LAARS M4-LHS - Installation Manual - Manual (Page 30)

HT# 059295-00
A
30
M4-LHS installation and Operation Manual
Offset
Adjustable from 50Fº/28Cº to -50Fº/-28Cº Default: 0Fº/0Cº
Button: MENU/System Target/Offset
• The Offset adjust the starting points of the Reset Ratio curve. This means that, regardless
of the Outdoor Temperature (OD) or the Reset Ratio that has been selected, when the
Offset setting is changed, that change is directly added to or subtracted from the calculated
temperature. For example, if the Set Point was 130°F and the Offset was changed from 0F°
to 10F° (an increase of 10F°), then the Set Point temperature would increase to 140°F.
• The Offset setting does not change the ratio selection. What the Offset does is add or
subtract a constant temperature value. See "Outdoor Reset Concept" on page 5.
------- OFFSET ------
+0 o F
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• 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 1F° or
2F° for every 1F° you wish to change the building temperature.
Outdoor Cutoff Temperature
Adjustable: Off, from 20ºF / 70ºC - 100ºF / 38ºC, On Default: 65ºF/ 18ºC
Button: MENU/System Target/Offset/Outdoor Cutoff
• The control will turn heating off if the outside temperature rises above the Outdoor Cutoff.
This setting shall not affect any indirect DHW requirement.
• The Outdoor Cutoff screen will automatically appear after setting the Offset.
• When the outdoor temperature falls to the adjustable Outdoor Cutoff temperature, the
M4-LHS will operate the boilers to hold the calculated 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
• When the outdoor temperature rises to the Outdoor Cutoff plus a 2°F differential, the
M4-LHS 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-LHS will circulate is 70°F. If the Outdoor Cutoff is turned
ON and the Season is set to Winter, the M4-LHS 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.
- OUTDOOR CUTOFF -
65 o F
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Minimum Water Temp
Adjustable from 50ºF/10ºC to 180ºF/82ºC Hybrid Default: 70ºF/ 21ºC
Modulation Default: 120ºF/ 49ºC
Button: MENU/System Target/Offset/Outdoor Cutoff/Minimum Water Temp
• The Minimum Water Temperature must be set to the boiler manufacturer’s specification.
The M4-LHS will calculate the Set Point based on the Outdoor Temperature (OD), the Reset
Ratio, and the Offset value. The M4-LHS 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 70ºF/21ºC - 220ºF/104ºC Default: 200ºF/93ºC
Button: MENU/System Target/Offset/..../Maximum Water Temperature
• This is the highest temperature heating water the M4-LHS 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).
MAXIMUM WATER TEMP
200 o F
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