esp reading taken at blower?
esp reading taken at blower?
(OP)
Im still working on what seems to be low air flow to a kitchen in a public school. The blueprints for show two figures: Air Handler ESP= 0.87" RAF (return air fan) = ESP= 1.14. I've taken several readings and none of them match those numbers, nor even close.
Where, or what points did the installers take the readings that are printed on the blue prints? I have assumed the air handler esp reading is to be taken on the supply duct leaving the blower, but I get a reading of .27, not 0.87.
And I assume the raf reading is taken just after the return air fan, but I get a reading of .45, not 1.14".
Where, or what points did the installers take the readings that are printed on the blue prints? I have assumed the air handler esp reading is to be taken on the supply duct leaving the blower, but I get a reading of .27, not 0.87.
And I assume the raf reading is taken just after the return air fan, but I get a reading of .45, not 1.14".





RE: esp reading taken at blower?
RE: esp reading taken at blower?
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
RE: esp reading taken at blower?
RE: esp reading taken at blower?
There are a million reasons RA pressure is higher than SA pressure.
RE: esp reading taken at blower?
RE: esp reading taken at blower?
RE: esp reading taken at blower?
What next? Check voltage on this 1 hp motor, check amps, tighten belt some more, replace the belt? There are a set of as-builts but they do not include pressure readings, except for the proofing switches on the cabinet and raf. The proof switch on the cabinet is stated to be 0.5" to 1.0". I get 1.20" reading (twin tube input reading, cab before blower, duct after blower). The blueprints with the ESP spec's does not state if it is a design or commissioning spec.
I think I am at the point to buy me my first pitot tube, but I fear if will only confirm my findings. This is bugging me to death. Im spending too many hours on this unit, but I just have to figure it out somehow. The 1 hp motor is blueprinted for 1850 cfm (close enought) and I want to prove it is doing its job.
RE: esp reading taken at blower?
The next time you comission something, keep in mind your current frustrations, and red line the as-built drawing so that it will elimiate the frustration of the next guy to use those drawings.
We all thank you in advance.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
RE: esp reading taken at blower?
You didn't say how your amperage looked, when you checked it. It sounds like you may be starving the return fan or just turning the supply or return fan sheeves too slow. Is there a way to open a door at the inlet side of the return fan and then check the discharge static pressure of the return and supply?. It might indicate whether your getting enough air to the return fan or not. If the static doesn't rise close to your design on the return then it could be the return fan is turning too slow. If it does go up substantialy the the problem maybe on the return side ducting.
I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int.
RE: esp reading taken at blower?
This is good, I have something to follow up on tomorrow.
I haven't checked amps yet cause the rating will be hard to see where the motor is mounted, but I will do that too.
RE: esp reading taken at blower?
Get the serial number from the unit, get the blower curves from the original supplier and compare the pressure differential across each blower to their respective fan curves.
RE: esp reading taken at blower?
Have I committed an error in measurements?
If so, let me think. I recall: +0.27" blower outlet.
And when I connect the twin pipes of my monometer to both the blower outlet static probe and the cabinet static probe (blower inlet, although not same size duct since its the cabinet); I get reading of 1.17". But I believe that is -1.17". According to the specs, that twin pipe reading should be between 0.5 and 1.0". Hence not 1.17.
Today, I put on a new belt and got same readings. I checked amps and got 1.3 amps. The motor rating is 1.7.
RE: esp reading taken at blower?
If static pressure is low, there's a good chance that there may be duct leakage, or that the fan is dirty or damaged, also be certain to always read the nameplate data to determine the total static pressure that the unit was manufactured for. Also, obtaining a copy of the manufacturer's fan curve data can be very helpful in interpreting static pressure and airflow reading.
You need to take two readings: one on the supply side of the fan, and one on the return side of the fan.
RE: esp reading taken at blower?
Supply side verses return side. Those 2 points are but a few of the points in the system. Not sure where to take readings. This is a simple air handler. It is the smallest one in the school, without any variable factors such as vortex, etc. I got: Return register. return duct. return air fan. then on to: cabinet filters, cabinet coils, cabinet supply inlet, cabinet supply blower, cabinet blower outlet/duct.
My 0.27 reading is the cabinet blower outlet/duct (12x12 inch)
RE: esp reading taken at blower?
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RE: esp reading taken at blower?
RE: esp reading taken at blower?
At this point I would just break down and do the traverse of the supply duct it will tell you where you are at. You could be grinding away at this and may be with in 10% of the spec and not even know it.
I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int.
RE: esp reading taken at blower?
RE: esp reading taken at blower?
If not contact your local rep to see if they or the factory have the records on the units. I have at times done this and received info on equipment 30 years old.
RE: esp reading taken at blower?
I have a new thought about this problem of mine. While I wait for the pitot tube to arrive, I think I may have stumbled onto a cause. A clogged coil. I get a reading of +0.45" at the Return Air Fan (RAF) outlet. This fan is mounted on the ceiling above the air handler cabinet which is on the floor. About 15 feet of ductwork is between the two. I get a reading of -0.90" inside the cabinet- after the coil and at the supply blower inlet. Does this mean that I am getting a static pressure drop of 1.35" across my coil (and new filters)???
I look at the coil face and don't see any matted blankets of dirt that are restricting air flow. (I'm used to see these blanket type clogs on heat vav coils). However, I speculate that the coil could be clogged deeper in the coil. Would that be a common condition for a neglected unit?
Is there a rule of thumb for pressure drops across a coil?
RE: esp reading taken at blower?
I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI
RE: esp reading taken at blower?
500 F.P.M. it climbs to .055 in. of water/row. It would be prudent to call the unit manufacturer to find the design pressure drop vs. face velocity. Either way 1.35 in. of water seems pretty steep.
I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI
RE: esp reading taken at blower?
To say that this question has been engrossing would be an understatement. I've beeen going through my A.S.H.A.E. manuals and it's suprizing the data you can find!!!
Just a fote note to pressure drop across your coil, the max value I've found for pressure drop is .15 in.of water/row at 800F.P.M. air face velocity. That still puts your 1.35 inches way up there. I don't want to mislead your investigation, so check with the manufacturer it will keep you from coming to the wrong conclusion. I would feel bad if I lead your in the wrong direction
I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI
RE: esp reading taken at blower?
Where do I start? I dunno, so .... my return fan inlet ESP was 1.74" and the blue prints call for 1.17". Took me an hour to figure it out, then 30 min of kitchen ceiling return grid checking, but I found that the 3 kitchen ceiling return grids all had hidden (hard to see) louvers behind them. They louvers were all 95 percent closed! Can you believe that! THEY WERE ALL CLOSED! For at least 6 years, closed and maybe even 14 years since new!
Thanks a million for all who replied. I could never had solved this without the input from each and every poster. I was truely stumped. Maybe someday, I'll be able to post and help others.
Thank you gentlemen, ever so much!
RE: esp reading taken at blower?
I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI