Lochinvar FTxl 500 Service Manual page 36

2
Maintenance
Test low water flow conditions
This test is to be carried out once
NOTICE
the FTXL 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.
Test procedure
1. Locate the pinhole button above the RESET button on
the display board (see page 7). Insert a thin wire (such as
a paper clip) into the hole and press the button once and
hold for 5 seconds to place the boiler into Service Mode.
In Service Mode the boiler will fire at ignition speed and
will then modulate up to full fire.
2. Allow the unit to progress through its normal diagnostics
and pre-purge programming.
3. 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 (
is maintained.
4. 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.
5. While slowly shutting off the isolation valve, refer to the
Status Screens to watch the behavior of the boiler. These
screens allow you to monitor the inlet temperature,
outlet temperature, and
6. When the T reaches 70˚F (39°C), the control will
attempt to modulate the firing rate down to protect it
from low flow conditions.
7. When the T reaches 80°F (44°C), the control module
will turn off the burner.
down, the test was successful.
8. Completely open the isolation valve on the outlet piping
of the boiler.
9. Resume operation.
NOTE: This lockout is a soft lockout. Once the
decreased to an acceptable level and there is a call for
heat, the unit will fire again to meet the demand.
36
T.
If the control module shuts
T has
Figure 2-3 Adjust outlet isolation valve
ADJUST OUTLET
ISOLATION VALVE ONLY
T)
Service Manual
IMG00996