Unitrol Gas Valve Trouble Shooting Brief
User Manual: Unitrol-gas-valve-Trouble-Shooting-Brief
Open the PDF directly: View PDF 
.
Page Count: 6
Trouble Shooting
PROBLEM POSSIBLE CAUSE WHAT TO DO: Trouble Shooting
Pilot doesn’t light
Pilot will light but doesn’t
stay lit.
Pilot lights but burner
doesn’t.
Page 8
Rev 2/2007
1. Pilot burner not getting gas.
2. Pilot orice blocked.
3. Control Knob not in “Pilot” position
1. Check to see if tank valve is “ON”
2. Control off-on set to “pilot”
3. Red reset button depressed (it may take
30 to 60 seconds to bleed all air from
line)
1. Remove are nut and ¼” line. See Fig.1
No. 14.
2. Pull line back & remove orice.
3. Clean with compressed air, DO NOT use
drill bit or wire as this may change the
size of the orice and cause an improper
or unsafe ame.
1. Check to see if control knob is set in
“Pilot” position
1. Are you using a Low Pressure
Regulator?
2. Thermocouple not hot enough.
3. Damaged thermocouple or just
bad (Kinked, hole, frozen, etc)
4. Pilot ame in wrong position.
5. Pilot ame is wrong size.
6. Weak magnet.
7. Red Button Melted or Deformed
1. If a Low Pressure Regulator is not being
used, install one. Operation of unit with
out one could ruin the Robert Shaw
Unitrol unit. (Blow out the bellows)
1. Hold red reset button down longer. It
should not take more than 30-40 seconds.
1. Replace with new one.
2. Tighten thermocouple nut nger tight
plus ¼ turn and NO MORE. Overtightening
may damage thermocouple or magnet.
1. Flame should Contact the upper 1/3 and
including the tip of the thermocouple
(3/8” to 1/2”) Bend ame deector
hood as needed. Operates best when
bent in “L”.
1. Adjust pilot adjustment screw. See Fig.
2b. If thermocouple has swelled, ame is
too hot and thermocouple may be dam
aged. (Order a new one.)
1. Replace gas valve (Unitrol).
NOTE: See test procedure No. 2.
1. The knob will not push down into correct
position. Replace Red Knob
1. Control off-on set to “PILOT.”
2. Temperature dial too low.
3. Temperature sensing bulb too
warm.
1. Turn Control off-on to “ON.”
1. Turn temperature dial to a higher
number.
1. Bulb must be less than 60 degrees to light
Burner. If bulb is less than 40 degrees &
burner still won’t light, see next cause.
Sensing bulb must be below water level
in bulb guide.
4. Temperature sensing bulb or line is
damaged. 1. Dents in temperature sensing bulb par
tially crushed due to water freezing in the
bulb tube guide (see Fig. No. 2) or sharp
bends in the line may cause the control
to “think’ the temperature is higher
than it is. It the damage is major, a new
gas valve (Unitrol) is required. Tempera
ture sensing bulb not sold Separately.
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#Unitrol
Trouble Shooting Trouble Shooting
PROBLEM POSSIBLE CAUSE WHAT TO DO:
Page 9
Rev 2/2007
1. Check to see if tank valve is “ON”
2. Control off-on set to “pilot”
3. Red reset button depressed (it may take
30 to 60 seconds to bleed all air from
line)
1. Remove are nut and ¼” line. See Fig.1
No. 14.
2. Pull line back & remove orice.
3. Clean with compressed air, DO NOT use
drill bit or wire as this may change the
size of the orice and cause an improper
or unsafe ame.
1. If a Low Pressure Regulator is not being
used, install one. Operation of unit with
out one could ruin the Robert Shaw
Unitrol unit. (Blow out the bellows)
1. Hold red reset button down longer. It
should not take more than 30-40 seconds.
1. Replace with new one.
2. Tighten thermocouple nut nger tight
plus ¼ turn and NO MORE. Overtightening
may damage thermocouple or magnet.
