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10
Operation
(continued)
Table 10-20: Response Speed Adjustment Guidelines-20
9. Domestic Hot Water Parameters
Select
to access the following parameters.
Priority Time
When Priority Time is greater than zero and Domestic Hot Water (DHW) heat demand
is "on", DHW demand will take "Priority" over Central Heat (space heating) demand.
When the System and Boiler pumps are configured as "Central Heat (off DHW
priority)" or "Central Heat, Optional Priority" then they will be forced "off" during
Priority Time. Priority Time provides "Priority Protection" time for the event of a failed
or excessive long DHW demand. "Priority Time" is the time that the priority of the
boiler will shift away from Central Heat to satisfy a Domestic Hot Water call for heat.
Setpoint
Setpoint is used to create a boiler water temperature setpoint that is used when DHW
heat demand is "on". When the DHW heat demand is not "on" (i.e. the contact is
open or not wired), this setpoint is ignored.
Time of Day Setpoint
Used when an EnviraCOM thermostat is connected to the boiler and is in Sleep or
Away mode. When setback is "on" the time of day setback setpoint shifts the DHW
setpoint to lower the DHW temperature and to save energy while building is in a
reduced room temperature mode.
Difference Above
The boiler stops when the water temperature rises 'Difference Above' degrees above
the setpoint.
Difference Below
The boiler starts when the water temperature drops 'Difference Below' degrees
below the setpoint.
Domestic Low Fire Hold Time
"Low Fire Hold Time" is the number of minutes the control will wait at low fire
modulation rate before being released to modulate. After ignition and flame
stabilization periods the firing rate is held at low fire for "Low Fire Hold Time". This
delay allows heat to travel out to the system and provide system feedback prior to
the control modulating firing rate.
Response Speed
This parameter adjusts the Domestic Hot Water temperature controller Proportion
Integral Derivative (PID) values. Higher values cause a larger firing rate change for
each degree of temperature change. If set too high firing rate "overshoots" required
value, increases to high fire causing the temperature to exceed the "Difference
Above" setpoint and cycle the boiler unnecessarily. Lower values cause a smaller
firing rate change for each degree of temperature change. If set too low, the firing
rate response will be sluggish and temperature will wander away from setpoint. Refer
to Table 10-20 for PID values used by these selections.
106308-05 - 3/23
Parameter and Description
APEX
Installation, Operating, & Service Instructions
Factory Setting
60 min
170°F
(76.7°C)
160°F
(71.1°C)
7°F
(-13.9°C)
5°F
(-15°C)
10 seconds
Range / Choices
0 to 90 min
50 to 190°F
(10 to 87.8°C)
50 to 190°F
(10 to 87.8°C)
3 to 29°F
(-16.1 to 1.7°C)
3 to 29°F
(-16.1 to 1.7°C)
0 to 1,800 seconds
3
1 to 5
95
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