Review – Chinese heating / cooling controller ITC-308

The Inkbird ITC-308 is a digital heating / cooling controller with two independent outputs for heating and cooling, and using a thermistor temperature sensor.


Above is the ITC-308 package.

Above is the rating plate on the ITC-308. It is rated for 10A, but there is no indication of the basis of that rating (eg resistive, inductive, high inrush, motor etc).

Above, the relay rating plate. This is a form A relay, and from the datasheet rated for 10A resistive load at 277VAC. It needs derating for a motor load (such as a refrigerator or air conditioner compressor).

The output sockets suit Australian plugs. It is worth checking that it is the active line that is switched for standards compliance, some early production appears to have not been so.

Above, a the interior of the controller. In a sense, it was not really designed for a three wire mains cord, the protective earth is connected through using the white crimp joiner at left, and the colour code is non-standard.

At the top of the view is a switched mode power supplies. These are a great RFI / EMC risk, but without measuring emissions according to the standards, a quick test reveals low emissions detected on a HF radio nearby.

No detail is given of the thermistor, though replacements are sold on eBay for about $10.

The circuit was traced out and measurements made to deduce the thermistor parameters. The thermistor appears in series with a 10kΩ resistor from 5V. The voltage across the thermistor was measured at two displayed temperatures, and the resistance calculated for each condition.

The thermistor parameters can be calculated from the temperature,resistance pairs.

Above, the calculator gives values which are probably from a common nominal 10kΩ B=3435 NTC thermistor.

A subsequent test (after the connectors were inserted in the sensor cable) was supplying a known resistance and recording the displayed temperature.

Again these are very close to the common 10kΩ B=3435 NTC thermistor.

As always, you may need to adjust the calibration around the temperature of interest using the set CA facility. Budget NTCs are not precision things, and the curve fit is only an approximation, a poor one in some thermostats.


The Inkbird ITC-308 is a nicely packaged and convenient temperature controller with independent heating and cooling outputs.

It is rated at 10A for resistive loads (AC-1), but it is doubtful that AC-3 motor loads of more than 20-30% of that should be used.

The thermistor is a common 10kΩ B=3435 thermistor.

Update 28/12/2019

Some product is now shipping with a pair of connectors in the thermistor cable. The connector is a 3.5mm TRS line jack on the thermostat side, and 3.5mm TRS line plug on the thermistor side. Wiring is black to T, W to S.

This allows easy replacement of the thermistor (I see them on Amazon), and use of the controller with various systems with a thermistor embedded into each controlled system.