1. Flame should Contact the upper 1/3 and
including the tip of the thermocouple
(3/8” to 1/2”) Bend ame deector
hood as needed. Operates best when
bent in “L”.
1. Turn Control off-on to “ON.”
1. Turn temperature dial to a higher
number.
1. Bulb must be less than 60 degrees to light
Burner. If bulb is less than 40 degrees &
burner still won’t light, see next cause.
Sensing bulb must be below water level
in bulb guide.
1. Dents in temperature sensing bulb par
tially crushed due to water freezing in the
bulb tube guide (see Fig. No. 2) or sharp
bends in the line may cause the control
to “think’ the temperature is higher
than it is. It the damage is major, a new
gas valve (Unitrol) is required. Tempera
ture sensing bulb not sold Separately.
5. Temperature dial calibration wrong.
6. Damaged bellows.
7. Dirt in burner orice.
1. See Fig No. 4 for recalibration procedures.
1. Temperature sensing bulb exposed to
either high temperature or crushed due to
water freezing in the bulb tube guide. (The
bellows housing may exhibit a large gap to
the main valve body ) See Figure No 2.
2. May have to replace Robert Shaw UNITROL
unit.
1. Remove burner and orice.
2. Clean with compressed air. DO NOT use
drill bits or wire to clean. This may
change the orice size and cause im
proper or unsafe burner operation.
Burner lights but doesn’t
shut off.
Melted valve knobs
Sensing Bulb froze down in
tube
1. Temperature sensing bulb to cold.
3. Temperature dial.
4. Expanded Bellows
2. Temperature sensing bulb or line
damaged causing a leak.
1. Warm to 50 degrees and check.
1. If temperature sensing bulb has lost some
or all of Its uid, the control will “think”
the temperature is colder than it is.
2. Order a new gas valve (Unitrol). Tempera
ture sensing bulb not sold separately.
1. See Figure No. 4 for recalibration proce
dures.
1. Replace Robert Shaw UNITROL Unit
1. Main burner orice partly plugged
2. Low pressure or bad gas supply.
3. Burner assembly is not properly
inserted into casing
4. Chimney could be partially plugged.
1. Remove burner and clean
1. Correct gas supply.
1. Remove and re-insert burner assembly
making sure that it is all the way to the
bottom and tight against the boot.
2. Replace melted knobs
1. Remove burner assembly. Blow compressed
air into top of chimney to remove debris.
1. Frozen water in tube 1. Put vegetable oil in tube but keep close
watch, vegetable oil will oat on water.
Continued On Next Page
Trouble Shooting
PROBLEM POSSIBLE CAUSE WHAT TO DO:
Burner assembly works ne
outside of Casing, but goes out
when in Casing.
1. Wind blowing out ame. 1. Always keep top cover closed.
2. Try to point the tip of the boot into the
prevailing wind.
2. The stack (chimney) passage
plugged.
1. Clean out the passage (chimney).
3 Lack of air ue convection. 1. Allow sufcient time for the pilot light
heat to create a convection after installing
burner assembly in casing before starting
the main burner.
4. Excessive water (condensation)
build-up in Casing.
1. Empty water and operate at a
slightly higher temperature
dial setting. Runs best between
#4 and #6.
Storage Instructions
Specications
1. Remove the complete stock tank heater from the stock tank.
2. When possible: store complete stock tank heater in an air tight container and free from water, dirt, and dust.
3. If not possible to store complete stock tank heater in air tight container:
a) You should remove the complete burner assembly (the insides) from the casing. Place a plug in the gas
inlet opening or tape over the opening. Also, wrap the burner in a plastic bag. DO NOT COVER GAS
VALVE (Unitro1) with plastic bag! This could cause damage and result in replacing gas valve (Unitrol).
b) Turn casing upside down and if possible, cover up.
4. If the unit must be stored in an upright position, then it is important that it be protected from having water
accumulation in the casing. The burner assembly should not be exposed to water.
5. If you are leaving the stock tank heater in the stock tank you should leave the gas supply in tact and leave the
pilot lit. This will help prevent premature rusting and gas valve (Unitrol) failure and possible replacement.
