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lana
10-11-2006, 07:51 AM
Hi everybody,

Has anyone read Marc O'Brian's article about 2K or Not 2K? in the RAC magazine?
It is interesting, but my question is, if there is a good sub-cooling and also blocked filter, then how can we know about the blockage? The only way is to measure the pressure before and after the filter.
Any comments?
Cheers:)

fridg
10-11-2006, 08:41 AM
Being SC liquid , the pressure temperature relationship can be used for this , a temp probe either side of the filter , then convert to a pressure.

WebRam
10-11-2006, 11:54 AM
test post ..................... test

taz24
10-11-2006, 12:45 PM
Hi everybody,

Has anyone read Marc O'Brian's article about 2K or Not 2K? in the RAC magazine?
It is interesting, but my question is, if there is a good sub-cooling and also blocked filter, then how can we know about the blockage? The only way is to measure the pressure before and after the filter.
Any comments?
Cheers:)

Temp relates to pressure.
On most systems you will struggle to get pressure readings from both sides of the dryer.

Cheers taz.

lana
10-11-2006, 12:47 PM
Sorry about all that deleting. I am having a proble sending a reply. When I complete my message then it would not be delivered???!!!

Anyway I try again.

in the P-h diagram, in the sub-cooled region, the constant temp line is vertical therefore; any pressure drop would not show any temp drop. until the state point goes into the double phase region. in this region any pressure drop would show temp drop. this is the problem. if there is no SC then it is easy to know the filter is blcked because there would be a temp drop.

fridg
10-11-2006, 01:11 PM
I think this relates to Boyles & Charles Law of thermodynamics

P1 V1. . .P2 V2
----- = ------
T1 . . . . . T2

If pressure on a liquid is increased so will the temp.

lana
10-11-2006, 01:25 PM
No. We are talking about sub-cooled liquid. Have a look at the attached file.
Cheers

slingblade
10-11-2006, 01:43 PM
Yes i have read it. I say only this, i change driers when they are blocked and not when mr o'briens opinion says i should.;)

lana
10-11-2006, 01:51 PM
Good for you. This has nothing to do with Mr. O'brian's opinion. The truth is: this is well established in the industry that if there is more than 2K temp difference across filter then it is blocked but the reality is :
The filter could be badly blocked but you dont see any temp difference.
What I asked is : except from measuring the pressure before and after the filter what can we do to know it is blocked(easy way)?

cheers

slingblade
10-11-2006, 01:56 PM
Good for you. This has nothing to do with Mr. O'brian's opinion. The truth is: this is well established in the industry that if there is more than 2K temp difference across filter then it is blocked but the reality is :
The filter could be badly blocked but you dont see any temp difference.
What I asked is : except from measuring the pressure before and after the filter what can we do to know it is blocked(easy way)?

cheers

How about low suction pressure for starters?

poor duty?

low discharge and low condensor heat rejection?


have you ever worked on fridge plant before?

lana
10-11-2006, 02:03 PM
Yes Sir I have.

Low suction pressure could be from the followings :
1- Lack of expansion device capacity.
2- Lack of refrigerant charge.
3- Lack of evaporator capacity.
4- Pre- expansion.

So the 4th and the 1st one has exactly the same symptoms except : temp difference in the liquid line.

The question still remains....

Cheers

Josip
10-11-2006, 07:59 PM
Hi, Iana :)

what about to install sight glass after filter-dryer;)

Best regards, Josip :)

Andy
10-11-2006, 08:28 PM
Yes i have read it. I say only this, i change driers when they are blocked and not when mr o'briens opinion says i should.;)

How about the liquid line sightglass after the drier:) all systems have this, most don't have pressure tappings before and after the drier:)

Kind Regards Andy:)

lana
10-11-2006, 09:08 PM
Thanks guys.

Sight glass would help;) but bubbles in the sight glass could be from another reason.:confused:

Cheers.:)

US Iceman
10-11-2006, 09:28 PM
I just noticed this thread and thought I might offer some comments.

If the liquid refrigerant is subcooled, then measuring the temperature drop across a filter-drier is worthless. Lana has the right logic for this.

You cannot measure any temperature loss until the liquid is at a saturated condition.

So, the only reliable method for measuring this is a pressure tap on both sides of the filter-drier if subcooled liquid is present.

I don't think the use of a site glass is entirely reliable. The system could be sllightly undercharged, so the bubbles form when the TXV opens up momentarily, or some other logical reason.

Having said that, I like Josip's idea of putting the site glass downstream of the filter-drier to check for bubbles, as long as someone does not add refrigerant just because there are bubbles.

