LAARS Heating Systems
Page 28
8.E Operating Temperature Control
Mini-Therm JVi
Page 31
ITEMS14, 39
AND INSULATION
NOT SHOWN
Control Access Panel
Note: The Dip switch panel and LED panel can be
found under the Control Access Panel after removing
the bolts.
When a call for HEAT and/or DHW is present the
boiler pump will turn on. Post purge can be selected via
dip switch #5, Pump Post Purge Inactive (Off) /Active
3 min. (On). In the On position the pump will continue
to run for 3 min after the last call has been satisfied.
When the dip switch is Off there is no post purge of the
pump, the pump turns off immediately after the last call
is removed. Laars strongly recommends using a pump
post purge. During WWSD and a call for HEAT is
present the pump will remain off.
Pump Exercising
The control exercises the
boiler pump every 3 days of inactivity. While the
control is exercising the pump all LEDs will turn off
and the power LED will flash for 10 seconds.
Staging (where applicable – factory setting
):
Dip #1 is used to select the number of stages: 2-Stage
(Off) / Single Stage (On).
For 2-stage operation, the first stage is cycled on
Proportional error and the second stage is cycled
based on PI according to a fixed algorithm. No user
adjustment is necessary.
Note: All stages are turned off when the water outlet
temperature reaches the Maximum setting that is elected
via dip switch #4, Boiler Maximum 210°F (Off) / 190°F
(On). Commercial boilers have dip switch #2 set for
‘Off’ to allow setpoint control. Utilize dial to set desired
outlet temp.
Auto Boiler Target Setpoint: Space Heating:
The boiler target temperature is automatically
determined from Space Heating and DHW
requirements. Space heating is based on outdoor reset.
When both a Heat Call and a DHW Call are present
at the same time, the control operates to provide the
higher boiler target temperature.
Heating Curve (Outdoor Temperature Reset)
The control uses a linear heating curve to calculate
a target setpoint. The following data are used
to calculate the target setpoint from the outdoor
temperature.
1. The heating curve or reset ratio (RR) is set by the
potentiometer with a range of 0.4 to 3.6.
2. The room temperature is fixed at 70 deg F.
3. Boiler target =
70 deg F + RR X
(70 deg F - outdoor temp)
Outdoor
Heating Curve=Reset Ratio (RR)=
Temp F
1.0
2.0
3.0
Boiler Target F
-30
170
210
210
-20
160
-10
150
0
140
10
130
190
20
130
170
30
150
190
40
130
160
50
130
60
70
WWSD OFF
Reset Ratio Calculation:
Boiler Target =
70 deg F + RR X
(70 deg F - outdoor temp)
DHW Operation
The boiler target for DHW calls
is fixed at 180 deg F.
Note: There is no control of a DHW pump, so the
boiler pump runs with the call for DHW.
Limiting
The boiler target is limited to a
minimum and a maximum target to ensure that the
water temperature does not exceed the limits.
1. Target Min
- The boiler target minimum is
the point at which the stages will start to turn on to
maintain a minimum water temperature. The Boiler
Minimum water temperature is 130 deg F, regardless
of other calculated targets. To ensure that the water
temperature is greater than the Boiler Minimum water
temperature the target is increased to allow the stages
to cycle on by the Boiler Minimum water temperature,
Boiler Minimum target is set to Boiler M
differential/2.
2. Target Max
- The boiler target maximum is
the point at which the stages will start to turn off to
maintain a maximum water temperature. The Boiler
Maximum water temperature is set by setting dip
switch #4: Boiler Maximum 210°F (Off) / 190°F (On).
To ensure that the water temperature is less than the
Boiler Maximum water temperature the target is
decreased to allow the stages to cycle off by the Boiler
Maximum water temperature, Boiler Maximum target
is set to Boiler Maximum - differential/2.
Auto Differential
The control automatically
adjusts differential to prevent short cycling and
maximize the lifetime of components.
WWSD Operation
Warm Weather Shutdown -
WWSD feature is selected via dip switch #3, WWSD
Inactive (Off) / Active 70°F (On). WWSD point is
fixed at 70 deg F. Control exits WWSD when the
outdoor temp falls to 65 F. When there is a call for
