Operating Modes
Mode 1
– Not recommended.
Mode 2
– Setpoint operation using primary/secondary
piping. The control operates the heater to satisfy a
remote system sensor. The heater is turned off based
on boiler max and boiler differential (factory default).
See Fig. 31.
Mode 3
– Dedicated DHW operation using UniTemp
80 piping. A call for heat is determined by the DHW
sensor and the DHW boiler target. The heater outlet
water is also controlled to the boiler target tempera-
ture. See Fig. 32.
Mode 4
– Not recommended.
Mode 5
– Outdoor reset using primary/secondary pip-
ing. The heater is operated as in Mode 2. However, the
target temperature is based on outdoor reset. See Fig.
33.
Mode 6
– Not recommended.
Mode 7
– Designed for an external input signal with
primary/secondary piping. The external input signal
can be provided from a BMS, an EMS or a sequenc-
ing control. The external input signal changes the
boiler target according to a linear scale. The control
operates the boiler burner to maintain the boiler target
at the remote system sensor. See Fig. 34 on the fol-
lowing page.
Mode 8
– This mode is used for remote control of the
heater. The Boil Max setting is the heater shutdown
temperature. The heater is enabled with a control sig-
nal ≥ 0.5 VDC. 0.5 VDC corresponds to minimum fire
an 10 VDC corresponds to 100% firing rate. The
BOIL
MAX
setting is the heater shutdown temperature.
31
MODULATING
*
Fig. 31: Mode 2 Primary/Secondary Piping
MODULATING
Fig. 32: Mode 3 Dedicated DHW
MODULATING
*
Fig. 33: Mode 5 Primary/Secondary Piping with
Outdoor Reset
*Maximum 4 times the pipe diameter or 12”, whichever is less.
*Maximum 4 times the pipe diameter or 12”, whichever is less.
*Some models.
California Hot Water Supply, Inc.
(800) 249-7244
31
