Weil-McLain Evergreen EVG 110, Manual

Page: 108 / 144

Troubleshooting
(continued)
Check control fuses
ALWAYS check control fuses before replacing the
control or any major components (blower, etc.).
If one of these fuses is blown, it can prevent the
control or other components from operating.
1. Turn OFF power to boiler at external line switch. Then
remove the jacket door.
2. Locate fuses using Figure 93 .
3. Remove and inspect the two (2) fuses (items 1 and 2,
Figure 93 ).
4. If necessary, replace one or both of the fuses:
a. Low voltage circuit fuse is 3-amp fast-blow
(Littelfuse 0287003).
b. Line voltage circuit fuse is 12-amp fast-blow
(Littelfuse 0314012MXP or Bussman ABC-12-R).
Do not jumper either fuse or replace with any fuse
except as specifi ed. Failure to comply could result
in severe personal injury, death or substantial
property damage.
Checking temperature sensors
1. The boiler temperature sensors (fl ue, outdoor, return water,
supply water and system) are all resistance-type devices.
Figure 92 shows the correct value for the sensor at various
temperatures. For dual sensors, the temperature difference
between the sensors must be no more than 10°F.
2. Use the resistance values at 32°F, 60°F, 70°F and 212°F to
measure the sensor resistance at known temperatures (ice
point, room temperature and sea level boiling point). For
ice point and boiling point, insert the sensor in water at that
temperature. Use an ohmmeter to read resistance value.
3. To check whether the control is correctly sensing temperature,
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.
Figure 92
Sensor resistance values
Part number 550-100-191/0917
108
®
g
as-fired water boiler —
70/110/155
Boiler Manual
Temp
(°F)
Sensor ohms Temp
(°F)
Sensor ohms Temp
(°F)
Sensor ohms
Min Max Min Max Min Max
32 34265 37871 90 8504 9399 150 2517 2782
40 27834 30764 100 6847 7568 160 2091 2311
50 21630 23907 110 5545 6129 170 1744 1928
60 16944 18727 120 4517 4992 180 1461 1615
70 13372 14780 130 3698 4088 190 1229 1359
80 10629 11747 140 3043 3364 200 1038 1147
Figure 93 Control fuses
2
Line Voltage
1
Low
Voltage