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  1. #1
    Join Date
    Sep 2004
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    51
    Is anyone able to explain the differences in these two products and how to determine which is correct for controlling drafts into a house when the furnace as well as other combustion appliances are operating? Is one more efficient than the other? The application in question is a forced air natural gas mid eff. furnace, I am unsure of the benefits of dumping the air into the cold air return, especially in Michigan.

    Also, will either one of them provide replacment air into the house when a 500cfm range hood fan is operating?

  2. #2
    Join Date
    Apr 2002
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    11,808
    500 CFM is a large amount of air to exhaust from you home and neither of these products can handle that for you. The range hood sounds like an Italian one kitchen guys love to sell.

    500 CFM can cause down drafting problems of any gas burning appliances and will give your induced draft furnace some grief. A house with that much exhaust should have direct vent furnaces and water heaters.

    Skuttle may be able to sell you a larger inlet with a motorized damper that you could interlock with the range hood fan, I would not dump this air into an area with water pipes.

    Equilizair will recommend that you open a window when you run this hood. Not bad advice in this situation, open a kitchen one. Don't do a lot of grilling in January

    Fresh air intakes into the return of non condensing furnaces such as yours makes the air entering the furnace cooler. There is a greater temperature difference between the hot gas inside the furnace heat exchanger and the air it is heating. The greater the temperature difference, the more heat transfer and greater effciency. It can become too efficient and will turn your 80% AFUE furnace into a condensing furnace.

    Your furnace is not designed to handle acidic condensate and this could rot your heat exchanger out. You need to be careful here.

    Both the Skuttle and the Equilizair will pressurize your home with air to stop drafts. The Equilaizair has a second intake duct built into it that is a combustion air intake.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  3. #3
    Join Date
    Sep 2004
    Posts
    51
    Thanks for the advice on the range vent fan, you are right it is one of those stainless steel hoods with a halogen lights and the works! We have been getting into the habit of cracking the kitchen window, as I suspected we were drawing a lot of air when we started smelling the soot from the fireplace this summer.

    I understand the concept of feeding the combustion chamber with frigid air, so I guess I will just have the unit dump into the basement. One contractor is offering to actually make a fresh air intake through the use of a barometric damper and hood, dumping the air about 12" off the basement floor. Will this work? How do we make sure that enough air is coming in, yet a stron gust of wind does not blow it open? Maybe the damper goes low on the pipe?

  4. #4
    Join Date
    Apr 2002
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    11,808
    That is an extreme amount of exhaust from a home.

    Use a motorized damper, interlocked with the hood fan. Keep it away from water pipes. If you are in a sub zero area, it would be a lot of electric heat just to temper that air. That is a lot of air even for a passive intake, you could consider a make up fan with an electric heater.

    Every degree you heat that 500 CFM by would require 540 Btu/hr or 158 watts.

    I would not do a lot of grilling on a cold day.

    Really think about a direct vent furnace.

    Maybe in the Fireplace forum someone can advise you on direct vent insert for your fireplace whether it burns wood or gas.

    [Edited by Carnak on 11-04-2004 at 12:47 PM]
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  5. #5
    Join Date
    Aug 2003
    Posts
    626
    The answer to your question is neither. What controls drafts in homes is the number and size of the holes and the temperature difference from outside to inside. This happens 24/7 so temperary use of even a large 500 cfm kithen fan is not that important.

  6. #6
    Join Date
    Dec 2000
    Location
    Michigan
    Posts
    724

    Hmm Make - up and Combustion AIr

    Thanks Carnak for the information, but unfortunately it is not accurate. I have been answering this question with DATA for 25 years (ever since I invented EQUALIZ-AIR) As you ask for data you solve the following equation: furnace fan at 1000 cfms, t-stat set at 70 degrees F with two degree operation, outside temperature 25 degrees F, size of inlet 4 inch diameter and static in the system is .1 inches.

    Using this data Carnak what is the change in return air temperature gong over the heat exchanger?

    Again, EQUALIZ-AIR will not pressurize a home! Only a one hose system like a Skuttle or Broam or the one in your home will!

