Refrigerant overcharge

[frank]

Now then lads ! who can beat this?

We were called out to a VRV system (24hp Daikin) as it was not operating correctly. After investigating we arrived at the conclusion that the inverter compresser was not running, even thougth the contactor was pulled in (doesn't take Sherlock Holmes does it?? ).

Anyhow, before we are prepared to fit a replacement we need to know why the pot failed so we start with recovering the refrigerent (R407C). Calculating the pipework lengths and factory charge we determine that the total charge should be 43.4kg. We have just finished recovering after 2 days and have just sent 67.3kg for destruction!!

Have you ever had to deal with a system that was overcharged by 23.9kg??

[rbartlett]

i thought daikin had an 'overcharge' sensor??
i remember speaking to someone about correct charge and he mentioned it

maybe it was mitsi/toshi...

anyway

i asked 'in that case why not charge it to 'overcharge' and remove some rather than waste time measuring pipelengths?'


cheers

richard

[frank]

Hi Richard

The new VRV II systems have a refrigerant charge sensor on the accumulator but this particular one is 18 months old and just a bog standard VRV Plus on R407C without any sensors. We did not install this system, but, as it is more than 12 months old our client has asked us to take the servicing on board. We Spoke to Daikin and they recommend that all 3 compressors are replaced as the 2 on/off compressors will have been damaged.

Bet we hold the world record for an overcharged system

[Latte]

Hi Guys,
I know its a stupid question but here goes anyway!!!!,
Why dont manufactures fit sightglasses on a/c's
I appreciate that some units have the expansion device on the outdoor unit but surely something could be put in after the condenser to aid gas charging ?

regards

Raymond

[rbartlett]

primarily because they don't use tev's/receivers

therefore a s/g would not be relevent and lead to overcharging (which happens enough anyway i guess..)

cheers

richard

[rbartlett]

btw i remember marc and i starting to reclaim out of a carrier chiller late one night..

we filled a big reclaim bottle and were nowhere near -so we naffed off home...

i think we heard later it had 90kg in it when it should of had only 60..

cheers

richard

[frank]

Richard

Our charge was 23.9kg / 43.4 * 100 = 55.069% overcharge.

Your system was 30kg / 60 * 100 = 50% overcharge.

We still hold the world record

[bernard]

Hello

Ref sight glass-does that mean they should not be fitted on small cellar cooling systems as lots of people do ?

Ref overcharge-I thought it took me longer than usual to charge that system

[rbartlett]

Hello

Ref sight glass-does that mean they should not be fitted on small cellar cooling systems as lots of people do ?

Ref overcharge-I thought it took me longer than usual to charge that system

again it depends which type of cellar cooler..tev/receiver -yes

capilary/no reciever -not really necessary and could lead to overcharging,,

however we used to fit them to these imi/qualitair cellar coolers too

(note mastair used to recommend charging by sweating of the last run of the evap....)

cheers

richard

[Andy]

Hi the simplest task on a fridge is setting a TEV, the next is determining the refrigerant charge...................So why do trained mechanics get it wrong so often
Maybe I just come accross all the bad ones but more increasingly often I find valves set up the left and over charged systems, why can't people just serve their time properly, is it a wage problem, are we just attracting the brain dead apprentice who has neither the skill, ability or education to be a good journey man
Kind Regards. Andy.

[RogGoetsch]

Hi the simplest task on a fridge is setting a TEV, the next is determining the refrigerant charge...................So why do trained mechanics get it wrong so often
Maybe I just come accross all the bad ones Andy.

I think the problem is with the word "trained". That term covers so much ground.

First of all, half of any group is below average!

For most, refrigeration is just a job that pays the bills, in my opinion. Most mechanics aren't spending time on refrigeration discussion boards. What's wrong with us? No life?

We are the lucky ones who found a job that we find interesting enough to spend extra time on. Most mechanics, in my experience, will not show up for training sessions on their own time.

I wonder if that's equally true in the medical profession? A thought to ponder on the next time you go under the knife!

Rog

[chemi-cool]

I wonder if that's equally true in the medical profession? A thought to ponder on the next time you go under the knife!

