Crest Audio FBN0751, Service Manual

Page: 36 / 56

2
Maintenance
Service Manual
Figure 2-3 Adjust outlet isolation valve
Test procedure
1. Place the unit into Service Mode. Navigate to the Service
Screen from the Home Screen by pressing the MAIN
MENU button and then the SERVICE button.
2. On the Service Screen place heater into Service Mode by
selecting the START button. In Service Mode the boiler
will fire at ignition speed and will then modulate up to full
fire.
3. Allow the unit to progress through its normal diagnostics
and pre-purge programming.
4. Allow the unit to fire and operate until the temperatures
stabilize. This occurs when the inlet and outlet
temperatures are rising together and the Delta T (
T) is
maintained.
5. When the unit stabilizes, begin to slowly shut off the
isolation valve on the outlet piping of the boiler (see FIG.
2-3). This will begin to restrict the flow and simulate a
low flow condition.
6. While slowly shutting off the isolation valve, refer to the
Status Screen to watch the behavior of the boiler. This
screen allows you to monitor the inlet temperature, outlet
temperature, and
T.
7. When the T reaches 70˚F, the control will attempt to
modulate the firing rate down to protect it from low flow
conditions.
8. When the T reaches 80°F, the control module will turn
off the burner. If the control module shuts down, the test
was successful.
9. Completely open the isolation valve on the outlet piping
of the boiler.
10. Resume operation.
IMG01035
ADJUST OUTLET
ISOLATION VALVE
ONLY
36
Test low water flow conditions
NOTICE
This test is to be carried out once the
Crest boiler is completely piped in with
adequate gas and water flow. Once
the test is completed, ensure that the
isolation valve is opened up to allow full
water flow.