INSTALLATION AND OPERATION INSTRUCTIONS
SEQ-3 DIGI-E
lItE
Hydronic Multi-Stage Boiler Control
R
Blue (Output B)
White (Output C)
Yellow (Output A)
Boiler
SYS
Pump
DHW
Pump
SET
®
C O R P O R A T I O N
R
SYSTEM =
147F
TARGET =
150F
A
B
C
2 Line Alphanumeric Display
Displays sensor values and
menu settings
Output Lights indicate
output status
Display Section Locking Screws
Black (120VAC power)
®
WARNING
This Heat-Timer control is strictly an operating control;
it should never be used as a primary limit or safety
control. All equipment must have its own certified
limit and safety controls required by local codes. The
installer must verify proper operation and correct any
safety problems prior to the installation of this Heat-
Timer control.
Hot Water Control with Outdoor Reset, Set Point and
DHW for Hydronic Applications
The SEQ-3 DIGI-SPAN Elite is a multi-boiler or multi-stage
outdoor reset hydronic heating control. It establishes ambient
comfort by varying the temperature of the heating system’s
circulating hot water in response to changes in the outdoor
temperature. In addition, it provides an outdoor temperature
based cutoff, heating system pump control, and domestic hot
water (DHW) pump control. Two unique features have been
added to this control including a customized reset ratio curve.
A Set Point option was added for applications where outdoor
reset will not apply.
Two sensors are used, one to monitor the outdoor temperature
and one to monitor the circulating hot water temperature in
the heating system. When the outdoor temperature falls below
the outdoor cutoff setting, the heating system is activated
and the target water temperature is increased proportionally
to satisfy the load. Should it get warmer outdoors, the target
water temperature is automatically lowered by the control. If
the outdoor temperature continues to rise to the outdoor cutoff
setting then the heating system is turned off.
Because of the many different physical characteristics of
buildings including the type of radiation; i.e., baseboard or
radiant, the heat loss varies. In one building, a 1-degree
outdoors temperature change may require a change of 1 degree
in heating water temperature; for another it may require a
change of 2, 3, or even 4 degrees in order to gain the desired
comfort level. This is known as the Reset Ratio. The Reset
Ratio chart shows the wide range of Reset Ratios available for
the SEQ-3 in addition to the customized reset ratio. See page 2.
The installer fits the SEQ-3 to a specific building by adjusting
the Reset Ratio curve. With curve number 4 (2:1 reset ratio)
a 2-degree change in outdoor temperature will change the
circulating target temperature by 1 degree; at curve number
11(1:3 reset ratio) an outdoor change of 1 degree will change
the target temperature by 3 degrees. Most buildings with
baseboard radiation require a curve of 6, 7, or 8. Radiant heat
