Bradford-White Corp Hydronic Boiler, Water Volume Heater, BMT2V, BMT2H Operating Instructions

Page 26 BRADFORD WHITE CORP.

5.3 External Staging Control Wiring

WARNING

Improper field wiring may result in fire or explosion which can cause property damage, severe injury, or death. Make only wiring connections which are in accordance with the Installation and Operation manual.

AVERTISSEMENT

Un câblage incorrect lors de l’installation peut causer un incendie ou une explosion pouvant entraîner des dommages matériels, de graves blessures ou la mort. Ne faire seulement que les connexions conformes au Manuel d’installation et d’exploitation.

If controlling the stages of the BMT2 from an

external source (multiple boiler control, BAS, etc.), wire Stage 1 to the terminals marked "Input Stage 1" and "Stage 1", and wire Stage 2 to the terminals marked "Input Stage 2" and "Stage 2". The "Local/Remote" selector switch above the terminal strip must be placed in the "Remote" position for the external controller to manage the staging.

If it is intended to use the BMT2's on-board 2- stage controller, no extra wiring is necessary. Ensure the Local/Remote selector switch is in the "Local" position.

SECTION 6.

Operating Instructions

6.1 Sequence of Operation

Upon initiation of the main power switch, 120V will be sent to multiple items. Among these are the open contact fan relays, open contact ignitor relay, open contact pump relay, ignition control module(s) and open contact lock out indicators (the optional alarm package uses this). In addition to these, 24V will travel through the optional gas pressure switches and optional auto reset high limit. 24V will then travel through the block flue switch and the manual reset high limit to the temperature controller.

Upon a call for heat from the BMT2’s internal control or an external staging control, 24V travels through the field interlock (if closed) and then to the ignition control(s) “T-stat” terminal (500-750 models are equipped with one ignition control and models 1000- 2000 are equipped with two ignition controls).

When “T-stat” on an ignition control is energized, its fan will energize and the ignition control will seek signal from the “pressure circuit”. The pressure circuits consist of the flow switch and proof of fan.

Sizes 500-1000 calls for fan, fan prove, initiate pump then prove flow, after which “pressure circuit” has been satisfied.

Sizes 1250-2000 calls for pump, proof of flow, initiate fan then prove fan, after which “pressure circuit” has been satisfied. The fan prove will only occur for the active stage that has been called.

When pressure circuit has been satisfied, proving combustion air and adequate water flow, the hot surface igniter will initiate. The ignition control checks that the igniter current reached a predetermined level then will dwell momentarily. When dwell time is complete the gas valve will open.

After a 4-second trial for ignition, the igniter switches off. Unless a flame is detected by the flame sensor (a minimum value of 0.4µA), the gas valve will close and The ignition module will either attempt ignition again (up to three times) or will lock out if the optional lockout ignition module is used.

If flame is sensed, the burner will continue to fire as long as there is a call for heat and adequate flame signal. If there is a subsequent loss of flame signal, the burner will attempt re-ignition up to three times (only once if optional lockout ignition is used.) When the call for heat is satisfied, the gas valves(s) close and the blowers continues to run for 30 seconds.

The pump will continue to run for 0.1 to 10 minutes, depending on what the pump time delay has been set to. Brute Deluxe sizes 1,000-2,000 have two ignition controls that control the individual stages. If one ignition control should fail for any reason, the remaining module can operate its burners independently. (Note that if a single blower is disabled on units 1250-2000, the other fan will continue to operate and safely allow the boiler to run with a single stage.)

6.2 Filling the System

1.Ensure the system is fully connected. Close all bleeding devices and open make-up water valve. Allow system to fill slowly.

2.If make-up water pump is employed, adjust pressure switch on pumping system to provide a minimum of 12 psi (81.8 kPa) at the highest point in the heating loop.

3.If a water pressure regulator is provided on the make-up water line, adjust the pressure regulator to provide at least 12 psi (81.8 kPa) at the highest point in the heating loop.

4.Open bleeding devices on all radiation units at the high points in the piping throughout the system, unless automatic air bleeders are provided at such points.

5.Run system circulating pump for a minimum of 30 minutes with the boiler shut off.

6.Open all strainers in the circulating system, check flow switch operation, and check for debris. If debris is present, clean out to ensure proper circulation.

7.Recheck all air bleeders as described in Step 4.

8.Check liquid level in expansion tank. With the system full of water and under normal operating pressure, the level of water in the expansion tank should not exceed ¼ of the total, with the balance filled with air.

9.Start up system according to the procedure in this manual. Operate the entire system, including the