ECO Throttle and heavily inductive loads like refridgerators.

ECO throttle and heavily inductive loads

Is ECO throttle really all that great? Well yeah actually it is pretty great. On a scale of 1 to 10 I’d have to give it a 9 as a damned good idea. Why only 9/10? Well there is one chink in the ECO throttle idea that came to light when one of my customers, Ron, was trying to use a Honda EU30is to power his pizza catering wagon.

In his wagon the most significant load is a refrigerator. With a rated consumption of around 500w it should in theory have presented no problem to the EU30is. Indeed with ECO throttle turned off the fridge started and the generator didn’t even miss a beat. However with ECO throttle engaged the generator would cough and sputter a bit before finally building up speed to meet the demand of the refrigerator starting current. We estimated the starting current to be between 2 and 3kw in order to have this effect on the generator.

Ron was quite rightly concerned that this struggling would leave the fridge motor in the starting phase for longer than it was designed to be, thus shortening the life of the refrigerator and maybe even placing an unnecessary strain on the generator.

To address this problem I designed a very simple circuit to switch off the ECO throttle mode just before the refrigerator motor starts, using a couple of identical 20A relays and a Power On Delay relay.

The ECO throttle switch is normally engaged on the generator simply by making or breaking a connection using the ECO throttle switch on the control panel. I took one of the wires leading to the ECO throttle switch and presented it to an XLR socket on the front of the generator. Another XLR socket was fitted to the catering wagon and the connection between the two made with an XLR lead as used by musicians. Then the live wire leading to the refrigerator motor was interrupted with the circuit described below. The whole affair proved to be great success and later Ron changed Relay 1 for a timer relay so that the ECO throttle mode was disengaged only for a few moments during the start-up phase rather than all the time when the refrigerator motor was running.

Disconnect the live wire from the fridge motor and call it “Ls”. Leave the Neutral connected and call it “Ns”

Relay 1 (was eventually changed for a short timer relay)

Pin 9                  Eco switch
Pin 11                Eco switch via tiny inline fuse
Pin 2                  Ns
Pin10                 Ls

Power on Delay

Pin 7                 Ns
Pin2                  Ls
Pin 8                 Ls
Pin 6                 Pin10 on Relay 2

Relay 2

Pin2                 Ns
Pin11               Live connection on motor
Pin 9                Ls
Pin10               pin6 on Power on Delay

Sequence of operation is

1) Fridge sends power to Ls
2)Relay 1 operates making connection to the eco switch through pins 9 and 11 on Relay1

This switches off the ECO throttle mode
3)Power On Delay powers up and the delay period begins
4)Delay expires and pins 8(Ls) and pin6 of the POD connect sending power to pin 10 of

Relay 2. Powering up Relay 2 connects pins 9(Ls) and 11 thus sending power to the motor.

5) When the supply to Ls is switched off by the refrigerator thermostat then the circuit returns to rest mode re-engaging the ECO throttle mode

Bish Bash Bosh (optional)

The finished device looked like this

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