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  1. #1
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    Apr 2005
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    Not sure if this should be here or in the fireplace section. I am trying to add more returns and the options are limited. The best place seems to be the floor about 20 inches from the edge of a wood burning fireplace with a gas starter. One contractor didn't see this as a problem but the next one said it was too close to the fireplace. Are there codes that cover this?

    [Edited by heetseeker on 05-03-2005 at 09:57 PM]

  2. #2
    Join Date
    Jul 2004
    Location
    West TN
    Posts
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    All tech's here....
    Don't bash me for trying to help.
    I'm fixing to go well above the call of duty here.
    I'm not trying to help him DIY....
    I've been keeping an eye on his posts and he needs
    serious help or he's gonna be in serious discontent
    no matter what he gets.
    My intention is not to full out design the system site unseen. I'm just trying to get to the bottom of things.


    Heetseeker,

    I picked a random post of yours to get in touch with you.

    I can see that you've been trying to wade through your
    system upgrade delima.
    I see its been giving you troubles trying to
    get the answers you need when your not sure of what questions to ask.

    Lemme see if I can help guide you the best I can.

    First off...
    Have you had a load calculation performed on your house?

    Are you interested in zoning by means of electronicly controled dampers? (if you are interested in zoning, then from what I remember.... there is a different load calculation for that. You end up with a smaller overall unit size. Its been forever since I've done a load calcuation... I'm a full time tech. There is someone else in our company that does the load calc's)

    How big are your current Air conditioners?
    Has the house been added onto since they were installed?
    If so... how many square foot? (I can't size equipment
    based on this... in all reality, I probably can't do a whole lot with this.... but I'll try hehe)
    I understand you have two systems.
    One for the main house(119k btuh furnace), and another for a sun room(71k btuh furnace). By the way... those numbers sure sound strange.... Are these the Output Btuh ratings?
    GO ahead and give me Input Btuh and Output Btuh ratings if available.

    Main Unit.
    Return.
    Does the inside of the duct have insulation in it?
    If so... how thick is it?
    16 x 9 branch duct goes to what size return grille.
    What kind of grille is it? Filter Grille, Floor furnace grate, or what
    30 x 10 branch duct... same question.

    10 x 8 supply duct to LR znd DR.
    What size and how many supply grilles does it feed. Describe the grilles. Are they in the floor, baseboard, low sidewall, high sidewall, etc.
    Give me a rough idea how long you think the duct is.
    (I'm not planning on doing a full out 'manual D'
    I'm just trying to see if your worry of the static pressures are anything to worry about. Your current
    readings don't say much to me since I dont' know how much air the system is actually moving. By the way... is your current furnace belt drive? Does the blower have a belt on it?)

    18 x 8 feeding 4 bedrooms.
    I've got 6 grilles total off it. Is this correct?
    2 of those are 6" flex runs to something (forgot what)

    Errrr....
    Lets try it this way...

    Main Return
    24 x 8
    How Long? 4ft
    Duct Liner? Y/N/What size?
    25 x 10 Branch duct
    How Long?
    Duct Liner? Y/N/What size?
    How many elbows do you think you have?
    How Many Return Grilles?
    List size and style for each grille.
    16 x 9 Branch Duct
    Same questions

    Main Supply
    26 x 10
    How long? (between furnace and first connection)
    Duct Liner? Y/N/What Size?
    Number of elbows? (before first connection)
    Which duct comes off this first? 10x8/18x8/16x8?
    Does duct reduce in size after first duct comes off? If so, what size does it reduce to?

    First branch duct.
    What size?
    How long? (duct itself, not the pipes feeding vents)
    How many supply grilles does it feed?
    What size grilles?
    What style grilles?
    How long? (from duct to vent on longest run)
    Is this area comfortable?

    Main supply after first branch duct.
    What size?
    How long? (between first branch duct and second branch duct)
    Number of Elbows?

    Second branch duct.
    What size?
    How long? (duct itself, not the pipes feeding vents)
    How many supply grilles does it feed?
    What size grilles?
    What style grilles?
    How long? (from duct to vent on longest run)
    Is this area comfortable?

    Main supply after Second branch duct.
    What size?
    How long? (between second branch duct and third branch duct)
    Number of Elbows?

    Third branch duct.
    What size?
    How long? (duct itself, not the pipes feeding vents)
    How many supply grilles does it feed?
    What size grilles?
    What style grilles?
    How long? (from duct to vent on longest run)
    Is this area comfortable?


