The TD-17 timer should not be used with our DFK. When trying to use the TD-17 in series with W1 from the thermostat and W1 on the HP thermostat terminal strip on our DFK (to delay bringing on the auxiliary heat), W1 will not energize on a call for emergency heat. The TD-17 is a power stealing device that requires a minimum load to close the circuit. On just a call for emergency heat there is not enough load to close the circuit. If Y1 is energized first and then the thermostat calls for auxiliary heat, we now have two relays in parallel and now there would be enough loads to close the circuit. The risk in using a TD-17 with our DFK is the homeowner going straight to emergency and thus we would not be able to bring on the auxiliary heat.