(Podcast) TXV Operation, Diagnosis, and Failure w/ Jamie Kitchen

(Audio Only) In this episode of the HVAC School podcast, Bryan talks with Jamie Kitchen from Danfoss about TXV Operation, Diagnosis, and Failure.
As fixed orifices become a dying breed with the development of higher-efficiency systems, TXVs take over the mantle as the primary method of expansion. Expansion valves meter the flow of refrigerant by aiming for a certain suction line superheat value. Unlike a fixed orifice, which has an opening of a constant diameter, an expansion valve adjusts the opening size to the evaporator based on suction superheat readings.
TXVs have a sensing bulb, diaphragm, spring, and cap tubes. Various pressures act on these components: bulb pressure, spring pressure, and evaporator pressure. The sensing bulb picks up the suction superheat adjusts its pressure on the diaphragm based on the superheat it detects. Spring pressure and evaporator pressure act against the bulb pressure. The combination of all three pressures (bulb vs. spring + evaporator) dictates the opening of the TXV orifice into the evaporator. The bulb pressure is an opening force, and the spring and evaporator pressures are closing forces.
You can cause TXV failure by adjusting it or brazing it in improperly. When too much heat is applied to the TXV, the components inside can warp. Some TXV failures also occur due to contamination. Flowing nitrogen while brazing flushes carbon and oxygen contaminants out and reduces your risk of TXV failure later on.
Bryan and Jamie also talk about:
TXV anatomy (powerhead, spring, etc.)
Internal vs. external equalization
Pressure drop across the distributor
Subcooling and its relationship with the TXV
Solenoid and ball valve (upstream) malfunctions
Filter-dryer placement
TXV assessment during commissioning
Locating restrictions
Residential system airflow
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[@dizziedallas]

Bryan, Thanks very much for making these podcast. I know it take a lot of your time but you are changing the hvac thought pattern one podcast at a time.

[@CHOMAHOMA]

Excellent podcast. I listen to it more than once. Very Important subject

[@ianfawcett5265]

This topic has been very informative and educational. As a newcomer to the HVAC trade . I truly appreciate all your videos and presentations.

[@pincheburro956]

Excellent podcast, I hope to continue learning from you guys

[@jamesladeroute6127]

Very informative. Thank you!

[@ivemovedmountainswithless1571]

This is awesome stuff. A lot of these videos are somewhat remedial, which is not a bad thing. I always pick up something I didn’t know. But this is a very advanced discussion, I think. Very good listen for in between calls are with your coffee in the morning. Great job, thank you for doing this.

[@chickedwin7194]

You (host) are awesome for the interesting service

[@thoughtrevolution5034]

I loved listening to this.

[@pablogaviria9265]

Excellent Video !

[@stevebracken8400]

This was very interesting, thanks

[@mrcrux213]

My thoughts on the fully closed TXV. In A/C never happen as part of normal operations but in the other hand on refrigeration it will happen and that's were it is critical a good working TXV superheat. Just a thought 🤔

[@Mikecianfrocco]

Learned alot

[@Mikecianfrocco]

Nice!

[@jasoncurtis4404]

I have a 3 year old ameristar system giving problems. On ab90+ degree day, it wont keep up. 2 ton heat pump 14 seer brand new install about 1000 sq ft old house. 1960s about. Suction pressure was up around 170, head pressure like 240 or so. Its anpiston, so cant be bad txv. Tech said compressor was bad cuz it was pulling 4.6 amps, rated for 13.5. Replaced compressor, now pressure is better looking, still not keeping up. I'm thinking the reversing valve solenoid isn't going all the way over, thus freon bleeding thru. Any other suggestions?

[@SombraLocs]

What would the symptoms of a plugged distributor line be?

[@mikeclark1756]

I was taught to use staybrie # 8 when installing a TXV

[@gene-khvacr]

How long have you used #8 staybrite ,have you experienced any issues ? all my peers used for 40 plus years they love it.

[@DWAYNE2ism]

hey quick question can i use stay brite soft solder to install txv or tev?

[@HVACS]

Staybrite 8 is often used although I don’t

[@erickalief]

Even if the coil is starting to freeze up will it still have a low to normal superheat?

[@erickalief]

Freezing up due to low air flow

[@mikeclark1756]

Back in the day manufatures used Silver wire on txv

[@anthonynunez164]

I work at an equipment manufacturer and I've probably brazed in hundreds of TXVs on these units. I can tell you that some brazers do better jobs than others and I worry about damaged txvs.

[@anthonynunez164]

I think using silver is probably smarter.

[@Guyhakverdi]

Normal SC 10, 3SH Normal pressures. WHY IS NOT 10-15 SH?

[@hvac01453]

Man.... this guy sounds just like Christian Slater, don't you think???

[@jaimegutierrez9930]

😂