Lochinvar 400-801 service manual Test low water flow conditions, Test procedure

2 Maintenance

Test low water flow conditions

NOTICE	This test is to be carried out once the
	Knight XL 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.Set the [SH1 SETPOINT:] set point to the max user set point (reference Section 10 of the Knight XL Installation and Operation Manual). Max user set point will allow the boiler to operate without reaching this set point. The boiler will require a load large enough to dissipate a large portion of the heat it is generating.

2.Simulate a call for heat by placing a jumper wire across the enable contacts #19 and 20 on the low voltage terminal strip located at the rear of the unit (FIG. 2-6).

3.Allow the unit to progress through its normal diagnostics and pre-purge programming.

4.Locate the pinhole button below 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.

Service Manual

9. When the T reaches 60°F, the control module will turn off the burner. If the control module shuts down, the test was successful.

10.Disconnect the jumper wire from the low voltage terminal strip connected in Step 2.

11.Completely open the isolation valve on the outlet piping of the boiler.

12.Resume operation.

NOTE: This lockout is a soft lockout. Once the T has decreased to an acceptable level and there is a call for heat, the unit will fire again to meet the demand.

Figure 2-6Low voltage terminal strip and enable contacts

LOW VOLTAGE CONNECTION BOARD

ENABLE

CONTACTS

IMG00103

5.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.

6.When the unit stabilizes, begin to slowly shut off the isolation valve on the outlet piping of the boiler (see FIG. 2-7). This will begin to restrict the flow and simulate a low flow condition.

7.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 T.

8. When the T reaches 55˚F, the control will attempt to modulate the firing rate down to protect it from low flow conditions.

Figure 2-7Adjust outlet isolation valve

ADJUST OUTLET

ISOLATION VALVE

ONLY

IMG00098

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