Install Instructions

Page 54
LAARS Heating Systems
SECTION 11 OPERATING
DETAILS AND
TROUBLESHOOTING
11.A Normal Startup and Initialization
When power to the unit is turned on, the controller will
automatically go through a startup and initialization
procedure. At rst the interface will display some
information about the control software. See Figure 39.
Figure 39. – First Initialization Display
Next, the interface will search for the SOLA controller that
will actually control the boiler. See Figure 40.
Figure 40. – Second Initialization Display
Once the interface makes the connection to the controller,
it will display the address it is using to communicate (the
“Modbus address”). The interface will download a series of
values from the SOLA controller (or “synchronize” with the
controller).
When the synchronization is nished, the display will
change to the Home screen shown in Figure 21.
11.B Sequence of Operation
This unit is a cold-start appliance. It should start only
when it receives a call for heat from a tank aquastat,
room thermostat, zone valve end switch or other space
temperature control device.
1. The unit receives a call for heat.
2. The controller checks the safety chain.
3. The fan starts and waits to achieve prepurge RPM.
4. The prepurge timer is started once the prepurge
RPM is achieved.
5. There is a pre-ignition time of two seconds to check
the ame sensor operation and status. During this
period an intermittent spark can be seen.
6. Next there is a trial for ignition period of four seconds.
The direct spark ignition switches to constant spark
for three seconds. During this time the gas valve is
open. For the last second of the ignition period, direct
spark is de-energized and the ame sensor checks
for established ame. If ame is sensed, the control
enters Run to satisfy the demand. If ame is not
established, the control enters a retry, starting from
step 2. If ame has not been established after the
preset number of retries, the control will lockout with
a 109 error code.
7. The call for heat signal is removed.
8. The gas valve shuts o󰀨.
9. The fan and pump continue to run for the over-run
times to purge the system.
This is the basic operating sequence for a DHW or
hydronic call for heat.
11.C Modulation Control
The control uses a PID algorithm to adjust the ring rate of
the boiler as the control point is approached. The goal of
the control is to operate at a minimum ring rate to match
the load on the unit. This is done by using a setpoint, and
on/ o󰀨 di󰀨erentials. The control modulates to achieve the
setpoint temperature, which could be several degrees
away from the actual o󰀨 point. The o󰀨 point is calculated
by adding the setpoint plus the o󰀨 di󰀨erential. The setpoint
and di󰀨erentials used in operation are dependent upon the
type of call for heat being applied. If there is a DHW call,
the DHW setpoint and o󰀨 di󰀨erentials are used. If there
is a hydronic call, the CH setpoint and o󰀨 di󰀨erentials are
used. When the setpoint plus the o󰀨 di󰀨erential is reached,
the control prevents the unit from ring until the water
temperature reaches the setpoint minus the on di󰀨erential.
11.D Pump Control
The control can operate three pumps. The boiler pump
is active any time there is a call for heat applied to the
control. The DHW and system pumps are active based
upon the call and priority of the heat demand being
supplied. When there is a hydronic call supplied, the
system pump is active. If there is a DHW call supplied
while the hydronic call is active, with DHW priority enabled,
the system pump turns o󰀨 and the DHW pump turns on.
Domestic hot water priority forces the control to attempt
to satisfy the domestic water demand before the hydronic
demand. Once the last heat demand has been satised,
the boiler pump enters an overrun time.
11.E Anti-Short-Cycle (ASC)
Because the unit is a modulating boiler, and its input will
decrease when there is a reduction in the heating load,
short cycling is greatly reduced. If the heating load drops
below the minimum input of the boiler for an extended
period, the boiler will have a tendency to short cycle.