Honeywell modulation motors

HEATEC TEC-NOTE
Publication No. 1-07-184 Revised 4-24-07
Troubleshooting modulation motors
Purpose
This document provides a guide for troubleshooting burner modulation motors (Figure 1), which
are commonly called mod motors. They are also
known as modulation actuators.
Scope
This document applies to Honeywell mod motors
M7284C-1000, M9174C-1025, and M9184F-1034
used on Heatec HC and HCS heaters.
motor operates the linkage as it rotates within an
arc of 90 degrees.
Key components of concern
•
•
•
•
What the mod motor does
The mod motor is connected to mechanical linkage
that opens and closes fuel valves and air dampers
of the burner (Figure 1). It provides proportional
control of its firing rate. The shaft of the mod
Low-fire cam and low-fire proof switch.
High-fire cam and high-fire proof switch.
Resistor board or resistor harness.
Transformer.
NOTICE: For clarity some photos of mod
motor are shown not installed on the heater.
It is not necessary to remove it to perform
the checks and adjustments described.
SHAFT
MOD MOTOR
LINKAGE
LINKAGE
Figure1. Honeywell mod motor M7284C-1000 installed on heater.
Page TRANSFORMER
120 VAC TO 24 VAC
HIGH-FIRE
PROOF SWITCH
HIGH-FIRE
CAM (BLUE)
LOW-FIRE
CAM (RED)
LOW-FIRE
PROOF SWITCH
TERMINAL
BOARD
Figure 2. Top view of Honeywell mod motor M7284C-1000.
Model differences
have modulating burners. There are important
differences in the way the switches and cams are
configured. Figure 2 shows the motor now used.
The following table identifies the models of mod
motors used on Heatec HC and HCS heaters that
Key differences
Heatec heaters used on
Color of low-fire cam
Wiring of low-fire proof switch
Wires used, low-fire proof switch
Color of high-fire cam
Honeywell mod motors
M7284C-1000
M9174C-1025
M9184F-1034
HC & HCS
12-06 & after
HC & HCS
prior to 12-06
HC & HCS
early units with
modulating burners
Red
Blue
Red
Normally closed
Normally open
(held closed)
Normally closed
Red=common
Yellow=Normally closed
Red=common
Yellow=Normally open
Red=common
Yellow=Normally closed
Blue
Blue
Blue
Normally open
Normally open
Normally open
Wires used, high-fire proof switch
Black/red=common
Black/blue=Normally open
Black/red=common
Black/blue=Normally open
Black/red=common
Black/blue=Normally open
Resistor board or resistor harness
(Not used)
Yes
Yes
Wiring of high-fire proof switch
Publication No. 1-07-184
Page • On mod motors with a blue low-fire cam
the cam holds the low-fire proof switch in
its closed position while the damper is fully
closed. After the damper begins to open, the
cam opens the switch.
• On all mod motors, the high-fire cam closes the
high-fire proof switch when the damper reaches
a preset open position. After the damper begins
to close, the cam opens the switch.
SHOCK HAZARD. High voltage is present on
certain terminals and wires inside the main control
panel, inside the mod motor and inside the burner
panel. Touching them will cause death or serious
injury.
40
AUTO
FLAME SIGNAL
SCRL
Do not work on these components unless you are
a qualified technician familar with the hazards of
electricity.
MODE
FLAME-MONITOR
Some circuits in the main control panel may
receive power from remote sources. Thus, the
breaker operator on the door may not deenergize
all exposed live parts.
Figure 3. Fireye flame monitor.
Always use a voltage tester to make sure there is
no voltage on the terminals or bare wires you may
touch.
Interaction with Honeywell modulation
controller (Figure 4)
Interaction with Fireye flame
monitor (Figure 3)
The Fireye flame monitor monitors the open/
closed status of the low-fire and high-fire proof
switches in the mod motor while the burner is
being purged. The low-fire proof switch is wired
between terminals m and d. The high-fire proof
switch is wired between terminals d and 8. Thus,
the flame monitor shows either m-d limit or d-8
limit when indicating the status of these switches.
Each switch is activated and de-deactivated by its
own rotating cam in the mod motor.
• On mod motors with a red low-fire cam the
low-fire proof switch remains in its normally
closed position while the damper is fully
closed. After the damper begins to open, the
cam opens the switch.
RESET
The modulation controller controls the mod motor
using a circuit that provides an output of 4 to 20
mA. With a 4 mA signal the mod motor should
be in the low-fire position with the damper fully
closed. With a 20 mA signal the mod motor should
open the damper to the high-fire position.
Figure 4. Honeywell modulation controller.
