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Form RZ-NA I-UDA, Mfg #195673 Rev 5, Page 7
If the heater is being installed at an elevation above 2000 ft (610M), the input rate
will have to be derated. This is done by adjusting the valve outlet pressure.
In addition, if the heater is being installed at an altitude above 6000 ft (1830M), the
pressure switch will have to be changed. If ordered with the unit as Option DJ20 or
DJ21, the pressure switch is shipped separately.
Adjusting the valve outlet pressure is done after the heater is in operation; follow
the instructions in Paragraph 12. Capacities and inputs for derated units are also
listed in Paragraph 12.
If the pressure switch needs to be changed, do that before the heater is operated;
follow the instructions in FIGURE 4.
7. High Altitude
Operation
FIGURE 4 - Installing High Altitude Pressure Switch required above 6000 ft (1830M) elevation
Gas valve adjustment for
high altitude can only be
done after heater is
operating; see
Paragraph 12.
Units must be installed so that the clearances in the table are provided for combus-
tion air space, inspection and service, and for proper spacing from combustible
construction. Clearance to combustibles is defined as the minimum distance from
the heater to a surface or object that is necessary to ensure that a surface tempera-
ture of 90°F above the surrounding ambient temperature is not exceeded.
8. Clearances
Clearances
inches mm inches mm inches mm inches mm inches mm inches mm
30-125 1 25 6 152 18 457 1 25 1 25 18 457
150-400 4 102 6 152 18 457 2 51 1 25 18 457
*Suspend the heater so that the bottom is a minimum of 5 feet (1.5M) above the floor.
Bottom* Rear
Size
To
p
Flue Connector Access Panel Non-Access Side
Instructions for Changing Pressure Switch
1. In the control compartment, locate the pressure switch.
Sizes 30-125 - On the back wall of the control compartment.
Sizes 150-400 - On the bracket on the bottom of the control compartment.
2. Mark and disconnect the two wires attached to the pressure switch.
3. Disconnect the sensing tube from the pressure switch.
4. Locate the two screws holding the switch mounting bracket. Remove the
screws (save screws) and the pressure switch.
5. Using the same screws, install the high altitude pressure switch. Attach the
sensing tube and wires.
Pressure Switch
Model UDAP
Size 30 45 60 75 100 125 150 175 200 225 250 300 350 400
High Altitude Switch P/N
Negative Pressure OFF Setpoint "w.c.
Label color
Model UDAP-CV with Option AV6 for Common Venting
Size 30 45 60 75 100
High Altitude Switch P/N 197029 197032 196388
Negative Pressure OFF Setpoint "w.c. 0.60 0.45 0.50
Label color Lt Blue Pin
k
Oran
g
e
Model UDAS
Size 30 45 60 75 100 125 150 175 200 225 250 300 350 400
High Altitude Switch P/N 196388 197030
Differential Pressure OFF Setpoint "w.c. 0.50 0.40
Label color Oran
g
eGreen
201160 201161
197031
0.35
Pur
p
le
Pur
p
le
197031
0.35
Lt. Blue
White
Pur
p
le Pink
196362
0.55
197029
0.60
197031 197032
0.35 0.45
201161
Brown
Brown
White
White
1.00
201160
1.30
1.00 1.30