LAARS M4-Ext - Installation Manual - Manual (Page 23)

Installation Manual 23
• The Offset setting does not change the ratio selection. For instance, with 1.00 (OD):1.00
(SYS) Reset Ratio, the System water temperature (SYS) will always increase one degree
for each degree change in the Outdoor temperature (OD). What the Offset does is add or
subtract a constant temperature value. See "Outdoor Reset Concept" on page 7.
• If required: Adjust the Water Offset in mild weather. If the ambient building
temperatures are too warm in mild weather, decrease the offset. If the ambient building
temperatures are too cold in mild weather, increase the Water Offset. The rule of thumb
for baseboard radiation is to change the offset 4°F for every 1°F you wish to change the
building temperature. In radiant heat applications, change the offset 1°F or 2°F for every
1°F you wish to change the building temperature.
Outdoor Temperature (in °F)
70 60 50 40 20 30 0 -10 10 -20
120
140
130
150
160
170
180
100
110
W
ater
Temperature (in °F)
Custom Reset Ratio
Point1: System=120°F
Oudoor=60°F
Point2: System=170°F
Oudoor=0°F
Point1
Point2
Customized Reset Ratio
Max Target
Min Target
Outdoor Temperature (in °F)
70 60 50 40 20 30 0 -10 10 -20
120
140
130
150
160
170
180
100
110
W
ater
Temperature (in °F)
Target Offset
Offset=10°F
Reset Ratio=1.5 : 1.0
Reset Ratio
Max Target
Min Target
Reset Ratio + 10F Offset
Min Target=120°F
Max Target=170°F
OUTdOOR CUTOFF TEMPERATURE
Adjustable: Off, from 20ºF / 70ºC - 100ºF / 38ºC, On Default: 65ºF/ 18ºC
Button: MENU/Set Point/Offset/Outdoor Cutoff
• The Outdoor Cutoff screen will automatically appear after the offset has been selected.
• When the outdoor temperature falls to the adjustable Outdoor Cutoff temperature, the
M4-CNC will control and modulate boilers to hold the calculated temperature.
- OUTDOOR CUTOFF -
65 o F
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• When the outdoor temperature rises to the Outdoor Cutoff plus a 2°F differential, the M4-CNC will turn all boilers off. The System
relay will remain energized for the Run-On delay then de-energize.
• The Outdoor Cutoff can be set from 20°F to 100°F. In addition, it can be set to ON or OFF. In the ON position, the System Relay
will run regardless of the Outdoor temperature (OD) and the burner stages will be active to hold the calculated water temperature.
(Note: The lowest water temperature the M4-CNC will circulate is 70°F. If the Outdoor Cutoff is turned ON and the Season is set
to Winter, the M4-CNC will circulate at least 70°F water even in the hottest of weather.) In the OFF position, the system pump will
always be off and all burner stages will be off.
MiNiMUM WATER TEMP
Adjustable from 70ºF/21ºC to 180ºF/82ºC Default: 70ºF/ 21ºC
Button: MENU/Set Point/Offset/Outdoor Cutoff/Minimum Water Temp
• The Minimum Water Temperature must be set to the boiler manufacturer’s specification.
The M4-CNC will calculate the Set Point based on the Outdoor temperature (OD), the Reset
Ratio, and the Offset value. The M4-CNC will control all boilers to hold either the Set Point
temperature, or the Minimum Water Temperature, whichever is higher.
• The Minimum Water Temperature must be at least 20°F lower than the Maximum
Temperature (See next setting).
MINIMUM WATER TEMP
70 o F
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MAxiMUM WATER TEMP
Adjustable 90ºF/21ºC - 240ºF/116ºC Default: 240ºF/116ºC
Button: MENU/Set Point/Offset/..../Maximum Water Temperature
• This is the highest temperature heating water the M4-CNC will circulate through the heating
system.
• When using a radiation system, it should be set according to the tubing or floor
manufacturer’s specification.
• The Maximum Temperature must be at least 20°F higher than the Minimum Temperature
(See previous setting).
• The Maximum Temperature must be set lower than the boilers high limit for correct system
temperature control.
MAXIMUM WATER TEMP
240 o F
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LAARS Modulating Controls M4 & M4-EXT
HT# 059104-00 B