Temperature Controller
From RTAW Reefpedia
Contents |
Introduction
Temperature controllers are automated devices which monitor the water temperature using a temperature probe then activate other pieces of equipment to heat (heaters) or cool (chillers, fans) the system as required.
The temperature controller generally use a thermo-couple device as a sensor (probe) which is immersed in the system water (either the tank or sump) to monitor the water temperature. The results of measurements are monitored by a micro-processor which then decides based on it's settings when to activate the the appropriate equipment to heat or cool the water.
Devices
Popular devices which can do this include:
- Profilux Controllers
- ATC 800/ATC 800+
- Ranco ETC (Electronic Temperature Control) Controllers - available in both Single (Model CD-22890) or Dual Stage (Model CD-22889), pre-wired or control unit only. Manufactured for commercial equipment and the food industry they are suitable for chillers up to 1/2hp.
Set Up
When setting up a temperature controller, there are 4 important things to take into account:
- target temperature,
- hysteresis,
- switched devices, and
- switched devices setup.
Target Temperature
The target temperature will depend on the livestock and their tolerances, but most marine systems operate in the region of 25oC to 27oC. See temperature for more details.
Hysteresis
Hysteresis refers to systems which have memory; that is, the effects of the current input to the system are not felt at the same instant.[1] In respect to marine aquaria, this is considered to be the temperature fluctuation that the controller is setup to tolerate before stepping to make a correction. Typically, the better the controller, the smaller the temperature range that can be set before corrective steps are taken. A 1oC resolution is more than sufficient for most situations.
Coupled to hysteresis is the controller feature to protect chiller compressors, a quality controller will not allow a chiller to be reactivated within 2 to 3 minutes of it last being switched off. This will improve the lifespan of the chiller unit. This is not required for fans or heaters.
Switched Devices
The controller has to be rated to at handle the total wattage of heaters to be connected to the heating circuit and the chiller connected to the cooling circuit. A margin of error should be introduced to ensure that rated wattage is not exceeded.
The switched devices need to have their own thermostats set so that they will not compete with the controller.
Great care should be taken in connecting the inputs and outputs to the controller, with a licensed electrician engaged to perform / inspect all aspects of a DIY project.
Switched Devices Setup
Heater
Set to 2oC higher than the target temperature. This allows for the controller to activate the heater and not the heaters internal thermostat. If the controller happens to fail and leave the heater on, then the internal thermostat will kick it before the system gets too hot.
Chiller
Set to 2oC below the target temperature. This allows for the controller to activate the chiller and not the chillers internal thermostat. As with a heater, if the controller fails and leaves the chiller on, then the internal thermostat will shut it off before the system gets too cold.
