fig. 11 Water Flow Sensor
CENTRAL HEATING AND DOMESTIC HOT WATER (NTC) TEMPERATURE
SENSORS
13
The central heating and domestic hot water temperature sensors are NTC (
N
egative
T
emperature
C
oefficient) type. In NTC sensor, temperature and sensor resistance are inversely proportional; the
sensor resistance decrease as temperature increases and vice versa. NTC sensors are usually defined
by their nominal resistance at 25
°
C, but this value does not completely define the nominal R-T
curve of the NTC. The R-T relation of the NTC sensors used in our appliances
are shown in
Table 14.
Temperature sensors measures the temperature of the central heating and domestic hot water and
send signals to the main board. Two types of temperature sensors are used in bithermic types,
surface mounted sensors for domestic water and direct immersion sensors for central heating. Only
direct immersion NTC sensors are used in monothermic types.
In bithermic models, the surface mounted temperature sensor is directly mounted on the domestic
water delivery (outlet) pipe and the direct immersion temperature sensor is mounted on the central
heating flow of the heat-exchanger. In monothermic types, the direct immersion temperature
sensors (CH & DHW) are mounted on the outlet manifold of the hydroblock (3 way electric valve).
Central heating circuit over-heat safety (electronic limit - 95
°
C) is secured by the central heating
NTC sensor and domestic water over-heat safety (electronic limit - 75
°
C) is secured by the
domestic water NTC sensor.
Table 13 NTC Temperature Sensors
Surface mounted temperature sensor connection
With Klips
Direct immersion temperature sensor connection
1/8” (external thread)
a)
surface mount
b)
Direct immersion
fig. 12 NTC Temperature Sensors
21
