White Rodgers 921 User Manual

2

Input and Frequency: 120 VAC, 60 Hz
Output Ratings:
  Ignitor Load: 2 Amps maximum
  Inducer Draft Motor: 3 Amps Full Load, 4 Amps Locked  

 

 

 

           Rotor

  Current:

 0.2 Amps @ 120 VAC

Range of Regulation (Btu/Hr)
 

Minimum: 30,000       Maximum: 150,000

Pressure Regulator Setting: Factory set to 3.5” or 4.0” W.C.
 

 

 

 

     Adjustable 2.5” to 5.0” W.C.

100,000 Btu/Hr

 

a

Based on 1000 Btu/ft

3

, 0.64 specify gravity natural gas

Maximum Inlet Pressure: 1/2 PSI maximum
Ambient Temperature Rating: 
 

32

o

F 

to 160

o

F 

(0

o

C 

to 70

o

C 

) 

Single-Use Type, 185

o

F(82

o

C

)

5 Seconds

Ignitor Warm-up Time:  20

 Seconds

Trial for Ignition Period:  4

 Seconds

Inter-purge Time:  5

 Seconds

Post-purge Time:  5

 Seconds

Ignition Retries:  2 Retries; 3 Trials before lockout
Ignition Recycles:  2 Recycles, 3 Losses of flame before  
 

                          lockout

Right angle with a 1/2” NPT inlet and a 1/2” inverted flare  

 

outlet

Limited Horizontal/Vertical

detect unodorized gas, you must have a gas detector, 
which can be purchased from your gas company.  If 
you do not have a detector and have the slightest 
suspicion that gas may be present, get out of the 
house and call the gas company.  DO NOT RELY 
TOTALLY ON YOUR NOSE. 

1.  Shut off the gas to the water heater
2.  Turn off electrical power to the water heater. 
3.  Remove the two plastic wire connectors that plug 

into the bottom of the control.  The connectors have 
latches which must be depressed. DO NOT FORCE 
THE CONNECTORS, DAMAGE TO THE WIRING MAY 
RESULT.

4.  Shut off the water at the cold water inlet.
5.  Connect a hose to the water heater drain cock.  Drain the 

water to a nearby drain. Open a hot water faucet for faster 
draining.

6.  Disconnect the gas line at the union (Figure 1).  Remove 

the piping from the old control.

7.  Remove the control by turning it counterclockwise

 (

).

All piping must comply with local and state ordinances or 
with the National Fuel Gas Code (ANSI Z223.1-NFPA 54), 
whichever applies.

Dirt or contamination in the gas line can block the control 
from operating creating a risk of explosion, injury, or death.  
To protect the control from dirt and contamination, a drip leg 
or sediment trap (see Figure 1) must be installed in the piping 
leading to the control.
1.  Apply pipe compound to the male threads of the pipe that 

goes into the control, leaving the first two or three threads 
clean.

2.  Install control in the tank.  Turn clockwise (

). Use a 

short piece of pipe to help in turning.  Align the control so 
that the burner tube may be connected. 

3.  Make the main burner connection.  Do not use pipe joint 

compound or Teflon tape.

4.  Connect the gas line. Use new black iron pipe that  has 

been properly reamed. If old pipe is used, be sure it 
is clean and free from rust and scale.  Use pipe joint 
compound on male threads only. (Use pipe joint compound 
approved for natural and LP gas service.) Do not use 
TEFLON tape.  Do not apply compound to the first two 
threads.

5.  DO NOT use joint compound or tape on the union 

connection.

6.  Make the electrical connections to the control. There are 

two plastic connectors that plug into the bottom of the 
control. The connectors are “keyed” so that they can only 
be inserted one way.  Make sure that the connectors 
are properly aligned before attempting to insert.  

7.  To fill the water heater with water:

a.  Close the water heater drain valve by turning the  

handle to the right (clockwise).  The drain valve is on 
the lower front of the water heater.

b.  Open the cold water supply valve to the water heater.
c.  To ensure complete filling of the tank, let air exit by 

opening the nearest hot water faucet. Allow water to 
run until a constant flow is obtained. This will let air out 
of the water heater and the piping.