39
Table 18 — Check Valve Functions
Table 19 — EconoMi$erIV Input/Output Logic
*For single enthalpy control, the module compares outdoor
enthalpy to the ABCD set point.
†Power at N terminal determines Occupied/Unoccupied setting:
24 vac (Occupied), no power (Unoccupied).
**Modulation is based on the supply air sensor signal.
††Modulation is based on the DCV signal.
***Modulation is based on the greater of DCV and supply air sensor
signals, between minimum position and either maximum position
(DCV) or fully open (supply air signal).
†††Modulation is based on the greater of DCV and supply air sen-
sor signals, between closed and either maximum position (DCV)
or fully open (supply air signal).
CHECK VALVE
IDENTIFICATION
(See Fig. 53)
LOCATION
COOLING
CYCLE
HEATING
CYCLE
COOLING CYCLE
CHECK VALVE STUCK
HEATING CYCLE
CHECK VALVE STUCK
Open Closed Open Closed
A
Outdoor coil;
Header
Closed Open
Lose circuiting in
outdoor coil. Acts
like low charge.
Normal Normal
Bottom 3 circuits
restricted
B
Outdoor coil;
Liquid line feeding
fixed orifice
Open Closed Normal
Lose some
capacity
Restricted outdoor
fixed orifice
Normal
C
Outdoor coil;
Liquid line leaving
coil
Closed Open
Restricted
liquid line
Normal Normal
Flooding outdoor
coil and compressor
D
Indoor coil; Liquid
line feeding fixed
orifice
Open Closed Normal
Restricted
indoor
fixed orifice
Lose some capacity Normal
E
Indoor coil; Liquid
line leaving coil
Closed Open
Bypasses coil and
floods compressor
Normal Normal
Restricted
liquid line
F
Indoor coil;
Header
Open Closed Normal
Bottom
circuits
of indoor
coil inactive
Lose indoor coil
circuiting — symptom
of low charge
Normal
INPUTS OUTPUTS
Demand Control
Ventilation (DCV)
Enthalpy*
Y1 Y2
Compressor N Terminal†
Outdoor Return
Stage
1
Stage
2
Occupied Unoccupied
Damper
Below set
(DCV LED Off)
High
(Free Cooling LED Off)
Low On On On On Minimum position Closed
On Off On Off
Off Off Off Off
Low
(Free Cooling LED On)
High On On On Off Modulating** (between min.
position and full-open)
Modulating** (between
closed and full-open)
On Off Off Off
Off Off Off Off Minimum position Closed
Above set
(DCV LED On)
High
(Free Cooling LED Off)
Low On On On On Modulating†† (between min.
position and DCV maximum)
Modulating†† (between
closed and DCV
maximum)
On Off On Off
Off Off Off Off
Low
(Free Cooling LED On)
High On On On Off Modulating*** Modulating†††
On Off Off Off
Off Off Off Off
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