LAARS NeoTherm NTV (Sizes 150–850 MBTU/h) - Install and Operating Manual - Manual (Page 43)

Page 39 N eo T herm Boilers and Water heaters
• As the temperature begins to rise above 32°F, the Outdoor
Reset function causes the setpoint to be lowered. At these
warmer temperatures, the heating load on the system is
not as great, so the system does not have to reach as high a
temperature to handle the load.
• As you can see from the display, at an outdoor temperature
of about 70°F, the system stops adjusting the setpoint.
Above 70°F, the setpoint is constant at 100°F (or another
value that you choose).
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 .8° for every 1° increase in
the outdoor temperature (See Figure 37). 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.
Here are instructions for setting up the Outdoor Reset
function. Notice that these instructions will be different,
depending on whether you have a single boiler or more than
one boiler (using Lead/Lag operation).
Wiring Connections -
Connect the outdoor temperature sensor:
If your system has just one boiler –
Connect the sensor across terminals 1 and 2 on TB-7.
If your system has more than one boiler, and is controlled
using the Lead/ Lag function –
Connect the sensor across terminals 1 and 2 on TB-7 on the
boiler which will be used as the Lead/Lag Master.
Setting Up the Control Functions -
1.
Enable the Outdoor Reset function:
Note: This function can be Enabled/Disabled only by a
factory trained technician.
2. Set the maximum outdoor temperature:
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 earlier, the Max. Outdoor Temp. is set to
70°F. If the outdoor temperature rises above 70°F, the system
will use 100°F (the Low Water Temp.) as the setpoint.
If your system has just one boiler –
How to get there: From the “Home” screen, press “I”
to go to “Info/ Install.” Choose “Advanced Setup,”
then go to “CH Configuration.” Select “Outdoor Reset
Configuration.” Set the value on the line for “Max.
Outdoor Temp.”
If your system has more than one boiler, and is controlled
using the Lead/ Lag function –
How to get there: From the “Home” screen, press “I” to
go to “Info/ Install.” Choose “Advanced Setup,” then go
to “Lead/ Lag Configuration.” Select “Lead/ Lag Outdoor
Reset.” Set the value on the line for “Max. Outdoor Temp.”
3. Set the minimum outdoor temperature:
If the outdoor temperature drops to this value or below, the
system will not compensate for the outdoor temperature. In
the example shown earlier, the Min. Outdoor Temp. is set to
32°F. If the outdoor temperature is below 32°F, the system
will use the normal system setpoint (130°F in this example).
If your system has just one boiler –
How to get there: From the “Home” screen, press “I”
to go to “Info/ Install.” Choose “Advanced Setup,”
then go to “CH Configuration.” Select “Outdoor Reset
Configuration.” Set the value on the line for “Min.
Outdoor Temp.”
If your system has more than one boiler, and is controlled
using the Lead/ Lag function –
How to get there: From the “Home” screen, press “I” to
go to “Info/ Install.” Choose “Advanced Setup,” then go
to “Lead/ Lag Configuration.” Select “Lead/ Lag Outdoor
Reset.” Set the value on the line for “Min. Outdoor Temp.”
4. Set the low water temperature:
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 earlier, 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
(example - 100°F) as the setpoint.
If your system has just one boiler –
How to get there: From the “Home” screen, press “I”
to go to “Info/ Install.” Choose “Advanced Setup,”
then go to “CH Configuration.” Select “Outdoor Reset
Configuration.” Set the value on the line for “Low Water
Temp.”
If your system has more than one boiler, and is controlled
using the Lead/ Lag function –
How to get there: From the “Home” screen, press “I” to
go to “Info/ Install.” Choose “Advanced Setup,” then go
to “Lead/ Lag Configuration.” Select “Lead/ Lag Outdoor
Reset.” Set the value on the line for “Low Water Temp.”
5. Set the minimum boiler water temperature:
If a value is entered here, the temperature in the boiler will
never be allowed to drop below this temperature. This will
protect the boiler against possible damage due to expansion of
ice inside the unit. (Notice that this is different from the “low
water temperature” described above.)
If your system has just one boiler –
How to get there: From the “Home” screen, press “I”
to go to “Info/ Install.” Choose “Advanced Setup,”