r404a
05-30-2005, 01:29 PM
Here are a couple of questions about static pressure readings....
I understand that it is the general consensus that a standard residential or light commercial air handler should work against a max external static of .5"wc. Some units publish on the data tag max external static, and some I have seen list "Test" static pressure. Now, I would assume that this meant the "Ideal" conditions for this unit. I recently saw a unit that listed both "Test" and Max static readings. So, short of having a unit curve (it would be nice if every unit had one taped to the side) we use the .5"wc benchmark. Now, if you are looking at a unit and lets say you see .65"wc static across the inlet and outlet of the unit, we know that too much static exists and there is a supply or return restriction. What I would like to know, and I am sure that some of you Gents (and Ladies) know, is a ballpark or rule of thumb indicator. What I mean is, we verify that we have too much static for full cfm flow. Now, if we take a return static, referenced to atmosphere and get, lets say -.35" wc ( negative) and a supply static reading, referenced to atmosphere of .3"wc (positive pressure) can you look at these and say "OK, I have an unusually low suction on the blower inlet, my restriction is Return side" or the same for the supply side. Thanks in advance.
r404a
I understand that it is the general consensus that a standard residential or light commercial air handler should work against a max external static of .5"wc. Some units publish on the data tag max external static, and some I have seen list "Test" static pressure. Now, I would assume that this meant the "Ideal" conditions for this unit. I recently saw a unit that listed both "Test" and Max static readings. So, short of having a unit curve (it would be nice if every unit had one taped to the side) we use the .5"wc benchmark. Now, if you are looking at a unit and lets say you see .65"wc static across the inlet and outlet of the unit, we know that too much static exists and there is a supply or return restriction. What I would like to know, and I am sure that some of you Gents (and Ladies) know, is a ballpark or rule of thumb indicator. What I mean is, we verify that we have too much static for full cfm flow. Now, if we take a return static, referenced to atmosphere and get, lets say -.35" wc ( negative) and a supply static reading, referenced to atmosphere of .3"wc (positive pressure) can you look at these and say "OK, I have an unusually low suction on the blower inlet, my restriction is Return side" or the same for the supply side. Thanks in advance.
r404a