Carrier WeatherExpert 48N2 - Page 66

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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
continually checked against the capacity ranges of the next
higher staging patterns. Since each stage has a range of capaci-
ties, and the capacities of some stages overlap, the control se-
lects 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
sufficient 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 out-
puts 7 and 8 are located on the CXB. The heat stage selected
(Run Status→VIEW→HT.ST) is clamped between 0 and the
maximum number of stages possible (Run Sta-
tus→VIEW→H.MAX). See Tables 39- 42.
SCR Electric Heat Staging
— For all SCR electric heat units
there is only 1 heat stage. Whenever the heat is energized, all
heaters will be active will be modulatied through The SCR
control.
Table 38 — Modulating Gas Heat
Table 39 — Modulating Gas Heat Control Steps (HT.ST = 0)
* ON when Outputs  HEAT  H1.CP > 54%, OFF when Outputs  HEAT  H1.CP < 46%.
Table 40 — Modulating Gas Heat Control Steps (HT.ST = 1)
* ON when Outputs  HEAT  H1.CP > 54%, OFF when Outputs  HEAT  H1.CP < 46%.
Table 41 — Modulating Gas Heat Control Steps (HT.ST = 2)
* ON when Outputs  HEAT  H1.CP > 54%, OFF when Outputs  HEAT  H1.CP < 46%.
NUMBER
OF
STAGES
HT.ST
CONFIG.
No. of
Heat
Exchanger
Sections
UNIT SIZE
48N
HEAT
SIZE
3 0 2 75, 90, 105 Low
4 13
75 High
90, 105 Med
120,130,150 Low
5 24
90-105 High
120,130,150 Med
7 3 5 120,130,150 High
STAGE
RELAY OUTPUT
CAPACITY
%
Heat 1 Heat 2 Heat 3 Heat 4
MBB-RLY8 TR1-CR SCB-RLY1 SCB-RLY2
IGC1 MGV1 IGC2 MGV2 MIN MAX
0 OFF OFF OFF OFF 0 0
1 ON OFF/ON* OFF OFF 15 50
2 ON OFF/ON* ON OFF 52 88
3 ON OFF/ON* ON ON 65 100
STAGE
RELAY OUTPUT
CAPACITY
%
Heat 1 Heat 2 Heat 3 Heat 4 Heat 5 Heat 6
MBB-RLY8 TR1-CR SCB-RLY1 SCB-RLY2 SCB-RLY3 SCB-RLY4
IGC1 MGV1 IGC2 MGV2 IGC3 MGV3 MIN MAX
0 OFF OFF OFF OFF OFF OFF 0 0
1 ON OFF/ON* OFF OFF OFF OFF 10 33
2 ON OFF/ON* ON OFF OFF OFF 35 58
3 ON OFF/ON* ON OFF ON OFF 60 83
4 ONOFF/ON*ONONONON76100
STAGE
RELAY OUTPUT
CAPACITY
%
Heat 1 Heat 2 Heat 3 Heat 4 Heat 5 Heat 6 Heat 7 Heat 8
MBB-RLY8 TR1-CR SCB-RLY1 SCB-RLY2 SCB-RLY3 SCB-RLY4 MBB-RLY9 MBB-RLY10
IGC1 MGV1 IGC2 MGV2 IGC3 MGV3 IGC4 MGV4 MIN MAX
0 OFFOFFOFFOFFOFFOFFOFFOFF00
1 ON OFF/ON* OFF OFF OFF OFF OFF OFF 7 25
2 ON OFF/ON* ON OFF OFF OFF OFF OFF 26 44
3 ON OFF/ON* ON OFF ON OFF OFF OFF 45 63
4 ON OFF/ON* ON OFF ON OFF ON OFF 64 81
5 ONOFF/ON*ONONONONONON82100