LAARS NeoTherm LC NTV1700 - Install and Operating Manual - Manual (Page 74)

LAARS Heating Systems Page 70
When Outdoor Reset is enabled, and the outdoor
temperature falls between the maximum and
minimum outdoor temperatures (70° and 32° in
the example above), the setpoint will be adjusted
down by about 1° for every 2° increase in the
outdoor temperature. For example, if the outdoor
temperature rises by 10°, the Outdoor Reset function
will adjust the setpoint down by about 5°. (This
ratio between outdoor temperature and water
temperature is adjustable.)
When you set up the Outdoor Reset feature, you
can set the “turning points” on the adjusted setpoint
curve. If you go back to Fig. 91, the Outdoor Reset
screen, you see that the system records these values:
Enable -
Enable = Outdoor Reset feature turned on
Max. outdoor temp. -
If the outdoor temperature reaches this value
or above, the system will use the Low Water
Temp value as the setpoint. In the example
shown in Fig. 91, the Max. Outdoor Temp.
is set to 70°F. If the outdoor temperature is
70°F or above, the system will use 100°F
(the Low Water Temp.) as the setpoint.
Min. outdoor temp. -
If the outdoor temperature reaches this value
or below, the system will not compensate
for the outdoor temperature. In the example
shown in Fig. 91, the Min. Outdoor Temp.
is set to 32°F. If the outdoor temperature
reaches 32°F or below, the system will
use the normal Lead/Lag System setpoint
(120°F in this example).
Low water temp. -
If the outdoor temperature reaches the Max.
Outdoor Temp. or higher, the system will
use the Low Water Temp value as the new
setpoint. In the example shown in Fig. 91,
the Max. Outdoor Temp. is set to 70°F. If
the outdoor temperature reaches 70°F or
above, the system will use the Low Water
Temp. value (100°F) as the setpoint.
There is one other part of this system, and it is
located on a different screen:
LL CH setpoint -
On a system set up for Outdoor Reset, this
will be the maximum water temperature
setting. This is located on the main Lead/
Lag Configuration screen.
How to get there – Lead/Lag Master Configuration
Screen
Home Page Lead/
Lag Screen Lead/ Lag Master
Configuration Screen
Job L - Building Automation or Multiple
Boiler Control Thermostat Demand
(This is a Lead/Lag function – do this once for the whole Lead/
Lag system. Make the connections to the controller set up as
the Lead/Lag Master – usually the Primary controller on Boiler
1.)
1. Supply the controller which is acting as
the Lead/Lag Master (usually the Primary
controller on Boiler 1) with a thermostat
closure from the Building Automation
System or multiple boiler control. Connect to
terminals 5 and 6 on TB7.
2. Adjust the Lead Lag Central Heat setpoint.
How to get there – Lead/ Lag Central Heat Setpoint
Home Page Lead/
Lag Screen Lead/ Lag Master
Configuration Screen
Line 2 = CH Setpoint
Note - Laars offers “gateways” to allow connections
to BACnet, LON, and other communications
protocols. See Section 9.6.
Job M - Building Automation or Multiple
Boiler 4-20 mA Setpoint Control
(This is a Lead/Lag function – do this once for the whole Lead/
Lag system.)
In this type of installation, the CH Setpoint is
changed or modulated by a source outside of the
boiler. The low limit of the 4-20 mA signal (4 mA)
sets the low limit of the setpoint, and the high limit
of the 4-20 mA signal (20 mA) sets the high limit of
the setpoint.
1. Supply the controller which is acting as
the Lead/Lag Master (usually the Primary
controller on Boiler 1) with the 4-20 mA input
from the Building Automation System or
multiple boiler control. Connect to terminals 3
and 4 on TB7.
2. On the Lead/Lag Master settings, change the
setpoint source to 4-20 mA.
How to get there – Lead/ Lag Setpoint Control
Home Page Lead/
Lag Screen Lead Lag Master
Configuration Screen
Central Heat
Setpoint Source = 4-20 mA