adjusting txv's

[swinginutters]

i came across this a few times already in my 2 year career, today on a walk-in fridge top half of evap is iced up, txv iced up at distributor, good airflow, clean evap, fans run, checked pressures after de-icing, 35/205 r-22, full sight glass. didn't suspect charge issues with a full sight glass. high superheat at evap 30 degress. opened up the txv a few turns got the superheat to 12 degrees. everything seemed to run well after that

my question is, why would the txv need to be adjusted all of a sudden?, this walk-in has always ran well for the two years i've been servicing this restaurant, have never had isssues, is the txv getting restricted and i'm compinsating by opening it up some more? or is it slowly crapping out, or is that normal to need to adjust txv's at times ?

[crackertech]

Your power head could be week or your pins sticking.

[Dowadudda]

did you check the liquid inlet screen to the TXV.

[-frozen-ocean-]

was the box temp within 10* when checking that superheat reading?

[swinginutters]

yes, box temp was 45 degrees when i checked original superheat

[davidd_danfoss]

There are several possible reasons. But likely the power head has lost a very small amount of its charge, so then the spring pressure to power head pressure was out of whack, and you put in back in line when adjusted. Or a previous tech adjusted it when it wasn't the problem, and this was truly a call back.

[crackertech]

So swinginutters have you been back? give us a up date.

[balzano]

its mechanical, so its normal to be adjusted each few months, with the new electronic txv we will not have this problem, superheat adjusted= good refrigeration cycle= life time compressor.

[neumonic]

its mechanical, so its normal to be adjusted each few months, with the new electronic txv we will not have this problem, superheat adjusted= good refrigeration cycle= life time compressor.

there is an electronic txv now i havent seen that yet?

[beachtech]

there is an electronic txv now i havent seen that yet?

yes, there is and has been one for a lil while now

[beachtech]

its mechanical, so its normal to be adjusted each few months, with the new electronic txv we will not have this problem, superheat adjusted= good refrigeration cycle= life time compressor.

and we would glady use your money to purchase this new electronic valve :D

and, lmao

we have blamed pushrods, inlet screen, and powerhead loss of charge... what about installation? is the thing installed properly?

is the sensing bulb in the right location? what o'clock position is it on the suction line? is it on a vertical line? is it mounted in an oil trap?

i don't understand why someone would think a txv needs to be constantly adjusted :confused:

the only thing a TXV does, is adjust and maintain SH. right?

[Slatts]

there is an electronic txv now i havent seen that yet?
You've got your stepper valves that sense system SH with pressure transducer and temp sensor to compute superheat and drive the valve open or closed incrementally.
You've got your liquid injection valves that open on increase in superheat to squirt liquid through an orifice. They're an on / off type valve. They can be controlled the same as the stepper or with an inlet an an outlet temp sensor to work out the SH. Have you ever walked into a supermarket refrigerated section and heard a clicking from the cases? That's the injectors opening.
Then there's the old thermal type valve that has a variable resister in the suction line that feeds current to a heater in the top of the valve where yout TX valve power element sits. If I recall correctly, the heater heats a bimetallic disk that flexes in and out to drive pins as in a normal TX valve. It's the simplest of the 3 as it needs no electronics.

[neumonic]

yes, there is and has been one for a lil while now

i have only been in the trade a very short 2 years so i havent seen much yet thats why i was interested....ive seen the eeprs , just not any electronic txv
How do they operate?

[beachtech]

i have only been in the trade a very short 2 years so i havent seen much yet thats why i was interested....ive seen the eeprs , just not any electronic txv
How do they operate?

i just started 2 days ago... in comm refridge that is :)

slatts kinda summed up the two electronic types that i have read about in his post :)

[itsiceman]

the only thing a TXV does, is adjust and maintain SH. right?

They use an Electronic TXV like a pump down solinoid too :cool:

You sure you've only been doing this two days :p

[jpsmith1cm]

The EXV valve works functionally the same as an EEPR valve.

Transducer senses pressure, sensor senses temp. Electronics know refrigerant type. The only real variables are SH setting and refrigerant type.

The electronoc controller uses that information and drives a motor that opens and closes the valve.

[jpsmith1cm]

If you are constantly tinkering with a TXV


REPLACE IT!!!

[crackertech]

If you are constantly tinkering with a TXV


REPLACE IT!!!

Yup Ditto that.