I always installed the site glasses downstream of the filter-drier for this reason too.

Now, if the liquid is saturated, then the temperature loss would be a suitable check to be made as the liquid would flash off.

LRAC
10-11-2006, 09:35 PM
The reality is in any industry people write articles of correct applications or design protocols, engineers have a different view, many systems do not work or conform to text book writings and this is why we are called engineer's.If you have a method that can diagnose a blocked or partially blocked drier then all is fine, why break in to a system with the chance of adding moisture to the system because you have a 2K differential.
Unless the system is suffering from poor performance leave well alone unless moisture is present or your opening up the system.

regards
Lrac

Josip
10-11-2006, 09:38 PM
Hi, Iana :)


Thanks guys.

Sight glass would help;) but bubbles in the sight glass could be from another reason.:confused:

Cheers.:)

maybe to install by-pass valves;) like we do on industrial plants

Hope your answer is not to install filter-dryer with indicator:eek:

Best regards, Josip:)

Andy
10-11-2006, 09:43 PM
Thanks guys.

Sight glass would help;) but bubbles in the sight glass could be from another reason.:confused:

Cheers.:)

Hi Lana:)
being able to tell why the sightglass flashes is what I get paid for:) the sightglass is a tool for the wise:)

Kind Regards Andy:)

US Iceman
10-11-2006, 09:50 PM
the sightglass is a tool for the wise:)


That I agree with 100%. Too often someone sees bubbles and then feel they have to charge refrigerant into the system.



being able to tell why the sightglass flashes is what I get paid for:)


I like that!:cool:

Josip
10-11-2006, 10:28 PM
Hi,

what about this:

Where only vapor normally exist actual temperature is equal or above P-T relationship. Difference is superheat.

Where only liquid normally exist actual temperature is equal or below P-T relationship. Difference is Subcooling.

Where both liquid and vapor normally exist temperature is equal to P-T relationship.

Can we use this to determine what we have;)

Best regards, Josip :)

US Iceman
10-11-2006, 10:38 PM
Where only vapor normally exist actual temperature is equal or above P-T relationship. Difference is superheat.

Where only liquid normally exist actual temperature is equal or below P-T relationship. Difference is Subcooling.

Where both liquid and vapor normally exist temperature is equal to P-T relationship.

Can we use this to determine what we have;)


That sums everything up quite nicely.:cool:

Brian_UK
10-11-2006, 11:52 PM
Just a thought.....

Switch off condenser fans to reduce the subcooling and then check temperatures across the drier.

Abby Normal
11-11-2006, 04:37 AM
Hi,

what about this:

Where only vapor normally exist actual temperature is equal or above P-T relationship. Difference is superheat.

Where only liquid normally exist actual temperature is equal or below P-T relationship. Difference is Subcooling.

Where both liquid and vapor normally exist temperature is equal to P-T relationship.

Can we use this to determine what we have;)

Best regards, Josip :)

reminds me of an old usenet thread on receiver subcooling

fridg
11-11-2006, 01:22 PM
lana , try this site for some resource on the subject.

Let me know how it goes.


http://www.nzifst.org.nz/unitoperations/flfltheory5.htm#equipment

Dan
11-11-2006, 02:50 PM
If you cannot check the pressures, then you should remove the subcooling. If it is mechanical, turn it off. If it is from the condenser, cycle fans off, etc. Just a thought.

jamaladwani
11-11-2006, 09:15 PM
If you look for easy way,you can take in mind these notices:
1. The first level of filter blockage that could be effective will mostly be sensible: a temp difference between the inlet and outlet of the filter,the outlet will be colder.
2. The second level is visible, there will be condensd drops on the filter cold outlet .
3. The third level is visible too,there will be frost on the filter outlet.
4.The fourth level neither sensible nor visible,i.e when the filter is totaly blocked.There will be a vacuum reading ,but of course this vacuum will be a function of many other possible blockages and need detailed checks before discover the real cause of the blockage .

lana
13-11-2006, 03:29 PM
Hi everybody,

Mr O'Brian as always ......... But he is right. You can not fight with reality.
Andy you are 100%right we are paid for these things.:)
Actually I agree with you guys all.
My point to post this thread was to disscus it with others.
Sometimes people don't understand very simple logic but they can solve very difficult problems:D .
Anyway thanks everybody for your feedbacks.

Cheers

rbartlett
13-11-2006, 10:53 PM
Let's see what sling has to say now.

