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Acceptable system static pressure?

ChrisJChrisJ Member Posts: 8,649
I'm curious what the acceptable range is for static pressure on a system. I'm talking return and supply losses, even across the A\C coil. Basically measuring the difference from the return of the AH to the supply.

I've seen comments of some air handlers expect 0.5" or less, but I also see many show a range of 0.1 all the way to 0.9"

What's considered great, good, acceptable and poor? Also, what's typical?


It seems like a good pleated filter can have as much as 0.2" drop alone.
Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

Steam system pictures
https://goo.gl/photos/ZgpNUTyckkmiEdAf9
Central air project pictures
https://goo.gl/photos/4JjnLStEq42sWsQo8

Comments

  • bobbob Member Posts: 813
    It depends on the specs of the air handler. As long as the total pressure drop of the registers, ducts, filters doesn't exceed the total external static of the air handler you are in good shape. Check to verify if the coil (wet) is included.
    bob
  • ChrisJChrisJ Member Posts: 8,649
    bob said:

    It depends on the specs of the air handler. As long as the total pressure drop of the registers, ducts, filters doesn't exceed the total external static of the air handler you are in good shape. Check to verify if the coil (wet) is included.

    Have not bought the unit yet so I can't check the name plate, but this is what the manual shows.

    I assume the fact it shows it running as high as 0.9" suggests that's acceptable (with clogged filters, shut diffusers etc) ? I believe I'd want to use constant CFM mode rather than constant torque.

    I was more curious what most residential systems expect rather than this specific one.


    1.JPG 346.7K
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures
    https://goo.gl/photos/ZgpNUTyckkmiEdAf9
    Central air project pictures
    https://goo.gl/photos/4JjnLStEq42sWsQo8
  • ChrisJChrisJ Member Posts: 8,649
    Need to start this thread back up with what is hopefully an easy to answer question.

    If an air handler or furnace says it's designed for a total static pressure of 0.5", does this mean with new filters, or is that the ultimate pressure it wants to see with a dirty filter? I.E. never, ever let it go over 0.5"?

    I'm assuming 0.5" is the maximum with a new filter, expecting to creep up towards 1" with a dirty filter?

    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures
    https://goo.gl/photos/ZgpNUTyckkmiEdAf9
    Central air project pictures
    https://goo.gl/photos/4JjnLStEq42sWsQo8
  • Harvey RamerHarvey Ramer Member Posts: 1,969
    .5 is the max rated ESP.
    Ramer Mechanical
    ramermechanical.com
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • ChrisJChrisJ Member Posts: 8,649

    .5 is the max rated ESP.

    So, never expected to go over half an inch, ever.

    I wonder how often that actually happens in real life with typical duct work and typical filter changing habits?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures
    https://goo.gl/photos/ZgpNUTyckkmiEdAf9
    Central air project pictures
    https://goo.gl/photos/4JjnLStEq42sWsQo8
  • Harvey RamerHarvey Ramer Member Posts: 1,969
    ChrisJ said:

    .5 is the max rated ESP.

    So, never expected to go over half an inch, ever.

    I wonder how often that actually happens in real life with typical duct work and typical filter changing habits?
    Most systems go over .5. No doubt about it. Once you get above .8, you are out of the safe zone. 1" and up, guaranteed problems.

    With proper design and regular filter changes, you can stay below or at .5.
    Ramer Mechanical
    ramermechanical.com
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • ChrisJChrisJ Member Posts: 8,649

    ChrisJ said:

    .5 is the max rated ESP.

    So, never expected to go over half an inch, ever.

    I wonder how often that actually happens in real life with typical duct work and typical filter changing habits?
    Most systems go over .5. No doubt about it. Once you get above .8, you are out of the safe zone. 1" and up, guaranteed problems.

