Lead Boiler Rotation; Standby Time; Last Stage Hold; Lead Stages - heat-timer Mini-MOD-CNC Installation And Operation Instructions Manual

Condensing / non-condensing control
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• A common use for the System Run-On is to control a system pump in a heating system.
The extra time helps transfer the boiler residual heat to the heating system.
• The System Run-On time should be set based on the size and type of the boilers and
pumps used. In general, when setting the System Run-On consult the boiler and pump
manufacturers for the best setting.

lead BoIler rotatIon

Adjustable Manual, Time (1 hr to 60 Days), Last-On
Button: MENU/<System Settings>/Lead Rotation
• The Lead Boiler is the first boiler brought on when an output is needed.
• The Lead Boiler can be rotated automatically every specified time period, manually, or
based on Last-On. Time rotation is recommended.
• The current Lead Boiler is shown in brackets on the main display.
• Only boilers which are set to Auto Mode can be Lead. Therefore, not all the boilers may be
available when manually selecting a new Lead Boiler.

standBy tIMe

Adjustable from 1min to 60min
Button: MENU/<System Settings>/<More Settings>/Standby Time
• The Standby Time only applies to boilers in Standby Mode. See "Mode" on page 31.
• A boiler can be set to be a Standby boiler using the Stage Menu.
• A Standby boiler can only be activated after all the boilers in Auto Mode have run at 100%
modulation for the full Standby Time.
• Standby boilers are used for backup or extreme load conditions only. A Standby boiler can
never be a Lead Boiler.
• The full Standby Time must always elapse regardless of what happens to the system
temperature. Therefore, shorter Standby Times will result in smoother set point operation in
extreme conditions. On the other hand, longer Standby Times may prevent a Standby boiler
from firing if the other boilers can eventually meet the load, or if the load decreases.

last stage Hold

Adjustable from 0F°/0C° to 30F°/17C°
Button: MENU/<System Settings>/<More Settings>/Last Stg Hold
• The Last Stage Hold prevents short cycling of the Lead Stage during low demand periods.
• In these conditions, the system might require less output than the lowest lead Stage. When
the Mini-MOD-CNC brings on the Lead Stage, the Set Point is quickly exceeded, and the
Mini-MOD-CNC turns the Lead Stage off.
• To prolong the run time during this type of condition, use the Last Stage Hold setting to let
the system temperature exceed the Set Point by the number of degrees selected.
• For example, with a Set Point of 160°F and a Last Stage Hold setting of 10°F, the Lead
Stage boiler will de-energize after the Set Point exceeds 170°F.
• In many cases, it is better to overshoot slightly than to short cycle a boiler.
• When Soft-Off is set to other than 0 seconds, the Lead Boiler will need to remain at or
exceed the Last Stage Hold for the Soft-Off period before turning off.

lead stages

Condensing Lead, Non-Condensing Lead
Button: MENU/<System Settings>/<More Settings>/Lead Stages
• In addition to having a lead group, each group of boilers, Condensing Group and
Non-Condensing Group, will have its own lead boiler that can be selected from this menu.
• After assigning the lead boiler for each group, the lead will rotate based on the Lead
Rotation option selected. See "Lead Boiler Rotation" on page 25.
Mini-MOD-CNC & Mini-Extension Installation Manual
Default: Time (24Hours)
Default: 10min
Default: 0F°/0C°
Default: Condensing Lead
-- LEAD ROTATION --
Manual
Time
Last-On
BACK
-- LEAD ROTATION --
24hrs
[
BACK
-- STANDBY TIME --
10 min
[
BACK
LAST STAGE HOLD
0
o
F
[
BACK
--- LEAD STAGES ---
Cond Lead
Non-Cond Lead
BACK
SAVE
25
SAVE
]
SAVE
]
SAVE
]
SAVE
A
C

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