Installation Guide
Part number 550-100-066/0608
85
g a s -f i r e d w at e r b o i l e r — Boiler Manual
Troubleshooting (continued)
Checking temperature sensors
The boiler temperature sensors (ue, outdoor, return 1.
water and supply water) are all resistance-type de-
vices.
The table at right shows the correct value for the sensor 2.
at various temperatures.
Use the resistance values at 32°F, 60°F, 70°F and 212°F 3.
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.
To check whether the control module is correctly sensing 4.
temperature, you can use a resistance decade box. Con-
nect the decade box temporarily in place of a sensor and
read the corresponding temperature on the U-Control
display. The temperature should be close to the value
corresponding to the input resistance.
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
Display fault Display communications out for 30 seconds Resets automatically when communication is
re-established
Automatic reset limit open Set if auto reset limit open Reset after auto reset is closed for 2.5 minutes
Reset with manual reset on display
Supply water temperature high Set if the supply water temperature is higher than 200 °F Reset after heat exchanger outlet temperature is less
than burner on temperature
Reset with manual reset on display
Return water temperature high (heat
exchanger input)
Set if the return water temperature is higher than 200 °F Reset after heat exchanger inlet temperature is less
than burner on temperature
Reset with manual reset on display
Return water temperature greater than
supply water temperature
Set if heat exchanger inlet temperature is higher than the heat exchanger outlet
temperature + 10 °F
Reset when return temperature minus 9 °F is less
than supply temperature or Reset with manual reset
on display
Supply water rising too fast Set if supply water temperature rises faster than 2 °F per second Reset after 1 minute delay
Reset with manual reset on display
Supply greater than return by 58 °F Set if current heat exchanger outlet temperature is greater than the heat exchanger
inlet temperature + 58 °F
Reset after 0.5 minute delay
Reset with manual reset on display
Temperature sensors Supply sensor open or shorted
Return sensor open or shorted
Set if flue sensor not balanced (more than10 °F difference between sensors)
Set if heat exchanger outlet sensor not balanced (more than10 °F difference
between sensors)
Reset if sensors balance
Flue temperature high Set if flue temperature over 210 °F Reset after 1.5 minute delay
LWCO fault Set if LWCO open goes to manual reset lockout if open more than 1 second Reset when closed
Conditions that will cause an automatic reset problem notification (screen constant red, with exclamation mark symbol)
U-Control fault indications
The U-Control provides information for both automatic reset 1.
conditions and manual reset conditions. See Figure 87, page 68
for information available on the U-Control display.
2. Figure 94 lists conditions that will cause the control to display a
constant red screen. The boiler will automatically restart if the
condition self-corrects or the technician uses the U-Control’s
manual reset screens to reset.
3. Figure 95 shows the screen behavior during an auto-
matic or manual reset condition. The table below the
display illustration lists manual reset conditions and
how to reset from them.
Make sure to determine the causes of
outages. Do not leave the boiler operating
without a complete diagnosis.