INSTALLATION AND OPERATION INSTRUCTIONS
5-2
DC SERIES BOILERS / WATER HEATERS
DC 15-95, DC 15-96, DC 20-125, DC 33-160
ELECTRONIC COMPONENTS
This section details the method for troubleshooting the non-standard electronic
components on the boiler / water heater including the electronic water pressure
sensor – type LWCO and the temperature sensors.
5.2.1 Temperature Sensors
The resistance of the temperature sensors varies inversely with temperature. To
test, measure the temperature of the sensed environment and compare with the
value derived from the measurement of the resistance (obtained by connecting a
good quality test meter capable of measuring up to 5,000 kΩ (5,000,000Ω) at the
controller end of the sensor lead).
To obtain a resistance reading, remove power to the boiler / water heater. For
the supply water and return water temperature sensors, remove the wire leads
by disconnecting their respective Molex connectors. Place multi-meter probes
into sensor’s male Molex connector socket. Do not apply voltage to the sensor
(damage may result).
12KΩ Temperature Sensors supplied with boiler / water heater. See Table 14 for
resistance values.
SENSOR
TYPE
PURPOSE
LOCATION
S1
NTC 12KΩ
Supply Water Temperature Upper Left of Heat
Exchanger
S2
NTC 12KΩ
Return Water Temperature Lower Left of Heat
Exchanger
S3
NTC 12KΩ
Domestic Hot Water
DHW Supply Pipe
S4
NTC 10KΩ
Hot Water Tank
External Water Heater
S5
NTC 12KΩ
Outdoor Sensor
Outdoors (North side)
NTC 12KΩ
Flue Gas Temperature
Bottom of Heat Exchanger
at Flue outlet
Water Pressure
Heating Supply Pipe
Temperature and Pressure Sensors
5.2
Water temperature sensors
TEMPERATURE RESISTANCE
TEMPERATURE RESISTANCE
TEMPERATURE RESISTANCE
F / C
Ω - ohm
F / C
Ω - ohm
F / C
Ω - ohm
5F / -15C
76,020
77F / 25C
12,000
149F / 65C
2,752
14F / -10C
58,880
86F / 30C
9,805
158F / 70C
2,337
23F / -5C
45,950
95F / 35C
8,055
167F / 75C
1,994
32F / 0C
36,130
104F / 40C
6,653
176F / 80C
1,707
41F / 5C
28,600
113F / 45C
5,522
185F / 85C
1,467
50F / 10C
22,800
122F / 50C
4,609
194F / 90C
1,266
59F / 15C
18,300
131F / 55C
3,863
203F / 95C
1,096
68F / 20C
14,770
140F / 60C
3,253
212F / 100C
952
Table 14: Temperature Sensor Resistance Values – 12KΩ sensors.