    With proper design and regular filter changes, you can stay below or at .5.
    Is 0.5" a new standard, or has it been the standard for a long time?
    Or does it vary from appliance to appliance?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures
    https://goo.gl/photos/ZgpNUTyckkmiEdAf9
    Central air project pictures
    https://goo.gl/photos/4JjnLStEq42sWsQo8
  • Harvey RamerHarvey Ramer Member Posts: 1,969
    ChrisJ said:

    ChrisJ said:

    .5 is the max rated ESP.

    So, never expected to go over half an inch, ever.

    I wonder how often that actually happens in real life with typical duct work and typical filter changing habits?
    Most systems go over .5. No doubt about it. Once you get above .8, you are out of the safe zone. 1" and up, guaranteed problems.

    With proper design and regular filter changes, you can stay below or at .5.
    Is 0.5" a new standard, or has it been the standard for a long time?
    Or does it vary from appliance to appliance?
    Pretty much all current equipment uses a .5 standard, save some high static commercial units.
    Ramer Mechanical
    ramermechanical.com
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • newagedawnnewagedawn Member Posts: 287
    every system comes with a rated static pressure before duct is attached, weather it is .05 or .09 each static pressure should push a certain amount of CFM, for heating or cooling or both, when duct is attached and flex and diffusers and coils and filters this can change.the static pressure of the system,
    thats why after the system is installed you need to check static and CFM to see where it falls, and make your adjustments accordingly, some retrofits the duct is to small and there are problems with air flow(CFM), others the duct is sized properly and it works within the manufactures specs,.but the only way to know is to test it after install.
    there are ways to tell if the duct is sized properly before install but thats another question
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 2,708
    Start with the basics. ANY air handler is a box with air going through it. In most cases the "size of the box" is determined by the square footage of the chilled water or DX coil. Max air flow velocity through a cooling coil (chilled or dx) is in the neighborhood of 500fpm. If the air goes faster water gets pulled off the coil. Can't defy mother nature

    In a specialized commercial job I have seen 6-700fpm but you get into mist elimenator territory and potential problems.

    so once the required cfm is determined the size of the cooling coil face area is determined once that is selected the "size of the box" is known.

    To change the amount of cooling the coil is made thicker or thinner to get the capacity needed for the selected cfm. Cooling determines the ahu physical size because heating coils can take much higher velocities 1000fpm.

    Once all the accessories are installed, coils , filters the manufacture calculates the required blower size. . there is static required to move air through the ahu plus whatever ESP (external static) both of them together =total static external static is for the ductwork.

    as far a residential jobs It's not my area but .5 sounds right
  • ChrisJChrisJ Member Posts: 8,649
    The air handler I'm working with states 0.5"WC but then shows a chart of what CFM you get from 0.1" all the way to 0.9" and they're fairly close as it's a variable speed AHU.

    But it seemed confusing to specify 0.5" but then show a chart all the way to 0.9".
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures
    https://goo.gl/photos/ZgpNUTyckkmiEdAf9
    Central air project pictures
    https://goo.gl/photos/4JjnLStEq42sWsQo8
  • ChrisJChrisJ Member Posts: 8,649
    My guess was the 0.5" standard is to ensure the cabinet meets leakage requirements which are apparently done at 0.5" and or 1".



    For example :




    Thoughts? Opinions?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures
    https://goo.gl/photos/ZgpNUTyckkmiEdAf9
    Central air project pictures
    https://goo.gl/photos/4JjnLStEq42sWsQo8
  • RichRich Member Posts: 2,262
    Follow this series ChrisJ .

    http://www.energyvanguard.com/blog/basic-principles-duct-design



    The total system static pressure when complete should not exceed .5" . Unfortunately computer programs have even very good duct designers installers believing they are doing well . Not the case since the program does not recognize velocities low enough for newer buildings to promote COMFORT in almost every sense of the word . Think ASHRAE 55 .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC 732-751-1560
    Serving most of New Jersey , Eastern Pa .
    Consultation , Design & Installation
    Rich McGrath 732-581-3833
  • Harvey RamerHarvey Ramer Member Posts: 1,969
    At or above .8" an ecm motor begins hunting. The constant cfm it is designed to provide is reduced and it may not receive adequate cooling any more. At this level, the life expectancy of the motor is greatly reduced.

