ESP or Diagnosis

[honglo]

There must be a better way!
ESP varies with model/manufacturer.
Coil static pressures vary with the same.
Filter static pressures..... likewise.

Suppose we drill 4 holes in a functioning unit.
For Gas and Electric units (coil on top or downstream from the blower) the holes would be designated:
P = Plenum
C = Coil (blower exit side pressure/coil inlet side)
B = Blower intake (just outside squirrel cage)
F = Filter (reading just prior to the filter)

Then:

P+C= Coil static pressure
C+B= Total static pressure
B+F= Filter static pressure
P+F= External static pressure

On the more modern Air Handlers (Coil inside cabinet)

P+B= Total static pressure
B+C= Coil static pressure
C+F= Filter static pressure
P+F= External static pressure

Examples were for upflow and horizontal/upflow type units only. (not downflows)

If (standards) for P,C,B,and F, or rather, TSP,CSP,FSP and ESP could be establised, I see a possible diagnostic use for these readings.
Since (ranges) vary so much though, with no set standard, how can these readings be used for anything other than an ESP(Extra Sensory Perception)prognosis?

My goal is to set up a spreadsheet that, given the readings, would (diagnose) the (apparent) functionality of the indoor section. ie..., total CFM, condition of coil, condition of supply ducts and conditon of return setup.

Don't want to re-invent the wheel here but it might lead to a better mouse trap.

Any suggestions????

[Green Mountain]

Good post and well thought out. It is true that when you mention static pressure to a technician it goes right over there heads. Static pressure has a different meaning for everyone so the technicians think that only engineers should be concerned about it.

[hvac r us 2]

Originally posted by benncool
Good post and well thought out. It is true that when you mention static pressure to a technician it goes right over there heads. Static pressure has a different meaning for everyone so the technicians think that only engineers should be concerned about it.

Very true, you mention total ESP over the phone and you wouldnt believe the answers you get. To bad many of them are missing a great troubleshooting tool!

[Diceman]

I thought this was gonna be about how when ya think about a customer or past job, they call the next day.
Happens to me all the time, must be my alien genes.

[midhvac]

I like the spreadsheet idea. Much of what we do is easier to handle in that format. Baldloonie made up a cool one for heat pump setpoints once.

[honglo]

Yes, but how to proceed? I'm thinking of using a format of L,N,H (Lower than normal, Normal, Higher than normal) for setting up a 2 dimensional array. Problem is, What is NORMAL when everything is different? Could it be that it is not the actual reading that needs to be considered but the % instead? Say that Total CFM = 100%. What % of the CFM should the coil consume? What % should the Supply consume and what % should the Return/Filter consume?

Example: I think it is pretty much understood, (at least I get uneasy seeing anything less than) .1"wc in the Supply plenum. After all, don't we design our flex duct at .08" and sheet metal duct at .1" (or there abouts)????

Now if I see for example a supply plenum static pressure of .05"wc, I get uneasy and suspect 1 of two things. 1: Blower speed is inadequate due to wrong speed setting or air restriction (.ie... dirty coil/filter/poor return). Or.
2: I suspect a leaky supply plenum/duct/oversized duct/too much duct.

Without having some (standard) of coil static pressure/total static pressure/esp/filter static pressure, the reading of .05"wc in the Supply plenum is meaningless.

As you can see, Looking at the picture as a whole, it would be a more precise representation of what was actually going on. Kind of like looking at your suction gauge and attempting to set your subcooling....

So, how about it..... What would you set the (STANDARD) at?

ESP = (X%of total CFM)
TSP = (X%of total CFM)
CSP = (X%of total CFM)
FSP = (X%of total CFM)

In other words, set the values up as percentages and view the problem as an electric circuit. Each component needs to absorb a % of the voltage and all components need to absorb the entire voltage else something overheats and shorts out.

ANY TAKERS?



[Edited by honglo on 09-14-2004 at 08:42 PM]

[mark beiser]

Originally posted by honglo
After all, don't we design our flex duct at .08" and sheet metal duct at .1" (or there abouts)????

Hehe, wait till you start running across duct systems that are sized the way they teach in the ACCA/Oncor class you have to take to be part of the rebate program, lol. They seem to be in love with .05 static for flex duct, or did last year. You end up with 3 ton systems that look like they have enough duct for a 5 ton system. Sure as heck is quiet though...

[honglo]

Let me explain my dilemma this way:

Let us for example take an Upflow Gas furnace or an electric furnace (with coil on top).

With the understanding of the acronyms:

CSP=Coil Static Pressure
TSP=Total Static Pressure (Difference across blower)
FSP=Filter Static Pressure
ESP=External Static Pressure (Difference of S/R plenums)

Lets now take 4 (sp) readings:
P= Supply Plenum/C=prior to coil/B=prior to blower/F=prior to filter, and we see:

P = 0.15
C = 0.30
B = 0.50
F = 0.10

And if:

P+C=CSP
C+B=TSP
B+F=FSP
P+F=ESP

Then:

CSP = 0.45
TSP = 0.80
FSP = 0.60
ESP = 0.25

(Intresting Note: ESP=CSP-(TSP-FSP)

Now, what can we tell from these readings? We should somehow be able to diagnose the entire indoor unit as to proper duct sizing, dirty/clean coil, clean/dirty filter and proper return air.

Regardless of Factory/Manufacturers specs, the ratio of static pressures measured should show where the problem exists!

Since ESP is affected by both the design of the Supply and the Return. Without isolating either the Supply or the Return, how do these readings tell you where to look for the problem?

[honglo]

OK!
Silence is golden. You either havent a clue what I asked or think my question is too stupid to answer.

Will somebody please just shoot me!

[Diceman]

I'm too stupid...:D

[Diceman]

I will, however, shoot you if you pay for the bullet.