Carrier WEATHERMASTER 48/50Z030-105 - Manual (Page 58)

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Table 46 — Staged Gas Configuration
*Some configurations are model number dependent.
Heat Control Derv. Gain (HT.D) — This configuration is the
derivative term for the PID which runs in the HVAC mode
LOW HEAT.
Heat PID Rate Config (HT.TM) — This configuration is the
PID run time rate.
Staged Gas Heating Logic
If the HVAC mode is HIGH HEAT:
• The supply fan for staged gas heating is controlled by the
48Z Integrated Gas Control (IGC) boards and unless the
supply fan is on for a different reason, will be controlled
by the IGC IFO input.
• Command all stages of heat ON
If the HVAC mode is LOW HEAT:
• The supply fan for staged gas heating is controlled by the
integrated gas control (IGC) boards and unless the
supply fan is on for a different reason, will be controlled
by the IGC IFO input.
• The unit will control stages of heat to the heating control
point (Run Status → VIEW → HT.C.P). The heating con-
trol point in a LOW HEAT HVAC mode for staged gas is
the heating supply air set point (Setpoints → SA.HT).
Staged Gas Heating PID Logic — The heat control loop is a
PID design with exceptions, overrides and clamps. Capacity
rises and falls based on set point and supply-air temperature.
When the staged gas control is in Low Heat or Tempering
Mode (HVAC mode), the algorithm calculates the desired heat
capacity. The basic factors that govern the controlling tech-
nique are:
• how fast the algorithm is run.
• the amount of proportional and derivative gain applied.
• the maximum allowed capacity change each time this
algorithm is run.
• deadband hold-off range when rate is low.
This routine is run once every “HT.TM” seconds. Every
time the routine is run, the calculated sum is added to the con-
trol output value. In this manner, integral effect is achieved.
Every time this algorithm is run, the following calculation is
performed:
Error = HT.C.P – LAT
Error_last = error calculated previous time
P = HT.P*(Error)
D = HT.D*(Error – Error_last)
The P and D terms are overridden to zero if:
Error < S.G.DB AND Error > – S.G.DB AND D < M.R.DB
AND D > – M.R.DB “P + D” are then clamped based on
CAP.M. This sum can be no larger or no smaller than +CAP.M
or –CAP.M.
Finally, the desired capacity is calculated:
Staged Gas Capacity Calculation = “P + D” + old Staged Gas
Capacity Calculation
NOTE: The PID values should not be modified without
approval from Carrier.
Staged Gas Heat Staging — Different unit sizes will control
heat stages differently based on the amount of heating capacity
included. These staging patterns are selected based on the mod-
el number. The selection of a set of staging patterns is con-
trolled via the heat stage type configuration parameter (HT.ST).
As the heating capacity rises and falls based on demand, the
staged gas control logic will stage the heat relay patterns up and
down, respectively. The Heat Stage Type configuration selects
one of 5 staging patterns that the stage gas control will use. In
addition to the staging patterns, the capacity for each stage
is also determined by the staged gas heating PID control. There-
fore, choosing the heat relay outputs is a function of the capaci-
ty desired, the heat staging patterns based on the heat stage type
(HT.ST) and the capacity presented by each staging pattern. As
the staged gas control desired capacity rises, it is continually
checked against the capacity of the next staging pattern.
When the desired capacity is greater than or equal to the
capacity of the next staging pattern, the next heat stage is se-
lected (Run Status → VIEW → HT.ST = Run Status → VIEW →
HT.ST + 1). Similarly, as the capacity of the control drops, the
desired capacity is continually checked against the next lower
stage. When the desired capacity is less than or equal to the
next lower staging pattern, the next lower heat stage pattern
is selected (Run Status → VIEW → HT.ST = Run Status
→ VIEW → HT.ST – 1). The first two staged gas heat outputs
are located on the MBB board and outputs 3, 4, 5, and 6 are
located on the SCB board. These outputs are used to yield from
2 to 9 stages as shown in Table 47. The heat stage selected
(Run Status → VIEW → HT.ST) is clamped between 0 and the
maximum number of stages possible (Run Status → VIEW
→ H.MAX) for the chosen set of staging patterns. See
Tables 48-50.
ITEM EXPANSION RANGE UNITS CCN POINT DEFAULT
SG.CF STAGED GAS CONFIGS
HT.ST Staged Gas Heat Type 0 - 4 HTSTGTYP 0*
CAP.M Max Cap Change per Cycle 5 - 45 HTCAPMAX 45*
M.R.DB S.Gas DB min.dF/PID Rate 0 - 5 HT_MR_DB 0.5
S.G.DB St.Gas Temp. Dead Band 0 - 5 ^F HT_SG_DB 2
RISE Heat Rise dF/sec Clamp 0.05 - 0.2 HTSGRISE 0.06
LAT.L LAT Limit Config 0 - 20 ^F HTLATLIM 10
LIM.M Limit Switch Monitoring? Yes/No HTLIMMON Yes
SW.H.T Limit Switch High Temp 110 - 180 dF HT_LIMHI 170*
SW.L.T Limit Switch Low Temp 100 - 170 dF HT_LIMLO 160*
HT.P Heat Control Prop. Gain 0 - 1.5 HT_PGAIN 1
HT.D Heat Control Derv. Gain 0 - 1.5 HT_DGAIN 1
HT.TM Heat PID Rate Config 60 - 300 sec HTSGPIDR 90
IMPORTANT: When gas or electric heat is used in a VAV
application with third party terminals, the HIR relay output
must be connected to the VAV terminals in the system in
order to enforce a minimum heating cfm. The installer is
responsible to ensure the total minimum heating cfm is not
below limits set for the equipment. Failure to do so will
result in limit switch tripping and may void warranty.