Cheers

Richard

WebRam
13-11-2006, 11:08 PM
to make more sense of that last comment, members should realise that Marc also posts as Richard.
<O:p</O:p
Just to keep you all up to date LOL<O:p</O:p

rbartlett
13-11-2006, 11:10 PM
to make more sense of that last comment, members should realise that Marc also posts as Richard.
<O:p</O:p
Just to keep you all up to date LOL<O:p</O:p

Unless he has hijacked my account he has never written under my name..So I demand where you get this info from

Cheers

Richard

WebRam
13-11-2006, 11:11 PM
yea, yea LOL

Andy
13-11-2006, 11:15 PM
Unless he has hijacked my account he has never written under my name..So I demand where you get this info from

Cheers

Richard

Richard:)

style, Marc's style is un-mistakable:)

Kind Regards Andy:)

rbartlett
13-11-2006, 11:18 PM
Richard:)

style, Marc's style is un-mistakable:)

Kind Regards Andy:)

Firstly marc would write pages of stuff and i know he'd be horrified to read someone thought anyone else was him. He has NEVER to my knowledge posted under my name.I wouldn't want it either

cheers

richard

taz24
14-11-2006, 01:54 AM
Post deleted

Abby Normal
14-11-2006, 08:33 PM
Firstly marc would write pages of stuff and i know he'd be horrified to read someone thought anyone else was him. He has NEVER to my knowledge posted under my name.I wouldn't want it either

cheers

richard
I must have known you and Marc 'online' a good 8 years or so Richard, you have always had integrity even when giving the seppos a political barb or two.

chillin out
14-11-2006, 10:01 PM
I must have known you and Marc 'online' a good 8 years or so Richard, you have always had integrity even when giving the seppos a political barb or two.
LOL...
It's called manipulation.

Chillin:) :)

slingblade
16-11-2006, 05:23 PM
Good grief, what has gone on. I dont visit for a couple of days and it's all changed.


Let's see what sling has to say now.



Nothing, everyone is entitled to his/her opinion.


As for Marc posting as Richard, i'm not so sure. i exchanged several pm's with Richard recently and did not suspect Marc was involved {other than on a background discussion level}.



Chillin, congrats on the mods job.
Hope you "clean the place up" like you said.;)

A1onetime
17-11-2006, 12:08 AM
hello all, its my first post on here.

whats happened to all the interesting people?

Marc O
Richard
Mark F
Gary
Botrous
Herefishy
Aiyub
Shogun

is there is some sort of Meglomania going on ??

regards

no A1 for me anymore

chillin out
17-11-2006, 12:20 AM
Chillin, congrats on the mods job.
Hope you "clean the place up" like you said
Thanks Sling.

Marc O .....Decided to leave
Richard .....Decided to leave
Mark F .... Still here, as far as I know
Gary ..... Still here, as far as I know
Botrous ..... Dodging bombs but thankfully is still here
Herefishy .....? but I am sure he is still here
Shogun ..... Left long time ago

Hope this clears a few things up.

Chillin:) :)

Dan
23-11-2006, 01:39 AM
I think Chillin out is pretty accurate. Some people doing their own things for their own reasons.

Mark
27-11-2006, 06:58 PM
Some are still reinstalling programs on there computer:(

DTLarca
18-12-2010, 02:38 PM
Hi everybody,

Has anyone read Marc O'Brian's article about 2K or Not 2K? in the RAC magazine?
It is interesting, but my question is, if there is a good sub-cooling and also blocked filter, then how can we know about the blockage? The only way is to measure the pressure before and after the filter.
Any comments?
Cheers:)

You could raise the head pressure to reduce the subcool at commissioning and note where the sight glass starts flashing. Assuming design conditions are at the same time approximated of course.

Then at each service visit do the same and note how much earlier in the subcool reduction curve the sight glass flashes.

I have attached the article as I sent it to the RAC Service Engineer Editor.


Hi everybody,

Mr O'Brian as always ......... But he is right. You can not fight with reality.

Thank you Lana :)

monkey spanners
18-12-2010, 05:02 PM
I have a method to find if a drier is blocked that has never failed to find one that is restricted even if there is no drop in temperature across the drier.

What you do is blow through it, if a resistance is noted then its blocked, if no significant resistance is observed it was ok till it was tested....

Jon :)

DTLarca
18-12-2010, 05:53 PM
Yes i have read it. I say only this, i change driers when they are blocked and not when mr o'briens opinion says i should.;)

It's not my opinion :)

It's my proposition supported by argument and evidence - it is not my testament - it's truth lies completely and utterly outside and thus independent of my opinions.

