TXV bulb install question

[alamo1718]

Several weeks ago I followed the failed maintenance supers's(several guys) attempts to fix a no cool. I found contaminated R-22 and a TXV installed with the piston still installed. The bulb was also not secured to the piping, nor was it touching anything, just sitting in the air stream. I removed the TXV, pulled a good vacuum and charged the system with new R-22, problem fixed.

Returned to the same property last week, different apartment. This system showed low on Freon, I don't remember the exact numbers but the SH was high and the Subcool was low. It also had a TXV, also not secured to anything just floating around the air stream. I didn't pump down and check for a piston. The pressures did change however when I held the bulb in my hand. I added Freon and left the Subcool at 10. They haven't called back saying it isn't working, but it's created a question in my mind.

These are old Suntherm units, Heat pump. A coil, the bulb jammed between the cover panel and the U bends at the edge of the coil, so not really out in the middle of the air stream.

The question is; Does a TXV bulb always have to be in contact with the piping? What will happen if it isn't? I did notice that when I added R-22, High side would shoot up very quickly, then slowly fall and stabilize.

[hewitt]

The bulb must be attached to the outlet of evaporator and insulated. It response to the amount of super .most are installed at the 10 or 2 o'clock position

[drife678]

ive always thought i heard 5 and 7 o clock

[caheiman30]

When I was in school they said anywhere from 6 to 9 o clock or 3 to 6 o clock


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[hewitt]

No oil from refrigerant settles On bottom.Vapor rises therefore 3 ,9,2,or5 gives u best reading.

[hewitt]

I'm sorry 3,9,2,10 o'clock position

[caheiman30]

I'm sorry 3,9,2,10 o'clock position

mmm, cause the powerpoints that I got from when in school say different

[hewitt]

Some books say as long as it's mounted horizontal

[hewitt]

This is becoming interesting.Going to move a bulb around and check some numbers

[caheiman30]

Some books say as long as it's mounted horizontal

Refrigeration Training Services/NATE training slides say Must sense true suction temperature
- not bottom of pipe
- not top of pipe

[hewitt]

So what position does nate say is the correct placement

[caheiman30]

So what position does nate say is the correct placement

from there power points 3 and 9 o clock are the best areas

[hewitt]

Service valves where u hook up gauges are 3 or9 if u look at them.If these ports were located on top would the boiling are saturation temp be the same on gauges or would it make that much difference