Bryant UNIT 379H - Manual (Page 5)

Water Manometer
When using a water manometer to measure the mani­
fold pressure, proceed as follows to adjust the gas in­
put:
1. Turn off gas to unit. Connect manometer to 1/8-
inch pressure tap at outlet of gas valve.
2. Turn on gas to unit. With burners fired and both
first and second stage gas valves open, adjust the
pressure regulator to obtain the correct manifold
pressure as shown in Table II. Check with local gas
utility for Btu value and specific gravity of gas in the
area.
TABLE II
BTU Specific Gravity
Value 0.59 0.61 0.63 0.65 0.67
900 3.8 3.9 4.0 4.1 4.2'
950 3.3 3.4 3.5 3.6 3.7
1000 3.0 3.1 3.2 3.3 3.4
1025 2.8 2.9 3.0 3.1 3.2
1050 2.7 2.8 2.9 3.0 3.1
1100 2.4 2.5 .L.C 2.7 2.8
Example; Heating value of gas in the area is 1030
Btu; Specific gravity is 0.62.
(a) From Table II the manifold pressure required for
450,000 Btuh is 3.0 inches wc.
(b) Set manifold pressure to 3.0 inches water column
by adjusting gas pressure regulating screw.
If the required manifold pressure exceeds 3.3 inches
w.c. or is less than 2.7 inches w.c., the orifices should
be sized according to unit requirements.
CAUTION: Do not redrill orifices under any circum­
stances.
Air Shutter Adjustment
To adjust the primary air to each burner, partially
close the air shutter until there is a slight yellow tip
on the top of the flame, then open the air shutter until
the yellow tip just disappears. This should be done af­
ter the burners have been operating at full input for 5
or 10 minutes (approximately).
Temperature Rise
Models 450-379H, 180R-, and 240R-379 are designed
for operation within a temperature rise range of 20 °F
to 75°F against an external static pressure up to 1.0
inch water column.
NOTE: Temperature rise is the difference between
the temperature of the air in the return air duct and
the temperature of the air in the discharge duct near
the heating section.
SECTION VIII. MAINTENANCE
Lubrication: Refer to the rating plate for the blower
motor lubrication requirements.
Cleaning the Heating Unit
1. Be sure that main line disconnect switch is in OFF
p o s i t i o n .
TAG SWITCH WITH SUITABLE WARNING
LABEL.
2. Remove front access panel.
3. Turn off manual gas valve and pilot valve.
4. Disconnect pilot and escapement tubing.
5. Remove burners.
6. Remove flue baffle retainer and the flue baffles.
7. Clean flue passages with suitable brush.
8. Reassemble furnace by reversing above procedure,
making sure all seals are reinstalled properly.
9. Check belt conditions and for proper belt tension
(1/2 inch deflection).
Filter
Filters in Models 240R- and 450-379H are of the
permanent type and should be inspected and cleaned
at regular intervals. Filters used in Model 180R-379H
are of the disposable type and should be inspected
and replaced with filters of the same type and size. In­
spections should be made on a regular basis; the time
interval between inspection will depend on the type
of application.
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