Adjust Temperature Rise - International comfort products N9MSB Service And Technical Support Manual

SERVICE AND TECHNICAL SUPPORT MANUAL
Table 3 (CONT.) Orifice Size and Manifold Pressure (in. w.c.) for Gas Input Rate − Single Stage
(TABULATED DATA BASED ON 20,000 BTUH PER BURNER, DERATED 2%/1000 FT (305M) ABOVE SEA LEVEL)
ALTITUDE
RANGE
AT ALTITUDE
ft (m)
7001
(2134)
to
8000
(2438)
8001
(2439)
to
9000
(2743)
9001
(2744)
to
10000
(3048)
* Orifice numbers shown in BOLD are factory-installed.

Adjust Temperature Rise

NOTE: Blower door must be installed when taking temperature
rise reading. Leaving blower door off will result in incorrect
temperature measurements, due to possible changes in duct
static pressure and airflow.
CAUTION
!
FURNACE DAMAGE HAZARD
Failure to follow this caution may result in:
S
Overheating the heat exchangers or condensing
flue gases in heat exchanger areas not designed
for condensate.
S
Shortened furnace life.
S
Component damage.
Temperature rise must be within limits specified on furnace
rating plate. Recommended operation is at midpoint of rise
range or slightly above.
Jumper R to W to check gas-heat temperature rise. Do not
exceed temperature rise ranges specified on unit rating plate.
This furnace must operate within the temperature rise ranges
specified on the furnace rating plate. Determine the air
temperature as follows:
1. Place duct thermometers in return and supply ducts as
close to furnace as possible. Be sure thermometers do
10
SINGLE-STAGE FURNACE
A V G . G A S
HEAT VALUE 0.58
Orifice Manifold
(Btu/cu ft) No. Pressure
650 42 3.4
675 43 3.8
700 43 3.5
725 44 3.8
750 44 3.5
775 44 3.3
800 44 3.1
825 44 2.9
625 42 3.4
650 43 3.8
675 43 3.5
700 44 3.7
725 44 3.5
750 44 3.3
775 44 3.0
600 42 3.3
625 43 3.7
650 43 3.5
675 44 3.7
700 44 3.4
725 44 3.2
Specifications subject to change without notice.
S P E C F I C I G R A V T I Y O F N A T U R
0.60 0.62
Orifice Manifold Orifice
No. Pressure No.
42 3.5 42
42 3.2 42
43 3.7 43
43 3.4 43
44 3.7 44
44 3.4 44
44 3.2 44
44 3.0 44
42 3.5 42
42 3.2 42
43 3.6 43
43 3.4 43
44 3.6 44
44 3.4 44
44 3.2 44
42 3.4 42
42 3.2 42
43 3.6 43
44 3.8 43
44 3.5 44
44 3.3 44
not "see" heat exchangers so that radiant heat does not
affect thermometer
important with straight−run ducts.
2. When thermometer readings stabilize, subtract return−air
temperature from supply−air temperature to determine
temperature rise.
If the temperature rise is outside this range, check the
following:
1. Gas input rate.
2. Derate for altitude if applicable.
3. Return and supply ducts for excessive restrictions
causing static pressures greater than 0.50−in. w.c. (125
Pa)
4. Adjust temperature rise by adjusting blower speed.
S
Increase blower speed to reduce temperature rise.
S
Decrease blower speed to increase temperature rise.
WARNING
!
ELECTRICAL OPERATION HAZARD
Failure to follow this warning could result in personal injury
or death.
Disconnect 115vac electrical power before changing speed
tap.
Gas Furnace: N9MSB
A L G A S
0.64
Manifold Orifice Manifold
Pressure No. Pressure
3.6 42 3.7
3.3 42 3.4
3.8 42 3.2
3.5 43 3.6
3.8 43 3.4
3.5 44 3.7
3.3 44 3.4
3.1 44 3.2
3.6 42 3.7
3.3 42 3.4
3.7 42 3.2
3.5 43 3.6
3.7 44 3.8
3.5 44 3.6
3.3 44 3.4
3.6 42 3.7
3.3 42 3.4
3.7 43 3.8
3.4 43 3.5
3.7 44 3.8
3.4 44 3.5
readings. This is particularly
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A11253B