6. To restore operation, be sure the casing is free of nests, etc. before starting up.
Page 10
Rev 2/2007
Operating Instructions Trouble Shooting
NOTE: The following warning applies to installations using LP., Propane Gas.
WARNING
To avoid possible injury, tire, and explosion, please read and follow these precautions and all instructions on
this appliance before lighting the pilot. This appliance uses L.P. (Propane) gas that is heavier than air and will
remain at low levels if there is a leak. Before lighting, sniff air at low levels. If you smell gas, follow these
rules: 1 ) Shut off gas at L.P. tank and 2) DO NOT attempt to light.
If your L.P. tank runs out of fuel, turn off gas at the stock tank heater. After L.P. tank is relled, stock tank
heater must be re-lit according to manufacturer’s instructions. If the gas control has been exposed to WATER in
any way, DO NOT try to use it. It must be replaced. DO NOT attempt repair on gas control or appliance.
Tampering is DANGEROUS and voids all warranties
Make sure gas piping is pressure tested before gas valve (Unitrol) is connected. High pressure can damage gas
valve (Unitrol) causing a hazardous condition. Do not subject gas valve (Unitrol) to more than 1/2 P.,S.I. (14”
W.C.) inlet pressure.
1 Pilot may be lit by raising the burner assembly out of the casing (be sure the temperature sensing bulb is free
to be raised with the burner assembly),
2- Turn Control off-on to “OFF” position. (See Figure 2 in Trouble Shooting section for gas valve (Unitrol)
locations.)
3. Turn temperature dial to lowest reading.
4. Turn Control off-on to pilot position.
5. Light match and hold at pilot.
6. While holding lit match at pilot, completely depress red reset button and light pilot. May take several seconds
for gas to reach pilot.
7. After pilot lights, hold red reset button down for 60 seconds.
8. Release red reset button.
9. If pilot goes out, turn control off-on clockwise to “OFF” and repeat steps four through eight.
10. After pilot is properly lit, it is very important NOT to turn control off-on to “ON” position until after the
burner is lowered to the bottom of the casing-then turn the control off-on to “ON” position. If the burner is
turned on while lowering the pilot and burner to the bottom of the casing, the unit will go out from lack of
oxygen before draft is started.
11. Re-insert the temperature sensing bulb in the bulb tube guide. Being careful NOT to bend, dent, or crimp the
temperature sensing bulb. This can cause breakage or damage to the temperature sensing bulb, may result in
replacement of Unitrol, and VOIDS all warranties
12. Turn temperature dial to desired setting.
Temperature Dial Markings correspond approximately to the following OFF temperatures:
* Suggested starting temperature
Page 11
Rev 2/2007
Figure No. 2: Gas Valve ( Unitrol )
2a. Top View
2b. Side View
2c. End View
1. Reset Button
“Red” No. 15416
1. Reset Button
“Red” No. 15416
1. Reset Button
“Red” No. 15416
2. Control Off-On
No. 15414
2. Control Off-On
No. 15414
2. Control Off-On
No. 15414
3. Temp. Dial
No. 15415
3. Temp. Dial
No. 15415
3. Temp. Dial
No. 15415
Pilot Adjustment
Screw
Pilot Connection
Temperature
Sensing Bulb
Damaged Sensing Bulb
Look for a crushed bulb
Factory Calibration
Crimps
1/2” Pipe Inlet
Bellows
Housing Thermocouple
Connection
Damaged Bellows:
Look for the gap to be
greater than 1/8”
Trouble Shooting Assembly Instructions
Pilot Burner Adjustment (see Figure 2 and 3)