    Keep in mind that I'm not doing a full out duct calculation. Just get close and I'll go from there.

    The duct leaks you've mentioned somewhere.
    Are these part of the original duct system?
    Or are they the result of people coming in and adding
    pipes/flex?
    Have you had anyone repair the leaks yet? (aside from the flex runs)

    The area(s) the flex feeds.... is it uncomfortable?
    How close/which branch closest to the furnace can these pipes come off of?
    You've mentioned its coming off the 18 x 8, can it come off a different branch or even at the furnace itself?

    How big is the room that the furnaces are in?
    Does it have outside combustion air?
    Is the room along an outside wall?
    How far is the room from the outside wall you've mentioned
    venting out of?
    What room is on top of the furnace room?

    Are your filters located at the furnaces?

    The other system....
    I have two 6 x 12 returns on a 24 x 8 duct.
    Describe the grilles.
    Duct liner?
    I'm confused... are they in the furnace room in the basement? Is there a return grille in the basement in the furnace room? Does the sunroom have return grilles in it?

    Supply
    20 x 8 feeding six grilles
    guess how long the duct is.
    any elbows?
    describe the grilles
    Size, style, etc

    Note any grilles that are noisy.
    'singing' or loud with air turbelance

    How hard would you say the grilles blow.
    (this is a bad question in all reality...
    your hand will lie to you. A meter is required really.
    describe the air flow the best you can. I'll take it
    with a grain of salt.)

    Is your sunroom comfortable?

    Are there any vents in the basement?
    If so... what are they coming off of?
    How big is your basement?
    Is it being used?


    These are all the questions I can think of for now.
    Should keep you busy for a while

















  3. #3
    Join Date
    Aug 2002
    Location
    Westlake, Ohio
    Posts
    2,538
    Originally posted by heetseeker
    Not sure if this should be here or in the fireplace section. I am trying to add more returns and the options are limited. The best place seems to be the floor about 20 inches from the edge of a wood burning fireplace with a gas starter. One contractor didn't see this as a problem but the next one said it was too close to the fireplace. Are there codes that cover this?

    [Edited by heetseeker on 05-03-2005 at 09:57 PM]
    Not any codes that I know of. It doesn't matter if it is one foot or ten feet from the firplace if the return is bigger in the room than the supplies. This will cause the room to be in a negative pressure and pull fumes from the fireplace when the blower is running. Any time a large return is in the same room as a fireplace the blower should not be operated when the fireplace is in use unless the room can be tested for positive pressure and the fireplace for venting.
    captain CO

  4. #4
    Join Date
    Apr 2005
    Location
    illinois
    Posts
    257
    Jim Davis
    Once again you tell me something that makes sense but doesn't make me happy. In the family room where the fireplace is there is a large return spanning two stud bays. I was happy recently to find that one of the returns had been blocked by a piece of metal at the bottom of the stud bay. I think it probably was there since the house was built 35 years ago. I removed and thought it would be a nice way to decrease my high static [.5 to .58] on the return side. Now I worry that the fireplace will not vent properly since the family room has no supplies. The room however is in the center of the house and has two large passageways to the sunroom[sunroom served by a different furnace but has 6 supply vents ] as well as being completely open to the kithen [ no returns there but two supplies working with the same furnace]Will it be obvious that the fireplace is not working such as smelling smoke in the room?

  5. #5
    Join Date
    Apr 2005
    Location
    illinois
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    Wormy I posted this elsewher but I suspect you didn't see it
    Thanks for your replies and your interest. I wish you could see my house too. For my static pressures I had a contractor come out who checked the pressures. Search under my name and see my post on high static pressures.
    I have been busy. I took down the drywall in my basement and found out that my 3 supply ducts to the master bedroom are all faulty. The two long runs to the addition to the bedroom were basically disconnected from the main trunk. When they added the flexduct they probably moved the hard duct enough to have the connection to the main run fall apart. The ducts were held together with dried up duct tape.In addition the connection between the hard ducts and the flex duct had big gaps. The third duct to the bedroom has a big air leak where the hard duct meets the supply vent. No wonder the bedroom was cold in the winter. I guess the best solution for this last problem is lots of mastic.
    I also found out that one of my wall return ducts was blocked by a piece of metal at the floor after I opened the metal between the joists in the basement . Apparently the original installer when they built the house had tacked up metal to seal the return but forgot to remove it.
    This should reduce the return static on my big furnace. The return static on the big furnace was .5 and the supply was .35 the first time they measured it. They came back and when they remeasured it they got the following measurements. There is an open grill on the return drop of the large furnace. we measured the static with the grill open and covered. Unfortunately they had no solution to the static. They said they install lots of furnaces with similar static.