Your position cannot be supported by any good reasoning - only by selfish motives.

DTLarca
18-12-2010, 05:55 PM
Nothing, everyone is entitled to his/her opinion.

No one has any such entitlement :)

slingblade
21-12-2010, 10:22 PM
No one has any such entitlement :)

Wrong, I have.:p

DTLarca
21-12-2010, 11:14 PM
Wrong, I have.:p

You can't be serious :)

You have no say in what your beliefs are. So you cannot have any say in what your opinions are.

If you believe a certain colleague to be out on a certain site when the next second you see them in the office corridors you can't help but now believe they are not at that certain site. You cannot close your eyes telling yourself "No, no, I want to keep my belief that he is on site!".

So if you cannot choose what your beliefs are - if your beliefs change through no choice of your own then the only way for you to keep your beliefs would be to limit your exposure to argument and evidence that might change your beliefs.

So saying "I am entitled to my own opinion" can only mean you have a right to close your ears, eye's and the rest to the world. And you might indeed have that right but then you are forfeiting your right to comment on the world around you given that you are professing to be deliberately ignorant of it.

Invoking the said right implicitly pronounces or confesses ones own preference for ignorance.

slingblade
24-12-2010, 12:14 AM
You can't be serious :)

You have no say in what your beliefs are. So you cannot have any say in what your opinions are.

If you believe a certain colleague to be out on a certain site when the next second you see them in the office corridors you can't help but now believe they are not at that certain site. You cannot close your eyes telling yourself "No, no, I want to keep my belief that he is on site!".

So if you cannot choose what your beliefs are - if your beliefs change through no choice of your own then the only way for you to keep your beliefs would be to limit your exposure to argument and evidence that might change your beliefs.

So saying "I am entitled to my own opinion" can only mean you have a right to close your ears, eye's and the rest to the world. And you might indeed have that right but then you are forfeiting your right to comment on the world around you given that you are professing to be deliberately ignorant of it.

Invoking the said right implicitly pronounces or confesses ones own preference for ignorance.


Yes, quite serious. I i were to say it's cold outside in my opinion, I have no belief other than it's cold outside. If someone in the same room as me, from the North pole, were to counter that by saying it's quite mild outside in my opinion, then we are both expressing a personal point of view. Niether of us are correct or incorrect, and are not ignorant in any way. More to the point neither has breeched any Law. So my point stands, We are all entitled to our own opinion.

slingblade
27-12-2010, 01:44 AM
Has the Cat got your tongue Marc. I expected nonsense in response long before now. It's not a problem, the more silence you bring to this forum the better, in my opinion, cheers. Merry christmas.

DTLarca
27-12-2010, 05:56 PM
Yes, quite serious. I i were to say it's cold outside in my opinion, I have no belief other than it's cold outside. If someone in the same room as me, from the North pole, were to counter that by saying it's quite mild outside in my opinion, then we are both expressing a personal point of view. Niether of us are correct or incorrect, and are not ignorant in any way. More to the point neither has breeched any Law. So my point stands, We are all entitled to our own opinion.

You've committed the fallacy of high redefinition. You've slid from a discussion of contingent truths to necessary truths having changed the implied subject of facts out in the world, such as the temperature outside, to matters of taste such as do I like it when it is that temperature outside. This is also called the no true Scotsman fallacy - when we slip between synthetic and analytic statements.

desA
27-12-2010, 06:02 PM
2K or not 2K? That is the question. :D

monkey spanners
27-12-2010, 07:05 PM
2K or not 2K? That is the question. :D

Whether tis nobler in the field,
To measure inlet and outlet temperatures,
Or to take spanners against them,
And by opposing them, undo reluctant flares;
No more! replacements brazed, say we an end
The heart-ache of a thousand leaks
The F-gas is here to stay!
Devoutly to be wish'd. The drier to sieve;
To sieve, perchance to dry, ay there's the rub;
For in that sieve and dry what temp drops may come
When we have suffered blocked evaporator coils,
Must give us pause: there's the restriction
That makes calamity of long system life:
For who would bear the whips and scorns of customers,
The compressors wrong, the pressure switches continuity,
The pins of depressed schreader cores delay,
The insolence in the office, and the sporlans
The patient merit of unworthy tasks
When he himself might quit this job....

