RESISTANCE THERMISTOR PRIMARY

Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4

Set Multimeter to Resistance

Remove the connector from the primary thermistor
It may be possible to check thermistor in situ, if not, drain primary system water from boiler and remove thermistor for testing

Measurement:

Measure the resistance between the two pins of the primary thermistor.

Temperature Range (°C)	Resistance Range
0°C to 10°C	27.0kΩ - 18.0kΩ
10°C to 20°C	18.0kΩ - 12.0kΩ
20°C to 30°C	12.0kΩ - 8.4kΩ
30°C to 40°C	8.4kΩ - 6.0kΩ
40°C to 50°C	6.0kΩ - 4.4kΩ
50°C to 60°C	4.4kΩ - 3.2kΩ
60°C to 70°C	3.2kΩ - 2.4kΩ
70°C to 80°C	2.4kΩ - 1.9kΩ
80°C to 90°C	1.9kΩ - 1.5kΩ
90°C to 100°C	1.5kΩ - 1.2kΩ

Resistances vary with temperature and should conform approximately to the table below:

Note: Clicking on the resistance table will switch between table and graph view.