Bradford-White Corp BNTV, BNTH SECTION Trouble Shooting, Sequence of Operation, Short Cycling

Brute Elite Page 49

11.2.9Gas Pressure Switches (optional)

The high and low gas pressure switches are 24V

manual reset switches that act to cut power to the gas valves if the gas pressure is too low or too high for proper operation. The gas pressure switches used are integrally vent limited, and do not require venting to atmosphere. To remove a switch, remove the screw on the plastic housing and pull the clear cover off. Disconnect the two wires from the screw terminals. Twist the switch off the pipe nipple. Reassemble in reverse order. For natural gas, set the low gas pressure switch to 3" w.c. For propane, set the low gas pressure switch to 5" w.c. For natural and propane, set the high gas pressure switch to 14".

11.2.10 Gas Conversion

Brute Elite units can be converted from natural to propane gas or from propane to natural gas easily in the field. Some units require the addition of a gas orifice along with proper gas valve adjustment. Other units require no additional parts, only proper gas valve adjustment. Please contact the Bradford White factory for specific information regarding the gas conversion of an appliance. If a gas conversion is performed, the unit must be identified with the appropriate gas labels and a conversion sticker to allow technicians performing maintenance in the future to properly identify the gas type of the appliance.

SIZE (MBTU)	KIT NUMBER
80	CA006201
105	CA006202
150	CA006203
199	CA006204
210	CA006204
285	CA006205
399	CA006207
500	CA006207
600	CA006207
750	CA006207
850	CA006207

Table 17. Propane Gas Conversion Kits.

SECTION 12.

Trouble Shooting

12.1 Sequence of Operation

Brute Elite is a cold start appliance that should start only on a call for heat from a tank aquastat, room thermostat, zone valve end switch or other space temperature control device.

1.Upon a call for heat: (a) the internal pump and system pump will start; (b) the blower will begin a 30 second pre-purge.

2.Following the prepurge cycle the direct spark ignition will spark and will begin a 4 second trial for ignition. The unit is allowed one or three ignition retries.

3.The gas valve will then be energized and a reduced rate ignition will occur. The unit will remain in a reduced rate start-up period for several seconds.

4.After the reduced rate start time is over, the unit will be in normal operation. Firing rate will modulate based on the heating load via the temperature controller settings and readings.

5.When the call for heat is complete, or the unit reaches its setpoint temperature, the gas valve will close, and the fan will continue to run for its 20 second post- purge. If a pump delay time is used, the pump will continue to run for the specified amount of time (adjustable from 0.1 to 10 minutes).

12.2 Short Cycling

Because Brute Elite is a modulating boiler, and its input will decrease when there is a reduction in heating load, short cycling is greatly reduced. If the heating load drops below the minimum input of the boiler for an extended period, the boiler will have a tendency to short cycle. This can be a symptom of improper control strategy or setpoints, or a load distribution problem. Brute Elite has a built-in anti-short cycle (ASC) feature. ASC is a timed setting that will delay the boiler start for a specified time after one call for heat is completed. ASC time may be adjusted as desired (see Section 8 for more information).

12.3 Error Codes - See Table 18.