IM 778 / Page 23
14-Position Terminal Strip
Pin
Designation
Description
1
C
Transformer ground (Ovac)
2
R
Transformer supply (24vac)
3
V
-DC power connection
4
P
Pump request output
5
A
Alarm fault output
6
U
Unoccupied input
7
L
Load shed input
8
E
Remote shutdown input
9
F
+DC power connection
10
Y1
Occupied cooling mode input
11
W1
Occupied heating mode input
12
G
Fan only input
13
W2
Unoccupied heating mode input
14
O`
Tenant override input
Board Status LED’s
Fault Output
Mode
Yellow
Green
Red
Terminal A
Occupied
Off
On
Off
Energized
Unoccupied
On
On
Of
Energized
Load Shed
Off
Off
On
Energized
Condensate Overflow
On
Dim
Off
De-Energized
High/Low Pressure Fault
Off
Off
Flash
De-Energized
Low Temperature Fault*
Flash
Off
Off
De-Energized
Brownout
Off
Flash
Off
De-Energized
Emergency Shutdown
Off
Flash
Off
De-Energized
*in heating mode only
Note: The fault output is energized when no faults exist. The fault ouput is
de-energized during faults and when unit power is off.
The Mark IV/AC control board is provided with three drive terminals, R(24vac),
F(24vdc), and C(Ovac) that can be used by the end user to drive the thermostat
inputs (G, Y1, W1, and W2) and control inputs (U, L, E, and O). Any combination of
a single board drive terminal (R, F, or C) may be used to operate the Mark IV/AC
board’s control or thermostat inputs. However, only one drive terminal (R, F, or C)
can be connected to any individual input terminal or damage will occur. Some of the
control inputs are used within the Water Source Heat Pump and not accessible to
the end user. For example, HP, LT, and COF are not available for use by the end user.
Typically the Mark IV/AC board’s R(24vac) terminal is used to drive the board’s ther-
mostat inputs and control inputs by connecting it to the R terminal of an industry
standard thermostat. The control outputs of the standard thermostat are then con-
nected to the Mark IV/AC board thermostat inputs and control inputs as needed.
Any remaining board input(s) may be operated by additional thermostat outputs or
remote relays (dry contacts only).
All Mark IV/AC board inputs must be operated by dry contacts powered by the con-
trol board’s power terminals. No solid state devices (Triacs) may be used to operate
Mark IV/AC board inputs. No outside power source may be used to operate Mark
IV/AC board inputs.
Using Drive
Using Drive
Using Drive
Terminal R (24vac)
Terminal F (24vdc)
Terminal C (ground)
De-engergized Energized D-energized Energized De-energized Energized
Place the Meters
Red (+) Lead on
Place the Meters
Place the Meters
Place the Meters
Input to be
on Black (-) Lead
Black (-) Lead
Black (-) Lead
checked
on C
on V
on R
U, L, E, Y1, W1,
10 to
22 to
Ovdc
30 to
10 to
22 to
G. W2. P
14vac
26vac
33vdc
14vac
26vac
LED Status and Fault Output Status
General Use and Information
Mark IV/AC Sequence of Operation
Read Outputs
Check Timers
Hi
Pres. Sw ?
Brown Out ?
Low Temp Sw ?
Lo Shed ?
N S B ?
Cond. Overflow?
R - W 1 ?
R -Y 1 ?
Stop Comp.
Flash Red LED
Stop Fan
Flash Green LED
Stop Comp.
Htg Mode?
Stop Comp.
Flash Yellow LED
Stop Comp.
Turn On Red LED
R - W 2 ?
Start Comp.
Cooling Mode
Turn On Yellow LED
Stop Comp.
Reversing Valve On
Time Delay
Start Comp.
Start Comp.
No
No
Ye s
No
Ye s
No
No
No
No
No
No
No
No
Ye s
Ye s
Ye s
Ye s
Ye s
Ye s
Ye s
Ye s
