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RH Sensor Configuration for Differential Enthalpy — To
configure the RH sensors for differential enthalpy, press
to enter into the Service function. Enter the pass-
word. Press
to enter into the User Configuration sub-
function. Scroll down to HUSN. The current configuration will
be shown. The default is 0 (no sensor). Press
figure the control for two sensors.
Economizer Algorithms — See Table 18 for economizer op-
eration definitions.
SRV Formula:
ECONSR = PID function on (Demand term)
where
VAV: (Demand term) = DPSP – SAT
DPSP = SASP + SPT RESET – ECSO
CV: (Demand term) = DPSP – Space Temperature
DPSP = (see chart below)
DPSP Determination (CV):
Zone A
|
<---------------------|----------------------------|--------------------->
Decreasing
NTLO
Outdoor Air Temp
Zone A: OAT ≤ NTLO
Control assumes heating is required.
DPSP = OCSP –1
Outdoor air damper position will be mostly closed.
Zone B: NTLO < OAT < 68 F
DPSP = (OCSP + OHSP)/2
Zone C: OAT ≥ 68 F
Control assumes cooling is required.
DPSP = OHSP + 1
Outside air damper position will be mostly open.
NOTE: For more information on NTLO, refer to Nighttime/
Unoccupied Free Cooling section below.
NIGHTTIME/UNOCCUPIED
(NTFC) — Nighttime/Unoccupied Free Cooling will start the
supply fan on cool nights to pre-cool the structure mass by us-
ing only outdoor air. Nighttime Free Cooling is mode 33. See
Table 20.
Nighttime Free Cooling is not permitted if the system is al-
ready in Unoccupied Heating mode, Unoccupied Cooling
mode, or Optimal Start mode; or if space temperature reading
or outdoor-air temperature readings are not available.
Nighttime Free Cooling is permitted if the mode is Unoccu-
pied, if the OAT > NTLO, the time is between 3 A.M. and
7 A.M. (except sizes 088-104), and if the outdoor enthalpy
conditions are suitable. Nighttime Free Cooling is initiated
when:
Space Temperature > (NTSP + 2 F)
AND
Space Temperature > (Outside Air Temperature + 8 F)
where the NTSP is
NTSP = OCSP (VAV Units)
NTSP = (OCSP + OHSP)/2 (CV Units)
DESCRIPTION
Configure Economizer
Specify Minimum Damper Position
*If value changed, enable Data Reset before leaving
to con-
ENTER
Zone B
|
Zone C
68 F
Increasing
FREE
COOLING
Table 19 — Configuring Economizer
HOW TO CONFIGURE AT
HSIO
Fig. 9 — Enthalpy Controller Location
Fig. 10 — Psychrometric Chart for
SET POINT
ECON
MDP
.
21
CONTROL
CONTROL
POINT
CURVE
(approx Deg)
AT 50% RH
A
73
B
68
C
63
D
58
Enthalpy Control
RANGE
Air = 1; None = 0*
0 to 100%
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