[dirtyboy103us]

i came across this a few times already in my 2 year career, today on a walk-in fridge top half of evap is iced up, txv iced up at distributor, good airflow, clean evap, fans run, checked pressures after de-icing, 35/205 r-22, full sight glass. didn't suspect charge issues with a full sight glass. high superheat at evap 30 degress. opened up the txv a few turns got the superheat to 12 degrees. everything seemed to run well after that

my question is, why would the txv need to be adjusted all of a sudden?, this walk-in has always ran well for the two years i've been servicing this restaurant, have never had isssues, is the txv getting restricted and i'm compinsating by opening it up some more? or is it slowly crapping out, or is that normal to need to adjust txv's at times ?


most valves i have adjusted have stayed in the proper range for super heat setting because they were never set corectly from start up

i usally start by checking the screen and then setting and then if by chance i get a call back i replace power head

i use these setting for different applications

A/C 10 to 12 degrees
med temp 6 to 8
freezer 3 to 5

[neumonic]

The EXV valve works functionally the same as an EEPR valve.

Transducer senses pressure, sensor senses temp. Electronics know refrigerant type. The only real variables are SH setting and refrigerant type.

The electronoc controller uses that information and drives a motor that opens and closes the valve.

thanks jp! now hopefully i can see on in the field soon to get a better understanding of it but thanks anyhow for the info

[crackertech]

thanks jp! now hopefully i can see on in the field soon to get a better understanding of it but thanks anyhow for the info

neumonic here is some info to read on EXV valves.http://sporlan.jandrewschoen.com/100-20_092008.pdf

[neumonic]

neumonic here is some info to read on EXV valves.http://sporlan.jandrewschoen.com/100-20_092008.pdf

whats a good program to be able to open the pdf files my computer doesnt allow it , i dont really want to purchase the software is there anywhere i can download it for free?

[KLEINman]

get adobe acrobat reader, works great

[crackertech]

whats a good program to be able to open the pdf files my computer doesnt allow it , i dont really want to purchase the software is there anywhere i can download it for free?

http://www.adobe.com/products/reader/
It's free.:)

[sumdumguy]

You've got your stepper valves that sense system SH with pressure transducer and temp sensor to compute superheat and drive the valve open or closed incrementally.
You've got your liquid injection valves that open on increase in superheat to squirt liquid through an orifice. They're an on / off type valve. They can be controlled the same as the stepper or with an inlet an an outlet temp sensor to work out the SH. Have you ever walked into a supermarket refrigerated section and heard a clicking from the cases? That's the injectors opening.
Then there's the old thermal type valve that has a variable resister in the suction line that feeds current to a heater in the top of the valve where yout TX valve power element sits. If I recall correctly, the heater heats a bimetallic disk that flexes in and out to drive pins as in a normal TX valve. It's the simplest of the 3 as it needs no electronics.

so would these exv's be proportional integral or derivative also?

[neumonic]

http://www.adobe.com/products/reader/
It's free.:)

Hey thanks again crackertech! for this link and the sporlan link...took me 2 tries to get the adobe to work though but i got it now and its much appreciated

[crackertech]

Hey thanks again crackertech! for this link and the sporlan link...took me 2 tries to get the adobe to work though but i got it now and its much appreciated

Your welcome.:)

[jpsmith1cm]

so would these exv's be proportional integral or derivative also?

PID is a form of logic called "fuzzy logic", or method that computers "think" inasmuch as computers can actually think.

PID control could be applied to to EXV control, yes, but would not be necessary.

http://www.omega.com/techref/fuzzylogic.html

Hopefully, this is not a link to a competitor.

I have to admit that I don't completely understand PID, but the control is much smoother than non-PID type controls.

[sumdumguy]

same here but i almost think it could even be pulse width modualating but with a anolog input(ie transducer) to the cpu and back to the controller to open and close the valve with a digital output in steps...

[davidd_danfoss]

First, a properly installed, and set mechanical TXV does not need adjusting, unless something in the system has changed (eg, power head charge loss, changed heat load, changed evap temp. But I think most everyone here knows that.

An EEV is mechanically simple, but it is only as good as the programming behind it. PID stands for proportional, intergral, derivate... calculus level math. However, the basic idea is that you want the EEV to respond as the system changes to keep the SH stable. The algorithims and settings can either cause a slow reacting valve, hunting valve, or a stable efficient system.

[jpsmith1cm]

Sumdumacguy,

Let's not try to reinvent the wheel, stepper valves have been used successfully for many years.

Most of the time, the "heavy" thinking has been done by the manufacturer of whatever controller that you are using.
Hook up the valve to the valve output board, hook up transducers and sensors, plug information into controller and off you go.

You aren't going to run these on a dig output, they 'step' at 200/minute or so, that kind of cycle rate would smoke a relay in short order. Also, bipolar stepper valves have 2 coils (is that the proper term?), one to open the valve and one to close it.

There are dedicated controllers made by CPC and Danfoss and others, I'm sure, along with the controllers made by the valve manufacturers.

[sumdumguy]

Sumdumacguy,

Let's not try to reinvent the wheel, stepper valves have been used successfully for many years.

Most of the time, the "heavy" thinking has been done by the manufacturer of whatever controller that you are using.
Hook up the valve to the valve output board, hook up transducers and sensors, plug information into controller and off you go.

