This guide covers general guidance and 'good practice' for the installation of a thermoelectric assembly. It is suitable for the range of Adaptive thermoelectric assemblies but the general guidelines can be applied to other brands. It is not an exhaustive list, but provides some initial indicative guidance on installation and consideration for the system best performance.
Thermoelectric assemblies are typically mounted through a cut-out in a cabinet or enclosure in order to cool the electronics or system inside. In order to efficiently cool the target device, it is recommended that the cabinet/enclosure is insulated as much as practically possible without affecting the function of the target device, insulating aids the time in which the cooler can get to steady state temperature as well as reducing the power consumed by the device. This may also allow a reduction in power supply or even cooling power requirements.
Figure 1: An example of an insulated enclosure using Adaptive’s thermoelectric assembly test rig
Adaptive’s thermoelectric assembly range all have forced air cooled heatsink’s on the hot side (usually indicated by the red fan cover plate), this side of the assembly requires mounting external to the enclosure/cabinet. The hot side of the assembly requires good ventilation in order to draw ambient air into the fan and exhaust the heat on the heatsink, leave approximately 20-40mm clearance around the assembly for optimal heat exhaustion performance (smaller assemblies would have the lower end of the clearance scale).
AR-AR Thermoelectric coolers (Air to Air)
This type of cooler has a heatsink with forced air cooling on both sides of the assembly, this usually allows greater cooling power and a quicker reduction in temperature on the cold side.
DA-AR Thermoelectric Coolers (Direct to Air)
This type of cooler has a heatsink and fan on the hot side of the assembly and a mounting block on the cold side, usually with a selection of mounting holes in.
Condensation can collect on the cold side of a thermoelectric assembly (inside the cabinet) if the dew point is reached, therefore best practice is to follow the vertical mounting arrangement below.
Figure 2: Two assemblies mounted vertically on side of cabinet & one assembly mounted horizontally
The thermoelectric assembly, if mounted vertically will allow any condensation to run down and away from the assembly. If you need to mount horizontally then care must be taken in ensuring the device for cooling is protected from any potential condensation, one method of doing this is to raise one end of the assembly at an angle and encourage the condensation to run off in one direction. Best practise not to mount the cold side upwards, for condensation and convection reasons.
Figure 3: Example of the thermoelectric assembly upside down
Thermoelectric assemblies are provided with a selection of tapped mounting holes in the cold plate if it is direct to air cooler, these may be M4 or M5 depending on the assembly size, the position of the holes also changes respective to the size of the cooler. Air to air coolers have M4 or M5 tapped holes in the hot side heatsink and again positioning & thread is dependent on size. The coolers should always be mounted with captive screws or serrated washers to ensure the assemblies do not become loose from the enclosure over time as this will affect cooling performance. When using the cold plate on a DA-AR assembly it is important that whatever the cold plate is mounted to (device, enclosure or plate) has a good surface flatness of at least 0.05mm over 100mm2.
Figure 4: AR-AR mounting positions (left) DT-AT mounting positions (right)
To allow the thermoelectric assembly to be powered up or wired to the system in which is to be cooled, either flying leads or terminal connections are supplied (dependent on assembly size). These are commonly just the incoming DC power connections (which drive the fans & thermoelectric module) at the required voltage, usually 12 or 24V (48V is possible too). Often included is a temperature sensor (which goes open circuit when temperature reached) which can be connected in series with the incoming power source or used as an alarm output to another part of the system.
Figure 5: DT-AR-014 Wiring Example