1. Adjust pilot adjustment screw (Figure 2b) to provide properly sized ame (Figure 3).
2. Improper ame size can result in pilot light not staying lit (Figure 3).
Figure 3. Troubleshooting Pilot Flame
1. CORRECT FLAME 2. NOISY, LIFTING, BLOWING 3. LAZY, YELLOW FLAME
4. WAVING BLUE FLAME 5. HARD SHARP FLAME 6. SMALL BLUE FLAME
Check For:
• Wrong Orice
• Low Gas Pressure
• Clogged Pilot Line
Check For:
• High Gas Pressure
• Wrong Orice
Check For:
• Drafts At Pilot
Location
Check For:
• High Gas Pressure
• Too Small Orice
Check For:
• Clogged Primary Air
Opening
• Low Gas Pressure
• Clogged Orice
Test No. 2 To Test Magnet Using Millivolt Meter And
Robertshaw Adapter W75036 (see g. A)
1. After testing thermocouple and replacing if necessary
as described above, follow normal pilot lighting
procedure with adapter and
millivolt meter attached as shown
in g. A.
2. Allow pilot to burn for three
minutes.
3. Note millivolt reading on meter
and blow out pilot.
4. Magnet should continue to hold for
a drop of ve millivolts or more
before it releases. A “snap” can be
heard when magnet releases. If
magnet does not hold for a drop of
at least ve millivolts, replace
control. Magnet is good if it holds
for a drop of ve millivolts or more.
Test No. 1 To Test Thermocouple Using Millivolt
Meter And Robertshaw Adapter #75036* (see g. A)
1. Unscrew thermocouple from control.
2. Screw Robertshaw adapter #75036 into control.
3. Screw thermocouple into adapter.
4. Connect millivolt meter leads to
adapter and thermocouple as
shown in g. A.
5. Light pilot and allow it to heat tip
of thermocouple for three
minutes. If pilot will not stay lit,
hold red reset button down
during this test.
6. If meter reads below 13
millivolts, replace thermocouple.
If meter reads 13 millivolts or
more, the thermocouple is good.
Figure A.
RED
BLACK
Thermocouple
Adaptor
Thermocouple
Or
Thermopile
3/8” To 1/2”
Page 12
Rev 212007
Figure No. 1: 66B Stock Tank Heater
Item No. Part No. Description Price
1 11869 Robertshaw Unitrol 110SS 238.14
2 16628 Gas Hose Assembly 17.20
3 13989 Burner Plate 10.08
4 13994 1/4” Pilot Tube - 23” 6.52
5 13997 Pilot Assembly 17.02
6 13999 Round Cover 71.16
714428 #58 Orice - Main Burner - LP only 5.46
814429 24” Thermocouple 23.28
914441 Brass Locator Fitting 13.20
10 14442 Brass Inlet Fitting 10.08
11 14446 90° Orice Holder 8.04
12 15418 Pilot Orice Pkg. - LP 16.80
13 14488 Thermocouple Spring 0.60
14 14489 1/4” Ferrule & Sleeve for Pilot 3.66
15 14493 Pilot Tube - Unitrol Fitting Only 2.82
16 14962 1/8” x 18 9/16” Nipple Pipe 14.64
17 14963 1/8” x 5” Nipple Pipe 11.88
18 15006 Bulb Guide 10.92
19 15092 Cast Iron Burner w/ Screws 33.36
20 15414 On/Off Control Dial - Plastic
Temp. Control Dial - Plastic 15.34
21 15471 Casing & Heat Chamber Included w/ 20000
22 17190 1/8” NPT Pipe Cap 3.00
23 15467 Right Half-Band 14.82
24 15468 Left Half-Band 14.82
25 15469 Right Anchor Bracket 9.00
26 15470 Left Anchor Bracket 9.00
27 15472 Center Brace Hanger Included w/ 15563
28 14633 Bolt - 5/16 - 18 x 6” Included w/ 15563
29 14425 Bolt - 1/4 - 20 x 2 1/2” Included w/ 15563
30 11372 Nut - 5/16 - 18 HZP Steel Included w/ 15563
31 11369 Nut - 1/4 - 20 HZP Steel Includedw/ 15563
32 11365 Screw 3/8 - 16 x 2 1/2” Included w/ 15563
--- 15563 Parts Bag 10.01
-- 15564 Parts Box 58.20
-- 15466 Complete Burner Assembly 387.94
--- 20000 Complete Casing Assembly 367.94
Assembly Instructions
1. Refer to Figure 1 (page 5) to clarify the following assembly instructions. To avoid removal of the Cover
(6) from the Casing (23), the Anchor Brackets (27 & 28) should be assembled onto the Casing instead of
assembling the Anchor Brackets separately and sliding it onto the Casing. Slide the Right Hand Half
Band Assembly (25) between the Casing and the Bulb Tube Guide (18). This will help hold the Anchor
Brackets (27 & 28) in place to complete the assembly. Insert the 5/16” x 6” Hex Head Bolt (30) through
the non-threaded hole in the Left Hand Anchor Bracket (28) with the bolt head toward the leg side of the
angle (see Figure 1 page 5).