    Finally Carnak, I completely agree with your comments on the kitchen fan. First I would never install one and if installed I would never recommend using it! TOO BIG!

    DZD if you live in Michigan you must see or hear every week on Radio, TV or in print, that EQUALIZ-AIR is the preferred Make-Up and Combustion product. (Carnak not my opinion just fact!) Continue your research and make an informed decision. Good Luck!



    The quality of my performance, sometimes depends on the quality of my audience.
    Imitation (Plagiarism) is the best compliment one can get -- "Open A Window"

    To improve Indoor Air Quality: Control Indoor Air QUANTITY = "I.A.Q.Q."

  7. #7
    Join Date
    Jan 2001
    Location
    Pacific Coast of Canada
    Posts
    4,008
    We have a specific code dealing with large exhaust devices in homes. Calculate the total volume of air in a home (square footage x ceiling height), divide by 60 then multiply x .5 If your exhaust fan exceeds this number AND you have a b vent appliance in your home you MUST install active make up air as per Carnaks post. This means interlocking an intake fan with the exhaust fan.

    We just installled a 1600 cfm kitchen hood fan with 1600cfm's make up air.
    The 10 kw heater will temper the air on a day with freezing temperatures.

  8. #8
    Join Date
    Apr 2002
    Posts
    11,808

    Re: Make - up and Combustion AIr

    Originally posted by Xavier
    Thanks Carnak for the information, but unfortunately it is not accurate. I have been answering this question with DATA for 25 years (ever since I invented EQUALIZ-AIR) As you ask for data you solve the following equation: furnace fan at 1000 cfms, t-stat set at 70 degrees F with two degree operation, outside temperature 25 degrees F, size of inlet 4 inch diameter and static in the system is .1 inches.

    Using this data Carnak what is the change in return air temperature gong over the heat exchanger?

    Again, EQUALIZ-AIR will not pressurize a home! Only a one hose system like a Skuttle or Broam or the one in your home will!

    Finally Carnak, I completely agree with your comments on the kitchen fan. First I would never install one and if installed I would never recommend using it! TOO BIG!

    DZD if you live in Michigan you must see or hear every week on Radio, TV or in print, that EQUALIZ-AIR is the preferred Make-Up and Combustion product. (Carnak not my opinion just fact!) Continue your research and make an informed decision. Good Luck!
    Since this is an HVAC forum and not a forum on how to get a ladder company to respond faster to a five alarm fire, lets call them ducts or pipes, not hoses.

    Again X, you think a formula is data. You have zero data published so let's make some assumptions.

    Let's assume you have an equivalent length of 20 feet of 4 inch pipe ducted into the return air close to the furnace. If the return is -.1" with respect to atmosphere at this connection point and the pressure loss of your hood and flapper was zero, then you could be moving about 85 CFM.

    Could you post a CFM/pressure drop chart on the Equilizair here or put one on your website? This data is typical of most manufacturers but is not available on the equilizair website as far as I can tell.

    Perhaps even post 3 measured points of CFM vs pressure drop and we can fit a curve to your Data.

    We could then go through the mixed air calculation in a real life situation, 25F is a spring day.

    Commercials and advertisements will say how wonderful anything is. You can take a dump in a box, wrap it up and market it as sweeter smelling than Glade Solid, it does not make it true.









    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  9. #9
    Join Date
    Dec 2000
    Location
    Michigan
    Posts
    724

    Smile Algebra

    Carnak, I am impressed!

    "Let's assume you have an equivalent length of 20 feet of 4 inch pipe ducted into the return air close to the furnace. If the return is -.1" with respect to atmosphere at this connection point and the pressure loss of your hood and flapper was zero, then you could be moving about 85 CFM."

    Although my calculations show 50 CFM, you understand this part of the equation. Now how good is your Algebra to solve the equation?

    You will find that a 4-inch inlet will NOT lower the return air temperature very much even at 0 degrees F. Therefore, very little change in air temp over the heat exchanger, but you are correct again, directionally this will “increase” the efficiency of the energy transfer.

    I am completely confused if you understand these two concepts, why you do not understand my invention?

