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Home and Building Control Home and Building Control
Honeywell
Honeywell Limited-Honeywell Limitée
1985 Douglas Drive North
35 Dynamic Drive
Golden Valley, MN 55422
Scarborough, Ontario
M1V 4Z9
TROUBLESHOOTING GUIDE
WARNING
Fire or Explosion Hazard.
Can cause property damage, severe injury
or death.
Only a qualified service technician should
perform these troubleshooting procedures.
Use Fig. 8 and Table 2 as troubleshooting guides for the
VS8521.
Fig. 8. Identification of VS8521
terminals for troubleshooting.
Table 2. VS8521 Troubleshooting Table.
Procedure:
1.
Test A (Coil Resistance): Have thermostat contacts
open and Pilotstat knob turned to OFF. If coil
resistance exceeds 3.6 ohms, replace the valve.
2.
Test B (Thermopile): Have thermostat contacts
open and the pilot lit with Pilotstat knob turned to
PILOT. If the reading is less than 460 mV, replace
th thermopile.
3.
Test C (Thermocouple): Have thermostat contacts
open and pilot lit with Pilotstat knob turned to
PILOT. Reading should be a minimum of 12 mV in
a new ODS pilot burner assembly. If the reading is
less than 12 mV, replace the ODS pilot burner
assembly. The power unit will hold in down to 3
mV. If the output of the thermocouple is less than 3
mV, replace the ODS pilot burner assembly.
4.
Test D (Operator Pull-In): have thermostat contacts
open and pilot lit with Pilotstat knob turned to
PILOT. Close the thermostat contacts. Operator
will pull in with a minimum of 155 mV. Operator
makes audible sound during pull-in. If pull-in does
not occur, replace the valve.
5.
Test E (Resistance System): System resistance
from the remote switch or thermostat and lead
wires should not exceed 1.7 ohms. If resistance is
above 1.7 ohms, reduce the resistance.
TH
TH
TH
TP
TP
TP
TPTH
M17511
Test
Test Title
Connect Multimeter Between Terminals
Set Thermostat Meter Read Should Be
A
Coil Resistance
TP and TH
Open
Maximum of 3.6 ohms.
B
Thermopile
TP and TPTH
Open
Minimum of 460 mV.
C
Thermocouple
Tip (and Ground)
Open
Minimum of 12 mV.
D
Operator Pull-In
TH and TP
Open
Minimum of 155 mV.
E
Resistance System —
Closed
Maximum of 1.7 ohms.