Henny Penny MPC-1L Technical Manual page 8

1-4. TROUBLESHOOTING (Continued)
PROBLEM
Unit will not heat
Individual zone does
not heat
MPC-554
ZONE POSITIONS
Top
Side
Bottom
V1901-RH
Top
Side
Bottom
V1901-LH
July 2011
CAUSE
• Control board not calling
for heat
• Faulty heat relay
To avoid electrical shock, make con-
nections before applying power, take
reading, and remove power before
removing meter leads. The following
checks are performed with the wall
circuit breaker closed and the main
power switch in the ON position.
• Faulty heater
• Faulty heater RTD
Model MPC-1L, MPC-22, MPC-554
CORRECTION
• Verify set-point reading; if zone (see Zone
Positions at left) tempeature is below
setpoint and not calling for heat
(no 5 vdc), control board defective
Testing for proper relay operation:
1. With no power (5 vdc) going to the relay,
120 volts should show on the output side
of the relay, and 0 volts on the input
(5 volts). If no 120 volts, check for open
heater, and if heater is OK, replace relay.
2. With the component energized, 0 volts
should show on the output side of the relay,
and 5 vdc on the input side. If not,
replace relay. Also, check for reverse
polarity of 5 vdc to relay-reference wiring
diagram.
3. If voltage varies from steps 1 and 2,
remove power to unit pull input wires from
relay and place leads of meter onto input
wires. Reapply power to unit. When unit
is running, if the input wires to relay shows
5vdc, the relay is faulty.
• Refer to wiring diagrams in back of this
manual, and with the outputs on, check
across terminal #1 of the appropriate
relay and the neutral wire (#N5 on 554 or
#N2 on 1L or 22) at the transformer. If
meter shows full voltage (120V), but
heater is not heating, replace heater and
liner assy.
• Refer to wiring diagrams in back of this
manual, and disconnect 15-pin connector
at control board. With an ohm meter,
check between the appropriate terminals
on connector and the corresponding termi-
nal on the terminal block. Meter should
read 35 to 41 ohms at room temperature.
Replace liner and heater assy if necessary
• Refer to wiring diagram page 2-9, and
disconnect 15-pin connector at control
board. With an ohm meter, check between
the appropriate terminals on connector,
based upon which RTD is being checked.
Meter should read about 1080 ohms at
room temperature. Replace liner and
heater assy. if necessary.
1-3 FM06-038-B