Hired-Hand Farm Hand Series: Vent Master 24 - Manual (Page 5)

Part No. 4801-5124 rev 10-03 Farm Hand Vent Master 24 3
5. Static Pressure Overview
The Farm Hand Vent Master 24 has been designed with the producer in mind. Routine tasks such as
changing the pressure limits are easily reset, and are familiar in nature.
The Vent Master 24 has two basic pressure settings, a Target Pressure, and a Pressure Differential.
The Target Pressure is the static pressure that the system tries to maintain within the limits of the
Pressure Differential. The Pressure Differential is the range around the Target Pressure that is
considered satisfactory. From the Target Pressure and the Pressure Differential the High and Low
Pressure limits are calculated. The High Pressure limit is the Target Pressure plus half of the Pressure
Differential and the Low Pressure limit is the Target Pressure minus half of the Pressure Differential.
The controller will open and close the vents as needed to maintain pressure between the high and low
limits.
Low Pressure
High Pressure Limit
Low Pressure Limit
When pressure is
in this range, the
controller will not
adjust vents.
When pressure is
above the high
limit, the vent
machine will open
vents to lower
pressure.
When pressure is
below the low
limit, the vent
machine will close
vents to raise
pressure.
High Pressure
Room Pressure
Now that we know how the pressure limits are established, lets move on to how to set up those limits.
Press the mode button a few times, and you will see that the display changes each time. If you will
look just to the right of the display, you will see four green lights labeled Temperature, Static Pressure,
Var/Timer Percent, and Target. The green light tells you what setting you are looking at in the main
display. If the light beside Static Pressure is lit, the numbers in the display show you the current
pressure in your building. However, for viewing Target Temperature both the LEDs beside “Target”
and “Temperature” will be lit. For viewing Target Static Pressure both the LEDs beside “Target” and
“Static Pressure” will be lit.
Assume that you have this controller installed in your house, and you decide you want pressure to be
kept a little bit lower. You walk to the controller, press and release the mode button, watching the
green lights until the “Target” and “Static Pressure” LED is lit. If you look at the display now, you see
the present setting for the Target Pressure. To lower it, press and release the minus (-) button until you
see the new limit you want. The controller will now start operating using your new limit. If you want
the Vent Master 24 to maintain the Target Pressure within narrower limits decrease the Pressure
Differential. See Section 7 for a graphic example using the Target Pressure and Pressure Differential.
6. Why Use a Pressure Controller?
The Farm Hand Vent Master 24 is used to control vent inlets in agricultural enclosures. Maintaining a
slight negative pressure inside a building ensures that air flows in evenly from all openings in the
building. However, as static pressure increases, the speed and volume of the incoming air increases.
It is important to set the pressure at an appropriate level to ensure maximum efficiency. Too little
vacuum, and the livestock could suffer from drafting, and temperature shock. Too much vacuum, and
fan efficiency is reduced, increasing the levels of moisture, ammonia in the enclosure, and also driving
up electricity costs.