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esp reading taken at blower?

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".

RE: esp reading taken at blower?

Sounds like the fan is running backwards or the unit is installed backwards normally the supply side static pressure is higher then the return side, you show just the opposite?

RE: esp reading taken at blower?

It could also be that the numbers on the "blue print" is a design pressure, and what you are reading would be "installed", or "as-built" pressures.

"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?

(OP)
The belts have been ignored for so long on these units, that they are streched, running very loose for perhaps years and maybe they became glazed and unable to grip the pulley anymore, even after I tightned them. hmmm, just grasping for straws, but I wish I had a tachometer to read the blower rpms directly. I'm gonna look at this unit again tomorrow.

RE: esp reading taken at blower?

See if you can find the balance report from when the building was commissioned.....that should have realistic pressures.

There are a million reasons RA pressure is higher than SA pressure.

RE: esp reading taken at blower?

clogged filters?

RE: esp reading taken at blower?

change in system configuration since installation?

RE: esp reading taken at blower?

(OP)
Well, I took another close look today. It still a mystery to me.  The figures I posted were after I installed new filters and tightened both belts.  When I opened the cabinet door on the blower side, the reading increased from 0.27 to 0.44" on the supply duct, just after the blower.  I was hoping it would shoot up to 0.87", but alas, nope. I checked the blower fins today, there is no dirt build up and they look relatively clean. Belt is still tight and all looks great to the naked eye. I even checked all 3 return grills and they sucked up a paper towel in a heartbeat.  

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?

Welcome to the real world. Hee Hee. winky smile

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. smile

"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?

Mnchapman,
 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?

(OP)
Yorkman, I've been thinking along those same lines. There is no inlet door that I've seen, but tommorrow I will track the duct to find one. Most our ducts do have doors, so you have gave me something to look for tomorrow. Out of desparation, I might cut an opening myself and then close it with Z strips. Looks like I might be buying me a pair of the metal snips that cut and remove a 1/4" gulley.

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?

mnchapman,  did you take readings across each blower? Inlet and discharge pressures to get your blower sp, instead of discharge alone.  Or did I misread your post?
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?

(OP)
I did take readings on both sides of both blowers and have all the numbers written down at work. But the .027 reading I cited is from the outlet of the supply 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?

There are hundreds of combinations of different static pressure readings.  The basic premise is that if static pressure is high, there may be blockage, or the duct may be undersized.

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?

(OP)
Nameplate data? There are labels on the units, but no specs supplied nor printed on the units themselves. (1992 origin).  Fan curve data? How do I go about getting this information? Do I pay for a vendor rep visit?

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?

Whenever you need information you need to get and post every bit of information you have. For example you mention labels what does it say, who's the mfg.? and to get total ESP for any fan you need to read the fan inlet pressure and the outlet pressure. To get the velocity pressure you need a pitot tube  then you need to convert it to FPM and multiply this by the duct cubic feet. This may be of value to you:
http://www.dwyer-inst.com/htdocs/airvelocity/AirVelocityIntroduction.cfm

RE: esp reading taken at blower?

(OP)
Not Total ESP,just esp.  Labels have no information on them,, that was the point I was making.

RE: esp reading taken at blower?

Mnchapman,
   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?

(OP)
Yorkman, you are right again. I took several other units sp's today and could not determine anything useful.  I'm gonna break down and buy me a pitot tube.

RE: esp reading taken at blower?

mnchapman,  by chance did anyone leave the operations and maintenance books lying around?  Or did they get thrown out over time.  They may have the model number and manufacturer listed.
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?

(OP)
The only documentation is the blue prints, with regards to cfm, sp, etc. The unit does have the model number, but no air flow specs.

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 think that could be your problem, how many passes is your heating coil? The average pressure drop for a clean heating coil is aboout .027in. of water/number of rows. The way I read your post the sp. at the face of the coil and at the inlet to the supply fan is the same. So that the pressure drop of the duct work is minimal. The coil sounds like it could be dirty.

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?

Mnchapman, the pressure drop of .027 in. of water/row is for a face velocity of 350 F.P.M. at a face velocity of
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?

Mnchapman,
  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?

(OP)
Good news. I found the problem with kitchen!  I did not find it earlier because I was taking my manometer readings at the wrong locations, ( i.e. not at pitot reading locations, which I didn't even see one of them).  

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?

Congradulations!!! Perseverance is often the key to success. Glad that you found the problem and a relatively easy one to fix.

I'm not a real engineer, but I play one on T.V.
 A.J. Gest, York Int./JCI  

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