Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.
The Thermostatic Expansion Valve
Jeff Lawrence_25
Member Posts: 746
The other one
0
Comments
-
The Thermostatic Expansion Valve
The TXV, or TEV, is an often misunderstood system component. In reality, however, the TXV is a relatively simple component that has only a one line "job description". The ONLY purpose of the TXV is to maintain constant evaporator superheat. It does not maintain evaporator pressure. It does not maintain system capacity.
IT'S ONLY JOB IS TO MAINTAIN EVAPORATOR SUPERHEAT
If you are out there troubleshooting an air conditioning or refrigeration system and your superheat readings are correct, please leave the TXV alone!
Excessively high superheat readings can be caused by a system undercharge, liquid line restriction, clogged filter drier or clogged inlet strainer on the TXV.
When evaporator superheat is high on systems that are equipped with thermostatic expansion valves, the valve is likely open all the way but there is not enough refrigerant available to be fed to the evaporator. So, if the superheat is high, check the refrigerant charge, check for restrictions, check for blockages, check everything..... except the poor TXV!0 -
TXV's
Hi Eugene! Well said ,about those pesky TXV's! The darn things last 20 years or so,no screw ups,and once set PROPERLY, they don't need any readjustments for 20 years or so also. I just can't seem to find that many "BAD" TXV's0 -
txv types
Eugene- I'm not sure I understand what advantage a non-bleed type txv (or hard shut-off) offers vs. a bleed back style. Could you please enlighten?0 -
One of the main
One of the main differences is that metering devices that allow the system pressures to equalize during the off cycle enable the equipment manufacturers to use lower torque motors in the compressors as they do not have to start up with a large pressure difference across the compressor. Systems with, for example, capillary tubes typically have compressors with low starting torque.
I'm running out of the house right now but will post some more goodies later on.0 -
TXV
Greg In any system that has a non-equalizing TXV,the compressor manufactorer usually requirers the use of a "hard start kit " The compressor will start against an un- equalized pressure,between hiside and lowside0 -
sorry- double post!0 -
I understand
the hard start requirement, but why on earth do some manufacturers insist on non-bleed type TXV's in the first place? It causes a high torque start, resultingin the need for a hard start. But, is there any advantage to a non-bleed TXV? What is gained? Does it prevent refrigerant slugging the coil? Thanks!0 -
TXV's
Greg. Alot of commercial refrigeration systems operate on a "low pressure" control, which means the TXV has to be a "non bleed" type.The temp of the refrig unit slowly raises as does the pressure in the low side of the system.The bleed style TXV would allow the loside press to rise rapidly,causing the comp to come on again,long before the refrig case actually warms up.0 -
Well,
I don't think this one will maintain anything.0 -
those we
find to frequently on outdoor units.But I'll take one that fail closed, over one thats over feeding any day.
Good find Jeff.
0
This discussion has been closed.
Categories
- All Categories
- 86.2K THE MAIN WALL
- 3.1K A-C, Heat Pumps & Refrigeration
- 53 Biomass
- 422 Carbon Monoxide Awareness
- 90 Chimneys & Flues
- 2K Domestic Hot Water
- 5.4K Gas Heating
- 99 Geothermal
- 156 Indoor-Air Quality
- 3.4K Oil Heating
- 63 Pipe Deterioration
- 915 Plumbing
- 6K Radiant Heating
- 381 Solar
- 14.8K Strictly Steam
- 3.3K Thermostats and Controls
- 53 Water Quality
- 41 Industry Classes
- 47 Job Opportunities
- 17 Recall Announcements