LAARS M4-Ext - Installation Manual - Manual (Page 19)

Page 19 LAARS Modulating Controls M4 & M4-EXT
PURGE DELAY
Adjustable 0.0min to 10.0min Default: 1.0min
Button: MENU/<System Settings>/Purge Delay
•
Many boilers go through a purge cycle before they are brought on line.
• When the M4 activates a boiler, it does not start to calculate its output until the Purge
Delay is over. This allows the boiler to fully come on line and begin producing output.
• The Purge Delay helps to prevent short cycling of a newly activated burner. Once the
burner is activated, it MUST run through the entire Purge Delay period.
• The minimum Purge Delay setting MUST be set to the time required by the boiler
manufacturer. Time entry is in 0.1 of a minute (i.e. 1.5min will equal 90 seconds.)
• The Message Display Line will display Purge Delay and the amount of time remaining
in the purge.
BACK SAVE
--------- PURGE DELAY ---------
1.0
min
[ ]
CAUTION
Set Purge Delay as per boiler
manufacturer recommendation.
LAG DELAY
Adjustable 0min to 60min Default: 0min
Button: MENU/<System Settings>/Lag Delay
•
The Lag Delay requires the previous stage to remain at 100% modulation for the full
period of the Lag Delay before another Stage can be activated. For example, if the Lag
Delay was set to 10 minutes, the Lead Stage would need to remain at 100% modulation
for a full ten minutes (never backing down to even 99%) before a lag stage could be
activated. The Message Display Line will display Lag Delay and the remaining time.
BACK SAVE
----------- LAG DELAY -----------
0
min
[ ]
• Set the Lag Delay to 0 min when two or more Stages will generally be needed to hold the load.
• The Lag Delay is useful in installations where one unit should usually have enough output to hold the load unless it fails or load
conditions become extreme.
• The Lag Delay overrides the value of the Modulation Point selected for each stage. Regardless of that setting, the previous stage
must reach 100% and stay there before another Stage can be activated.
• The full Lag Delay must always elapse regardless of what happens to system temperature. Therefore, set the Lag Delay to 0 min
if you want smooth set point control using multiple units.
STANDBY TIME
Adjustable 1min to 60min Default: 10min
Button: MENU/<System Settings>/<More Settings>/Standby Time
•
The Standby Delay Time only applies to Boilers in Standby Mode.
• 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 Stage
BACK SAVE
-------- STANDBY DELAY --------
10
min
[ ]
• The full Standby Delay Time must always elapse regardless of what happens to system temperature. Therefore, shorter Standby
Times will result in smoother set point operation in extreme conditions. Longer Standby Times may prevent a Standby Boiler
from firing if the other boilers can eventually meet the load, or if the load decreases.
SYSTEM RUN-ON
Adjustable 0min to 360min Default: 0min
Button: MENU/<System Settings>/<More Settings>/System run-On
•
The SYS relay will energize whenever the Outdoor temperature (OD) is below the
Outdoor Cutoff. When the Outdoor temperature increases 2°F above the Outdoor Cutoff
after the last burner relay has de-energized, the SYS relay will stay on for a period set
by the System Run-On. This allows the Pump to dissipate the residual heat within the
boilers back into the system.
BACK SAVE
-------- SYSTEM RUN-ON --------
0
min
[ ]
• A common use for the System Run-On is to control a system pump in a heating system. The extra time helps transfer the heat
from the boilers to the heating system.
• The System Run-On time should be set based on the size and type of the boilers and pumps. In general, a boiler with low
water content and high horsepower will need a longer System Run-On than a boiler with the same horsepower and more water
content. (Refer to boiler manufacturer recommendation)