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106308-05 - 3/23
APEX Installation, Operating, & Service Instructions
11. Sequencer Master
Select to access the following parameters.
Parameter and Description
Factory
Setting
Range / Choices
Sequencer Master
The Sequencer Master Enable/Disable is used to “turn on” the multiple boiler lead-
lag control.
Disabled
Enable
Disable
Indirect Water Heater (IWH)
Boiler Piped Sequencer to respond to an Isolated DHW demand that is piped
to a single boiler. The individual boiler goes on “Leave” from the
Sequencer Master and goes to DHW Service.
Primary Piped The Sequence Master responds to the DHW Call For Heat. This
allows one or more boilers to provide heat to the IWH.
Boiler Piped
Boiler Piped
Primary Piped
DHW Two Boiler Start
If enabled, the sequencer will immediately start two boilers for a DHW call for heat.
Used when DHW is the largest demand. Only relevant when “Primary Piped IWH” is
selected.
One Boiler
One Boiler
Two Boiler
Boiler Start Delay
Slave boiler time delay after header temperature has dropped below Setpoint
minus Difference Below. Longer time delay prevents nuisance starts due to short
temperature swings.
5 min. 0.5 to 20 min.
Boiler Stop Delay
Slave boiler time delay after header temperature has risen above Setpoint plus
Difference Above. Longer time delay prevents nuisance stops due to short
temperature swings.
1 min. 0.5 to 5 min.
Base Load Rate
To maximize boiler efficiency, firing rate is limited to an adjustable value. Boilers are
kept at or below this firing rate as long as the boilers can handle the load. After last
available boiler has started, the modulation rate limit is released up to 100%.
70% 25 to 100 %
Lead Rotation Time
Time boilers will act as the lead before switching the lead to another boiler in the
boiler to boiler network.
24 hours 8 to 48 hours
Response Speed
This parameter adjusts the Central Heat 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 4-11 for PID values used by these selections.
3 0 to 5
Stop All Boilers
When this temperature is reached, all networked boilers are stopped at once
without any time delay. This setting allows the sequencer to respond to rapid load
increases.
195°F
(90.6°C)
Central Heat Setpoint to
195°F
(90.6°C)
10 Operation (continued)
NOTICE: Enable only one Sequencer Master
boiler within a group of networked boilers. Erratic
behavior will result if more than one Sequencer
Master is enabled.
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