TXV's

Paul Fredricks_3

Anyone running into an increase in TXV issues this year? I think I've condemned more this year than I have in the previous 29. Both 22 and 410A. 

Techman

txv's

Goodman had issues w/ their txv's so they changed txv mfg'ers and I had a defective txv from the new mfg. Changed out the txv and everything is now good. 14 x 2 =28

John Mills_5

TXVs

Everyone is having TXV issues. Driving us crazy. Sometimes the replacement ones are worse than the original. All brands from what we see. 

Paul Fredricks_3

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Glad to hear it isn't just us. So much for quality control.

Jean-David Beyer

Quality Control.

I think it was W. Edwards Deming who said: "Quality cannot be tested into a product or service; It must be designed in." He as said something like this at other times too.

He was an expert in the field of quality control.

John Mills_5

What's worse...

The epidemic of TXV failures or the epidemic and shortage of dual capacitors?



At least caps are a 2 minute change. Now the trick is getting them!

Paul Fredricks_3

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We've been using those universal ones. Turbo 200X. Keeps the truck stock down and they seem to be working fine.

Jim Pompetti

Yes Yes Yes

At least once a month . I bet in 30 years ,I've only came across 5

MacPHJr

Diagnoses?

Im just learning about AC. How do you diagnose a failed TXV valve?

Paul Fredricks_3

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I still find a bit tricky. What I find is I add refrigerant, and at some point I still have 30° of super heat and adding more refrigerant doesn't help. That means I just can't get enough refrigerant through to the coil, hence, a restriction of some sort. The TXV is the most likely source. I also take a TD across the dryer to make sure it's not plugged. You can also pull the bulb from the TXV off the pipe and warm it up. This should change the pressures. If the pressures don't move, the valve is stuck.



Please, correct me if I'm wrong!

JStar

Signs of a bad TXV.

TXV stuck closed.

High subcooling and high superheat.

Normal / low head pressure. Theoretically should be low, but sometimes won't look too low.

Low suction pressure.

Frozen indoor coil.



TXV stuck open.

Low subcooling and low superheat.

High/normal head pressure.

High suction pressure.

Frozen suction line and compressor.





I found a bad TXV by accident once when I was testing for a leak. I let the nitrogen into my high side and nothing registered on the low gauge. Went up to the attic and found a frozen coil. TXV was stuck closed.



TXV's become less complicated if you just remember the refrigeration cycle. On every service call when my gauges are on, I'm constantly replaying in my head what the refrigeration is doing at every point in the system. Think about flash points. Where are they in a correct system, and where do they appear in a faulty system. Visualize flash points. Superheat and subcooling will usually tell you everything.

Paul Fredricks_3

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The one thing that messes up a lot of guys is the high side pressure. They assume if the TXV is stuck closed or there is a blockage in the liquid line that the high side pressure will be high. It's just the opposite.

Eugene_Silberstein

Have you checked.....?

Before concluding that the TXV is stuck closed, be sure to check the inlet strainer that is located in the liquid line connection on the valve. There are a lot of us out there who do not realize that part of the male flare connection on the valve's inlet is actually a strainer. If this is clogged, there is no way that the TXV, even if wide open, will feed sufficient refrigerant to the evaporator.

Paul Fredricks_3

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You may well be correct that the strainer is clogged, but if I am going to go through the trouble to pump it down, and open up the duct work (assuming the TXV is inside) I'd rather have a new TXV with me and just swap it out. Most of the cost to the customer is labor anyway.

Eugene_Silberstein

You are Definitely Correct!

Better to have it and not need it than need it and not have it!

Paul Fredricks_3

Agreed

But if I have it, I will use it because the customer has already been given the price and agreed. If I don't use it, it will fall into that unused part void we have here so we'll be paying for it anyway.

dave_11

now that you mention it

I did have a system that (I think) eventually did the compressor in... Walk in Freezer - R404a - that as about 4 years went by from the original install gradually starved the coil.. I'm in a small town that's small enough that I'm the only guy that works on this stuff and this TXV eventually starved the coil enough that no adjustment worked at all... And there was no corrosion on the power head to indicate loss of charge but I concluded at that point in time that was the problem... BUT then I replaced the valve with a like-size 502 that was not externally equalized but internal (plugged the coil equalizer line) only because that was what I had on hand (weekend, only thing on hand, you know how it is) and the immediate response was perfect... Fed beautifully and thought problem solved.. Within 6 months the same problem returned, no adjustment would change anything and the coil was starving, big ice block around the TXV and that entire end of the evap... Only this time compressor operation was affected... Even with a third TXV replacement (back to external equalized) head pressure was too extreme with the original full charge of refrigerant... Looking at internal TXV parts revealed nothing unusual other than the typical stickiness feel of an R404 system I've grown accustomed to.. I'm of the opinion that filter drier replacements are to become common place on an annual basis with the HFC system instead of just one that needs servicing when a system is accessed... Eventually I replaced the compressor on this system to once again attain satisfactory running pressures and a normal sight glass... Time will tell how the 3rd TXV will endure normal operation...   Great post, cheers   -    kooler