    grill open
    .18 filter .5 blower .25 A coil .18

    grill closed
    .26 filter .58 blower .25 A coil .18

    The numbers are placed where the readings were taken in relation to the various furnace components. With my limited knowledge I figure my static is normally .83 [.58+.25] since I plan on closing the grills when the furnaces are replaced. With my newly functioning return I suspect the static pressure will fall closer to the .75 that I get with the grills open. I am thinking that if I get a vs 80 2 stage furnace that the static will be lower most of the time when the furnace is running on low fire[altho with less thermal efficiency].
    The a/c will still be a problem. I don't really want to go to a two stage a/c because of cost. Can you comment on how bad you think these pressures are?
    Again thanks for your interest.


    Thanks for trying to help. I am getting tired just thinking about answering all the questions you are asking.
    If you really think you can help I will try to answer your questions as best I can. I have doubts about how effective this will be givent the limitations of posting.
    See my post about adding larger branch ducts. I am pretty confident that fixing my disconnected ducts and sealing them will make me happy enough. The suggestion that I replace my long 6 inch ducts with 7 inch ducts has me scratching my head. Currently I am not looking at zoning since I have too many questions ie short cycling, limited returns, putting 4 tons of a/c into a 400 sq foot room, Bypass damper type etc. Let me know what you think.






  6. #6
    Join Date
    Jul 2004
    Location
    West TN
    Posts
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    In my opinion, the static pressures you have now have
    little relavance. This is what your current system is
    producing with your duct. Also, without the actual fan
    data for your furnace... we can only guestimate what your
    system is doing. Some older units couldn't move much air
    without any ductwork on it... then there are some units
    thats got unbelievable umph (especially belt driven
    blowers that are not set up right). You'll also get high
    readings if the CFM is just set up way too high. WIthout
    doing a load calculation... it may be that the unit is
    OVERSIZED for the duct rather than the duct undersized for
    the unit.
    So all in all...the numbers dont' give me a really definitive answer.

    By knowing your current duct system, I can give you an
    idea what you can do. I should be able to see if your
    duct system is truely too small or not. There are really
    too many unanswered questions to say for sure right now.



  7. #7
    Join Date
    Jul 2004
    Location
    West TN
    Posts
    983
    A picture is worth a thousand words.

    If there's any way you can draw the duct system and
    email the pic. It may cut down on alot of questions hehe.

    For now... if you could answer the first section of questions... I might can get a little closer to being able to help.
    ************************************************** *****

    Have you had a load calculation performed on your house?

    Are you interested in zoning by means of electronicly controled dampers? (if you are interested in zoning, then from what I remember.... there is a different load calculation for that. You end up with a smaller overall unit size. Its been forever since I've done a load calcuation... I'm a full time tech. There is someone else in our company that does the load calc's)

    How big are your current Air conditioners?
    Has the house been added onto since they were installed?
    If so... how many square foot? (I can't size equipment
    based on this... in all reality, I probably can't do a whole lot with this.... but I'll try hehe)
    I understand you have two systems.
    One for the main house(119k btuh furnace), and another for a sun room(71k btuh furnace). By the way... those numbers sure sound strange.... Are these the Output Btuh ratings?
    GO ahead and give me Input Btuh and Output Btuh ratings if available.

    ************************************************** *********

  8. #8
    Join Date
    Apr 2005
    Location
    illinois
    Posts
    257
    Wormy
    No real load calc.done.
    I have hesitated to do it myself since I think I could easily make a mistake and I have read that HVAC calc doesn't allow for figuring a partial crawl space. One saleman last year did measure the room sizes and windows and suggested a Carrier 80% 135k BTU input main furnace replacement. He didn't ask about insulation or any design temps.Current furnace is Carrier 119k BTU input 80% and seems to handle the coldest conditions here in chicago. Not sure of the size of my A/C wiring diagram is for a 4 or a 5 ton with most contractors doing assuming 4 ton. These units serve about 2600 sq ft of ranch house and the basement[ another 2000 ft ]
    Small furnace is 71k input 80% and the A/C is most likely a 2 ton carrier. Serves 400 ft of sun room which is north facing and shaded on the west by a large tree. I know the equip is oversized. The small system was added when the sun room was built in 1984 by the prior owners.
    I am not interested in zoning any longer. Too many questions and it doesn't seem like my contractors have the answers. The largest local carrier dealer has never installed the infinity system. The others rely on the discharge air sensor to keep the equip for hitting the limit. Seems like a recipe for short cycling esp on a/c.
    I think the sun room would be too small a zone for 4-5 tons of a/c.

