Greenheck MSX (470658) - Manual (Page 19)

19 Modular Supply Make-Up Air Unit
®
Optional Economizer
The following economizer sequences will function
to modulate the outdoor and return air dampers to
determine and maximize the availability of free cooling.
Although the Honeywell economizer controller contains
numerous set points, the adjustment of only a few is
necessary to ensure optimal performance.
Sequences
EC-1 Outdoor Air Temperature Reference
This mode compares the outdoor air temperature to the
dry bulb temperature set point (DRYBLB SET). Once
the outdoor air temperature is less than DRYBLB SET,
the unit will modulate the position of the dampers to
maintain a predetermined mixed air temperature (MAT
SET).
EC-2 Outdoor Air Enthalpy Reference
This mode compares the outdoor air enthalpy to a
preset enthalpy curve. When the outdoor air conditions
are within this curve, the dampers will modulate to
maintain a mixed air temperature (MAT SET).
EC-3 Differential Temperature Reference
This mode compares the outdoor air temperature and
the return air temperatures. If the outdoor air is cooler
than the return, the dampers will modulate to maintain a
preset mixed air temperature (MAT SET).
EC-4 Differential Enthalpy Reference
This mode compares the outdoor air enthalpy and the
return air enthalpy. If the outdoor air enthalpy
Relevant Set points
1. MAT SET - The mixed air temperature set point.
The control will modulate the damper to maintain
temperature as best as it can (Set point menu,
Default 53°F )
2. LOW T LOCK - The set point for the low temperature
mechanical cooling lockout. (Set point menu, Default
32°F)
3. DRYBLB SET - The outdoor air set point to call for
economizer. (Set point menu, Default 63°F)
4. MIN POS - The minimum signal voltage sent to
the dampers. This must be set to 2 VDC. (Set point
menu, Default 2.8 VDC)
5. AUX1 O – The controllers operating sequence
structure. (Set point menu, Default ‘None’)
6. ERV OAT SP - The set point for low temperature
economizer lockout. This is the low temperature set
point when AUX1 O is set to ERV. (Set point menu,
Default 32°F)
7. STG3 DLY - Time delay after second cooling stage is
enabled (Advanced setup menu, Default 2 hrs.)
Using the Keypad with Settings and
Parameters
To use the keypad when working with Set points,
System and Advanced Settings, Checkout tests, and
Alarms:
1. Navigate to the desired menu.
2. Press (enter) to display the first item in the
currently displayed menu.
3. Use the and buttons to scroll to the desired
parameter.
4. Press (enter) to display the value of the currently
displayed item.
5. Press the button to increase (change) the
displayed parameter value.a
6. Press the button to increase (change) the
displayed parameter value.a
7. Press (enter) to accept the displayed value and
store it in non-volatile RAM.
8. CHANGE STORED displays.
9. Press (enter) to return the current menu
parameter.
10. Press (escape) to return to the current menu
parameter.
a When values are displayed, pressing and holding the
or button causes the display to automatically
increment.
Modulate Dampers
1. Navigate to the Checkout menu and press (Enter).
2. The cooling should turn off
3. Navigate to Damper Open and press (enter) twice to
run the test.
4. Voltage between terminals ACT 2-10 and ACT COM
should be 10 VDC. This will open the outdoor air
damper and close the return air damper
5. Press (escape), navigate to Damper Close and press
(enter) twice to run the test.
6. Voltage between terminal ACT 2-10 and ACT COM
should be 2 VDC. This will close the outdoor air
damper and open the return air damper.