Carrier 48KHA - Manual (Page 11)

ADJUSTING BURNER AIR SHUTTERS-After burners
have operated at full input for at least 10 minutes, adjust
primary air to each burner to ensure optimum heating per­
formance. Make these adjustments when unit is being
installed and during routine maintenance inspections at
beginning of each heating season. Be sure each burner is
clean and free of deposits before adjusting primary air.
Primary air to each burner is regulated by burner air shut­
ter on each burner. See Fig. 9 (Burner Flames, Standard) for
location of burner air shutter. With all burners operating,
adjust primary air to each burner as follows:
1. Loosen locking screw that secures air shutter in place
on burner, then partially close air shutter until a slight
yellow tip appears on top of burner flames.
2. Open air shutter very slowly until yellow tip just disap­
pears, then secure air shutter in place with locking
screw.
3. Repeat steps 1 and 2 for each burner.
After air shutter adjustments have been completed, observe
that flames on each burner are light blue and soft in appear­
ance, and that flames are same height along entire length of
each burner. See Fig. 9.
CARRYOVER
AIR
SHUTTER
STANDARD
Fig. 9—Burner Flames
MANIFOLD
BLOWER HEAT-RELAY OPERATION-Heating relay
(see Fig. 6 and unit wiring diagram) is located in the control
box and adjusts to permit either longer or shorter OFF
cycles. The ON cycle automatically adjusts as OFF cycle
changes. Adjusting level on relay is factory-set at center
position to provide optimum performance for most installa­
tions. On unusual installations, or where line voltage is con­
siderably above or below rated voltage, an increase or
decrease may be required for length of time blower remains
on. To increase blower operation time, move adjusting lever
toward right-hand position. To decrease blower operation
time, move lever toward left-hand position.
AIRFLOW AND TEMPERATURE RISE-The heating
section of each size of unit is designed and approved for
heating operation within temperature rise range stamped on
unit rating plate.
Table 5 shows approved temperature rise range for each
unit and air delivery (cfm) at various temperature rises.
Heating operation airflow must produce a temperature rise
that falls within the approved range. Refer to Cooling Sec­
tion Start-Up and Adjustments—Indoor Airflow emd Air­
flow Adjustments to adjust heating airflow when required.
HEATING SEQUENCE OF OPERATION—See Fig. 10
Models 48KHA,KLA have an intermittent electric-spark
ignition system without a standing flame. When manual
shutoff is opened, gas flows to gas valve. On a call for heat­
ing by the thermostat, unit terminal R makes to unit termi­
nal W. Pilot veJve solenoid of gas valve and spark generator
are energized. Gas flows to pilot and the pilot is ignited
within 4 seconds. The flame sensor proves the presence of
pilot flame within 0.8 seconds after pilot ignition. The inter­
nal switching of gas valve de-energizes spark generator,
energizes meun valve solenoid and energizes heating delay
relay. Gas flows to medn burners and is ignited by pilot
flame. Contacts of heating relay close between 60 and 90
seconds after burners are ignited, and blower motor starts.
Heating cycle is now in normeil operation. Unit will continue
operating in heating cycle until thermostat is satisfied.
When this occurs, the thermostat switching removes 24-volt
control circuit voltage instantly; however, contacts of de­
energized heating relay remain closed and keep blower
motor running for an additional 2 to 3 minutes. Contacts of
heating relay open after 2- to 3-minute delay and blower
motor stops. Heating section is now in a standby condition
wmting for another call for heating from thermostat.
Table 5—Air Delivery (cfm) at Indicated Temperature
Rise and Rated Heating Input
MODEL 48-
HTG
INPUT TEMPERATURE RISE(F)
(Btuh) 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75
KLA118 40,000 794 751 712 678 646 617 591 567 545 524 505 487 471 455 441 427
_
— — — —
KLA124 40,000 794 751 712 678 646 617 591 567 545
KHA024 75,000 — — — — 1212 1158 1109 1063 1022 983 947 914 883 854 827 809 778 — — — —
KLA130 40,000 794 751 712 678 646 617 591 567 545 524 505 487 471 455
KHA030 75,000 — — 1271 1212 1158 1109 1063 1022 983 947 914 883 854
KLA136 60,000 1190 1126 1068 1016 969 926 887 850 817 786 758 731 706 683
KHA036/136 100,000 1984 1877 1781 1694 1615 1543 1478 1417 1362 1310 1263 1218 1177 1138 1102 1068 1036 1006 978 951 926
KHA036 125,000 — — — 2117 2019 1930 1846 1771 1701 1638 1579 1523 1472 1423 1378 1336 1296 1258 1223 1189 1158
KLA142 60,000 1190 1128 1068 1016 969 926 887 850 817 786 758 731 706 683 661 641 622 604 587 571 556
KHA042 125,000 — — ~ — _ 1930 1846 1771 1702 1638 1579 1523 1482 1423 1378 1326 1296 1258 1223 1189
—
KLA148 80,000 1587 1502 1425 1355 1292 1235 1182 1134 1089 1048 1010 975 942 911 — — — — — — —
KHA048 125,000 — — 2326 2117 2019 1930 1846 1771 1702 1638 1579 1523 1472 1423 1378 1336 1296 — — — —
KLA160 100,000 1984 1877 1781 1694 1815 1543 1478 1417 1362 1310 1263 1218 1177 1138 1102 — — —
_
— —
KHA060 150,000 — - — — —
2325 2226 2135 2051 1974 1902 1835 1773 1715 1660 1609 1561 1516 1493 1483 1395
NOTE: Bolder ratings in table fall
range of the unit Dashed areas of
below the approved temperature rise
the tabie faii beyond the air delivery capabiiity of the unit within the operating voitage range for aii voltage
options for each size unit.
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