FreezeCop
Operational Information

Overview

The FreezeCop TM digital freeze stat monitors one to five sensors which are affixed to a water-to-freon heat pump, and prevents the heat pump from freezing a heat exchanger and damaging itself. FreezeCop can reverse the freon flow and use some building heat to thaw a heat exchanger before it freezes. It can also disable the compressor(s) in a system should the need arise.

When FreezeCop determines the heat exchanger is going to freeze, it first attempts to warm the exchanger by reversing freon. Once the exchanger reaches a certain temperature, it continues heating for a number of seconds more before going back to normal operation. If the exchanger does not warm up fast enough, the system will shut down the compressor(s). FreezeCop counts the number of reverses it does to recover the system, and if there are too many reverses in a certain length of time (such as a low water flow situation), it will shut down the compressor(s) to avoid needless short-cycling.

Should FreezeCop shut the compressor(s) down, when the fault time-out expires, FreezeCop will check the temperature of the heat exchanger again. If it is not warm enough from geothermal loop or latent building heat (in other words it is frozen without a compressor even running), FreezeCop will not allow the compressor(s) to restart. This "extreme freeze fault" requires the FreezeCop to be power cycled before it will allow the compressor(s) to run again.

NOTE: During normal operation, if a temperature sensor becomes disconnected, FreezeCop will disable the compressor(s) to protect the heat pump.

Below, are the specifications, settings, and a technical description of how the FreezeCop does its job.

 

FreezeCop™ P/N 236-801-3 Time and Temperature Settings

*OEMs can order unique times, delays, cycle counts, and threshold temperatures.

 

Description

Power up

When power is first applied to the FreezeCop, all three LEDs will illuminate for 2 seconds.

Normal operation

During normal operation, contact 7 is open. Contacts 3 & 4 are closed to provide power to the compressor contactor and the Fault Indicator LED & the Reverse LED are off.

Reversing

Initially, when the temperature drops below the freeze temperature, contact 7 supplies 24 VAC to the reversing valve and the Reverse LED is illuminated.

Returning to normal

Assuming the temperature reaches the thaw temperature in less than the maximum thaw time, the controller enters the reversing delay period where the reversing valve remains energized even though the exchanger has thawed out. Afterwards, contact 7 returns to an open state and the Reverse LED goes off.

Fault from not thawing out

If the temperature does not reach the thaw temperature in less than the maximum thaw time, contact 7 is opened to return the reversing valve to its normal state and contact 3 & 4 are opened to break power to the compressor contactor. The Reverse LED goes off and the Fault Indicator LED goes on solid. The controller enters a fault delay and nothing is done during the fault delay.

Fault from too many reverses

If the number of reverses exceeds the fault threshold, contact 7 is opened to return the reversing valve to its normal state and contact 3 & 4 are opened to break power to the compressor contactor. The Reversing LED goes off and the Fault Indicator LED goes on solid. The controller enters a fault delay and nothing is done during the fault delay.

Returning to normal operation

Assuming the temperature is above the freeze temperature at the end of the fault delay, the controller will close contacts 3 & 4 to close the power circuit to the compressor contactor and the Fault Indicator LED will begin a 1 blink sequence.

Extreme freeze fault

If the temperature is at or below the freeze temperature at the end of the fault delay, the relays will remain unchanged, the Fault Indicator LED will begin a 2 blink sequence, and the FreezeCop will "lock" in this condition until the unit's power is cycled.

Other fault indicator functions

  1. During normal, reversed, and 1 blink operation, if the sensor becomes disconnected, the signal becomes illegible, or the temperature reported is considered to be absurd, the Fault Indicator LED will blink 3, 4, or 5 times to indicate the condition respectively. As soon as the fault is corrected, the 3, 4, or 5 blink indication will stop being displayed, and if there are no other faults, normal operation will be resumed immediately.
  2. Two faults can be stacked. That is to say for example, if running in the 1 blink mode (a fault has previously occurred) and the sensor becomes disconnected, the Fault Indicator LED will blink once, pause, then blink three times, pause, and then repeat.

Fault Indicator has the following modes

Off OK
On System currently in a fault timeout
1 Blink Fault happened at some point
2 Blink Extreme Freeze Fault, maintenance required
3 Blink No sensor present
4 Blink Noisy sensor, reroute hookup wires
5 Blink Sensor temperature out of range (above 212 ºF or below -4 ºF)

 

Specifications

General

Accuracy +/- 0.5 ºC (0.9 ºF) Max, +/- 0.25ºC (0.45ºF) Typical
Voltage 24 VAC 50/60 Hz
Current 50 mA
Max Sensors 5

Inputs

1 236-800-X Sensor Red Wire
2 236-800-X Sensor Black Wire
5 Temperature Select
6 Temperature Select
8 24 VAC Common
9 24 VAC Power

Outputs

3 NC Freeze Limit Contact #1
4 NC Freeze Limit Contact #2
7 Reversing Valve 24VAC
LED Green - Power Indicator
LED Red - Reversing Valve Indicator
LED Red - Fault Indicator

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