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Total Static Pressure

I had recently called tech support for work on a Goodman indoor section of a Heat Pump.
When I had voiced my concerns over indoor air flow, I was told to check total static pressure by adding (2) different static pressure values. I am not quite sure exactly why I
was taking these readings. Could anyone explain what Total Static Pressure is & why I
was instructed to do so?


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    Better take 'wiz' out of your screen name.
    Google it. It’s basic information, even for a beginner, to troubleshoot airflow issues, for starters.
    You were probably asked so tech support could evaluate your skill level.
    It’s like when they ask you for the voltage reading on your low voltage transformer and the tech says 'It was fine. It was 24 volts'.

    There was an error rendering this rich post.

    EBEBRATT-Ed Member Posts: 15,607
    Total static is static pressure + velocity pressure.

    Static pressure is like the air pressure in a basketball or a car tire...not moving.

    Velocity pressure is from moving air....in a given size duct
  • pedmec
    pedmec Member Posts: 987
    Your checking total static pressure so you can determine the actual airflow that is moving thru the air handler. if you open the I&O manual of the air handler, you look for the chart that gives you the cfm's against the total external static pressure. For example if you measure +.3 on the supply and -.3 on the return you drop the symbols and add the measurements together. So together the measurement would be .6 ESP. go to the column that is .6 ESP and follow it down and stop at the correct blower speed and that is the cfm's that the blower is moving. Also another term used to describe external static pressure is "resistant to airflow". Because that's what the blower has to move air against.

    When your measuring your static pressure you need to make sure that you are measuring at the right location and what the manufacturer is including or excluding from there measurement.
  • pecmsg
    pecmsg Member Posts: 4,882
    T E S P
    Thanks to rundawg on hvac-talk
  • ratio
    ratio Member Posts: 3,649
    Keep in mind that when you're using the mfgr's tables to cypher up airflow, you must use the locations specified by them (I've seen furnaces that specify a hole drilled in between the legs of the A coil), and the unit must be in the condition specified by them (certainly a clean coil, often a dry coil, etc.). Some mfgr's specify pressure drop across various accessories (heat strips, economizers, etc.) & you'll need to add them up to get to a total. Some things (getting into larger & specialized stuff now) have factory-drilled pressure holes. Those make it nice!
  • aircooled81
    aircooled81 Member Posts: 205
    poke around on the timeout with titus youtube channel too, they spell out some airflow basics very well
  • Iamgally
    Iamgally Member Posts: 2
    Depending on motor whether psc or ecm, your TES will effect airflow differently. Psc motors with high tesp will dramatically drop airflow because increased airflow resistance. Essentially the psc motor will do less work, pull less amps and then less cfm moving. This will lead to high limits tripped, freezing coils and any other comfort issues

    Ecms are effected by allowing ecm motor to ramp up whether they are constant torque or constant airflow. This will result in slightly lower airflow hit more energy consumption. Eventually if TESP is not fixed, it will burn out module and/or motor

    To take a correct TESP reading, Drill hole after filter and before coil if it is a split system furnace

    Air handler you'll take your readings after filter and before supply plenum since coil is included in casing. 

    To go even further, take readings in return plenum, across filter, TESP in furnace or air handler, across external coil and finally in supply plenum. This will tell you any restrictions or undersized/oversized duct work. Highly recommended to invest in a truflow grid that is the best tool aside from blower door test to read airflow measurements

    1" filters are naturally very restrictive to airflow and should be downgraded to thin fiberglass to allow maximum airflow at the cost of filtration. Upgrade to 4 or 5"