Carrier 48TC 04 Series, Service And Maintenance Instructions

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125,000/90,000 BTUH INPUT
180,000/120,000 BTUH INPUT
240,000/180,000 BTUH INPUT
250,000/200,000 BTUH INPUT
C08447
Fig. 66 -- Spark Adjustment (08--14)
5. If factory orifice has been removed, check that each
orifice is tight at its threads into the manifold pipe
and that orifice projection does not exceed maximum
valve. See Fig. 62.
6. Reinstall burners on rack in the same locations as
factory--installed. (The outside crossover flame re-
gions of the outermost burners are pinched off to pre-
vent excessive gas flow from the side of the burner
assembly. If the pinched crossovers are installed
between two burners, the flame will not ignite prop-
erly.)
7. Reinstall burner rack as described in Removal and
Replacement of Gas Train section, above.
Gas Valve — All three--phase models (except Low NOx)
are equipped with 2--stage gas valves. Single--phase
models and all Low NOx models are equipped with
single--stage gas valves. See Fig. 68 for locations of
adjustment screws and features on the gas valves.
To adjust gas valve pressure settings:
IMPORTANT : Leak check all gas connections including
the main service connection, gas valve, gas spuds, and
manifold pipe plug. All leaks must be repaired before
firing unit.
Check Unit Operation and Make Necessary Adjust-
ments
NOTE
: Gas supply pressure at gas valve inlet must be
within specified ranges for fuel type and unit size. See
Table 17 and Table 19.
1. Remove manifold pressure tap plug from manifold
and connect pressure gauge or manometer. See Fig.
63.
2. Turn on electrical supply.
3. Turn on unit main gas valve.
4. Set room thermostat to call for heat. If unit has two--
stage gas valve, verify high--stage heat operation be-
fore attempting to adjust manifold pressure.
5. When main burners ignite, check all fittings, mani-
fold, and orifices for leaks.
6. Adjust high--stage pressure to specified setting by
turning the plastic adjustment screw clockwise to in-
crease pressure, counter--clockwise to decrease pres-
sure.
7. For Two--Stage Gas Valves set room thermostat to
call for low--stage heat. Adjust low--stage pressure to
specified setting.
8. Replace regulator cover screw(s) when finished.
9. With burner access panel removed, observe unit
heating operation in both high stage and low stage
operation if so equipped. Observe burner flames to
see if they are blue in appearance, and that the flames
are approximately the same for each burner.
10. Turn off unit, remove pressure manometer and re-
place the 1/8 in. pipe fitting on the gas manifold. See
Fig. 63.
Limit Switch
Remove blower access panel. Limit switch is located on
the fan deck. See Fig. 56.
Burner Ignition
Unit is equipped with a direct spark ignition 100% lockout
system. Integrated Gas Unit Controller (IGC) is located in
the control box. See Fig. 64. The IGC contains a
self--diagnostic LED (light--emitting diode). A single LED
(see Fig. 69) on the IGC provides a visual display of
operational or sequential problems when the power supply
is uninterrupted.
When a break in power occurs, the IGC will be reset
(resulting in a loss of fault history) and the indoor
(evaporator) fan ON/OFF times will be reset. The LED
error code can be observed through the viewport. During
servicing refer to the label on the control box cover or
Table 14 for an explanation of LED error code
descriptions.
If lockout occurs, unit can be reset by interrupting power
supply to unit for at least 5 seconds.
48TC