    When ESP is measured should all the supply registers be open?

    Here is my return data on the large furnace Carrier 119k btu input 80%. .
    Filter aprilaire 2200 on the side of the furnace
    Return drop 24x8
    Main return trunk 25x10 about 8 feet
    Trunk A 12.5x9 [outside dimensions panned return]feeds main trunk . Seems three returns from the laundry room dining room and edge of the kitchen feed this trunk with grill openings of 13.5x 5.5 and 11.5x5.5 and 11.5x5.5 in. [ weak flow] Est length about 25 ft
    Trunk B 19x9 [O.D. panned return] feeds main return. The part of this return farthest from the furnace is 12x8 and this 12x8 metal duct is fed by three 11.5x 5.5 in. grill openings using the wall cavities in the 3 bedrooms. These three grills barely can hold up a kleenex when the fan is on. The return trunk then enlarges to enlarges to 16x8 in. and receives two more returns from the office [also weak flow]and basement with 11.5x5.5 grill openings. Then it goes into the 19x 9 inch section . total lenth about 25 feet
    Trunk C consists of a short approx 12 foot trunk that basically has panning across two adjacent joist spaces for a dimension of about 30x9 in. This serves a grill opening of 29.25x5.5 that spans two stud bays. This return pulls hard.
    Trunk D is a short trunk as well[about 12 feet] that is about 10x30 and serves a grill opening of about 29.25 x 5.5 that spans two stud bays. This also pulls hard.
    The return drop has an 9.5 by 5.5 in. open grill on the side of it. This also pulls hard.



    Small furnace return info: The filter is an aprilaire 2200. The main return is 18x8 and the return drop is 24x8. The return drop has an open grill on its side which is 11.5x5.5 in.
    The sun room is open to the adjacent room so it doesn't really pressurize. There are six supplies and two returns.
    The two return grill openings are 11x5.5 in. Weak flow here too. I can't size the return trunks since they are either enclosed in drywall or in a non accessible crawl under the sun room.

    I have some good news. Although my static is still a concern the duct fix seems to be working. Today was hot 85 and humid. I turned on the a/c and the master bedroom was actually colder by 1-2 degrees than the central hall. This is with unsealed ducts with a gap between the flex and the hard duct. If I can get the flex duct replaced by hard insulated duct and if I can find the more efficient register boots I may have the opposite problem of an over conditioned room.

    Thanks for your help.














    [Edited by heetseeker on 06-05-2005 at 04:32 PM]

  9. #9
    Join Date
    Aug 2002
    Location
    Westlake, Ohio
    Posts
    2,538
    If the fireplace isn't venting you will be smelling the smoke. The problem that is of major concern is when the fire is going out and smoldering. This is when the maximum co levels can be produced. Hopefully you will have a good CO alarm located in the right place.
    captain CO

  10. #10
    Join Date
    Jul 2004
    Location
    West TN
    Posts
    983
    Heetseeker,

    "When ESP is measured should all the supply registers be open?"
    Yep.
    Quick overview of whats going on.
    Trumpet player playing trumpet. THe pressure making his mouth push outward (like a chipmunk) is static pressure.
    Closing vents puts more resistance on the duct (sorta like putting a sock in the end of the poor fella trumpet)
    The pressure goes up, but since the trumpet player can't blow any harder... he moves less CFM.
    Take the sock out (open your vents) and the ESP goes down and since its easier to blow more air... the CFM goes up.


    The measurement should be taken at door to blower section of furnace (I'm picturing the filter assembly mounted to side of furnace.) for the return reading and between the
    evap coil and furnace for the supply.


    On to the ductwork...
    Is the Return Drop a duct standing up on one side of the furnace and connects into the 25x10?

    Does the duct tee off in different directions?

    I may be imagining this wrong...

