Adjustable versus non-adjustable

This is only for the curious. I have seen the cycle just go back and forth regarding the worthiness of having something adjustable versus having something non-adjustable.

In my narrow experience, I have this to offer:

There appears to be a time-cycle in our trade. That a trend goes toward making things non-adjustable for a while, then leans toward making things adjustable. Then just changes again?

Is there any chance that this reflects on our abilities and competence previous to each cycle? Or perhaps reflect on the manufacturers?

How often do techs bypass non-adjustable things? How often do techs wish things were not adjustable?

Dan

If there was ever a refrigeration component that should be made non-adjustable, hermetically sealed, and emblazoned with a glow-in-the-dark warning label that says, "DO NOT ADJUST", it is the thermostatic expansion valve.

Gary

After 33 years as a service technician, and author of 4 books on the subject, I note that I have finally graduated to the status of "Apprentice Engineer"...lol

Gary

you have a way to go yet, ya young puppy ;)

Let's hope so.

Gary

<i>If there was ever a refrigeration component that should be made non-adjustable, hermetically sealed, and emblazoned with a glow-in-the-dark warning label that says, "DO NOT ADJUST", it is the thermostatic expansion valve.</i>

If there was ever a call to play devil's advocate...... :)

Consider this issue from the perspective of the refrigerated case manufacturer. To use a non-adjustable TEV, each case manufactured would, of course, need to be tested with all refrigerants approved for that case so to establish valve settings. Invariably, some acceptable range of values for liquid temperature and pressure feeding the case would need to be established. For example, a TEV which is set properly at a 100°F condensing and 90°F liquid temperature may have to be reset if liquid temperature is subcooled to 40°F. Assuming we allow the case to be used with R-134a, R-22, R-404A, and R-507, this means four TEVs need to be set up for each case. If this manufacturer builds 100 different types of refrigerated cases, he may need to set up as many as 400 TEVs, though hopefully they can find some of the cases which can use the same valve capacity and setting. Then pity their salesmen who want to sell cases to a customer who wishes to use R-401A or R-402A or R-408A or R-409A or R-XYZ. The manufacturer, of course, could use adjustable TEVs for the less usual refrigerants, or for the more extreme operating conditions. So add prehaps another 16 TEVs to the specifications. Then pity their purchasing dept who must keep these valves in stock, while listening to their accounting dept whine about the largess of their purchased parts inventory.

Then consider the issue from the perspective of the smart service mechanic. He wants to convert an R-12 system to R-134a. But he finds non-adjustable TEVs being used, causing him to either replace the TEVs or find adjustment kits for them. Or he wishes to employ a mechanical subcooler to reduce the operating time of his compressors to save energy. But the non-adjustable TEVs don't hold their settings well enough at the low liquid temperatures....

Professor, of course you are right. The subtle difference between 404A and 507, for example is enough to cause the non-adjustable valve to feed differently, and thank goodness that Sporlan has kits to make the non-adjustable valves adjustable.

But Gary makes a very good point as well. I remember an old time sales engineer who did commercial warehouses. In his written specifications, he instructed the installer to NOT adjust expansion valves. I am sure he was wrong now and then, but he reserved the right to make the call if things were not working correctly. We did two installations for him, obeyed his specifications, and never had a problem. But down the road I bet the service techs twisted those stems back and forth until they discovered the real ailment.

Dan

It has occurred to the Prof that there might be some merit in designing a thermostatic expansion valve with a fixed setting, but supply it with an adjustment that had no effect on the valve. This would be rather simple to do. The novice mechanic could "adjust" the valve in and out to his hearts content without affecting the valve's setting....

Of course this type of valve might send a knowledgeable mechanic to the nearest liquor store for a six-pack of "Wee Heavies" ....... :)

Oh Boy, that made me laugh :):)

PS Prof, things hopping up in the pre draft moves ;)

LOL, Prof. I haven't a clue about what a wee-heavy is, though. But the nonadjustable adjustable things actually are a part of our life. Two examples that I know are real:

Pedestrian traffic light buttons in St. Louis.
Tram car buttons in Tampa's airport.

Oh! Let's not forget all the fake thermostats we install in supermarkets and drug stores for the clerks. Oops. That was supposed to be a secret.

<i>I haven't a clue about what a wee-heavy is</i>

Dan, you need to check out the "Home Brewing" thread under "Hobbies"... :)

Prof...okay..okay...I surrender...lol

Maybe we can just weld them in place after commissioning.

How about different springs for different refrigerants (somehow made easily replaceable). Can that be done?

Gary

hmmmm...or perhaps adjustment only within a very limited range?

Gary

Waxing philosophically, and drifting away from mechanical devices, let's ponder computer controls. The dreaded password hierarchy. It is a way, is it not, to control adjustment and yet have it available to those who prove themselves worthy?

With that thought in mind, should any of the following be password protected functions?

1. Manual defrost
2. Suction pressure set point
3. Condenser fan set point
4. Floating points
5. Acknowledging alarms
6. Force compressor run

Dan

Quote:

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Originally posted by Dan
With that thought in mind, should any of the following be password protected functions?

