Burnham RTC (Return Temperature Control) Instrukcja Instalacji Pobierz pdf (Strona 4)

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Section B: Control Operation

HEAT DEMAND

A heat demand is required in order for the control to provide heat by firing the boiler and opening the 3-way diverting valve. To

generate a heat demand, apply between 24 and 240 V (ac) across the Heat Demand terminals (1 and 2). Once voltage is applied,

the Demand pointer is displayed in the LCD.

When the heat demand is removed, the 3-way diverting valve is fully closed before the control is allowed to register a new heat

demand. The Demand pointer will be displayed whenever voltage is present on the Heat Demand terminals, even if the heat

demand is not registered. The 3-way diverting valve is closed to ensure the boiler is protected in the next boiler cycle.

Optionally, the control can be set up to target a setpoint mix supply temperature or outdoor reset temperature through the diverting

valve.

OUTDOOR RESET RATIO

When the control is used as a mixing reset control, the control uses

an outdoor sensor to measure the outdoor temperature. The reset

ratio increases the mix water temperature for every degree the outdoor

temperature falls. The slope of the reset ratio determines the rate at

which the temperature increases with falling outdoor temperatures.

The reset ratio is adjustable using the mix design (MIX DSGN) and the

outdoor design (OUTDR DSGN) settings.

Fixed PointFixed Point

By Changing

the Mix Design

and the Outdoor

Design settings

the Reset Ratio

changes.

By Changing

the Mix Design

and the Outdoor

Design settings

the Reset Ratio

changes.

70˚F

Outdoor Reset

When the outdoor design (OUTDR DSGN) setting is set to a temperature, the control calculates a mix supply temperature based

on the outdoor air temperature and the programmed reset ratio. An outdoor sensor and a mix supply sensor must be installed.

Setpoint Control

When the outdoor design (OUTDR DSGN) setting is set to OFF, and there is a mix supply sensor installed, the control supplies a

fixed mix supply temperature equal to the MIX TARGET setting. An outdoor sensor is not required during this mode of operation.

No Diverting Valve

If a diverting valve is not installed, the outdoor design (OUTDR DSGN) is set to OFF. The boiler return sensor must be installed

to provide monitoring of the boiler conditions.

Floating Action

A 24 V (ac) floating action actuator motor is connected directly to the control on the R, R and N terminals (9, 10 and 11). The

R on terminal 9 is used to open the 3-way diverting valve to the system. The valve can open either in the clockwise or the

counterclockwise direction depending on the orientation of the valve. The R on terminal 10 is used to close the valve. The control

pulses the actuating motor to open or close to maintain the correct mixed supply water temperature at the mix sensor when

there is a heat demand. A visual indication as to whether the control is currently opening or closing the 3-way diverting valve is

displayed in the LCD.

Boiler Protection

The control is capable of providing boiler protection from cold return water temperatures. If the boiler sensor temperature is

cooler than the BOIL MIN setting while the boiler is firing, the control reduces the output to the 3-way diverting valve. This limits

the amount of cool return water to the boiler and allows the boiler temperature to recover. This feature can only be used if a 3-way

diverting valve is installed.

Exercising

The control has a built-in exercising function. If the boiler recirculating pump or valve has not been operated at least once every

3 days, the control turns on the output for a minimum of 10 seconds. This minimizes the possibility of a pump or valve seizing

during a long period of inactivity. The control ensures that the diverting valve operates over its entire range at least once each

exercising period. While the control is exercising, the Test LED flashes.

Note: The exercising function does not work if power to the control, pump, or valve is disconnected.

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