    Coming off one side of furnace is a filter assembly.
    Ell's up and turns into 24x8 duct going up to ceiling. (about 4ft)
    24x8 duct connects into center of 25x10 duct. Basicly Tee's off in two directions.
    In one direction... the 25x10 duct has Trunk A and Trunk B
    The other direction carries Trunk B and Trunk C.

    Is that right?
    Or does it do this...
    24x8 goes up and connects to an ellbow. The ellbow changes size and connects to the 25x10 duct thats running horizontal across ceiling.

    All the panning ties into the top of the 25x10.


    How well is the panning sealed?
    It needs to be sealed at the bottom of the joists where
    the metal is screwed on AND at the top of the joists where the floor sits on top of the joist.

    Check all your connections to the panning to.
    Including Trunk B that starts as panning then goes back to
    a metal duct (16x9).


    SO FAR....
    With just the info you given.
    IF the 25x10 Tee's off like I described(one end connecting to Trunk A and B and other side of Tee connecting to trunk C and D) then the 25x10 is ok and the panning is ok.
    This is generic figuring for a 4 ton unit though.
    Give me a description of the supply and I can give a better
    idea of the system as a whole.

    On the other hand...
    If the 24x8 is connecting to one end of the 25x10 and its
    forming an ell... then the 25x10 is not big enough.

    Genericly speaking...
    the 25x10 can handle about 800 CFM
    So if its connected in the middle, then you can have 800 going one way and 800 going the other.


    The verticle duct (24x8) is definatly undersized though.
    It can only handle about 500 CFM
    It would be nice to have a second duct coming on the other
    side of the furnace to take air in on the other side of the blower. This is actually only required for 5 ton units (air coming in on both sides of furnace)
    The drawback is having to add another filter assembly though. The more filter area you have, the better though hehe. It might be a bit expensive to go that way though.
    The cheaper route would be to replace the 24x8 with a larger duct. 24x18 is about what you need for 4 tons of air. the 24x8 is creating a pretty big restriction.

    The 30x8 ducts will need some dampering too.
    THey are kinda oversized. You need the resistance to make
    the bedroom returns able to work right.
    A good meter would need to be used to balance your returns
    correctly.

    I don't have my grille book in front of me to double check the grille sizes. I'll have to check that tomorrow.

    I'm really curious about your supply duct







  11. #11
    Join Date
    Jul 2004
    Location
    West TN
    Posts
    983
    I forgot to mention..
    I'm assuming you have 1/2" duct liner in your ducts.
    Take your filter out and look inside the duct and see
    if there is any insulation glued to the inside.
    Its possible there's not any in there considering its in
    a finished basement.

  12. #12
    Join Date
    Apr 2005
    Location
    illinois
    Posts
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    Wormy Can't answer all the questions yet but wanted to answer at least some of them.

    I fiqured out that the ESP should be measured with all the registers open. The only guy who measured ESP didn't make sure I did that . I figured this out after he left.

    Is the Return Drop a duct standing up on one side of the furnace and connects into the 25x10? Yes

    Does the duct tee off in different directions? Yes

    I may be imagining this wrong...

    Coming off one side of furnace is a filter assembly.
    Ell's up and turns into 24x8 duct going up to ceiling. (about 4ft) Yes

    24x8 duct connects into center of 25x10 duct. Basicly Tee's off in two directions.
    No, 25x 10 duct is connected at one end to the 24x8. It is not the most efficient transition. The 24 inch long axis of the 24x8 drop is parallel to the direction of the length of the 25x10 duct. The air has to funnel into the 24x8 by narrowing the air current from side to side and turning 90 degrees down.


    In one direction... the 25x10 duct has Trunk A and Trunk B
    The other direction carries Trunk B and Trunk C.

    No,Trunk A comes from the east , trunks b,c and d come from the west. One correction trunk A has only two return grills feeding it, I miscounted.


    Is that right?
    Or does it do this...
    24x8 goes up and connects to an ellbow. The ellbow changes size and connects to the 25x10 duct thats running horizontal across ceiling. No elbow, just runs into each other.

    All the panning ties into the top of the 25x10.


    How well is the panning sealed? Just nailed, no mastic.
    It needs to be sealed at the bottom of the joists where
    the metal is screwed on AND at the top of the joists where the floor sits on top of the joist.

    Check all your connections to the panning to.
    Including Trunk B that starts as panning then goes back to
    a metal duct (16x9).