Rog

hi rog,

first, you right.

second, if we would get all the benefits MD get, belive me. refrigeration tecks will kill to get a seat!

third, the customers dont know that the knowlege of their service person is in many cases, out of date and the world had moved a giant step forword and they are paying the price.

the group here is unique.

chemi

[rbartlett]

[QUOTE=chemi-cool]hi rog,

first, you right.

there is an old saying 'doctors bury their mistakes'

and the dead ain't talking..

medical mispractice abounds and 'errors' are far more frequent than you'd want to believe...

cheers

richard

[bernard]

Hi Andy

I think there is a lot of employers out there who do not want to pay the going rate for a good engineer or train an apprentice.I had difficulty getting into the commercial refrigeration due to lack of experience.I have a electrical background with some transport refrigeration experience and sales.I spent a week with an engineer and was then sent on my own, my employer would not pay for any training and worked me into the ground he was not interested in a quality job.with plenty of book reading and picking other engineers brains i have learned a lot in ashort Period and recently gained new employment with a large company with plenty of training cources.You are obviously one of the lucky ones who do not make mistakes. But I do remember reading one of your threads about putting a drier in an oven and re using it ,this is not something I would expect from a trained engineer or maybe I,m wrong regards bernard

[chemi-cool]

hi bernard,

--------------------------------------------------------------------------------

Hello Chemi
remember having to dry silica bags out in an oven before re-using, also repairing shaft seal faces with cutting paste on piece of glass to get job away ie on ships, blueing up shafts and honing in big ends by eck them where the days
Regards Dave


I think this is what you saw and did not know what its all about.

I'm sure that andy will not put a drier in an oven, especialy after it was used in amonia system


chemi

[bernard]

Hi chemi

The one I meant is in tech discussions (solder v flared drier)

Regards

bernard

[FreezerGeezer]

Hi the simplest task on a fridge is setting a TEV, the next is determining the refrigerant charge...................So why do trained mechanics get it wrong so often
Maybe I just come accross all the bad ones but more increasingly often I find valves set up the left and over charged systems, why can't people just serve their time properly, is it a wage problem, are we just attracting the brain dead apprentice who has neither the skill, ability or education to be a good journey man
Kind Regards. Andy.

Hi Andy
I reckon that you're probably right - but also, how many companies are taking training seriously? And how many lecturers at all those technical colleges can actually teach (or even know the subject properly)?? I could tell a story about the (highly thought of) college where I did the NVQ & HNC!
We've just got a new guy started. He's Canadian, and tells me that they haven't hired a guy in the last 10 years who did not have his 2-year ticket. That's 2 years of full time refrigeration learning with exams & all! The U.K. has to get it's act together - it's not just the quality of the fresh labour.

Okay, that's tonight's rant over with!

[chemi-cool]

hi bernard,

I saw what you meant. no, that is something I would not do!!

chemi

[Andy]

Hi Bernard
taking a pop at me are you

Would a de-hydrated old drier not be preferable to a moisture ridden drier

When available a new drier is the thing, they do far more than dry the refrigerant, removing all sorts of contaminants. D&W have just sent out a Danfoss new letter, in it driers are discussed, one thing mentioned is activated aluminium driers should not be used first time on a new compressor with POE oil, as the drier removes the additives from the oil that aids boundary lubrication.

Bernard I do make mistakes, but the secret is to learn from them and move on. Perhaps it was ill advised to even mention re-hydrating driers, this was how all driers worked in the past and if you are working on a large system that has a high water content, including NH3 that is still the way to go.

Kind Regards. Andy.

[Dave Goodings]

Hello Chemi
remember having to dry silica bags out in an oven before re-using, also repairing shaft seal faces with cutting paste on piece of glass to get job away ie on ships, blueing up shafts and honing in big ends by eck them where the days
Regards Dave

Bernard/Chemi
Regarding the above posting these are the things you have to do to get jobs away in an emergency i.e. no spares available I have also worked in Canada and have all their licences, and over their on most jobs if you have a shaft seal leak you change out the compressor i.e. labour costs/warranty etc and the training is to quite a high standard.
Regards Dave

[chemi-cool]

hi dave,

I would be getting kicked in my behind if I would suggest to replace a compressor because of a leaking seal

but repering a worn shaft with a welding machine and a hand file was a rewording job!
even today I can file by hand a square bit to a complete round one +/- 0.1 mm.

chemi

[bernard]

Hi Andy

I felt your responce was having a dig at engineers who have not served an apprenticeship.I have worked with engineers who have served an apprenticeship and mopped up behind them because they do not have the stamina to see the job through or they cant feel when a bolts about to snap.Because they have done a colledge course and learned just enough to pass an exam.The basics every good engineer should have is the ability to use their most important tools they have, their hands eyes and ears.

Yes I do appologise to you as my responce was a bit O.T.T.but it was a friday night and I had just had a nice bottle of red wine given to me by one of my customers as graditude for my hard work.Note to ones self do not operate computer when drunk.

Andy I am still on a steep learning curve and should probably wind my kneck in a little.Now all the good engineers who have done an apprentiship can have a go a me.

Regards bernie

[frank]

Note to ones self do not operate computer when drunk.

