Originally Posted by
Jerry Peck
But ... where did you get that information from? That was the question.
The TD by itself is not telling you anything, and, unless you have reliable documentation which states otherwise, your numbers are WAY OFF, besides being meaningless numbers.
In Refrigeration and Air Conditioning Technology, 5E it states that based off of the return air temp to the suppy air temp should drop 20 degrees as it crosses over the evap coil. ie.. if you have a RA of 75 your SA should be 55 if you are at 50% relitive humidity. humidity will affect the reading, when we look for the 18 to 21 degrees of delta t (temp drop) that gives us a snap shot of how the system is operating. if it is out side of this range there could be some underlying issue that would involve further tests. But taking a Delta t reading
is just a snap shot. and you should use a probe thermometer not IR just before the filter, unless it has a humidifer bypass (before the bypass) and about 18 inches from the evap coil if possiable.