Weil-McLain 2 Series Manual page 94

®
SlimFit Series 2
Troubleshooting
Check the following:
1. Space heating:
a. Make sure thermostat is calling for heat and contacts (includ-
ing appropriate zone controls) are closed.
b. Check for 24VAC between thermostat wire nuts and ground.
2. DHW:
a. Make sure tank aquastat is calling for heat.
3. BMS systems:
a. Make sure the BMS is calling for heat.
4. Make sure all external limit controls are either installed (and
closed) or temporarily jumpered for testing.
5. Make sure that connectors to the control module are securely
plugged in at module and originating controls and harness con-
nectors.
6. Gas pressure must be as specified on page 45. Make sure gas pres-
sure switches are not tripped.
Always check Control module fuses
ALWAYS check control module fuses before replacing
control module or any major components (blower,
etc.). If one of these fuses is blown, it can prevent
control module or other components from operating.
1. Turn OFF power to boiler at external line switch.
2. Remove jacket top panel to expose the Control module and
Expansion module.
3. Remove and inspect the two (2) Control fuses and the Expansion
module fuse (located as shown below).
Control module fuse
Control module fuse
4. If necessary, replace the fuse:
a. Item 1 - Low voltage circuit fuse is a 3-amp fast-blow
(Littelfuse 0287003).
b. Item 2 - Line voltage circuit fuse is a 12-amp fast-blow (Lit-
telfuse 0314012 MXP or Bussman ABC-12-R).
Do not jumper fuse or replace with any fuse except
as specified. Failure to comply could result in severe
personal injury, death or substantial property damage.
94
COMMERCIAL CONDENSING GAS
(continued)
- — Boiler Manual
FIRED WATER BOILER
5. Reinstall jacket top panel and boiler jacket door after checking
the fuses.
6. Restore power to boiler at external line switch and verify boiler
operation after completing boiler service.
Checking temperature sensors
1. The boiler temperature sensors (flue, outdoor, boiler out, boiler
in, heat exchanger and system) are all resistance-type devices.
2. Figure 90, page 94 shows the correct value for the sensor at vari-
ous temperatures.
3. Use the resistance values at 32°F, 60°F, 70°F and 212°F to measure
the sensor resistance at known temperatures (freezing point, room
temperature and sea level boiling point). For freezing point and
boiling point, insert the sensor in water at that temperature. Use
an ohmmeter to read resistance value.
4. To check whether the control module is correctly sensing tem-
perature, you can use a resistance decade box. Connect the decade
box temporarily in place of a sensor and read the corresponding
temperature on the Control display. The temperature should be
close to the value corresponding to the input resistance.
Sensor resistance value
Sensor resistances for Flue temperature sensor,
Return sensor, Outdoor sensor, Header sensor
Sensor ohms
Temp
(°F)
Min Max
34265 37871
27834 30764
21630 23907
16944 18727
13372 14780
10629 11747
8504 9399
6847 7568
5545 6129
Sensor resistances for Boiler outlet sensor
Temp (°F) Sensor ohms
32 32624
25381
19897
15711
68 12493
77 10000
86
8056
6530
5324
4365
3599
Sensor ohms
Temp
(°F)
Min Max
4517 4992
3698 4088
3043 3364
2517 2782
2091 2311
1744 1928
1461 1615
1229 1359
1038 1147
Temp (°F) Sensor ohms
2982
2483
2079
1748
1476
1252
1066
912
782
674
Part number 550-100-180/0917