Reply to Thread

I typically use electrical contact cleaner as it evaporates quickly leaving behind no residue .. Some times you can blow them put with nitrogen..

Originally Posted by phxhvac

What is the best way to clean a TXV screen noe that it was mentioned. Just curious.

Sent from my DROID RAZR using Tapatalk 2

I've actually found that squeezing and rolling the screen between my fingers, then tapping it, open end down, on a hard surface cleans 99% of the debris out of them.

It's typically dry, flaky stuff and there is no need for cleaner.

Originally Posted by phxhvac

What is the best way to clean a TXV screen noe that it was mentioned. Just curious.

Sent from my DROID RAZR using Tapatalk 2

Electrical parts cleaner or PVC cleaner for me, since that's what we have on hand.

NOW...get in the habit of taking and posting pictures.

Originally Posted by yvnsteve

I took measurements across filter drier and is good. Held sensing bulb and got no change. Took apart tev and found clog screen. Cleaned and replaced. Running good super heat and subcooloing. Thanks for your input, appreciate the help to think it through. Thats the way learn and become a better tech. Thanks jpsmith and everyone that contributed!!

Good to hear.


If you keep up that kind of logical thinking, and investigative process, you'll do well in this trade.

I took measurements across filter drier and is good. Held sensing bulb and got no change. Took apart tev and found clog screen. Cleaned and replaced. Running good super heat and subcooloing. Thanks for your input, appreciate the help to think it through. Thats the way learn and become a better tech. Thanks jpsmith and everyone that contributed!!

Originally Posted by hvactech1977

I've seen them where they get black gup buildup on the internal parts not allowing it to move freely. That is even with a liquid drier on. You never know what all was done to the system in the past work wise from other techs or if a burnout ever happen. holding the bulb and trying to adjust it first is something I would try first too. check liquid drier for blockage. If the txv is flared in like some cooler/freezers are, I usually just change it with complete new. when a power head fails usually it is drastic.

I have only seen that black gunk on low temp r-22 systems.

Originally Posted by Tommy knocker

I would actually start cheeper. Try to adjust TEV and see if it will or pull the bulb and hold it in your hand. I'd wanna know if it responds before I take the system down and open it.

Well, based on the assumption (yeah, big assumption) that the unit was WORKING before he was called out, we must look at what has changed.

Typically, jumping in and adjusting a TEV before determining a problem just results in more work later.

I've seen them where they get black gup buildup on the internal parts not allowing it to move freely. That is even with a liquid drier on. You never know what all was done to the system in the past work wise from other techs or if a burnout ever happen. holding the bulb and trying to adjust it first is something I would try first too. check liquid drier for blockage. If the txv is flared in like some cooler/freezers are, I usually just change it with complete new. when a power head fails usually it is drastic.

I like to take them out and blast spray brake cleaner through them backwards. Although, unless there is no LL drier in the system, it very seldom ever needs doing.

PHM
------

Originally Posted by phxhvac

What is the best way to clean a TXV screen noe that it was mentioned. Just curious.

Sent from my DROID RAZR using Tapatalk 2

What is the best way to clean a TXV screen noe that it was mentioned. Just curious.

Sent from my DROID RAZR using Tapatalk 2

Originally Posted by jpsmith1cm

The problem with that is that, typically, a subcooling measurement on a refrigeration system like this isn't as meaningful as it is in a split residential AC unit.

You've got a good head pressure and a solid glass and that's about where your liquid side measurements end. Maybe need to look at the possibility of a plugged liquid drier, but other than that...


I don't think that bunny or I disagree with your assessment of a malfunctioning TEV. What we're trying to get you to do is to think bigger about how the system is operating and how one failure can cause or lead to another.

Start by examining the TEV inlet screen. That's a very common thing to plug and all you need to do is to clean the trash out of it and start it back up. If that's clean, replace the power element and sit back and see what happens. Maybe measure the pressure drop across the filter drier if possible. Take the temp drop across the filter-drier if not (although this isn't the BEST way to check them)

I would actually start cheeper. Try to adjust TEV and see if it will or pull the bulb and hold it in your hand. I'd wanna know if it responds before I take the system down and open it.

R-22 TXV ?

Any chance it has an R-22 valve on the coil?

What does the powerhead say?

PHM
-------

Originally Posted by yvnsteve

Have a R404a freezer with -11f evap temp 20f box temp 100f condenser temp. 50f super heat and 10f subcool. 75f ambient and 80%rh. any thoughts why not colder?

The problem with that is that, typically, a subcooling measurement on a refrigeration system like this isn't as meaningful as it is in a split residential AC unit.

You've got a good head pressure and a solid glass and that's about where your liquid side measurements end. Maybe need to look at the possibility of a plugged liquid drier, but other than that...


I don't think that bunny or I disagree with your assessment of a malfunctioning TEV. What we're trying to get you to do is to think bigger about how the system is operating and how one failure can cause or lead to another.

Start by examining the TEV inlet screen. That's a very common thing to plug and all you need to do is to clean the trash out of it and start it back up. If that's clean, replace the power element and sit back and see what happens. Maybe measure the pressure drop across the filter drier if possible. Take the temp drop across the filter-drier if not (although this isn't the BEST way to check them)

I am a new tech. i THought that if the tev is partialy blocked the evap would be starved giving me the high super heat and and cause a backing up of the refrigerant in the condenser giving it more time to subcool

Since you are a "tech", why don't you state your case for why the TEV restriction should lead to high sub cooling.

there was a large formation of ice on the txv along with the high super heat that leads me to believe the tev has an issue. if the tev is restricted, shouldn't the subcooling be high also?

I wouldn't "think" anything. I would investigate and determine WHY these things are happening.

This is the job of a technician.

A malfunctioning TEV is a good place to start, but there are a number of reasons that it could be malfunctioning. There are inlet screens that plug up and power heads that fail.

Sight glass is clear. I am thinking high superheat is caused by blocked txv?

NOW.... Let's get down to this.

Does the unit have a sightglass? If so, is it clear?

Are you not in the slightest concerned that the superheat is 50 degrees?