New Manual J produced to match installed equipment. - Page 2
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  1. #14
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,695
    Quote Originally Posted by como View Post
    The original Manual D called for all duct work to be run in sheet metal. It was all ran in air connector (not air duct) and is loose, each run is compressed in multiple places etc. It is supposed to be checked this week for CFM at each supply register, and I'm being told if each supply register is the correct CFM then the system is working fine and they are done.
    This is a great thread, all good comments, thanks for starting it.

    I like the idea of new rules of thumb. Rules of thumb will never go away. Seems pretty widely accepted by experienced knowledgable contractoer that old rules of thumb cause fear of deviation that leads to gross oversizing.

    Stuffy? What's the house cfm50 leakage rate? Do you have a erv or some type of fresh air system? Don't blame your hat for your wet feet.

    Here are just a couple problems with cfm at register. First, what IS the correct cfm? Was it in your design plans, or will it be a verbal "yep, that looks about right.".

    Second, how does this address static? (this problem probably includes insufficient filter- udarrell - how many sq inches need?)

    They don't hook garden hoses to a fire truck for a reason. Doesn't matter how much you turn up pressure if you don't have the volume. A hose that is designed for 1-5 gallons per minute just won't take 50. And if the need is for 1-5 gallons per minute, does it make sense to change the hose? A bigger hose will just kill all the plants.

    Unfortunatly the solution is likely to change for 50gpm pump to 5 gpm pump. Might see what deal they'll give on a trade to a 3 ton GREENSPEED.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  2. #15
    Join Date
    Aug 2012
    Posts
    11
    Quote Originally Posted by tedkidd View Post
    This is a great thread, all good comments, thanks for starting it.

    I like the idea of new rules of thumb. Rules of thumb will never go away. Seems pretty widely accepted by experienced knowledgable contractoer that old rules of thumb cause fear of deviation that leads to gross oversizing.

    Stuffy? What's the house cfm50 leakage rate? Do you have a erv or some type of fresh air system? Don't blame your hat for your wet feet.

    Here are just a couple problems with cfm at register. First, what IS the correct cfm? Was it in your design plans, or will it be a verbal "yep, that looks about right.".

    Second, how does this address static? (this problem probably includes insufficient filter- udarrell - how many sq inches need?)

    They don't hook garden hoses to a fire truck for a reason. Doesn't matter how much you turn up pressure if you don't have the volume. A hose that is designed for 1-5 gallons per minute just won't take 50. And if the need is for 1-5 gallons per minute, does it make sense to change the hose? A bigger hose will just kill all the plants.

    Unfortunatly the solution is likely to change for 50gpm pump to 5 gpm pump. Might see what deal they'll give on a trade to a 3 ton GREENSPEED.

    Sorry I guess I wasn't clear.

    The original Manual J called for a 3 Ton AC and a 71,000 BTU Heating Output furnace. The 3 TON AC was installed but a 54,000 Btuh furnace was installed. Once I questioned the furnace size not matching the original Manual J specification, a new Manual J was created that shows a 54,000 Btuh furance being required but it lowers the AC to 2 TONs. The 3 Ton AC is still installed and the furnace is what I'm wondering about. It doesn't seem right that the original manual j is discarded and a new manual J is created after installation to justify the equipment size.

    The duct work is also questionable but more complex and difficult for me to understand. I'll have to have an energy audit done if they are able to check the flow rate in addition to duct leakage to figure that out.

  3. #16
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,695
    Sorry, getting threads confused.

    They probably inadvertently did you a favor installing the smaller furnace. It will have longer (quieter, more even distribution, more efficient operation) cycles and be generally more comfortable.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  4. #17
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,695
    Sorry, getting threads confused. My fault, not yours.

    They probably inadvertently did you a favor installing the smaller furnace. It will have longer (quieter, more even distribution, more efficient operation) cycles and be generally more comfortable.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

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