult?

You've gotten good advice about improving the anti-smell functionality problems. But I want to make sure you understand that your description that the fan works better when you open a window you are precisely describing the condition where your fan may be capable of causing the draft on your gas or oil-fired furnace, water heater, fireplace and/or woodstove to reverse and draw carbon monoxide back into your house air. THIS IS VERY DANGEROUS - IT COULD RESULT IN DEATH.

Simply increasing the venting capability of the fan, without resolving the make-up air issue, will actually make the problem much more dangerous.

Please, until this is resolved always open a window when using the fan and try to get the issue fixed before the next heating season. If you are experiencing headaches, or feeling a little flu-ish after being the house when the fan is running, you are already feeling the effects of carbon monoxide poisoning. Shut the fan off, open up the house and get it fixed, ASAP. Carbon monoxide is odorless, colorless and deadly. You can buy a carbon monoxide detector at hardware or big box stores.

I, like Trailrunner, live in an ancient house so most fans probably would be barriers to the amount of air being exchanged in my insulation-challenged, unsealed-up house. All of my cumbustors (heat, hot water, woodstove, etc.) have dedicated outside air intakes, and even then I still keep carbon monoxide detectors sniffing all the time.

Good luck - your aesthetic sense (stinky food odors) may have saved your life. Don't ignore this chance to make a difference. I have been a volunteer firefighter called to houses with people were barely able to survive, just from mis-functioning vents. It's awful because there are few warning signs - except in hindsight the vent fans were noted to work better when a window was open. Just like your situation.

L.

I fully understand the danger of backdraft. We also have CO detectors hard-wired to the alarm system on every floor and basement. Good news (or bad since we prefer gas cooking!) is we have no gas supply on the street, so our HVAC is a dual-fuel HP with high efficiency propane backup with dedicated air intakes and combustion. Our WH is also electric and we dont ever use our fireplace.

I think I'll try the suggestion of replacing with larger ducts first to see if the situation improves. Our house was built around the early 80s, so its not as tight as the newer homes but we've added insulation and tighten it up as much as we can. Once again, if anyone has any recommended websites/stores to buy good rangehoods with 900+ cfm, I'd appreciate if you can provide the links. Thanks.

I'm glad you appreciate my warning and already have in place such good safety features. Sorry for the emphasis, but once you've been to a house and pulled out limp, nearly-dead kids just sleeping in their beds, one gets sort of militant on the subject. You do sound like you understand the risks so I'm sure you're on top of it.

Of course there are VentaHood and Wolf, and Modern Aire fans. There is also a company I think it is called ProLine. It is an internet supplier of fans, liners, blowers, and stuff. They are located in New Jersey. I think several people here have worked with them (and report being happy with them) and their prices seem good, though they don't have deep front to back fans I need with my big range.

Also I have seen fans for sale on eBay, some name brand but returns, display models, out of boxes, odd pieces, etc. That might also be a place to look if you need to upgrade the blowers. If you're in the metro NY/NJ/LI another place to look is Craigslist. I'm way upstate in the sticks so I don't see many appliances from dealers on my Craigslist. I think they are less likely to maintain invenory so don't need to unload stuff as often.

Good luck.

L.

I hope you will look at the Tradewind hoods/liners. To answer the cleaning question. It takes about 5-10 min a week. I do it every Sunday. i remove the 3 baffles, and spray them with full strength grease cutter, I use Awesome from Walmart, then I use a pastry brush to quickly go over all the baffles...we have a fair amount of brown residue that accumulates in the baffles. I then rinse them in hot water and dry them off with a towel and replace in the hood.

The only time the hood liner itself has ever had to be wiped out is if I go longer than a week on cleaning the baffles. Then DH wipes out the upper unit inside with a cloth that is sprayed with the grease cutter. Takes a few extra minutes. Rarely much in there.

That is it...easy peasy. i will post a pic below of the baffles. They do a great job...what you want is greasy messy baffles every single week :) If your baffles are clean...you aren't cooking or they aren't working ! c

after and before we put up the utensil/pot rack..LOVE the rack from Lee Valley !

Wow, I like how slim your hood is. I've seen 18" and 10" tall hoods. From an efficiency perspective, is it better to go with the taller 18" or the slim 9-10" works just as well? Are the blowers the same size for the 18" and 10" eventhough they all say 600 cfm? Based on my requirement of 36" wide hood, they all seem to have 600 cfm blowers unless I go with an external blower. Will this be enough for our cooking style?

liriodendron - I'm in SW Philly, so I'll definitely look at your recommendations. Thanks again.

You should be able to easily get 800-1000 cfm without having to go to an external blower. Take a look at the Vent-a-Hood,Kobe, Broan, or Thermador lines just to get started.

klingon...the whole wood unit that you see holds the baffles/lights/electric control...it is 8" top to bottom so the actual Tradewind liner is about 6" tall. The reason it is so slim is that our blower is on the roof...as dseng says...we have an external blower. You can indeed get a Tradewind hood that has the blower in it and not have the external blower. We did it so we could have the least noise...we have an inline silencer , since we wanted a lot of CFM. You should be fine w/o going the external route. Also I don't have any idea about the 10" vs 18" since I don't have a hood/blower all in one unit. Good Luck ! c

"Its flexible metal duct, not the PVC type"

Flex duct is not allowed for range hoods. Period.

Smooth sheet metal, ad be sure to tape the seams with metal foil duct tape.

One advantage of remote blowers is that they pout the duct under suction, preventing the blower from forcing greasy air out of any minor leaks in the duct.

The (quite expensive) Miele 625 cfm range hood that I bought has a 6" exit hole. Amazingly to me, it came with a 6"-to-5" adapter and a 5" flexible duct. I threw those away and went the other direction: I put it a 6"-to-8" adapter for my very short run of rigid duct.

I don't think I ever saw your reponse, Caroline. Thank you! I lose track of posts all the time.... You gave me a great explanation, but I don't think I'm as good a housekeeper as you. I clean my current filters every couple of months or so; I guess I could get used to doing so more frequently. Though I've read lots of threads on hoods, can I ask basically what you had to buy to outfit your hood? Are these it?

Liner
External blower
Silencer
Wood surround

hey sj..that is OK I know that we all get busy and lose threads. I would have to go and get the invoice out of my records but ...there were neoprene silencer rings that were extra and then the duct work which was purchased locally. The wood surround was made by my cabinet maker. After my GC built the framework for it. He simply placed the paintable cabinet material over the wooden base. Here is a pic.

It really isn't all that many pieces. Did you look at the detailed info on Tradewind liners ? That is where I found the diagrams and details of what I would need and how I put my order together. Let me know if you need more help. You can also email me through GW. c

Thank you, TR, you're so very helpful. I haven't delved into the website much yet as I'm currently overwhelmed with lots of decisions to make, and we are just now signing with a contractor. Do you mind if I print out your post? That is an excellent picture.

Nope ...go ahead. I can give you measurements if need be. I can also look back at Tradewind's site and send you the tech stuff that I think will be most helpful. Just let me know. I have a couple weeks here and then my next bike trip...all the way across Canada...so I will be out of touch for over 3 months ! ! You better get that kitchen planned asap :) c