Ultra Boiler Manual

Part number 550-100-440/0122
116
  
 (continued)

1. Make sure thermostat is calling for heat and con-
tacts (including appropriate zone controls) are
closed. Check for 24 VAC between thermostat wire
nuts and ground.
2. Make sure all external limit controls are either
installed (and closed) or temporarily jumpered
for testing.
3. Make sure that connectors to control module are se-
curely plugged in at module and originating control.
4. Gas pressures:
• Maximum: 13” w.c. with no ow (lockup) or
with boiler on
• Minimum: 4” w.c. (for all except 5” for -299)
for natural gas, or 4” w.c. for propane, with gas
owing (verify during startup with boiler at
high re)

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 door and jacket top panel. Rotate
the swing-away control panel forward to expose
the U-Control module.
3. Remove and inspect the two fuses (located as
shown below).
4. If necessary, replace the fuse:
a. Low voltage circuit fuse is 3-amp fast-blow
(Littelfuse 257003).
b. Line voltage circuit fuse is 12-amp slow-blow
(Littelfuse 326012P).
Do not jumper fuse or replace with any
fuse except as specied. Failure to comply
could result in severe personal injury,
death or substantial property damage.
5. Reinstall jacket top panel and boiler jacket door
aer checking the fuses.
6. Restore power to boiler at external line switch and
verify boiler operation after completing boiler
service.

1. The boiler temperature sensors (flue, outdoor,
return water and supply water) are all resistance-
type devices.
2. Figure123 shows the correct value for the sensor
at various temperatures.
3. 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.
4. To check whether the control module is correctly
sensing temperature, you can use a resistance de-
cade box. Connect the decade box temporarily in
place of a sensor and read the corresponding tem-
perature on the U-Control display. e temperature
should be close to the value corresponding to the
input resistance.
Figure 123 Sensor resistance values
Sensor resistance values
Temp
(°F)
Sensor ohms
Temp
(°F)
Sensor ohms
Min Max Min Max
32 34265 37871 120 4517 4992
40 27834 30764 130 3698 4088
50 21630 23907 140 3043 3364
60 16944 18727 150 2517 2782
70 13372 14780 160 2091 2311
80 10629 11747 170 1744 1928
90 8504 9399 180 1461 1615
100 6847 7568 190 1229 1359
110 5545 6129 200 1038 1147