Crown Aruba 5 Installation Manual

10) Once the ignition module detects the presence of a pilot ame, voltage is applied across the main valve (terminals MV and

MV/PV on the valve), opening the valve and establishing main ame.

11) If the water temperature climbs above the high limit setting during the call for heat, the burner will shut down, and the vent

damper close, while the Heating Circulator continues to operate. The ignition sequence will restart (from Step 4) when the

water temperature falls to the high limit setting (HL) minus the high limit dierential (HdF).

12) A call for DHW results in a sequence of operation that is identical to that described above except for omission of the thermal

purge function described in (3).

E. Safety Control Operation

Blocked Vent Switch - Automatically interrupts main burner operation in the event that a blocked vent causes ue gas to spill

from the draft diverter opening. This switch is equipped with a reset button which must be pressed to restore normal burner

operation. An open blocked vent switch is indicative of a problem with the vent system and/or the combustion air supply. If the

blocked vent switch opens, the cause of this problem must be found and corrected by a qualied gas service technician before the

blocked vent switch is reset.

Flame Roll-out Switch - Automatically interrupts boiler operation when ames or excessive heat are present in vestibule. The

ame roll-out switch is a single use device which must be replaced by an identical switch in order to restore normal operation.

An open ame roll-out switch is usually indicative of a plugged heat exchanger. The cause of the ame roll-out must be found

and corrected by a qualied gas service technician, and the switch replaced with an identical one, before the boiler is returned to

operation.

Low Water Cut-o (LWCO) – The probe type low water cut-o supplied with this boiler prevents the boiler from ring if the wa-

ter level in the boiler is below that of the supply tapping. The water temperature sensor is installed in a special insulated “electro

well” that doubles as an electrode for the LWCO. The LWCO applies voltage between this well and the boiler ground. If water is

present at the well, the LWCO sensing circuit will detect current owing from the well to ground through the water and will close

a set of contacts in the limit circuit, allowing the burners to re.

A green LED illuminates when the LWCO is powered. A yellow LED illuminates when water is not present at the level of the

well. The TEST button simulates the absence of water in the boiler by breaking the circuit described above.