< or > 90% efficiency oil furnace?

[paulmars]

I just bought a new thermostat for my central oil HVAC unit. Honeywell TH4110D. I can set it for oil heater <90% efficiency or >90% efficiency. I'm not sure which to set it at. I am hoping that my unit is not exactly 90%, cuz then I'm screwed. Bryant model 58cma105-12 installed in year 2001. Bryant wont help me. they insist that i pay a service tech to come here and tell me. That ain't happening.

Also, compressor cycle rate setting 3 is recommended for most compressors. I hope that is what I have.

Your thoughts?

tks,
pa

 

[Dana]

Anything over 87% is extremely rare for oil burners in the US.

If you take a peek at the table on p.4 of the 58CMA specification sheet you'll see that the heating capacity BTU to input BTU, is about 81%, independent of which nozzle is installed. Definitely sub-90%.

Even when fitted with a 0.50 gph nozzle it's more than 2x oversized for the heat load of most houses in FL, but that's not going to affect efficiency for a hot-air furnace, but longer burns with more modest exit-air temperatures at the registers are usually more comfortable. All oil burners are oversized for new code-minimum house.

 

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[paulmars]

thanks