Fan Airflow vs ESP

[EnOm]

Hi,

I've been looking at Equipment Schedules for Fan Coil Units. And I have some issues that I would be grateful if someone could clear up.

#1.
The Airflows in the Fan Coil Schedules are the ones that will actually occur in the zone based on the calculated ESP. However the SP stated in the schedule is (Total ESP). What is this Total ESP? (It's stated as 1 in.wg which seems quite high since most duct runs are 20-30 ft long for these FCUs, It's a private residence) What makes it more unclear is that this "Total ESP" is constant for all of the FCUs in the schedule regardless of their stated airflow and heat capacities.
What makes sense from my point of view is to state the calculated ESP in the schedule, since this would provide a more defined criteria for equipment selection by the contractor who will end up executing the project (i.e. I need an FCU that can provide X CFM at Y ESP).

#2. For small FCUs, there is no Fan Curve provided and what I have is FCU airflows at ESP increments of 0.05 in.wg. It is very unlikely that my calculated ESP will coincide with any one of these points exactly. The only solution I can think of is plotting these points and generating the fan curve myself.
On the other hand I am thinking that I'm trying to be too detailed since this is not exactly a critical application (as stated above, it's a residence). Is it acceptable if the eventual airflow upon installation deviates from the one stated in the schedule? As in, Equipment Schedules are guidelines for the contractors and not something that is to be executed precisely.

I apologize if my post is too long. Thank you.

Regards

 

[MintJulep]

And I have some issues that I would be grateful if someone could clear up.

The only someone who could clear this up is the someone that made the schedules that you are looking at.

Us anonymous someones here on the internet can only guess.

So my guess will be that the someone had a generic template and no clue what to fill in, so they filled in 1.

As for question #2, yes, plot the curve yourself if necessary. Although if you have a table at 0.05 in. wg increments just picking the nearest one is probably good enough.

 

[willard3]

ESP is external static pressure, ie, external to the machine
Static pressure is machine static pressure plus external static pressure

The static pressure will become important when the cooling or heating from the unit is not adequate and you can't figure out why.

 

[Drazen]

if you want to install fcu from different manufacturer, and don't have either ducting pressure loss or designer contracted to do design supervision, than you can:

1- stick to the specified model
or
2- calculate all ductworks' losses yourself
or
3-hire engineer to do calculations
or
4-install everything that comes to you hand and ignore later customer calls and hope he/she will not undertake more energetic actions against you

 

[EnOm]

Thank you.

 

[ChasBean1]

ESP is useless. It is External Static Pressure. It represents what the engineer thought the resistance of the system would be. The only thing that matters is TSP, which is Total Static Pressure. This is the pressure difference across your fan (static pressure at the outlet minus static pressure at the inlet). “Total ESP” is not a real thing…

 

[EnOm]

ChaseBean1:
Thank you for the information.

Regards