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65
Staged Gas Heat Staging
Different unit sizes will control heat stages differently based on
the amount of heating capacity included. These staging pat-
terns are selected based on the unit model number. The selec-
tion of a set of staging patterns is controlled via the heat stage
type configuration parameter
Configuration
HEAT
SG.CF
HT.ST
. Setting
HT.ST
to 0, 1, or 2 configures the unit
for Staged Gas Heat. The selection of
HT.ST = 0, 1, or 2
is
based on the unit size and heat size. See Table 45.
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 se-
lects one of the staging patterns that the staged gas control will
use. In addition to the staging patterns, the capacity for each
stage is also determined by the staged gas heating PID algo-
rithm. Therefore, choosing the heat relay outputs is a function
of the capacity desired, the available heat staging patterns con-
figured with heat stage type (
HT.ST
), and the capacity present-
ed by each staging pattern.
As the staged gas control desired capacity rises, it is continual-
ly checked against the capacity of the next staging pattern.
When the desired capacity is greater than or equal to the capac-
ity of the next staging pattern, the next heat stage is selected
(
Run Status
VIEW
HT.ST = Run Status
VIEW
HT.ST
+1).
Similarly, as the staged gas control desired capacity drops, it is
continually checked against the next lower stage. When the de-
sired capacity is less than or equal to the next lower staging
pattern, the next lower staging pattern is selected (
Run Sta-
tus
VIEW
HT.ST = Run Status
VIEW
HT.ST
–1).
The first two staged gas heat outputs are located on the MBB.
Outputs 3, 4, 5, and 6 are located on the SCB. These outputs
are used to yield from 2 to 9 stages as shown in Table 45. 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
). See Tables 47-49.
Modulating 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 unit model number. The selection of a set
of staging patterns is controlled via the heat stage type configura-
tion parameter
Configuration
→
HEAT
→
SG.CF
→
HT.ST
. Set-
ting
HT.ST
to 3, 4, or 5 configures the unit for Modulating Gas
Heat. The selection of
HT.ST = 3, 4, or 5
is based on the unit size
and heat size. See Table 46.
As the heating capacity rises and falls based on demand, the
modulating gas control logic will stage the heat relay patterns
up and down respectively (
Run Status
→
VIEW
→
HT.ST
) and
set the capacity of the Modulating Gas section (
Outputs
→
HEAT
→
H1.CP
). The Heat Stage Type configuration selects
one of the staging patterns that the modulating gas control will
use. In addition to the staging patterns, the capacity for each
stage is also determined by the modulating gas heating PID al-
gorithm. Therefore, choosing the heat relay outputs and setting
the modulating gas section capacity is a function of the capaci-
ty desired, the available heat staging patterns configured with
heat stage type (
HT.ST
), and the capacity range presented by
each staging pattern.
As the modulating gas control desired capacity rises, it is con-
tinually checked against the capacity ranges of the next higher
staging patterns. Since each stage has a range of capacities, and
the capacities of some stages overlap, the control selects the
highest stage with sufficient minimum capacity.
Similarly, as the modulating gas control desired capacity drops,
it is continually checked against the capacity ranges of the next
lower stages. The control selects the lowest stage with suffi-
cient maximum capacity.
The first two modulating gas heat outputs are located on the
MBB. Outputs 3, 4, 5, 6, and the analog output that sets the
modulating gas section capacity are located on the SCB. 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
). See Tables 50-52.
SCR Electric 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 unit model number. The selection of a set
of staging patterns is controlled via the heat stage type configura-
tion parameter
Configuration
→
HEAT
→
SG.CF
→
HT.ST
. Set-
ting
HT.ST
to 6, 7 or 8 configures the unit for SCR Electric Heat.
The selection of
HT.ST = 6, 7 or 8
is based on the unit size and
heat size. See Table 53.
For
HT.ST
=6 there is only 1 heat stage. Whenever the heat is
energized, all heaters will be active will be modulated through
the SCR control.
On 2 stage heat patterns (
HT.ST
=7 or 8), as the heating capaci-
ty rises and falls based on demand, the SCR electric heat con-
trol logic will stage the heat relay patterns up and down respec-
tively (
Run Status
→
VIEW
→
HT.ST
) and set the capacity of
the SCR Electric Heat section (
Outputs
→
HEAT
→
H1.CP
).
The Heat Stage Type configuration selects one of the staging
patterns that the SCR electric heat control will use. In addition
to the staging patterns, the capacity for each stage is also deter-
mined by the SCR electric heating PID algorithm.
Therefore, choosing the heat relay outputs and setting the SCR
electric heat section capacity is a function of the capacity de-
sired, the available heat staging patterns configured with heat
stage type (
HT.ST
), and the capacity range presented by each
staging pattern.
As SCR electric heat control desired capacity rises, it is contin-
ually checked against the capacity ranges of the next higher
staging patterns. Since each stage has a range of capacities, and
the capacities of some stages overlap, the control selects the
highest stage with sufficient minimum capacity.
Similarly, as the SCR electric heat control desired capacity
drops, it is continually checked against the capacity ranges of
the next lower stages. The control selects the lowest stage with
sufficient maximum capacity.
The electric heat outputs are located on the MBB. The analog
output that sets the SCR electric heat section capacity is locat-
ed on the SCB. The heat stage selected (
Run Status
→
VIEW
→
HT.ST
) is clamped between 0 and the maximum num-
ber of stages possible (
Run Status
→
VIEW
→
H.MAX
). See
Tables 54-56.
Limit Switch Temperature Monitoring (LIM.M)
Variable air volume applications in the low heat or tempering
mode can experience low airflow and as a result it is possible
for nuisance trips of the gas heat limit switch, thereby shutting
off all gas stages. In order to achieve consistent heating in a
tempering mode, a thermistor (
Temperatures
AIR.T
S.G.LS
) is placed next to the limit switch and monitored for
overheating. In order to control a tempering application where
the limit switch temperature has risen above either the upper or
lower configuration parameters (
SW.L.T, SW.H.T
), the staged
gas control will respond by clamping or dropping gas stages.
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.
Summary of Contents for Weathermaster 48P2030-100
Page 130: ...130 Fig 19 Typical Power Schematic Sizes 040 075 Shown ...
Page 131: ...131 Fig 20 Main Base Board Input Output Connections ...
Page 132: ...132 Fig 21 RXB EXB CEM SCB Input Output Connections ...
Page 133: ...133 Fig 22 Typical Gas Heat Unit Control Wiring 48P030 100 Units Shown ...
Page 134: ...134 Fig 23 Typical Electric Heat Wiring 50P030 100 Units Shown ...
Page 135: ...135 Fig 24 Typical Power Wiring 115 V ...
Page 136: ...136 Fig 25 Typical Gas Heat Section Size 030 050 Units Shown ...
Page 138: ...138 Fig 27 Component Arrangement Size 030 035 Units ...
Page 139: ...139 Fig 28 Component Arrangement Size 040 075 Units ...
Page 140: ...140 Fig 29 Component Arrangement Size 090 100 Units ...