Rheem 325 II Series Service Instructions Manual page 15

The circulator speed is then adjusted up or down to maintain the heat exchanger water
outlet temperature at a control point of 26°C. The circulator speed is adjusted every 30
seconds, in very small increments only. This ensures the controller is only able to maintain
the 26°C control point whilst the heat input from the refrigeration system is very low (as it is
at start-up).
As the refrigeration system begins to generate useful heat, the temperature at the heat
exchanger water outlet will rise more quickly and pull away from the control point. In this
way, the system will only proceed from Heat Pump Pre-Heating when the heat exchanger
water outlet temperature is rising at an acceptable rate.
The system goes to Heat Pump Heating under either of the following conditions:
Heat exchanger water outlet temperature is greater than 35°C for more than 2
minutes
The circulator speed reaches its maximum
Note: This means the system will always be in Heat Pump Pre-Heating for at least
2 minutes. This is because the circulator speed can not reach its maximum within 2
minutes, as it is only adjusted every 30 seconds.
Heat Pump Heating
During Heat Pump Heating, the green LED will display 3 flashes.
The compressor and fan continue to operate, and the circulator runs at full speed. The
system can not go from Heat Pump Heating back to Heat Pump Pre-Heating.
Heat Pump Heating ceases and the system returns to Standby Mode when the tank
sensor detects a temperature greater than 60°C.
ELEMENT MODE
At all times when power is available, the controller monitors the condition of the heat pump
system. Should the ambient temperature be outside the heat pump‟s operating limits or a
fault is detected, the controller initiates Element Mode which uses the booster element to
heat the water.
The booster element is controlled by the mechanical thermostat on the storage tank and
remains energised until the mechanical thermostat contacts open at approximately 70ºC,
at which point the element, controller and LEDS are de-energised.
Element Mode – Ambient
During Element Mode – Ambient, the green LED will display one long flash.
Element Mode – Ambient is utilised if the ambient temperature is outside the heat pump‟s
operating limits. The conditions for Element Mode – Ambient depend on whether or not the
heat pump is operating. Therefore, Element Mode – Ambient is utilised under the following
conditions:
The evaporator sensor temperature is less than 4°C or greater than 45°C when the
system is in Standby Mode and heating is required, and the compressor start delay
has elapsed (it has been 45 minutes since the compressor last ran)
TM077: 325 & 410 Series II Heat Pump Service Instructions
Rev 00: Issued April 2014
This document is stored and maintained electronically by Service. All printed copies are deemed uncontrolled.
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