Insert this bolt through one of the two rear holes in the Left Hand Half Band Assembly (26). The hole
selected depends on the thickness of the stock tank wall. Insert the bolt through the Center Brace Tube
(29), the Right Hand Half Band Assembly (25), and through the non-threaded hole in the Right Hand
Anchor Bracket (27). Install the 5/16” Nut (32) but do not tighten at this time. Install the 1/4” x 2 1/2”
Hex Bolt (31) through the front holes of the Half Band Assemblies (25 & 26) and loosely install the 1/4”
Nut (33). Install two 3/8” x 2 1/2” Bolts (34) in the threaded holes on the Anchor Brackets (27, 28).
Install 66B in the stock tank and slide hanger bracket to desired position. The unit should be installed as
level as possible. It may be desirable to tip the unit slightly so that the front of the boot (see Figure 1 page
5 for location of boot) is a little lower than the bottom of the casing. When in the desired position, tighten
the 5/16” bolt and nut (30 & 32) so the unit does not slide in the anchor bracket. Over-tightening this bolt
is unnecessary and may cause deformation of the anchor bracket.
2. Heater should be installed at least three feet from any building, board fence, or any structure to eliminated
downdrafts.
3. The temperature-sensing bulb has been placed in a protective tube or Bulb Guide (18) on the outside of the
Casing (23). At all times when the burner assembly is in operation, the temperature-sensing bulb must be
in the bulb tube guide. This is intended to allow easy withdrawal FOR ADJUSTMENTS OR REPAIR.
4. This unit may be used to heat a polyethylene stock tank as long as the stock tank heater is 4 inches from
the side of the stock tank.
5. A Pressure Regulator should rst be installed by your gas service man and set per recommended pressures
listed in the specications section. Regulator should be installed in line within 7 feet of this tank heater.
6. Flexible rubber hose is to be connected to the tting from the regulator and the bottle gas supply.
CAUTION: Be sure to blow out the piping before connecting to the heater hose to eliminate any moisture
from the lines.
7. Protect Hose Assembly (2) and the small temperature sensing bulb control (sensing tube) from being
damaged by livestock.
Page 13
Rev 2/2007
Trouble Shooting
Figure No. 4
Re-Calibration of the Robertshaw 110SS Gas Heating Control
(see Figure No. 2 for details)
If the burner will light but will not shut off, the temperature sensing bulb probably has lost some of its uid.
A new gas valve (Unitrol) will be required.
If there has been MINOR damage to the temperature sensing bulb or line on your gas valve (Unitrol), the
burner may not light. The temperature dial may be re-calibrated in this case. If the damage is major, it will
not be possible to re-calibrate and a new gas valve (Unitrol) will be required. Temperature sensing bulb is
not sold separately.
TO RE-CALIBRATE:
1. Remove the temperature dial.
2. Using needle-nose pliers, hold the pointer on the dial shaft.
3. Loosen the nut holding this pointer.
4. Move the pointer clockwise approximately 90 degrees (1/4 turn).
5. Re-tighten nut.
6. Replace temperature dial.
7. Turn temperature dial and note where valve “clicks” off. For correct calibration, the
temperature sensing bulb should be 52 degrees when the dial is at #5 position.
8. If this calibration is not suitable, repeat steps 1 through 7.
9. There is a limit to how much the unit can be calibrated. If these steps do not correct the
problem, a new gas valve (Unitrol) may be required.
Temperature sensing bulb not sold separately.
