Step 7 - Install Gas Piping; Step 8 - Install Supply-Air Thermistors (Staged And Modulating Gas Units Only) - Carrier WeatherMaker 48A020 Installation Instructions Manual

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Fig. 21 — Condensate Drain Trap Piping Details
(Typical Roof Curb or Slab Mount Shown)
Step 7 — Install Gas Piping —
use with natural gas. Installation must conform with local
building codes or, in the absence of local codes, with the Na-
tional Fuel Gas Code, ANSI Z223.1.
Install manual gas shutoff valve with a
for test gage connection at unit. Field gas piping must include
sediment trap and union. See Fig. 22. A
located on the gas manifold adjacent to the gas valve.
WARNING
Do not pressure test gas supply while connected to unit.
Always disconnect union before servicing. Personal injury
or damage to unit may occur.
IMPORTANT: Natural gas pressure at unit gas connection
must not be less than 5 in. wg or greater than 13.5 in. wg.
Size gas-supply piping for 0.5-in. wg maximum pressure drop.
Do not use supply pipe smaller than unit gas connection.
OPTIONAL STAGED GAS UNITS — See Table 7 for staged
gas information. Staging pattern is selected during controls
start-up.
For complete information and service instructions for staged
gas control units, see Controls, Start-Up, Operation, Service
and Troubleshooting literature.
PIN
THERMISTOR CONNECTION
POINT
SAT1 J8 – 1,2 (SGC)
SAT2 J8 – 3,4 (SGC)
SAT3 J8 – 5,6 (SGC)
J8 – 15,16
LIMTTEMP
(SGC)
SGC — Staged Gas Controller
Unit is equipped for
1 / -in. NPT pressure tap
8
1 / -in. NPT is also
8
Table 8 — SGC Thermistor Designations
FUNCTION AND LOCATION
Supply-Air Thermistor (SAT) — Inserted into supply section underneath the
gas heat section (factory-provided, field-installed)
Supply-Air Thermistor (SAT) — Inserted into supply section underneath the
gas heat section (factory-provided, field-installed)
Supply-Air Thermistor (SAT) — Inserted into supply section underneath the
gas heat section (factory-provided, field-installed)
Limit Switch Thermistor (LIMTTEMP) — Inserted next to the lower limit switch
(factory-installed)
23
Table 7 — 48A Series Staged Gas Control
MODEL NUMBER POSITION
NUMBER OF
STAGES
5
S
5 STAGES
T
7 STAGES T
9 STAGES T
11 STAGES S
Step 8 — Install Supply-Air Thermistors
(Staged and Modulating Gas Units Only) —
Supply-air thermistors are a field-installed, factory-provided
component. Three supply-air thermistors are shipped with
staged and modulating gas units inside the unit control box.
Thermistor wires must be connected to the SGC (staged gas
controller) in the unit control box. See Table 8. The supply-air
thermistors should be located in the supply duct with the fol-
lowing criteria:
• downstream of the heat exchanger cells
• equally spaced as far as possible from the heat
exchanger cells
• a duct location where none of the supply air thermistors
are within sight of the heat exchanger cells
• a duct location with good mixed supply air portion of the
unit.
Fig. 22 — Field Gas Piping
Thermistors
HEAT SIZE
6,7,8
020
025
027
030 Low
035
040
050
035
040 High
050
020
025
High
027
030
060 High
060 Low
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PART NO.
HH79NZ034