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Minimum Runtime
Options: 1 to 60 minutes
/<Settings>/<Stage>/Min. Runtime
SET
•
This is the minimum amount of time any stage will run.
•
The Minimum Runtime for the lowest firing stage on a boiler starts after the purge cycle.
•
Initially, set the Min. Runtime to half the Reaction Time.
•
If System tends to overshoot, reduce the Min. Runtime. If boilers tend to short cycle, increase the
Min. Runtime.
Lead Boiler (Not Available for Lo/Hi or 1-On/Off Output Modes)
Options: A, B, or C
/<Settings>/<Stage>/Lead
SET
•
The Lead boiler will always be the first boiler brought on when there is a call for output. As more
heat is needed, additional boilers are added.
Lead Rotation (Not Available for Lo/Hi or 1-On/Off Output Modes)
Lead Rotation Options: Manual or Time
Rotation Period Options: 1 to 999 Hours
/<Settings>/<Stage>/Lead
SET
/<Settings>/<Stage>/Lead/Rotate
SET
•
The Lead boiler can be rotated automatically based on time or manually. The Time rotation is
recommended for most applications.
•
If Time is selected, a second screen will allow the adjustment of the Auto Rotate Period If
24 Hours (default setting) was selected, the first rotation will take effect after 12 hours. The
following rotations will take place every 24 hours thereafter.
•
If Manual Lead Rotation is selected, it will be followed by the Lead Boiler selection option. (See
previous topic.)
Single On/Off Boiler and System Pump Settings
Differential (Available for Single-Boiler Applications only)
Options: From 1ºF/1ºC to 20ºF/11ºC
/<Settings>/Diff.
SET
•
The Differential controls boiler cycling. When there is a call for heat, the boiler will be activated until the Calculated temperature
is reached. The boiler will then turn off and stay off until the system water temperature falls to the Set Point less the Differential.
•
A smaller Differential setting will normally result in tighter control of the set point but will tend to increase the frequency of
boiler cycling. Larger Differential values will reduce boiler short cycling, but the system will be allowed to vary further from the
target value.
Run-On (Not Available for 3-On/Off Output Mode)
Options: From 0 min to 60 min
/<Settings>/Run On
SET
•
The System Pump relay will energize whenever the Outdoor temperature is below the Outdoor Cutoff. When the Outdoor
temperature increases 2°F above the Outdoor Cutoff and after the boiler relay has de-energized, the pump relay will stay on for a
period set by the Run-On. This allows the Pump to dissipate the residual heat within the boilers back into the system.
•
The Run-On time should be set based on the size and type of the boilers and pump. In general, a boiler with large water content
and high horsepower will need a longer Run-On than a boiler with the same horsepower and less water content. (Refer to boiler
manufacturer recommendation).
•
When DHW Priority is selected while the EXT+/EXT- (Enable/Disable terminals) are open or the outdoor temperature is above
the Outdoor Cutoff, a DHW call will energize only the DHW relay. When the DHW call expires, the DHW Pump relay will run
for the Run-On period then de-energize.
12
Default: 2 minutes
Default: A
Default: Time
Default: 24 Hours
Default: 5ºF/3ºC
Default: 2 min
Minimum Runtime:
2m
Lead Boiler:
A
Lead Rotation:
Time
Manual
Rotation Period:
24hrs
Differential:
5 F
Pump Run-On:
2m
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