I wonder if Robo would be so steadfastly defending the worst type of metering device in the industry if Goodman announced that they were switching 100% to TXV metering?
My veiwpoint on TXV vs fixed metering is shadowed by the fact that I live and work in a part of the country where it is common for me to be working on a system in outdoor ambient and indoor conditions that have a "-" by them on most manufacturers charging charts for fixed metered systems.
Heck, around here we have many hours a summer where, even with normal indoor conditions, there is a "-" on some charts for our outdoor ambient.
In my opinion, fixed metering has absolutely no place in a system that is expected to operate regularly in 100º+ ambient conditions.
I also am of the opinion that a manufacturer should not be allowed to sell equipment in an area unless they make available the performance data for that equipment in the ACCA design conditions for that area.
I can think of a number of brands that would have to publish it or pull out of my area if something like that went into affect, lol.
If more government is the answer, then it's a really stupid question.
better late then never
Actually a fixed Orifice Tube is fine for many applications.
Cost is an important factor to be sure but reliablity plus the inability to change the flow are other reasons. One of the most variable performing systems out there uses OTs (not all OEMs though). Your car . Pump speed is independent of needs of the system, ambient temperature variations are extreme, surging, heck even the operating conditions vary from moment to moment. Through all of this a fixed orifce tube is acceptable.
The vehicle systems that have an auxiliary metering device for the rear system applications I know use, OT and TXV. Dual TXV systems plumbed to operate together kind be very unstable under the wide range of operating conditions. (They are not plumbed like a heat pump for change in the direction of flow but rather each evap core has a customer demanded temperature so a metering device is needed for each evap core ).
IMhumbleO a TXV IS more efficient BUT not really needed under a wide range of operating conditions AND can get you in hot water when used as a retro-fit without checking the other components performance specs.
Disclaimer: Im hunting for answers to figure out an issue I'm having with a TXV based system design that is driving me up a wall.... so I might be a little biased today
Now Im off to learn some more from this site and all of you.
Thanks For Your Expertise