Honeywell S4965 Series, Product Handbook, Page: 10 / 16

EN2R-9053 0408R11-NE 10
DESCRIPTION OF SQUARE TECHNOLOGY
SQUARE is the abbreviation of Self adaptive, Quality, User
friendly, Adjustment free, Reliable, Environmental friendly.
SQUARE is able to control the load and burning process of a
fully premix heating appliance under varying gas quality
conditions. See fig. 8.
Features are :
•
Gas adaptive control over the full natural gas band, with a
modulation range of 1:5
•
Electronic gas-air at a constant gas quality with a
modulation range of 1:10
•
Automatic chimney lenth compensation
SQUARE is based on the phenomena that the ionisation
current is a measure of the gas quality at a specific range of
the burner load in a fully premix burner.
After calibration based on this phenomena, the burner can be
influenced by means of a micro bridge flow sensor. see fig. 8.
If the gasvalve is closed, the micro bridge acts as an airflow
meter in order to measure the chimney resistance.
Fig. 8. schematic SQUARE system
Pmix
u-bridge
CVI-M
FAN
GAS
AIR
Pair=1013hPa
Pgas