Jon :D

desA
27-12-2010, 07:07 PM
Bravo... :D

slingblade
28-12-2010, 03:10 AM
Whether tis nobler in the field,
To measure inlet and outlet temperatures,
Or to take spanners against them,
And by opposing them, undo reluctant flares;
No more! replacements brazed, say we an end
The heart-ache of a thousand leaks
The F-gas is here to stay!
Devoutly to be wish'd. The drier to sieve;
To sieve, perchance to dry, ay there's the rub;
For in that sieve and dry what temp drops may come
When we have suffered blocked evaporator coils,
Must give us pause: there's the restriction
That makes calamity of long system life:
For who would bear the whips and scorns of customers,
The compressors wrong, the pressure switches continuity,
The pins of depressed schreader cores delay,
The insolence in the office, and the sporlans
The patient merit of unworthy tasks
When he himself might quit this job....

Jon :D


LOL. Good one mate, i like it. However you commited a fallacy, i dont know which one, but the oracle will tell you when he decides your post is not worthy.

slingblade
28-12-2010, 03:15 AM
You've committed the fallacy of high redefinition. You've slid from a discussion of contingent truths to necessary truths having changed the implied subject of facts out in the world, such as the temperature outside, to matters of taste such as do I like it when it is that temperature outside. This is also called the no true Scotsman fallacy - when we slip between synthetic and analytic statements.

Utter Sh!te, Cheers Mate. Just what i expected.:)

install monkey
28-12-2010, 02:55 PM
any inline component will create a pressure drop. if the described system has a suspected blockage and no one bothered to fit gauge ports all over the system if it is working to its design criterea the drier should be sized correctly and as long as no muppet has worked on it-is anyone bothered that a slight resistance may be present in the drier but u cannot prove this-surely the customer aint gonna pay for u to pump it down,change it pressure test,vac and reinstate to then not notice a difference in performance.
sit tight and wait for the compressor failure.

DTLarca
28-12-2010, 08:42 PM
Utter Sh!te, Cheers Mate. Just what i expected.:)

What I said was - your opinion that the prevailing climate is comfortable is not of the same type as your opinion that London is in England.

The first opinion is made true in coincidence with your thinking, so, your thinking so itself is all that is required to make it true and so you saying so is true only if it reflects what you think. But the second opinion, that London is in England, is not made true merely on account of your thinking and later your saying so - it's truth value is contingent upon the world out there entirely independent of your thinking. You could pass away making the first opinion a nonsense while the second's truth value would not have changed in the slightest.

With regard to opinions of the second type - you have no rights unless the word "right" is used in the sense that it is deemed by all to be a true opinion in which case any discussion on the matter would have to be brought to a full conclusion before you can earn this type of right making any appeal to it, before the conclusion of a discussion, an irrelevance regarding the truth value. An opinion's truth value can give you this right but no right of any sort can give any opinion a truth value. Only argument and evidence can give opinions of the second type any rights of ownership.

For instance, what right do you have to the opinions that what I said was "Utter Sh!te", in the epistemic sense? None, you have no right - because you cannot give any argument or evidence for it. It is probably nothing more than a matter of wishful thinking.

Goober
29-12-2010, 01:09 AM
Have I said what a complete and utter load of sh1te this thread is? No? Well let me tell you this thread is a complete load of old sh1te.

mikeref
29-12-2010, 01:54 AM
Have I said what a complete and utter load of sh1te this thread is? No? Well let me tell you this thread is a complete load of old sh1te.
That is one way of looking it. May i offer my view? Anytime i change a drier, i always date it with liquid paper pen so its there for years, with short comment on steelwork nearby, (clogged, metal, or comp.replaced 7/08 for example). Should i happen to be on that plant again at a later date, sometimes many years later and say, TX is history, i always check drier date and liquid indicator. Clocked up 3 years and discoloured as comment... Toss it and redate. no time wasted playing mind games or taking temperature readings. Add the drier cost to the bill and tell client its $ well spent for a clean system.DONE, now move on.. Mike.:)

DTLarca
29-12-2010, 03:41 AM
Have I said what a complete and utter load of sh1te this thread is? No? Well let me tell you this thread is a complete load of old sh1te.

If you've never heard of the 2K rule of thumb (Many haven't) and don't think it anyway an interesting topic to muse over - then just ignore the thread.

Sight glasses seem to me to clear up after about 3K subcool. So if you measure 5K subcool leaving the condenser or receiver and yet still see some flashing in your sight-glass, located after the liquid line filter drier, then you would probably be right to arrange for a changing of the drier.

In other words - an alternative rule of thumb that would work would be "If the subcool drops by 2K or more through the filter drier, at full load, then the drier is either too small or is due for replacement."