Bradford-White Corp BNTV, BNTH warranty SECTION Modes of Operation, Hydronic Heating Demand

Page 40 BRADFORD WHITE CORP.

SECTION 9.

Modes of Operation

The Brute Elite control allows the boiler to operate in many different modes of operation. The mode must be selected based upon the requirements of the installation. The following sections describe the basic operation of the Brute Elite in each of the different modes. Familiarize yourself with each mode and how the operation of the boiler varies, depending upon the installation and inputs the control is monitoring.

9.1 Hydronic Heating Demand

When using the Brute Elite for hydronic heating a call for heat must be supplied to the "T-T or Interlock" terminal. Once the call is supplied the control starts the boiler and system pumps and begins the ignition process. The ignition process consists of a prepurge, trial for ignition, and run period. The prepurge period starts on a call for heat once the fan RPM reaches a preset level. The trial for ignition period follows once the start-up RPM of the fan is reached. The trial for ignition period lasts 4 seconds during which the direct spark ignition system and gas valve are energized. At the end of the trial for ignition period the flame signal is compared with the preset flame threshold value. If the flame signal is higher than the flame threshold the Brute Elite enters "run". If the flame signal is below the threshold the Brute Elite returns to prepurge and starts the ignition process over. In "run" the Brute Elite monitors the flame signal, call for heat, safeties, and water temperatures and modulates as needed between 100% and 20% of rate to satisfy the call for heat.

9.2 Hydronic Heating with Outdoor Reset

Outdoor reset varies the control point setpoint based on the actual outdoor temperature. The reset function works as shown in Figure 32. When the outdoor air temperature reaches the "high outdoor temperature setpoint (HOD), the control point setting is adjusted to the low boiler temperature setpoint (LBT). When the outdoor air temperature reaches the low outdoor temperature setpoint (LOD), the control setpoint is adjusted to the CH/Outlet water setpoint temperature. HOD, LOD and LBT can be adjusted by accessing SETUP mode. CH setpoint is adjustable from the USER menu structure.

9.3Hydronic Heating with Domestic Hot Water (DHW) Priority

When using the Brute Elite for hydronic heating with domestic hot water priority a call for heat must be supplied to the "T-T or Interlock" terminal. Once the call is supplied the control starts the boiler and system pumps and begins the ignition process. The ignition process consists of a prepurge, trial for ignition, and run period. The pre-purge period starts on a call for heat

once the fan RPM reaches a preset level. The trial for ignition period follows once the start-up RPM of the fan is reached. The trial for ignition period lasts 4 seconds during which, the direct spark ignition system and gas valve are energized. At the end of the trial for ignition period the flame signal is compared with the preset flame threshold value. If the flame signal is higher than the flame threshold the Brute Elite enters "run". If the flame signal is below the threshold the Brute Elite returns to pre-purge and starts the ignition process over. In "run" the Brute Elite monitors the flame signal, call for heat, safeties, and water temperatures modulating as needed between 100% and 20% of rate to satisfy the call for heat. When a DHW demand is applied during a hydronic call for heat the priority feature forces the boiler to switch to the DHW demand for the priority time. The DHW priority demand forces the control to operate to the DHW setpoint, de-energizes the system pump and energizes the DHW pump.

9.4Hydronic Heating Using External Modulation Control

When using the Brute Elite for hydronic heating with external modulation control a call for heat must be supplied to the "T-T or Interlock" terminal. Once the call is supplied the control starts the boiler and system pumps and begins the ignition process. The ignition process consists of a prepurge, trial for ignition, and run period. The prepurge period starts on a call for heat once the fan RPM reaches a preset level. The trial for ignition period follows once the start-up RPM of the fan is reached. The trial for ignition period lasts 4 seconds during which the direct spark ignition system and gas valve are energized. At the end of the trial for ignition period the flame signal is compared with the preset flame threshold value. If the flame signal is higher than the flame threshold the Brute Elite enters "run". If the flame signal is below the threshold the Brute Elite returns to prepurge and starts the ignition process over. In "run" the Brute Elite monitors the flame signal, call for heat, safeties, and water temperatures. The boiler

Figure 32. Outdoor Reset Setpoint Temperatures.