    Collin, we too have strict codes on exhaust fans, not sure if it is both commercial and residential, I will review the current codes.

    P.S. Carnak & Collin shipped two units to Canada today!
    The quality of my performance, sometimes depends on the quality of my audience.
    Imitation (Plagiarism) is the best compliment one can get -- "Open A Window"

    To improve Indoor Air Quality: Control Indoor Air QUANTITY = "I.A.Q.Q."

  10. #10
    Join Date
    Apr 2002
    Posts
    11,808
    Xavier

    Lesson for the day, your ductilator gives you the pressure drop per 100 ft.

    Why not post three measured data points, measured air flow vs pressure drop and we can discuss this.

    Surely as an inventer you must have at least measured what your prototype did.









    [Edited by Carnak on 11-11-2004 at 05:15 PM]
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  11. #11
    Join Date
    Sep 2004
    Posts
    51
    Wow!

    I did not realize that a question as simple as advice on two different approaches towards make up air would be the forum for a couple of interesting rants and raves!

    First, I have heard support for both Skuttle and Equalize Air on the Glenn Haege show. But commercials and advertisement do not always mean good products, look at Fabreeze vs. SmellsBGone.

    Second, I am a bit disappointed there is not more substanative data on the Xavier website, if you would really call it that. I am not interested in using a window as a housing for a make up air device; it would be much better to utilize a 6" hole in my opion. Maybe there is techinical data why I don't want to do that, but I have not found it. Further there is NO info on Xavier beyond the aol website.

    Finally, I am also a bit disapointed in a lack of generic information on barometric dampers, which I think the Skuttle really is. Lots of anecdoatal advice on using one, just not any real data.

    Oh and for the record I am not going to do any calculations on pressure drops, mass flow, etc. I did enough of that in theromdyamanics classes for my engineering degrees!!!

  12. #12
    Join Date
    Aug 2003
    Posts
    626
    Xavier-- I have done a lot of manometer testing on homes with fresh air vents from the outside to the return. Explain why Eqalized-air does not pressurize the home.

  13. #13
    Join Date
    Dec 2000
    Location
    Michigan
    Posts
    724

    Hmm Information

    DZD, I am completely confused by your last statement of having an Engineering degree and not understanding how make-up and combustion products operate.

    The majority of make-up products all use the "barometric damper" principle to open to allow outside air to enter the home. Unfortunately, as not all HVAC system are designed and installed correctly and that every home is different, it is impossible for any manufacturer to make “claims” on the amount of airflow through their product.

    If you listen to Glenn then you must have heard me as I have been on his show over a dozen times explaining how a home works. In addition, you must have heard listeners who have installed a “one-hose” system and they still get fireplace smoke and smell. The reason is simple; the return duct will not notice a change in pressure in the home as fast as my two-hose system.

    Furthermore, as show on my website by the three houses (Copied from Custom Builder Article dated 1985) the potential problem with a one hose system and a no hose system.

    I suggest you use your Engineering degree, calculate the amount of air leaving your home, and then design a system to supply that amount using a barometric damper that is sensitive enough to open on demand. Note, there are code requirements on the size of the openings of the screen that many other products do not meet.

    Regarding my website, you must remember that I invented EQUALIZ-AIR in 1978 when NO ONE even considered the importance of make-up and combustion air. Perhaps I should update my website, but based on the over 10,000 hits and question I get each day and the ones on this site, the majority of homeowners still do not understand why they must “open a window” in the winter. They do not know where the air for the dryer comes from, air for their fireplace, why they have Radon and they do not understand that HRV and ERV DO NOT add air to a home! So I think I will leave the site as is for now.

    As Glenn states: Do your research and make an informed decision. And as I say, “Houses don’t make Air” and “Water always wins that is why there is a Grand Canyon”!


    Uktra, because my flappers operate "Concurrently", you cannot pressurize the home! Please explain this to Carmak.
    The quality of my performance, sometimes depends on the quality of my audience.
    Imitation (Plagiarism) is the best compliment one can get -- "Open A Window"

    To improve Indoor Air Quality: Control Indoor Air QUANTITY = "I.A.Q.Q."

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