You aren't going to run these on a dig output, they 'step' at 200/minute or so, that kind of cycle rate would smoke a relay in short order. Also, bipolar stepper valves have 2 coils (is that the proper term?), one to open the valve and one to close it.

There are dedicated controllers made by CPC and Danfoss and others, I'm sure, along with the controllers made by the valve manufacturers.

that clarifies it thank you sir

[beachtech]

They use an Electronic TXV like a pump down solinoid too :cool:

You sure you've only been doing this two days :p

yes only two days :)

my boss is so amazingly smart! he talks all day long and my sponge like brain is soaking it all in :) well it's kinda overloaded, but i am trying to keep it all in :)

but i still don't understand why we (fellow members i don't have anyone in my pocket) completely bypassed basics and went straight to pushrods and the such right off the bat :confused:

[jpsmith1cm]

Basic TXV operation. 2 forces close the valve, suction pressure and spring pressure. These are countered by power element pressure to open the valve.

Assuming (yeah, I know...) that the valve was originally set properly and was running at 6-8 degrees superheat, WHAT CHANGED??

There was no major leap of logic here, just basic theory.

[balzano]

and we would glady use your money to purchase this new electronic valve :D

and, lmao

we have blamed pushrods, inlet screen, and powerhead loss of charge... what about installation? is the thing installed properly?

is the sensing bulb in the right location? what o'clock position is it on the suction line? is it on a vertical line? is it mounted in an oil trap?

i don't understand why someone would think a txv needs to be constantly adjusted :confused:

the only thing a TXV does, is adjust and maintain SH. right?

i said before its mecanical, i dont have experience wih small refrigeration, i am talking about commercial with EEPR Controller.

what the SH do in life? weel even in small ref, why copeland require Max 18F of SH at the compressor? its about compressor life time, the compressor cooled by the suction gas.

[refermech]

Save yourself time and headach just remove Install new TXV and be done with-it

[crackertech]

Save yourself time and headach just remove Install new TXV and be done with-it

That wont mean that you don't have to set superheat.

[jpsmith1cm]

You...You...You mean they aren't set from the factory??!!!???

Say it ain't so!


:D

[crackertech]

You...You...You mean they aren't set from the factory??!!!???

Say it ain't so!


:D

Sure they are;):D:D:D:D

[nesc522]

its mechanical, so its normal to be adjusted each few months, with the new electronic txv we will not have this problem, superheat adjusted= good refrigeration cycle= life time compressor.

Your kidding, right?

[crackertech]

Your kidding, right?

What you don't ajust your txv's every month.:(;):rolleyes::D

[Phase Loss]

If you are constantly wrenching on your TEV...replace it. Or repair the real problem as to why the TEV would seem to need adjustment in the first place.

good TEV link. http://www.intkorea.kr/data/sporlan/10-11.pdf

[nesc522]

What you don't ajust your txv's every month.:(;):rolleyes::D

Ya, sure. I'm the guy that comes at night and closes them back up after the guy that was there during the day opened up the txv , trying to use the stem like a t-stat. On the bright side, we get time and a half to follow these goons around. We have a chain that we work for, one of they're guys has made a habit of this. He busted up a carlyle 5H40 with a multideck meat case. Made some good money from that one. If I remember right, I had to turn that alco valve in something like 11 turns to get it where it was right.

[crackertech]

Ya, sure. I'm the guy that comes at night and closes them back up after the guy that was there during the day opened up the txv , trying to use the stem like a t-stat. On the bright side, we get time and a half to follow these goons around. We have a chain that we work for, one of they're guys has made a habit of this. He busted up a carlyle 5H40 with a multideck meat case. Made some good money from that one. If I remember right, I had to turn that alco valve in something like 11 turns to get it where it was right.

I hate guy's that do that bit like you said it's easy $$$$$.:D

[balzano]

Your kidding, right?


absolutely not, I did not say that it should be adjusted every month, or you should adjuste the txv if you dont have problems with, but with experience in the very precise monitoring of temperature graph, I can say that we had alot of problems because of txv adjustment, the tech will thing its the control, or the EEPR, but most of time its the superheat, anyways the superheat is the basis of refrigeration. and more,good superheat protect the compressor by protecting the oil viscocity.

so please let me know why you think that i am kidding...

thanks.

[crackertech]

absolutely not, I did not say that it should be adjusted every month, or you should adjuste the txv if you dont have problems with, but with experience in the very precise monitoring of temperature graph, I can say that we had alot of problems because of txv adjustment, the tech will thing its the control, or the EEPR, but most of time its the superheat, anyways the superheat is the basis of refrigeration. and more,good superheat protect the compressor by protecting the oil viscocity.

so please let me know why you think that i am kidding...

thanks.