    It's really a balance between fan design and motor design, the goal being to move the required amount of ait with the least amount of energy. To run a higher static, the fan blades should have a different pitch and the motor may need additional cooling.
    Ramer Mechanical
    ramermechanical.com
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • ChrisJChrisJ Member Posts: 8,649
    Rich said:

    Follow this series ChrisJ .

    http://www.energyvanguard.com/blog/basic-principles-duct-design



    The total system static pressure when complete should not exceed .5" . Unfortunately computer programs have even very good duct designers installers believing they are doing well . Not the case since the program does not recognize velocities low enough for newer buildings to promote COMFORT in almost every sense of the word . Think ASHRAE 55 .

    Thank you for commenting @Rich
    That's a good read, I remember reading one of their articles on flex duct (sags, turns etc) a few months ago.

    I'm reading a few more as we speak, I forgot about the website.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures
    https://goo.gl/photos/ZgpNUTyckkmiEdAf9
    Central air project pictures
    https://goo.gl/photos/4JjnLStEq42sWsQo8
  • RichRich Member Posts: 2,262
    edited May 25
    Allison promotes duct design how it's done by true ducted system Titans ChrisJ . I have collaborated on several projects with a few of them . They truly know how to do ducted right .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC 732-751-1560
    Serving most of New Jersey , Eastern Pa .
    Consultation , Design & Installation
    Rich McGrath 732-581-3833
  • RichRich Member Posts: 2,262
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC 732-751-1560
    Serving most of New Jersey , Eastern Pa .
    Consultation , Design & Installation
    Rich McGrath 732-581-3833
  • RichRich Member Posts: 2,262
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC 732-751-1560
    Serving most of New Jersey , Eastern Pa .
    Consultation , Design & Installation
    Rich McGrath 732-581-3833
  • RichRich Member Posts: 2,262
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC 732-751-1560
    Serving most of New Jersey , Eastern Pa .
    Consultation , Design & Installation
    Rich McGrath 732-581-3833
  • ChrisJChrisJ Member Posts: 8,649
    Total static in low stage







    Total static in high stage




    I'm using a MERV 8 20x25x5 AirBear.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures
    https://goo.gl/photos/ZgpNUTyckkmiEdAf9
    Central air project pictures
    https://goo.gl/photos/4JjnLStEq42sWsQo8
  • ratioratio Member Posts: 1,021
    I'm not sure that's enough static to keep the air from getting confused about which way to go. </humor> (???)
  • ChrisJChrisJ Member Posts: 8,649
    ratio said:

    I'm not sure that's enough static to keep the air from getting confused about which way to go. </humor> (???)

    It's a close race between the steam system and the central AC system.

    Steam runs around 0.25" when things are cold, around 0.5" during moderate use and 0.75" when things are kept fairly hot.

    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures
    https://goo.gl/photos/ZgpNUTyckkmiEdAf9
    Central air project pictures
    https://goo.gl/photos/4JjnLStEq42sWsQo8
  • ratioratio Member Posts: 1,021
    I'd take the static across my furnace, but I'm afraid it'd make me cry. :(
  • GordyGordy Member Posts: 7,122
    ratio said:

    I'd take the static across my furnace, but I'm afraid it'd make me cry. :(

    Is that a steam, water, or hot air furnace? @chris gets confused :D
  • ChrisJChrisJ Member Posts: 8,649
    > @Gordy said:
    > I'd take the static across my furnace, but I'm afraid it'd make me cry. :(
    >
    > Is that a steam, water, or hot air furnace? @chris gets confused :D



