I guess your talking about an outdoor ambient temp' of 30F so's the condenser does not freeze in the wintertime, first off I think that Honeywell 8000 has an option for a OA sensor, at least I know for a fact that it will sense remotely, but an LP switch set up to your high side will also turn it off when required, I dunno, maybe you ought to more specific!
if you are refering to a honeywell 8000 only to run a fossil fuel aux. It will work as long as your heatpump does not have a issue above outdoor lock out temp. Unless they have changed programming you have to use a iq tstat to get proper control. What will happen when you select fossil fuel as back up it, it will not bring on aux heat at all if heat pump is not locked out due to outdoor air. I had issue one time and called honeywell on this. What had happened it heatpump had issue when above outdoor temp lock out and tstat will not let heat pump and fossil fuel run at same time. The tsat will just sit there. If you put to emergency heat it will bring on gas but not as second stage. Hope that helps
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