Been there - done that

[richnor]

Don't know about those fridge TXV, but worse than an overcharge I rebuilt an open York Centifigal chiller got the motor all lined up. Hooked up the electrical and checked rotation forgeting about the gears and change of rotation. The chiller did not like running backwards it locked the input shaft right into the motor in a split second.

I guess I have done my share of over charging but not that it damaged anything.

[Andy]

Hi Bernard,
the problem is not the guys that haven't went thru college, but the ones who have and learn't nothing from it, taking the course was in their mind sufficient to become a mechanic alone, without having to learn anything
Learning is a life long thing, which never stops, college is just a way of starting this.

Kiss and make up all forgiven

Kind Regards. Andy

[Gary]

The schools all tend to teach the same things, yet the students are unable to perform satisfactorily. The student is usually blamed. It is seldom if ever questioned whether the schools are teaching what the student needs to know. It is assumed that the way it has always been taught is the way it should be taught. IMO, the schools are not teaching the student what he needs to know.

As to overcharging, for many years I have been removing more refrigerant from systems than I put into systems. Everyone overcharges. The truth is that people in the industry have no idea what is or is not an overcharge. They wouldn't know an overcharge if it bit them in the ass.

They are clueless because the schools are clueless because the textbooks are clueless because the authors are clueless. Textbooks are written by people who design systems, and service is entirely different from design. Most people who design systems are not qualified to service the systems they design.

Question: Who would know more about trouble shooting and repairing a system than the person who designed it?

Answer: Most of the people in this forum. It's what they do for a living.

[bernard]

Alright Andy

No problems Cheers

Bernard

[Abe]

I think you are either " a natural born engineer" or you arent.

I was in Canada just over a week ago, and stayed with an old freind, from back home.

Now this guy is a natural. He is a born engineer. He can rig, strip, erect, commission..........the works.

You can tell by the way they handle their tools, observe safety, and think logically, and are usually fit and hard working. They dont observe hours

I am not a natural.......But I am a thinker. I can work things out. Ive now run a fridge business goodness how long. In this time I have had countless excellent trouble shooting engineers work with me

Me, I still ask dumb questions..........But, as one engineer said to me........He will never underestimate me.

Things dont come naturally to me, engineering wise.......But I never give up...........I am only satisfied when I learn and acquire the knowledge. I am a tryer.

One day I will photograph all my installations............and still ask myself...........Did I really do all those ???????

[Blueboy]

Firstly let me agree with Andy, I think the level of pay we offer school leavers entering our industry is appauling. We do attract the brain dead, often those who cannot carry on in full time education. Obviously there are exceptions to the rule under achievers at school with parents who believe a trade is the best alternative and are prepared to subsidise the apprenticeship. How ever I personally believe the problem with training is bigger than that. Far to many firms invest in little or no training of existing refrigeration techs in regard to new advances in the industry. We have more and more part trained people in the industry there is room for these people but shouldn't employers be required to aleast offer further training to advance there existing empoyees?

In regard to overcharging I recently went to two systems on R404a running a freezer room, they had been running for two years however this was the first time the customer had exceeded the duty of the room and tech had been found the back preasure low and added gas. I went and found the wrong size cages in the TEV. I subsequently removed the entire refrigerant charge and rechaged both systems I added a total of 20.9KG of refrigarant. However I had removed 31kG in total. The systems were around 10.1 kG overcharged 50% I'd say.

[Latte]

Hi Guys,
How many companies operate apprentise schemes. To those that do, well done and keep it up. I would be scepical of enginneers that go to college full time before coming into the industry. the reason for this is that as we know in summer engineers can be out 14-16 hours a day, i think this would be a major shock & people would leave.

More need to be done to get companies to operate these schemes but first of all we need to training centres to run them


Regards

Raymond

[Latte]

Hi ,

We have an apprentice starting tommorow morning Mark

We're alright Jack !!! stuff the rest of you !!!


regards

Raymond

[Mark]

We're alright Jack !!! stuff the rest of you !!!

Your words, not mine .

[cowboy]

is it me or do apprentices get lazier and cheekier as i get older?

[Gary]

As I see it, more training is not what is needed but rather better (service oriented) training.

Most education in the industry is geared towards design, not service. People seem to be split on the issue, some believing that design training enables people to service systems (not true), and others believing that service cannot be taught, but must be learned by hands-on experience.

I think that service can be taught, although hands-on experience locks in the knowledge.

Given the lack of service oriented training throughout the industry, those who survive do so by virtue of mechanical aptitude alone, and learn the rest of it the hard way.

There is definitely room for improvement in the schools. Many schools offer limited hands-on training, but with no classroom preparation to relate it to. There is nothing that can be learned that cannot be taught, and service (trouble shooting in particular) principles are no exception.