    Do you live in a condo or apartment? I get the two confused ;)
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures
    https://goo.gl/photos/ZgpNUTyckkmiEdAf9
    Central air project pictures
    https://goo.gl/photos/4JjnLStEq42sWsQo8
  • GordyGordy Member Posts: 7,122
    Duplex.......
  • newagedawnnewagedawn Member Posts: 287
    i like to see around .5 total eternal static, if its higher there is a restriction( in duct, in filter, in coil), if its low there is to much leakage in duct
    FYI, had one last week on a 16 seer A/C was .82 with pleated filter with blue filter .52
    same on a rooftop .68 with pleated filter, .49 with blue filter
    im begining not to like the pleated filters
    why is this important, comes down to cfm and the energy the motors use the higher the static pressure the more energy is used to move the air
    hope that helped
  • ChrisJChrisJ Member Posts: 8,649

    i like to see around .5 total eternal static, if its higher there is a restriction( in duct, in filter, in coil), if its low there is to much leakage in duct
    FYI, had one last week on a 16 seer A/C was .82 with pleated filter with blue filter .52
    same on a rooftop .68 with pleated filter, .49 with blue filter
    im begining not to like the pleated filters
    why is this important, comes down to cfm and the energy the motors use the higher the static pressure the more energy is used to move the air
    hope that helped

    The problem is, I assume those blue filters are woven fiberglass?
    They don't work very good as a filter compared to a good pleated filter.

    Of course, if the system isn't set up to use a properly sized one, you're kind of stuck.

    It seems like 1" thick pleated filters are troublemakers. There's usually not enough surface area.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures
    https://goo.gl/photos/ZgpNUTyckkmiEdAf9
    Central air project pictures
    https://goo.gl/photos/4JjnLStEq42sWsQo8
  • RichRich Member Posts: 2,262

    i like to see around .5 total eternal static, if its higher there is a restriction( in duct, in filter, in coil), if its low there is to much leakage in duct
    FYI, had one last week on a 16 seer A/C was .82 with pleated filter with blue filter .52
    same on a rooftop .68 with pleated filter, .49 with blue filter
    im begining not to like the pleated filters
    why is this important, comes down to cfm and the energy the motors use the higher the static pressure the more energy is used to move the air
    hope that helped

    Sometimes a low external static pressure is a good thing . This is usually when the ductwork is ample enough to lower the esp and also quiet the system . As long as it is balanced there is no problem of the esp is below .5 .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC 732-751-1560
    Serving most of New Jersey , Eastern Pa .
    Consultation , Design & Installation
    Rich McGrath 732-581-3833
  • ChrisJChrisJ Member Posts: 8,649
    Biggest regret I have in my system, is running 10" round all the way to the first floor diffusers.

    If I was doing it again I'd do hard pipe into each closet from the attic, and then 5 or 6 feet of flex, and then continue with hard pipe through the floor to each diffuser.

    That 14" and 10" round pipe doesn't attenuate anything, at all.

    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures
    https://goo.gl/photos/ZgpNUTyckkmiEdAf9
    Central air project pictures
    https://goo.gl/photos/4JjnLStEq42sWsQo8
  • Harvey RamerHarvey Ramer Member Posts: 1,969
    Those ESP's look perfect Chris. Nice job!
    Ramer Mechanical
    ramermechanical.com
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • newagedawnnewagedawn Member Posts: 287
    chris said,The problem is, I assume those blue filters are woven fiberglass?
    They don't work very good as a filter compared to a good pleated filter.

    Of course, if the system isn't set up to use a properly sized one, you're kind of stuck.

    It seems like 1" thick pleated filters are troublemakers. There's usually not enough surface area.

    chris depends on your living habits, i just changed a blue filter in a long standing customers house yesterday and its been 2 yrs the filter was full of dust, but 1 its in the cieling and 2 she keeps her house clean, i have another customer that has floor returns, havnt changed that one yet but next yr we will see if it hold up to the dirt and debris from the floor, the point those blue filters do help lower static pressure if needed, but if you design and install your system correctly you WILL BE ABLE TO USE PLEATED FILTERS and have that pleated filter protection!!!
    if you really want clean air ,design your system around a hepa filter, but youd need to find the pressure drop of whatever manufacture you choose and factor that into the duct design
    hope that helps my friend
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