I'm not sure if it is high efficiency model. This was installed by the
previous owner I guess. Not sure how old it is also. This does not have
LEDs which indicate the status. It has an electronic ignition. When I
turn it on (set the temp to 70 deg) the pilot lights up for about 2-4
seconds and then dies down for about 2-4 seconds. During this time I
dont think the gas is released because I was holding a match stick. The
on-off cycle continues for some time and eventually in about 30 mins or
so the heater started to work. For now things seem to be ok. Any
suggestions as to what to do next? I'm wondering if there is a part
that is temperature sensitive and needs servicing or replacing.

Thanks