    SO FAR....
    With just the info you given.
    IF the 25x10 Tee's off like I described(one end connecting to Trunk A and B and other side of Tee connecting to trunk C and D) then the 25x10 is ok and the panning is ok.
    This is generic figuring for a 4 ton unit though.
    Give me a description of the supply and I can give a better
    idea of the system as a whole.

    On the other hand...
    If the 24x8 is connecting to one end of the 25x10 and its
    forming an ell... then the 25x10 is not big enough.

    BINGO, This may be a big part of the problem. The 25x10 may be pulling all the air it can handle from the bigger returns and not from the smaller returns. The static pressure may be high because both the 24x8 and the 24x10 are bothtoo small and are causing a bottle neck. If I am understanding this correctly I need to increase the size of the 25x10 return and the 24x8 drop. You said the 24x18 is what I need for 4 tons of air. That calculates to 432 sq inches. That is a lot more than what the 25x 10 has[250 sq inches]. To get 432 sq inches I would need 182 more area like an additional 18x 10 duct. Is that right?
    How much air flow can a spaceguard 2200 hundred handle without getting a big pressure drop. Does this make sense?


    Genericly speaking...
    the 25x10 can handle about 800 CFM
    So if its connected in the middle, then you can have 800 going one way and 800 going the other.


    The verticle duct (24x8) is definatly undersized though.
    It can only handle about 500 CFM
    It would be nice to have a second duct coming on the other
    side of the furnace to take air in on the other side of the blower. This is actually only required for 5 ton units (air coming in on both sides of furnace)
    The drawback is having to add another filter assembly though. The more filter area you have, the better though hehe. It might be a bit expensive to go that way though.
    The cheaper route would be to replace the 24x8 with a larger duct. 24x18 is about what you need for 4 tons of air. the 24x8 is creating a pretty big restriction.

    The 30x8 ducts will need some dampering too.
    They are kinda oversized. You need the resistance to make
    the bedroom returns able to work right.
    A good meter would need to be used to balance your returns
    correctly. Wormy, what kind of meter?

    I don't have my grille book in front of me to double check the grille sizes. I'll have to check that tomorrow.

    I'm really curious about your supply duct


    No duct liner. Some insulated flex duct in the crawl space which is an area about 12x 20 sq ft
    Wormy I will try to answer more of your questions later. MUCH, MUCH THANKS. You are extraordinarily generous with your time and extensive knowledge. I still have not figured out how to draw the duct system. If I could get your e mail I could send some pictures.

    [Edited by heetseeker on 06-08-2005 at 10:07 AM]

  13. #13
    Join Date
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    West TN
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    Heetseeker,

    This is from Aprilaires websight.

    Aprilaire FAQ
    7. What is the MERV rating of the Models 2200 and 2400?
    They have a MERV rating of 10 at 1200 cubic feet per minute. When comparing air cleaners always look at the overall picture. The MERV rating is a general statement of the cleaning effectiveness when the air cleaner is new, but it ignores the service life of the media (how often maintenance is required), whether the cleaning effectiveness increases or decreases over time, and how much the resistance of the air cleaner will affect the performance of the furnace. So keep the MERV rating in perspective
    Since you will typically want 1600 CFM for a 4 ton unit.
    Then two filters would be better. And overall less restrictive. Its harder to shove 1600 cfm though a filter rated for 1200. OR you could say... Its easier to shove 1600 cfm through filters rated for 2400 cfm. Make since?

    I'll refigure duct sizes based on no duct liner in returns. Also have to figure up those grille sizes.

    Email is rlwsmail@bellsouth.net
    Gimme some digital picks hehe.

    Here's some examples of meters used to balance your returns...
    Flowhoods

    Velometers

    As you can see... these tools are not cheap.
    The velometers are not going to be as accurate as the flowhood because you have to measure the air stream 1" from the face of the grille and have the manufacturers data
    in order to convert the air speed (FPM) to air volume (CFM).

    The flowhoods measure the CFM directly without need of manufacturers data. But they are pretty costly.
    I can balance with either one... cuz I got ermmmm "Mad Skillz" hehe couldn't help myself... gotta make a fool outta myself everyonce in a while hehe. I wouldn't be able to tell someone else how to do it. Then again...
    wouldn't get that deep on here especially for a homeowner.


    Gotta spend time with the family...
    more to come later



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