We have an oil fired (1998 Brock) furnace. The return air temp can be obtained with no temp (approx 68 ) variation at any point along the return duct path to the fan compartment.
Where is the heated supply air best measured? A probe thermometer inserted any where in the supply plenum near the heat exchanger can vary many ,many degrees from a probe that is inserted 24" higher.
Within 2" of exchanger it is 160
at 12" above exchanger it is 150
at 24" it is 140
And downstream from this plenum a few feet it is approx 120
The furnace's manual says a 55-85 rise is ok.
but it does not say from WHERE these temps are taken taken.
IMO,the probe location can make or break the safe "rise"
Any out there got any ideas?
[Edited by deejoe on 10-23-2005 at 03:56 PM]