# Thread: What is static pressure?

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## What is static pressure?

Guys about got my Infinity furnace system installed and watched the thermostat do a static pressure check.

Have seen this on several other threads.

Well what is it? Whats a good number to have?

Thanks

2. static pressure is exerted on a duct in all directions and is something that velocity pressure(air moving down the duct) has to overcome...The higher the number the lower the airflow...

3. Originally Posted by Hrdworkingacguy
static pressure is exerted on a duct in all directions and is something that velocity pressure(air moving down the duct) has to overcome...The higher the number the lower the airflow...
velocity pressure does not have to over come static pressure

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Fair enough, thanks

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## definition

Its what I felt when i came home with no roses or chocolates-can lead to cold feet.

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take a five gallon water bottle with a 1/2" hose on the outlet. full of water, and turn it upside down. the amount of water coming out is like cfm. and the pressure in the bottle itself would relate to static pressure

7. Static pressure is the pressure on the discharge side of your ductwork or fan system. Typically you would measure this with a magnahelic that reads in inches of water column. The high side port would be inserted through the side of the duct.....same as reading the pressure of air inside of a balloon.

Total static pressure would be the pressure across a fan system or AC unit.
High side probe would be inserted on the discharge side of the system and the low side inserted on the return or negative side of the system.

Example 2 inches discharge pressure + .5 inches negative pressure = 2.5 inces total static pressure

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## Long Enough ?

Originally Posted by Pegsmi98
Fair enough, thanks

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Airflow is likely different between heating and cooling cfms,so both need to be checked.

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Originally Posted by dash
Airflow is likely different between heating and cooling cfms,so both need to be checked.
simply ain't gonna happen

11. A good number to have...

0.5 IWC or less.

12. Originally Posted by chillerfreak
Static pressure is the pressure on the discharge side of your ductwork or fan system. Typically you would measure this with a magnahelic that reads in inches of water column. The high side port would be inserted through the side of the duct.....same as reading the pressure of air inside of a balloon.

Total static pressure would be the pressure across a fan system or AC unit.
High side probe would be inserted on the discharge side of the system and the low side inserted on the return or negative side of the system.

Example 2 inches discharge pressure + .5 inches negative pressure = 2.5 inces total static pressure
never seen 2 inches on "discharge" supply side

the data plate will let you know what to shoot for. checking static pressure should be done every time before checking charge in my opinion.

13. Infinity system would let you know if the static pressure was to high, because it would shut -down . Most run between .50 and .75 @ the measure cfm of ductwork. Static can be checked with Magnahelic.

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