Bradford White BWCH Operations Instructions download pdf (Page 43)

Page 43

COPPER BRUTE II (500 - 2000)

Figure 29. Temperature Control Min & Max.

minimum amount of time before turning on the next

stage. After the minimum time delay between stages

has expired, the control examines the control error to

determine when the next stage is to re. The control

error is determined using PID logic.

Proportional compares the actual operating

sensor temperature to the boiler target temperature.

The colder the temperature, the sooner the next stage

is turned on.

Integral compares the actual operating sensor

temperature to the boiler target temperature over a

period of time.

Derivative determines how fast or slow the

operating sensor temperature is changing. If the

temperature is increasing slowly, the next stage is

turned on sooner. If the temperature is increasing

quickly, the next stage is turned on later, if at all.

Boiler Mass (BOIL MASS) – The boiler mass

setting allows the installer to adjust the control to the

thermal mass of different types of heat sources used.

The boiler mass setting automatically determines the

interstage differential, interstage delay on, interstage

delay off, minimum on time and minimum off time of

the stages when PID staging is used. A higher thermal

mass setting provides slower staging, while a lower

thermal mass setting provides faster staging. Copper

Brute II boilers and water heaters are low-mass

appliances, and therefore, should be used with the

lower thermal mass setting. Set BOIL MASS to “1”.

6.4.3 Boiler Minimum (BOIL MIN)

The minimum boiler setting (BOIL MIN) is the

lowest water temperature that the control is allowed

to use as a target temperature. During mild conditions,

if the control calculates a target temperature that is

below this setting, the target temperature is adjusted to

at least the minimum setting. During this condition, if

the unit is operating, the MIN segment turns on in the

LCD while the target temperature or operating sensor

temperature is viewed. For Copper Brute II units, this

must be set no lower than 120°F (49°C) to protect the

unit

from condensing on the heat exchanger (see Figure 29).

6.4.4 Boiler Maximum (BOIL MAX)

The boiler maximum (BOIL MAX) is the highest

water temperature that the control is allowed to use

as a target temperature. If the control does target

BOIL MAX, and the boiler outlet sensor is near the

BOIL MAX temperature, the MAX segment turns on

in the LCD while the target, inlet, outlet or supply

temperature is viewed (see Figure 29).

6.4.5 Boiler Target Temperature

The target temperature is determined from

the mode of operation. The control displays the

temperature that is currently trying to maintain at the

operating sensor as BOIL TARGET in the View menu.

The operating sensor for modes 1, 3 and 4 is the outlet

sensor (on the Copper Brute II). The operating sensor

for modes 2 and 5 is the supply sensor (in the system

or primary loop). If the control does not presently have

a requirement for heat, it displays “- - -” in the LCD.

There is no target temperature generated in mode 6

(external controller mode).

6.4.6 Pump Operation

The pump terminals (Pmp Pmp) are energized

with 24 VAC to control a eld supplied pump

contactor. During setpoint operation (modes 1 and 2),

the terminals are energized whenever there is a heat

demand. During dedicated DHW operation (mode

3), the terminals are energized whenever there is an

internal heat demand. During outdoor reset (modes 4

and 5), the terminals are energized whenever there is

either a heat demand and the control is not in Warm

Weather Shut Down (WWSD), or whenever there is

a setpoint demand. During WWSD, if the pump has

not operated at least once every 70 hours, the control

energizes the terminals for 10 seconds. This minimizes

the possibility of the pump seizing during a long

period of inactivity. During External Boiler Operation

(mode 6), the pump contact closes whenever there is a

heat demand.

Boiler Purge (PUMP DLY) – After a demand

is satised, the control continues to operate the pump

for a period of time. The length of time that the

pump continues to run is based on the pump delay

setting. Once the last stage of the control turns off,

the control keeps the pump contacts energized for

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Bradford White BWCH Operations Instructions Page 43

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