Thomas & Betts LDAP 1200 - Manual (Page 12)

Form RZ-NA-I-LDAP, P/N 207733 (Rev 2), Page 12
12. Gas
Pressures
(cont’d)
Derate by Valve Outlet Pressure Adjustment for High
Altitude Operation
Instructions for High Altitude Derate
1. Determine the required valve outlet pressure for the elevation where the heater
will be operating. If unsure of the elevation, contact the local gas supplier.
Check Valve Outlet
Pressure (can only
be done after heater
is operating)
NOTE: If operating at high
altitude, outlet pressure
requires adjustment. Follow
instructions below.
Valve Outlet Pressure Settings by Elevation
NOTES: If installation is
above 6000 ft (1830M), a
high altitude pressure switch
is required on each heat
section (all sizes). See
Paragraph 5.
The main combustion air
pressure switch (Sizes 800
and 1200 only) does not need
to be changed for high
altitude installation.
FIGURE 8 - Top View of
Valves showing Outlet
Pressure Tap and
Adjustment Locations
2. Locate the 1/8” output pressure tap on the first valve (See FIGURE 8). Turn
the knob on the top of the valve to “OFF”. Connect a manometer to the 1/8"
pipe outlet pressure tap in the valve. Use a water column manometer that is
readable to the nearest tenth of an inch.
3. Single-Stage and Two-Stage High Fire - Turn the knob on the top of the
valve to “ON”. Remove the cap from the pressure adjusting screw and adjust
the gas train pressure to the pressure selected from the table above. Adjust
pressure by turning the regulator screw IN (clockwise) to increase pressure or
OUT (counterclockwise) to decrease pressure.
Two-Stage Low Fire - Disconnect the wire from the “HI” terminal on the gas
valve and check the low fire pressure. Turn the regulator screw to adjust the low
fire outlet pressure to the “Low Fire” pressure selected from the table. Re-
connect the wire to the gas valve.
Instructions
1) Locate the 1/8” output pressure tap on the first valve (See FIGURE 8). With
the manual valve turned off to prevent flow to the gas valve, connect a manom-
eter to the 1/8" pipe outlet pressure tap in the valve. NOTE: A manometer (fluid-
filled gauge) is recommended rather than a spring type gauge due to the difficulty
of maintaining calibration of a spring type gauge.
2) Open the manual valve and operate the heater. Measure the outlet pressure of
the gas valve. To measure low-stage pressure on a Size 400 unit equipped with a
two-stage valve, disconnect the wire from the “HI” terminal on the valve. (Be
sure to reconnect wire after testing.)
Normally when operating at sea level, adjustments should not be necessary to the
factory setting(s). (For high altitude settings, see below.) If adjustment is neces-
sary, remove the cap from the adjustment screw(s). Set pressure to correct
settings by turning the regulator screw IN (clockwise) to increase pressure. Turn
regulator screw OUT (counterclockwise) to decrease pressure.
3) If installing a Model LDAP 800, repeat to verify outlet pressure on second valve.
If installing a Model LDAP 1200, repeat to verify outlet pressure check on
second and third valve.
Feet Meters
Single-Stage and
Two-Stage High Fire
Two-Stage
Low Fire
Single-Stage and
Two-Stage High Fire
Two-Stage
Low Fire
0-2000 0-610 3.5 2.0 10.0 5.6
2001-3000 611-915 3.1 1.7 8.8 5.0
3001-4000 916-1220 3.0 1.7 8.5 4.8
4001-5000 1221-1525 2.8 1.6 8.1 4.6
5001-6000 1526-1830 2.7 1.5 7.7 4.4
6001-7000 1831-2135 2.6 1.5 7.4 4.2
7001-8000 2136-2440 2.5 1.4 7.1 4.0
8001-9000 2441-2745 2.4 1.3 6.7 3.8
9001-10000 2746-3045 2.4 1.3 6.7 3.6
Feet Meters
Single-Stage and
Two-Stage High Fire
Two-Stage
Low Fire
Single-Stage and
Two-Stage High Fire
Two-Stage
Low Fire
0-2000 0-610 3.5 2.0 10.0 5.6
2001-4500 611-1373 2.8 1.6 8.1 4.6
Manifold Pressure Settings by Altitude for the UNITED STATES
Manifold Pressure Settings by Altitude for CANADA
Altitude Natural Gas (inches w.c.) Propane Gas (inches w.c.)
Altitude Natural Gas (inches w.c.) Propane Gas (inches w.c.)
Single-Stage Valve
1/8” Output
Pressure
Tap
Adjust Low
Pressure
Output
Adjust High
Pressure
Output
1/8” Output
Pressure Tap
Inlet
Pressure
Tap
Inlet
Pressure
Tap
Two -Stage Valve (optional
on Model LDAP 400 only)
Output
Adjustment
Screw