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Discussion Starter · #1 · (Edited)
I want to measure the evaporator temperature on a Goodman horizontal cased coil attached to Goodman GMP80 furnace in an attic and I need some advice on exacted where to check it . (use IR or dial thermometer?). Is this late 1990s model this a fixed orifice or TXV unit ?

BTW, the delta between the return and the suppiy register closest to the unit (about 8 ft duct) is about 12 degrees F (80-68). The unit is located in the attic. Should the delta be higher ?


I also plan to check the superheat and subcooling calculations. Any other advice to add to that mentioned in the reference below -

http://www.udarrell.com/ac-trouble-shooting-superheat-subcooling.html
 

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Discussion Starter · #2 ·
Just for a quick check, I connected the low side gauge only and turn the condensing unit back on. The low side pressure would slowly move between 55 and 70 psi (back and fourth) .
The unit of the same make and model serving the downstairs did not seem to behaving this way . What does this mean (TXV sticking or something) ? My downstairs unit of the same make and model did not seem to behaving this way . What are these symptom indicative of ? - Thanks
 

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Since you have the tools we're going to make you get some real data. Liquid line temp,suction line temp,suction pressure ,head pressure,outdoor ambient, return temp at a grill,return temp at the furnace, supply temp at a register and supply temp 3' from the coil. Then wrap a damp tissue around the thermometer and check the supply and return again at the furnace, will be you wet bulb temps. With that info we can help without guessing too much.
 
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