Marc O'Brian's artickle about 2K

[lana]

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]

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]

test post ..................... test

[taz24]

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]

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]

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]

No. We are talking about sub-cooled liquid. Have a look at the attached file.
Cheers

[slingblade]

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]

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]

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]

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]

Hi, Iana

what about to install sight glass after filter-dryer

Best regards, Josip

[Andy]

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]

Thanks guys.

Sight glass would help but bubbles in the sight glass could be from another reason.

Cheers.

[US Iceman]

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]

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]

Hi, Iana

Thanks guys.

Sight glass would help but bubbles in the sight glass could be from another reason.

Cheers.

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

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

Best regards, Josip

[Andy]

Thanks guys.

Sight glass would help but bubbles in the sight glass could be from another reason.

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]

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!

[Josip]

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]

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.

[Brian_UK]

Just a thought.....

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

[Abby Normal]

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]

lana , try this site for some resource on the subject.

Let me know how it goes.


http://www.nzifst.org.nz/unitoperati....htm#equipment

[Dan]

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]

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]

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 .
Anyway thanks everybody for your feedbacks.

Cheers

[rbartlett]

Let's see what sling has to say now.

Cheers

Richard

[WebRam]

to make more sense of that last comment, members should realise that Marc also posts as Richard.

Just to keep you all up to date LOL

[rbartlett]

to make more sense of that last comment, members should realise that Marc also posts as Richard.

Just to keep you all up to date LOL

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]

yea, yea LOL

[Andy]

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]

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]

Post deleted

[Abby Normal]

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]

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]

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]

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]

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]

I think Chillin out is pretty accurate. Some people doing their own things for their own reasons.

[Mark]

Some are still reinstalling programs on there computer

[DTLarca]

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]

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]

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]

Nothing, everyone is entitled to his/her opinion.

No one has any such entitlement

[slingblade]

No one has any such entitlement

Wrong, I have.

[DTLarca]

Wrong, I have.

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]

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]

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]

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.