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Series 8900 Hydronic Space Heating Control System

Series 8900 Hydronic Space Heating Control System Overview: This control panel allows for a proportional, dynamic response based on an accurate calculation of required return temperature based on the programmable difference between outside design temperature, outside air temperature, and outside cutoff temperature.

8900 Operational Sequence
1) The control panel monitors the outdoor and return line temperatures and takes action based on control factors entered into the keypad.

2) The cycle begins with the monitoring of outside air temperature, and information on desired setback operations.

3) As the temperature drops below the outdoor cutoff temperature, the system begins to maintain the minimum return water line temperature. The lead boiler is then brought on line where it will fire intermittently while heat is called for by the system controller. The lead boiler will shut off once the return line temperature reaches the required temperature. Also, when the lead boiler is brought on line the control cycle count begins.

4) At the next control cycle, which is adjusted by a rate-of-change factor, the next stage is activated if the return line temperature is still below the required temperature. At each cycle point, additional boilers will be brought on line. However, before bringing additional boilers on or off line, the system will consider the existing and required return water line temperatures, control cycle, and the calculated (or manually entered) reset ratio.

5) The controller continues to monitor the outdoor air temperature and checks for setback periods. The required return line temperature will be adjusted if a setback period is entered. The system anticipates recovery from setback periods and may bring on fewer boilers to fire longer.

6) As the return temperature rises above the required temperature, the lead boiler will be taken off line. At each of the following control cycles, additional boilers will be taken off line. The lead boiler is taken off first to ensure that the last boiler on line completes at least one full cycle.

7) As the outdoor temperature rises above the cutoff temperature, the system will return to the minimum required return line temperature and then discontinue its call for heat.

Features

The Series 8900 controls up to 12 boilers (expandable to 24 boilers) and includes the following features:

  • Adjustable staging order with control of minimum cycle times
  • Setbacks of "same-as" or "7-day"
  • Up to four cycles per day
  • Look-ahead recovery from setback
  • Delayed setback
  • Override setback
  • Manual system override
  • Keyboard lockout
  • Extra temperature monitoring capability
  • LED Display
  • Rechargeable battery backup
  • Fail-safe mode that reverts to the individual boiler controls
  • Five-year warranty
The outdoor temperature sensor is enclosed in a weatherproof painted steel enclosure with a key lock and a password protected keypad entry.