2 Flex correlates furnace heat output directly with the building heat-demand by sensing the outdoor temperature.

When installed with a dual-heating system house thermostat demand for aux. heat can now be satisfied without interrupting heat-pump operation. This drastically improves the overall heating system performance and lowers furnace electricity use.

Net benefits also include an even, more comfortable house temperature during normal heating and heat-pump defrost cycles when measured furnace heat is enabled to temper cold air influx from the heat-pump.

Because the heat-pump now runs for longer intervals and at lower outdoor temperatures its duty cycle and operating efficiency are greatly improved, while less frequent cycling (switching off/on) of the heat-pump reduce wear and tear on the unit.

By installing our new 2-Flex electric furnace control unit, home heating costs can be reduced by up to 20% while eliminating unwanted temperature fluctuations created by electric furnace or dual-heat with heat-pump.

A typical electric furnace is configured to operate in single stage on or off mode. It always produces the same amount of heat, independent of actual outdoor temperature and demand for heat from the building. This creates unwanted temperature fluctuations and warm air stratification, as some of the excessive heat produced by the unregulated furnace rapidly rises to the ceiling instead of distributing gently throughout the house, as desired.

Dual-heating systems can produce excessive heat whenever the house thermostat calls for aux. heat to supplement the heat-pump with furnace heat in order to raise the house temperature back to daytime set-point. Together, the heat-pump and furnace can rapidly overheat the indoor space, resulting in shut-down of both heating appliances until the indoor temperature has dropped again below thermostat  set-point.

To disable the heat-pump at a preset low temperature point an outdoor thermostat is added. It is sometimes set at only several degrees below freezing point to avoid discomfort experienced when at lower temperatures the heat-pump produces heat with insufficient intensity to make the house feel comfortable, thereby further reducing the benefits of the heat-pump as a very efficient heat source.

     2-Flex installation and operation

The 2 flex control module is designed for installation inside the electric furnace control compartment, using minimal space for fast installation requiring minimal wiring changes and additions. 3 Dry contacts rated at 2 Amps each are connected to the furnace external thermostat control inputs.

In case insufficient heating stage control outputs are assigned at the furnace control input terminal block, similar results can be achieved by connecting 2 Flex control outputs H1-3 in series with select 24VAC sequencer control wires by following the furnace specific wiring diagram.

Fig 2A shows the interconnect wiring diagram for a dual-heating system installation.

Fig.2B shows the same for a typical electric furnace with AC unit.

The 2-Flex outdoor sensor is normally installed at the heat-pump or AC outdoor unit, using 2 spare wires from the existing control cable. Dry contacts H1-3 are activated sequentially after the house thermostat calls for heat and the outdoor temperature has dropped below preset threshold points.

All 2-Flex dry contacts are configured as N.C. This to prevent a furnace and heat-pump interruption in an unlikely event of a 2-flex malfunction such as a accidentally disconnected temperature sensor. 

2-Flex dual-heat operation: 

The heat-pump heats the house down to +3°C/37°F (adjustable). Below this point and following

a demand for aux. heat, stage1 electric heat is also activated. Stage 2 kicks in at -6°C/23°F.

The heat pump enable “Y” wire has a separate in and output at the 2-Flex module. When the outdoor temperature drops below -12°C/10°F (adjustable) the heat-pump is disabled and furnace stages 1-4 are activated. At any time when a call for aux. heat is not satisfied within a 15/30 min. delay (programmable) furnace stages 1-4 and heat pump are activated until aux. heat is satisfied (normally only during

“first-heat” recovery). When in thermostat “E heat” mode furnace heating stages 1-4 are activated.

2-Flex electric furnace only operation: Stage1 heat is activated following a request for heat. Stage 2 activates when the outdoor temperature reaches approx. +3°C/37°F (adjustable). More stages are activated following additional 6°C/10°F temperature drops. When “W” heat is not satisfied within a 15/30/60 min. delay (programmable) furnace stages1-4 are enabled until such time “W” heat is satisfied.

2-Flex for electric furnaces  reduces home heating cost.