Yes you did.

its mechanical, so its normal to be adjusted each few months, with the new electronic txv we will not have this problem, superheat adjusted= good refrigeration cycle= life time compressor.

[nesc522]

[QUOTE=balzano;2127792]its mechanical, so its normal to be adjusted each few monthsQUOTE]
Thats BS. Tim

[balzano]

[QUOTE=balzano;2127792]its mechanical, so its normal to be adjusted each few monthsQUOTE]
Thats BS. Tim

for sure you will not touch the txv if you dont problem with, i think this is clear for everyone here. and the superheat is not the same few moths after the adjustment. also sure that the superheat has an effect on the compressor life.
anyways, in the next few months we will start monitoring working with the EXV, and will back to this thread when i have some graphs in hand, about how the EXV react with time.

regards.

[sumdumguy]

usually the guy that opens his mouth usually inserts foot but if you know your right then you should get familiar with my signature...

[dirtyboy103us]

this thread is starting to show some real potential:D:D:D

now guys keep it clean DING DING DING

[dirtyboy103us]

[QUOTE=nesc522;2375982]


anyways, in the next few months we will start monitoring working with the EXV, and will back to this thread when i have some graphs in hand, about how the EXV react with time.

regards.

EXV been there done that and they tend to really suck.... the sensors go bad and the rack looks like a snow cone so be careful what you wish for

[balzano]

[QUOTE=balzano;2378822]

EXV been there done that and they tend to really suck.... the sensors go bad and the rack looks like a snow cone so be careful what you wish for


Thank you for the information.

[joker1022]

OK. I may regret this but...I have been watching this thread for a bit. Knowing who balzano is, I feel that his meaning isn't being clearly expressed so hopefully this will help.
1) "its mechanical, so its normal to be adjusted each few months" The thought is...You may not have lost any gas from the powerhead, or any of that but you may have lost some strength in the spring. If one where to install a new TXV, set it perfectly, come back 3 months later, chances are the SH will have changed, even if ever so slightly. Is it affecting performance? Probably not. But it has changed. So to keep that perfect setting you would have to adjust it regularly to compensate for the gradual mechanical weakening. Now, is that what really happens? No. Got you thinking though.
2) "with the new electronic txv we will not have this problem, superheat adjusted= good refrigeration cycle= life time compressor." With an EXV we remove some of the mechanical parts that weaken or fail thus helping insure properly adjusted superheat which in turn, as we all know, can make or break a compressor.
3) "the sensors go bad and the rack looks like a snow cone You provided him with some insight on known problems that will be considered during his testing.

Be it a TXV or EXV certain basics still apply. Know how to set it and how it should be set. That can go a long way in diagnosing a problem or preventing one. The original poster stated that he had no problems and out of nowhere...pow. I think if you have to crank on the valve a bunch to get it back in proper working order, you probably need to change the powerhead, and who knows, maybe the valve too.
More than anything, the "metering" device is one of the four major components of a refrigeration system and often the most over looked, least thought about and most misunderstood. I hope I helped some.

[itsiceman]

Haven't really been following this thread but wouldn't a fluctuating head pressure affect the SH then a guy might be adjusting SH when the head changes in stead of working on maintaining a steady head pressure

[swinginutters]

So swinginutters have you been back? give us a up date.

went back about a week later, it's holding temp at 38 nicely, no ice on the evap.

[dirtyboy103us]

here you go joker here is all the reseach you will need happy reading
http://sporlan.jandrewschoen.com/

http://sporlan.jandrewschoen.com/100-9.pdf

[Executioner]

Ok my 2 cents.

Mechanical TXV's have been around ALOT longer than electronics, a regular txv will not need ANY adjustment once it has been set properly.
It's the same as the thermostat...set and forget! If there is a superheat problem after more than 1 week from initial proper setup of a txv and all other possible causes are eliminated then there is no question, the txv is failing.

Yes you can adjust again or multiple times but I know for a fact there are 20+ yr old txv's that are functioning perfectly fine.
Don't be overly critical on superheat when your on location, you only see a "snapshot" of what the superheat is in the coarse of 24hrs that the unit is running, it compensates for load from opening the door and throttles on startup every cycle.
If you have a situation where half the coil is frosting and you have a full sight glass, CHANGE THE VALVE! only adjust until a replacement can be obtained or done during normal hours.


I have to say I see alot of discussion about adjustments, superheat,subcooling and a bunch of other stuff thats basically overkill.
It's ALWAYS going to be either a failed part,dirt or charge.

If ANY system needs ANY adjustments after the first year then there is a failed part,dirt or improper setup during the first year.

The reason I say first year is a system using no head master Will need tweaking when transitioning from summer to winter.



I'm basically saying stop over anylising things.

No offense to anyone but I get a chuckle when there are 5 or more pages of responses on adjustments when ALL adjustments should be set and forget.