1. Manual defrost
2. Suction pressure set point
3. Condenser fan set point
4. Floating points
5. Acknowledging alarms
6. Force compressor run

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I would suggest all expect number 1 but are we trying to protect the equipment and product from attack by either the end user or the dubious mechanic?

Brian

The end user has every right to screw up his equipment.

And, besides, it's good for business...lol

Quote:

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Originally posted by Gary
The end user has every right to screw up his equipment.

And, besides, it's good for business...lol

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Yes, you are of course quite right and I rofl at the simplicity of the statement.

Brian

Service techs, on the other hand need to know when to adjust and when not to adjust.

Teaching them how it works and how to adjust it JUST ISN'T GOOD ENOUGH.

Quote:

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Originally posted by Brian_UK

Quote:

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Originally posted by Dan
With that thought in mind, should any of the following be password protected functions?

1. Manual defrost
2. Suction pressure set point
3. Condenser fan set point
4. Floating points
5. Acknowledging alarms
6. Force compressor run

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I would suggest all except number 1 but are we trying to protect the equipment and product from attack by either the end user or the dubious mechanic?

Brian

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Good point, Brian. What are the purposes of passwords? I would like to think they protect the equipment being adjusted by competitors, or ill-willed ex-employees, and certainly store personnel. There have been times that I would have liked to use them to protect the equipment from service techs too.

Conversely, I have had competent technicians frustrated that they couldn't effectively respond to an emergency service call because they couldn't get the password.

But I agree. Manual defrost is a good one to keep available to everybody, as long as it cycles properly out of defrost during it's alloted time span.

Dan

Quote:

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Originally posted by Gary
Service techs, on the other hand need to know when to adjust and when not to adjust.

Teaching them how it works and how to adjust it JUST ISN'T GOOD ENOUGH.

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Hahahaha. So true. I just had a major food loss which is attributable to "adjusting things." A marginal service tech ran a call and diagnosed properly a shorted out fan that tripped the breaker on two of four unit coolers in an ice cream walk-in with glass doors. He de-iced the coils and went home for the evening with a follow-up scheduled in the morning.

The unit coolers, in this application, are actually mounted above the ceiling of the walk-in and plenumed to discharge the air directly down the interior of the glass doors.

At 3 pm, the store manager called and begged for a supervisor. He has lost all his ice cream. When the supervisor showed up, the tech had gauges and thermometers hooked up to one of the evaporators and the entire cap removed from the plenumed unit coolers! He was trying to adjust superheats! On a system that has been operating fine for 2 years! $16,000.00

Grrrr!

Quote:

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Originally posted by Gary
If there was ever a refrigeration component that should be made non-adjustable, hermetically sealed, and emblazoned with a glow-in-the-dark warning label that says, "DO NOT ADJUST", it is the thermostatic expansion valve.

Gary

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I totally agree with you. Serviceman from Iceland

This is something that new service techs seem to have a hard time understanding.

On a new system startup, the TXV may need adjustment, but it is highly unlikely.

Once that system is running properly, the TXV may someday need to be replaced, but it will never ever need to be adjusted again. Ever.


[Edited by Gary on 28-04-2001 at 08:09 AM]

The low pressure control. Seems its adjustment is the first thing that a marginal technician will play with when other things are going wrong.

Dan

Here is a question for you... why do contractors install refrigeration with LPC's for temperature control? That is like going deer hunting with grenades. It works, but it has problems and most techs will adjust it and leave only to find they have to return for possible even another problem now.

LPC's are excellent when used in conjunction with temperature controls.

Temperature controls themselves get jacked all around the scale sometimes too, then they wonder why it runs all the time! LOL!!

:p~ "but don't that make it colder mister repairman?"

Quote:

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Originally posted by subzero*psia
Here is a question for you... why do contractors install refrigeration with LPC's for temperature control?

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'cos the contractor is still looking in an 'old' refrigeration book and hasn't learnt yet about the new fangled electric thermostat.

Brian

I'm a sls rep for an ac line Spacepak and we never have any problems when the condensor has a TEV but the minute someone uses a piston "bullet " style when the temperature drops we get calls on unit performance, seems like a self regulating valve would always be used and never a "bullet " style, of course I'm just a sla rep and dont know any better, Ken :confused:

LOL DAN -

YA know those darn stats "we don't know about"? Turns out I cut my teeth on them. After 1/2 a day fooling arouind with one and up and down the ladder 10 times to see if this did that and didnt do this...... wasnt even wired in.... I didnt know why til a few weeks later the same customer had a freeze up on his Box.

Any way I suspect the non-adjustable components are there and suitable for 1 thing and 1 thing alone - what the origonal intent was.

Adjustable Components have to be in place for the same reason from the intended outcome but someone realized conditions are not uniform everywhere and so wa - la, the ingenious adjustiable what ever. Its a good thing too. If all things were equal we'd only need 1 type of refrigeration and one type of mechanic.

