Optimum, Heater, models:

GC-1400	Instruction Manual
GC-1500	Operating Instructions Manual
GPQ-10A	Operating Instructions Manual
HNC-2000	Operating Instructions Manual
HNC-2012	Operating Instructions Manual
OK-91	Operating Instructions Manual
OK-9110	Operating Instructions Manual
OK-9400	Operating Instructions Manual
OK-9500	Operating Instructions Manual
OS-1609	Operating Instructions Manual
OS-1711	Operating Instructions Manual
OST-1611	Operating Instructions Manual
PTC-1500	Operating Instructions Manual