Gas and Oil Home Heating Furnaces - Wiring a Humidistat

I'm installing a 'Hamilton 10-HF' (bypass type) humidistat on my central HVAC system. I hooked up everything the way the directions say without a problem BUT, on the 'Load' side of the 24V transformer has 5 terminals. W R Y G O.
Can you tell me which two do I hook up my wires too?

By the way, I have a 100,000 BTU (80% efficient) Armstrong heater with all metal Galv. ducts, on an approcimate 1500Sq Ft house.
The heater is 12yo.


PS. It sickens me to throw 20,000 BTU out the chimeny. Is there anyway to recover some of this heat?

Thanks,
J. M. Claymont, DE

W and C will power up during heat. i like to add a "model 50" relay, a current sensing relay that will close the circuit once the fan comes on, as there is a delay between burner on, (W), and fan. since there is no need for power to the humidifier before fan, this accomodates for the delay

Thanks SOOO much