Im sure you know this though. You left me the way to add to the thread and I thank you. :) :)

A manager is usually happier with fewer things adjustable. His technicians are usually happier with more things adjustable.

It's a happy-happy sort of thing that usually comes to a conclusion when the controller asks why certain customers are not paying their bills.

Then we get into the adjustability versus non-adjustability of the billing and paying process. Even accountants share this dilemma. Receivables people prefer non-adjustable payments and payables people prefer adjustable payments.:)

Quote:

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Originally posted by Dan
Oh! Let's not forget all the fake thermostats we install in supermarkets and drug stores for the clerks. Oops. That was supposed to be a secret.

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Nope.... They taught that in 1980 at Cal Poly in the Junior Design class/lab.

Got a service call from a client lady who was always complaning about no air. The diffusers were about 20 feet up because the building was an old department store now being used as an office building, Large open area with many desks. What to do? there was no way I could reach those diffusers but I had to prove to her that air was coming out. I found a ceiling T bar cut the end to make a hook then put toilet paper on the end. when I talked to her I said I had a special adjustment tool with me I proceeded to adjust the diffusers and she could see the toilet paper waving and fluttering. She was a happy customer. being a service mechanic you have to adapt, improvise and be able to BS at times when you can't spend any money to improve the situation.:D
Roger

hehe toilet paper! i'll have to remember that one... :)

i got christmas tinsel on all the grills in an open plain mail sorting centre here... just to prove that "air" is actually coming out of all of the defusers... even if their digi temp tells them its cold enough, they still wanted proof air was coming out...

me thinks they need to spend more time doing there job seriously!

dan,

the fake thermostate trick is very old. what I hate about it, is that some smart asses are cheating clients and throw the s*h*i*t in our face.

every time I see those fake ones, I tear them off the wall and leave a sign says: temperature control in the machine room.

more distinguished, more professional. think about it.

chemi :mad:

roger.

in most parts of the world toilet paper is used for different application.



a picture that will guide you is attached.

chemi :D :D :D :D

hehe chemi...

i would much rather use toilet paper on that butt then my own!

I see parts of this thread are quite old, but always timely.

I agree with both Gary and the Prof: adjust the expansion valves at commissioning, if necessary, and then leave the *** things alone.

In an early refrigeration conversation with my father, also a self-employed refr tech and a very bright guy, I was astonished to receive his advice never to adjust a TXV, but to replace it instead!

His rationale was that a TXV that needed adjustment once would need it again. Better to replace it at the earlier service call before damage had occurred, but also before the customer expected another adjustment to be done under warranty!

With the time constraints that sometimes exist in this business, I have amended my practices. I will adjust a valve if unable to replace, but I have a space on my invoice to list uncompleted work. I always note that valve adjustment has been required and a replacement valve will be installed at the next service if the problem repeats.

(I should add that valve adjustment or replacement is one of the rarest things I do, and that the only valve I use is Sporlan, though I have no actual data regarding its superiority.)

I also impress on my commercial accounts that temperature adjustment on any box is at no charge if it can wait a day or two until I am in the area, UNLESS they have tried to adjust it first!

Of course I usually find that there is an underlying problem which has caused the temperature change: an evap fan free-wheeling, dirty condenser, leak, etc. I charge for the work but give them a break on the "Truck & Travel" charges, which makes everyone happy.

Rog

Non-Adjustable sounds good to me.

If if goes wrong you just change it and therefore don't get people p***ing around with them.

If the system is designed right then they should work OK as preset.

At the end of the day the more things that are non-adjustable the let things you have to worry about that someone else has come in and changed.

Regards

Raymond

hi raymond,

I will have to disagree with you on that one.
TEV's come preset for what?
it depend on the orifice you put in, on working conditions and superheat.

its a good thing they are adjustable.
there are non adjustable TEV's for spacial applications like injection TEV

of course it would be easier if they was'nt, but sometimes, its the turn of the screw at the bottom of the TEV that makes all the difference.

chemi :)

what would be nice is a One time adjustable valve that you can break off the stem once setup.

Best of both worlds. Apprenti proof and cost effective

Well, one could use electronic "TXVs" controlled by a Jessica Simpson micro, so a JTAG interface would be needed to adjust the values.
Or a much easier, low tech solution would be to put "Warranty void if label is tampered" stickers over the adjustments after the initial adjustment.

Quote:

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Originally Posted by Gary

This is something that new service techs seem to have a hard time understanding.

On a new system startup, the TXV may need adjustment, but it is highly unlikely.

Once that system is running properly, the TXV may someday need to be replaced, but it will never ever need to be adjusted again. Ever.


[Edited by Gary on 28-04-2001 at 08:09 AM]

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Every install I do..............I adjust the TEV
So the superheat is spot on


Only time you DONT NEED to adjust is

WHEN the TEV ORIFICE is selected spot on........
When all components are balanced, condensing unit, evaporator, pipe sizes, lengths


These days the TEV manufacturers do not factory set TEV's any longer

Up to the Commissioning Engineer to ensure its right

Might be different in US