Page Publication No. 1-07-184
A common problem
Symptoms of problems
Faulty electrical connections are common causes
of mod motor malfunctions. Faulty connections
can be caused from loose connections, dust, or
corrosion from moisture. Connection problems
may occur at the following locations:
• Mod motor fails to move when burner is first
turned on.
• Flame monitor (Figure 3) indicates abnormal
status of either m-d limit or d-8 limit.
• Mod motor fails to operate the linkage.
• Modulation controller (Figure 4) fails to
modulate the mod motor.
• Terminals in mod motor. (Figure 5)
• Terminals on Temperature controller
(Figure 6).
• Terminal strip on back plate of heater panel
(Figure 7).
• Terminal strip in burner junction box
(Figure 8).
Other problems
• Failure of resistor board or resistor harness
(Figures 11 and 12).
• Slippage of cams (Figure 2).
Remedy for faulty electrical connections
All wire connections that pertain to the mod
motor have either screw terminals or cageclamp spring terminals. (See Figures 5, 6, 7 and
8) On connections with screw terminals use a
screwdriver to slightly loosen the screws and
retighten them. On connections with cage clamps,
push on the wire, wiggle it and then pull on it to
make sure it is held tightly.
• Failure of transformer (Figure 2).
Figure 5. Terminal connections in mod motor.
Figure 7. Terminal connections on back plate of heater panel.
Figure 6. Terminal connections on Honeywell modulation
controller.
Figure 8. Terminal connections in burner junction box.
Publication No. 1-07-184
Page 5. In order to make sure the cams are positioned
properly you may need to rotate them until you
can see their target lobes (indicated by yellow
dots in Figure 10) and then reset them to their
proper positions. NOTE: The yellow dots are
only shown in Figure 10. There are no dots on
the actual lobes.
Checking and resetting cams
1. Remove the top cover so that you can gain
access to the tops of the cams (Figure 2).
2. Make sure the shaft of the mod motor is rotated
to its position for a fully closed damper.
3. Check positions of the target lobes of the
cams. The cams have click stops that hold
them in position. Repositioning a cam does not
turn the drive shaft of the mod motor.
6. You can also use the blade of a small
screwdriver to press on the actuating arms of
the switches to determine whether they are
actuated. All switches except the blue low-fire
switch should not be actuated while the damper
is closed. Thus you should hear a distinct click
if you press on their actuating arms.
4. You may be able to rotate the cams with
your fingers. Otherwise insert the blade of a
screwdriver in the slots of the cam (Figure 9)
and rotate them.
7. Because the blue low-fire switch should be
actuated or held closed by the cam when the
damper is closed, you should not be able to
move its actuating arm. Note that it is shown
with its arm in the actuated position in Figure
10.
8. Make sure the target lobes of the two cams are
rotated to the positions shown relative to the
actuating arms of the two switches as shown
in Figure 10. The U-shaped ends of the switch
arms should rest on the cams as shown in
12
Figure 10.
Figure 9. Using screwdriver to position cams.
1
MODULATING MOTOR M7284C-1000
Honeywell
Controller UDC2500
Thermocouple
Type J Duplex
–
+
27
25
19
–
+
26
+
21
–
12
White
Shielded
Pair #1
12
10
Jum
6
5
Red
S-1
9
Alarm-2
GND
8
Red
–
T1
11
11
13
X
Black
F
24 vac
T2
Honeywell Modulating
Motor
L2
9
Alarm-1
+
12
Set at 20 degrees above setpoint.
White
–
13
Red
Gnd
Page 10
Shld
Gnd
L1
120 vac
+
4–20 mA Signal Modulation Circuit
Circuit Breaker
CB-4
8
White
Shielded Pair #2
LOW FIRE HOLD
HOLD
NORMAL
per
Figure 9A. Wiring diagram for mod motor
currently used.
1A
2
White
15
Red
16
Shield
14
Burner Control Relay
(13)
(14)
BC 1
LEGEND
Optional
Auxiliary Output
To Chatterbox
4–20mA Signal
Denotes terminal on Fireye Flame Monitor.
Denotes terminal on Modulating Controller.
Denotes terminal on terminal strip in control panel.
Publication No. 1-07-184
HONEYWELL MODELS
M7284C-1000 AND MF9184F-1034
BLUE (NO)
BLK/YELLOW (NC)
YELLOW (NC)
TOP VIEW
RED
(COMMON)
HIGH-FIRE
CAM
LOW-FIRE
PROOF SWITCH
(NORMALLY CLOSED
BLK/BLUE (NO)
BLK/RED
(COMMON)
HIGH-FIRE
PROOF SWITCH
(NORMALLY OPEN)
LOW-FIRE
CAM
90°
SHAFT
YELLOW DOTS INDICATE
TARGET LOBES. CAMS
ROTATE CLOCKWISE AS
DAMPER OPENS.
