Product information 

Enjoy an important energy savings feature available only on some high-end heat-pumps.

Ever wondered why your heat-pump initiates those annoying defrost cycles even with little or no ice build-up on the outdoor coil?

Install the  “T-eco” and eliminate unwanted defrost cycles. And start enjoying much improved home comfort

heat-pump efficiency and reduced home heating cost.

T-eco front panel view.

          T-eco demand defrost control key features and advantages:

— Installed as “add- on” with most heat-pumps.

— Suitable for single or 2 stage air source heat-pump with time-defrost.

— No modifications required for the heat-pump defrost control board.

— Straight forward installation can be performed by most homeowners.

— Compact and robust, sealed 3”x 3” x 1.5” outdoor enclosure.

— LED status indicator and operational diagnostics.

— Rated for –25°C (-13°F) active /–40°C (-40°F) standby mode.

— Power consumption < 1W @ 24v AC

— Fewer defrost cycles result in higher heat-pump operating efficiency, improved home comfort and reduced heat-pump wear & tear.

— Optional “compressor saver” heat-pump shutdown circuit detects absence of a defrost cycle 95 minutes after command is given by T-eco to start a defrost cycle.








Air based heat-pump operation

Most heat-pumps on the market use inefficient “time-based“ defrost to melt ice build-up on the outdoor coil.

A typical time-based defrost control board can be identified by the presence of “30/60 and 90 min.” delay jumper options.

When the outdoor temperature drops below approx. +5°C/41°F the defrost timer is activated.

A defrost cycle is initiated when the total accumulated compressor run time matches the selected jumper delay.

During defrost the heat-pump operates in AC mode with the outdoor fan disabled. Warm indoor air now is removed from the house to heat the outdoor coil.

Depending on the outdoor temperature the defrost cycle can last up to 10 minutes.

Because the sensor mechanism is time/temperature based, defrost cycles are initiated even with little or no ice build-up on the outdoor coil.

As result, up to 70% * of all defrost cycles initiated by the heat-pump may not be required wasting energy and money.

Defrost cycles cause discomfort to its occupants when cold air is dispersed throughout the house.


* climate dependent.

T-eco installed below the defrost control compartment of a 36000 BTU heat-pump.

Operation and installation.


A combination of ambient sensors and control logic prevents unnecessary defrost cycles from occurring. The unit takes control of the heat-pump outdoor coil thermostat output by sending a 24vAC command to the heat-pump defrost control board only when actual coil frosting conditions are detected.

After about 8 hours of compressor run time without outdoor coil ice build-up and ambient temperatures below +5°C/41°F a defrost cycle command is initiated to re-circulate heat-pump lubricants.

T-eco reverts to “sleep mode” when the ambient temperature exceeds approx.  +8°C/46°F.


The LED indicator on the T-eco is lit when the heat-pump outdoor coil thermostat  is closed.

A flashing LED indicates T-eco has not issued a defrost command to the heat-pump control board.

A solid “on” LED indicates a 24vAC command is given to the heat-pump defrost control board to initiate a defrost cycle after the total compressor run time has reached the set delay.



Step by step instructions are provided for installation by the owner.

Basic hand tools, multi-meter and electric drill are required. 

The T-eco must be installed outdoors to operate correctly.

An 18”, 4 pair, 24 gauge pigtail cable is factory installed onto the unit.



— 5(6) Wires, R/C (24vAC) and control wires Y(Y1)/W/O are connected to the same designation on the multi-pair cable from the indoor thermostat, at the heat-pump cable entrance junction point, typically using the existing Marr connectors.


2 Wires connect between the heat-pump liquid line thermostat and the defrost control board quick connect, designated as “DFT or coil”.





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T-eco is designed to increase the operating efficiency and life expectancy of heat-pumps with time-based defrost. We are not liable for any damage caused to heating equipment as result of faulty installation of the T-eco or normal wear and tear of a heat-pump with T-eco.