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GT INSTALLATION AND OPERATION INSTRUCTIONSPage 28
Determining Reset Temperature HI
Calc
Once the Sentry 2100T control identifi es the presence
of a good outdoor sensor, the control will automatically
reduce the HI setting based upon the outdoor
temperature. For example, if Hi = 200°F, 93°C, RES =
70°F, 21°C and the Air Temperature = 32°F, 0°C, the HI
setpoint, HI
Calc
, would be calculated as follows:
RESET RATIO
= (High Setting - RES)/RES
= (200°F, 93°C - 70°F, 21°C) /70°F, 21°C
= 1.85
RESET TEMPERATURE HI
Calc
=[(RES-Outdoor Air) x Reset Ratio] + RES
=[(70°F, 21°C - 32°F, 0°C) x 1.85] + 70°F, 21°C
=[70.6°F, 21°C] + 70°F, 21°C
=140.6 F, 42°C
NOTE: The design temperature is 0°F, -18°C outside
air, so at 0°F, -18°C or less, the hi setting is used,
and not surpassed.
Figures 39 & 40 are examples of reset temperatures
based upon different set points and outdoor air temper-
atures. The vertical axis is the water temperature that
the boiler will maintain and is also the Hi setting of the
Sentry 2100T control. The Horizontal axis is the outdoor
air temperature.
Figures 39 - Reset Curve For Res = 85 °F, 29°C
Figures 40 - Reset Curve For Res = 70 °F, 21°C