90°
HIGH-FIRE CAM (BLUE)
DAMPER CLOSED
LOW-FIRE CAM (RED)
DAMPER CLOSED
HONEYWELL MODEL M9174C-1025
BLK/YELLOW (NC)
YELLOW (NO)
BLUE (NC)
TOP VIEW
RED
(COMMON)
HIGH-FIRE
CAM
LOW-FIRE
PROOF SWITCH
(NORMALLY OPEN
BUT HELD CLOSED)
HIGH-FIRE
PROOF SWITCH
(NORMALLY OPEN)
LOW-FIRE
CAM
90°
90°
SHAFT
YELLOW DOTS INDICATE
TARGET LOBES. CAMS
ROTATE CLOCKWISE AS
DAMPER OPENS.
HIGH-FIRE CAM (BLUE)
DAMPER CLOSED
LOW-FIRE CAM (BLUE)
DAMPER CLOSED
Figure10. Configuration of cams and switches.
Publication No. 1-07-184
BLK/RED
(COMMON)
Page BLK/BLUE (NO)
4. Disconnect wires from terminals r, w and b of
the resistor board.
Checking transformer in the mod motor
1. Make sure heater control switch is set to
off.
2. Make sure there is 120 Vac on the primary
winding of the transformer using an ac
voltmeter. Check for 24 Vac on its secondary
winding. The transformer is defective if there
is no voltage on its secondary winding.
5. Temporarily connect a short jumper wire from
terminals r to b. The motor of the actuator
should go to high-fire, which indicates that the
motor is okay and its particular circuit on the
resistor board is okay. Otherwise, either the
motor or the resistor board is bad.
Checking resistor board and motor (Fig. 11)
1. Make sure heater control switch is set to
off.
2. Make sure that the dipswitch settings are
correct as indicated in Figure 11. Use a
ballpoint pen to make sure that switches are
fully depressed. (Partially depressed switches
have been a problem in the past.)
3. Make sure its transformer is not defective.
Refer to instructions above.
1
OPEN
2
OPEN
3
OPEN
6. Temporarily connect a short jumper wire from
terminals w to r. The motor of the actuator
should go to low-fire (if it is not already there),
which indicates that the motor is okay and its
particular circuit on the resistor board is okay.
Otherwise, either the motor or the resistor
board is defective and should be replaced.
7. Remove the resistor board.
8. Connect the two wires from the secondary side
of the transformer to terminals t1 and t2 of
the circuit board where the resistor board was
removed.
DIP SWITCH SETTINGS
4
5
6
7
OPEN CLOSED CLOSED OPEN
8
CLOSED
9
OPEN
10
OPEN
SWITCH IS OPEN WHEN BLUE
BAR APPEARS NEXT TO SWITCH
NUMBER
DIP SWITCHES
Figure11. Resistor board, Heatec PN 5004718, Honeywell PN 221508A.
Page Publication No. 1-07-184
9. Using a short jumper wire, temporarily connect
from terminal r to b on the circuit board. If the
motor works, the resistor board is defective
and should be replaced.
Replacing mod motor
The Model M7284C-1000 Honeywell motor
replaces all inoperable mod motors used on past
and present Heatec HC and HCS heaters with
modulating burner. Do not use a resistor harness or
resistor board (Figures 11 and 12) with this motor.
Be sure to use the new wires that come with the
new mod motor (Figure 13) and connect directly
to the low-fire and high-fire switches. Do not use
the old wires. Although the old wire colors may
be the same as the new wires they may not be
connected to the same terminals on the low-fire
and high-fire switches.
Figure 13. Wires furnished with Model M7284C-1000 Honeywell
mod motor.
See wiring diagram (Figure 9A) and cover of mod
motor (Figure 14) for wiring information. Note
differences in terminal markings indicated below:
TERMINAL MARKINGS IN MOD MOTORS
M7284C-1000
M9174C-1025
M9184F-1034
+
W
–
R
F
B
66.5 OHM
RESISTOR
237 OHM
RESISTOR
NOTE: Special precision
resistors are used. Do not
use substitutes
Figure 12. Resistor kit (harness), Heatec PN 5018099, Honeywell PN 4074EDC.
Figure 14. Information in cover of mod motor.
Heatec, Inc. 5200 Wilson Road Chattanooga, Tennessee 37410 www.heatec.com (423) 821-5200 (800) 235-5200 Fax (423) 821-7673
Publication No. 1-07-184
Page © 2007 Heatec, Inc.