What little trouble shooting is taught in the schools is, in my opinion, back-asswards. If you tell a student what the problem is, he can tell you the symptoms, but if you tell him the symptoms, he cannot tell you the problem. The latter is what we do for a living, not the former.

To make matters worse, many systems have multiple problems with mixed or even conflicting symptoms. The student has no basis for sorting them out, because conventional trouble shooting assumes single problems. Multiple problems require a logical step by step process of elimination.

[Blueboy]

is it me or do apprentices get lazier and cheekier as i get older?

It's you!!


There have always been 3 types of apprentice "The can't do's" "The won't do's" and "the cans". The problem is rooting them out in time. "The can'ts" are usally just plain unsutable and therefore appear to be "the won'ts", "The won'ts" often appear to be "cans" until it's too late and "the cans" , well it usally takes to years training (not colledge to find these) and when you do somebody offers them more money and the go eleswhere and finish there training.

Often the best trainees come in to the game a little older, when they need to learn!, and put a lot more in to a lot less time. Of course it's harder for them becase for some reason the industry thinks that if you start a 20 with a driving licence and some life skills you should be paid and treated like a 16 year old was 30 years ago.

[the chiller1]

I think you are either " a natural born engineer" or you arent.

I was in Canada just over a week ago, and stayed with an old freind, from back home.

Now this guy is a natural. He is a born engineer. He can rig, strip, erect, commission..........the works.

You can tell by the way they handle their tools, observe safety, and think logically, and are usually fit and hard working. They dont observe hours

I am not a natural.......But I am a thinker. I can work things out. Ive now run a fridge business goodness how long. In this time I have had countless excellent trouble shooting engineers work with me

Me, I still ask dumb questions..........But, as one engineer said to me........He will never underestimate me.

Things dont come naturally to me, engineering wise.......But I never give up...........I am only satisfied when I learn and acquire the knowledge. I am a tryer.

One day I will photograph all my installations............and still ask myself...........Did I really do all those ???????

i agree with u.i am told that i am a so called natural.soma things you just cant teach.its called talent i think.
anyone with a little knowledge can charge a system up but its all the little things that count.controls in the correct location and understanding how exactly they work and overall standard of work is what counts.

[Superheatman]

Hi all....tomorrow I am up at 4am...working at the National Physical laboratory with two of our apprentices....while I am getting a horizontal screw laser aligned and starting commissioning they will be using lifting gear to remove a four cylinder copeland from a set of four on a Dunham Bush ..the senior of the apprentices has done the job twice as assistant...tomorrow he is in charge of the job although I will only be a matter of a few feet away and will obviously keep a close eye..I will try not to interfere unless he is going badly wrong or there is a health and safety issue...we find that it builds the apprentices confidense to work in this way.....they have one day at college every week...also we do inhouse training nights when appropiate...the company pays us to stay behind for an extra hour on a weekly basis just to keep up with technology...that hour sometimes stretches to an extra hour unpaid because we all contribute and get quite into itand the time just flies.

[airefresco]

College training is a complete waste of time. I went to college for 4 years and learned nothing. Everything they were teaching us was either stuff I will need or stuff i already knew or had done. We had maybe in total 1 1/2 years of learning and 1/2 of that was health and safety, which is just common sense.

I have an NVQ level 3 and didn't have to show any basic knowledge to get it. We were marked on jobs we had done. The only proof we needed to show we had realy done the job were,

a. A job sheet/work report signed by the customer.
b. A letter from your employer to say you had really done the job.
C. A copy of any reciepts for parts bought for the job.

This is hardly showing you can do the job. anyone can fill a job sheet in and get there mum to sign it. Most employers want you to get through college asap so they will just sign the letter. And how reciepts are easy to get as we most people buy loads from NRS or HRP every week.

I honestly did every job that I used for college and all the paperwork was 100% genuine, (apart from 1 install was slightly exagerated, but i was on the job).

Now there was a lad in our class who was basically a sweeper-upper in the workshop for another company in Manchester and he got an engineer to do all his reports for him, his boss to sign the letter and got his NVQ level 2. He had no knowledge at all but was qualified.

Thats the problem

[Mark]

An NVQ is assesed throughout the year.On and off site.

Lets not forget the merits of training as well.

[frank]

he got an engineer to do all his reports for him, his boss to sign the letter and got his NVQ level 2. He had no knowledge at all but was qualified.

I'm an employer and I don't consider that someone with an NVQII is qualified. Rather that I think he has the basic training and has lots more to learn.

What other trade do you know where they think they are qualified after just 2 years of training?

[airefresco]

So what are regarded as a decent qualification nowadays? We were always told at colege that level 2 is qualified and level 3 is a higher level to work on system higher than 10kW. Is this not the case?