U.S. Boiler Company PVG3, Installation, Operating And Service Instructions

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IX. OPERATION
A.
Boiler Sequence of Operation
NORMAL OPERATION
1. The PVG Boilers are equipped with an Intelligent
Hydronic Control (control). This control replaces the
traditional separate ignition control, high limit switch,
blower relay and circulator relay and adds energy
saving thermal purge features. Energy is saved by
starting the circulator and delaying the burner start
when there is residual heat available in the boiler.
2. The boiler’s sequence of operation is shown in Table 11.
3. When the thermostat calls for heat the control
starts the system circulator and the thermal purge
(circulator Pre-purge time) begins. If the time is
completed or boiler temperature is less than the
Start Temperature (140°F default) the start sequence
continues by energizing the blower. Once the
pressure switch is proven, the ignition sequence is
started allowing gas flow and ignition of the burners.
4. If the thermostat is not satisfied and the operating
setpoint is reached the system circulator will continue
to operate and the burner will stop. When the
boiler water temperature drops below the setpoint
less the differential setting the burner will restart.
5. After the thermostat is satisfied the burner, circulator
and blower are stopped.
6. When a indirect water heater aquastat call for heat is
wired to the DHW input the control starts the Domestic
Hot Water circulator and, if the boiler temperature
is less than the operating setpoint less differential,
the blower is energized without delay. Once the
pressure switch is proven, the ignition sequence is
started allowing gas flow and ignition of the burners.
B.
Boiler Fault
In the event the boiler fails to start, the control provides status
information to help determine the cause of the problem. Table
12 provides a list of boiler status codes that are reported.
Refer to the Troubleshooting Section for more information.
C.
Using Display
The control is located inside the boiler front door.
(Figure 25).
Figure 25: Intelligent Hydronic Control
Status Codes displayed in
STA
Mode
Status
STA
Description
Standby
(Burner off
Circulator off)
1
No call for heat detected
Circulator
Pre-purge
(burner off
circulator on)
1
Either condition is true:
a. Call for heat detected and boiler
temperature higher than
operating setpoint.
b. Call for heat detected and boiler
temperature higher than Start
Temperature (140°F default) and
Circulator Pre-purge Time has
not expired.
Self Test
17
Control internal checking
Waiting for
Pressure
Switch to Close
(Blower on)
3
The blower is turned on. The
control is waiting for the pressure
switch to close.
Pre-purge
4
The blower is run for a 30 second
pre-purge
Spark
6
The pilot fuel valve is open and
sparking is started.
Flame Proving
7
The main fuel valve is open and
flame is being proven.
Running
8
The burner runs until the call for
heat is satisfied or the operating
setpoint is reached.
Table 11: Sequence of Operation
Status Codes displayed in
STA
Mode
Status
STA
Description
Retry / Recycle
Delay
10
If the burner fails to light off (no
flame signal), it waits 5 minutes and
retries or if the control loses flame
signal during running, it will wait 10
seconds and then recycle.
Pressure
Switch Failed
to Open
11
The blower is off and the pressure
switch as failed to open.
Pressure
Switch Failed
to Close
12
The blower is on and the pressure
switch has failed to close.
Soft Lockout
13
System is shutdown and will restart
following a one hour enforced delay.
Hard Lockout
14
System is locked out. A manual or
power reset is required to be able to
light off again.
Limit Open
15
There is a call for heat from the
thermostat, but a Safety Limit is
open.
Flame
Present Out of
Sequence
16
Flame signal is still present when
expected to be 0 (no flame).
Table 12: Sequence Fault