R22 - 407 gas change 1

[airtight]

We have recently changed our gas charge from R22 to 407. This is on a fairly small (15 kw) seawater cooled glycol chiller.

The system seems to struggle and with the seawater cooling side running less cold than it used to (32 degrees C seawater) we are having trouble getting the glycol really cold .

Generally no less than 10 degrees C.

Can anyone tell me what the difference is in efficiency is between the two gasses ?

Also would there be any change in expansion valve settings?

Im not to hot when it comes to refridgeration but I know the basics.

Thanks in advance.

Neville
Scotland

 

[cvanoverbeke]

Without getting into to much technical issues. R22 is an HCFC where the second C stands for chlorine. R407 is an HFC no, chlorine. From what I have read about R407 and R22 replacments, there are different properties. It is not abnormal that a one for one replacment may not work.

When you state you changed the refrigerant, what do you mean by that? Did a qualified refrigerant mechanic do the change? Did they discuss the fact that the chiller may not perform the same with a new refrigerant.

My advise, hire a COMPETENT chiller contractor who can discuss the differences in performance of R22 and R407

Cvanoverbeke

 

[imok2]

Read this for a comparison I would have chosen 422d as a better fit

http://refrigerants.dupont.com/Suva/en_US/pdf/h71061.pdf

 

[engair]

I do not believe that they have 422d out yet for large aplications. You can buy the refridgerant but not all the components you would need. Yes there is a difference between them, and you can not do a simple change out like what you did. You will need to change your expansion valves, and compressors. 407C runs at higher saturation temperatures so you are going to run into problems on that end if your system isnt designed to get rid of all the extra heat.

 

[airtight]

Thanks for your input.

The HP side is at present 18 Bar which is alot higher than these compressors like to run (bitzer).

Our problem is at present we are offshore vietnam and this system is in use - it forms part of our dive ships life support system for the divers.

I think the best short term measure is to fit new larger seawater condensers at our next port call. If there is still a problem I may fire the R22 back in and await the original contractor to sort the mess out !


Cheers

Neville

 

[lowedogg]

407c is not a drop-in replacement for 22. different refrigerants have different operating pressures and heat transfer characteristics. all equipment is designed to operate with a specific refrigerant. a modification of the the equipment is almost always required when changing refrigerants. at the very least, there will be a degredation in performance.

 

[Waramanga]

The most important question is who did the retrofit? If they had experience with the proceedure they would check charge and superheat. 18 bar means that it is condensing at 46 degrees C which could be OK. You need to know sub-cooling that is the temp coming out of the condenser. It should be about 5k less than condensing temperature. Much more than that is a symptom of overcharge (amoungst other things!!)

 

[hoorain]

hello I have been studying Air conditioning and refrigeration technology 5th edition (A book from USA)I have no experience in air con and refrigeration I am Novice in this field so to speak.In responce to the above question its very important as to who did the retrofitting bcause to start with a higher saturation presuure and temp. means higher compression ratios or in other words extra load on the compressor like some one suggested to check the subcooling and super heat values and further these can be matched with the design P/T of the unit and difference worked out or an amp draw test on the comppressor would yield any abnormalities from the FLA and LRA on the compressor further if its a TXV than it definatly needs adjusting considering the high subcooling value stated in the question there was no mention if the system was deep evacuated, leak checked,and charged properly or fractionation and temp glide are occuring due to old refrigerant still present in the system so any non codenseables, in the system can relate to the above symptoms. I am working as an electricians mate and have a years experience in domestic installations I am interested in doing an HVAC course and someone has suggested that i do F gas 2079 to get my first step in the industry.What I have learned from the book has given me a tremendous insight into the hvac industry and I have a good understanding of the basic techniques such as how and when to charge a unit,how to charge a unit,i.e. vapour and liquid charging,system evcuation,leak checks under standing pressure test,calculating superheat and subcooling,fault diagnostics etc etc. my question is I am financially weak and can jut afford to do the F gas 2079 can someone give me an honest opinion as to whwt would be the best course of action to get a job in the HVAC industry before i enrol for the course as I am 49 years old and due to a late marriage i have a 3 year and a one year old child to support so im in no position of taking chances and would only spend money on a course if it brings any fruit. apart from electrical wiring work i also have experience as a helper to install residential split units so I am familiar with pipe work,hanging indoor units on the walls, fitting wall mounting brackets for out door units, insulation of the liquid and suction lines and fitting ducts for pipework them,cleaning condensor and evaporator coils, return air filters,etc. So please give me an honest opinion thanks in advance.

 

[Waramanga]

hey hoorain, I am a refrigeration mechanic and electrican who has just finished my Mech Engineering degree. I was self employed too. I think you should FIRST find a good (I mean really good) refrigeration mechanic or company and ask for a job. Let him know what you can do (electrics, controls, install hardware etc) then tell him your plans to get skills, do a course in refrigeration etc. If he can make use of your current skills then you can make it a condition of employment that you learn refrigeration skills (if he's good) and you will get a lot more from your schooling. If you cant make use of your existing skills then you will be on apprentice wages unforunately. I am back on apprentice wages as a grad engineer with a couple of kids....but I love my new job. Go for it, job 1st then the course in my opinion.

 

[hoorain]

thanks a lot you have encouraged me by replying my post(though i was expecting more responses from other fellow hvacrs) nevertheless you have given an honest advice woooh my road to achieve what i have set out to do seems very very long at the moment but i shall try out and apply to as many companies i can my initial thaught was that in U.K. it is very important to have some sort of a document to prove to the employer that you are able enough or have the core skills to do the job (I WISH SOMEONE WOULD JUST GIVE ME CHANCE TO PROVE MY SELF) or atleast thats what i was told by two or three professional hvacrs that the minimum that i would definately require is the F gas 2079 before any employer can even think of hiring you but one did say the same thing as you said to tell the employers what you can do, as he did SAME and thats how he got the job, and then he did his courses afterwards. Any way i admire and congradulate you on your engineering degree so whats the work like did you have any practical experience before thanks agin and i shall await your and other fellow engs. kind replies.

 

[hoorain]

Also i forgot to ask you what did you think of my novice response to the R-22 to 407 retrofit problem though i have just read the book and i have no experience but i cant believe how people can get these jobs and do things the way it was explained im surprised by what was posted either it was ill explained or who so ever did the job certainly did not think of a proper retrofit procedure otherwise this problem would not have been posted if it was done properly. thanks

 

[engair]

hoorain, your response was mostly right but you didnt finish it. 407C is not a drop in refridg for R-22 as explained above. They would need a new system as the condenser will be undersized, and the compressors will not work properly with 407C. You are right about all of the components they will need, but having to replace all of the components of a whole system isnt really a retrofit its a replacement.

 

[hoorain]

Yes you are very right it indeed is a total replacement and thanks for your comment i am delighted that just by reading the book i have atleast identified some of the things and i do need advice from pros like your self to build even a deeper knowledge of air conditioning and refrigeration,One thing i dont understand what was the need to charge the system in the first place other than of R-22 or is it that my book is 1995 edition and laws have changed thanks .

 

[engair]

R-22 is being discontinued as a refridgerant, and in larger applications a direct drop in has not yet been approved. My understanding is they needed to charge the system and were not able to purchase R-22. No matter the reason it was probably just a mistake. There are alot of them get made and the most important part is resolving them properly without causing more damage

 

[hoorain]

yes absalutely right thats the most important thing