Retrofitting or Replacement of Large Capacity Chillers 1

[Mechya]

Hi everybody

With the scheduled phase out of the CFC based refrigerant(R-12) in the near future, what would be the correct and economical solution for the existing chillers with R-12 refrigerant, is it retrofitting or replacement?.Views and suggestions of the experts in the field are highly appreciated. Thanks in advance.

 

[imok2]

In my estimation retrofitting an old R-12 centrigugal is not a good choice because the kw/ton is probably not very good and if the system hasen't been well maintained you could find yourself having to replace it sooner then you want too in a short time. My suggestion is to do a complete review of the existing plant and come up with some etimation on costs between retrofit and replacement. Remember that you need to concern yourself with operating energy cost because they will certainly go up every year.

 

[tombmech]

I agree with imok2's suggestion completely. Good advice.

 

[Trigout]

What size are the chillers and how many?
imok2 has a great suggestion.
I am not an expert but have spent many years maintaining
chillers for air washers and process chilled water.
imok2 is correct in the assumption that "usually" the maintanence on chillers is at best adequate.
If the units are more than 7-10 years old then you are most likely going to have to replace them. Do the study and present the costs to management. They may want to go with the expense costs of the retrofit even though there may be more hidden costs in the future as things rust and fail.
You will also have less efficiency from the older units than
what you should be able to get with new.
I am assuming that since you say R-12 then these are smaller 10-30 ton process chillers with two to four compressors each.
More information would be helpful.

 

[Mechya]

Trigot
Thanks, The chillers in discussion are in 500 to 1000 Tons range, water cooled semi hermetic R-12 centrifugal chillers and are used for comfort air conditioning. These chillers are almost 20 to 25 years old and still working fine without major breakdown or severe problems. Definately as u have mentioned that the old chillers, even if they are retrofitted would be less efficient and high KW/Ton.

 

[Trigout]

Bigger dilema with the larger chillers than the smaller ones.
imok2 is still correct that you need to do a cost comparison for the two options. You should include estimated operating costs for both options.
Hopefully your contractor for the chillers will have some
efficiency figures for the retrofitted refrigerant.
It is a waste to replace the larger centrifugal chillers
while they are still operational but the demise of R-12
is unstoppable.

 

[KiwiMace]

20-25 year old gear has lived out it's life - for sure you should replace it, but plan your time to do it. You'll take a year or two to get it by the accountant! Note that:
* The energy savings alone with new chillers could potentially payback the system over 5-10yrs.
* Spin the replacement as a PR exercise for the company.

There are other factors: Refrigerant leakage, condition of the condensor tubes, cooling towers, pumping and distribution system efficiency; Decide and plan with consideration of the whole system.

 

[Yorkman]

Mechya,
I would go along with changing out the chillers. I know York has made some pretty amazing advances in VSD technology and graphic panel displays. I've see some pretty good KW/ton with R-134a. I do start up work for the Denver CO. area and have seen several 1500+ ton machines go in here. With the VSD and cold condenser water temps (55F) these machines can run at 30 Hz. with as little as 1 - .5 degrees delta T accross the evap. That makes for a smooth transition when coming out of flat plate cooling. A.J. Gest York International

 

[TradeSchoolTeacher]

Depending on your location, NH3 may be a viable option--or not. A 2 stage NH3 absorption machine's slightly higher cost per BTU is easily offset by the extremely low maintenance cost and outstanding reliability. Maintenance runs about 5 to 10% of recip units and has about 2% of the unscheduled downtime. The fly in the ointment is the familiarity of the local authorities with NH3. Some of them just plain outlaw them. And a lot of HVAC engineers quake in their boots just at the mention of R717. The refrigerant is dirt cheap and will never be outlawed and is easily stored and disposed of if necessary. Contrary to popular belief, more and more NH3 units are being installed world-wide, especially in Asia and Europe. None in Antartica as of yet, but I am putting together a package for just such a unit.

 

[tbedford]

R-717 does have its problems but pound for pound it moves more heat than all other refrigerants at the fabulous low maintenance and price!!

t

 

[Yorkman]

Don't forget water R-718 !! In a LiBr/H2o absorber it'll out do R-717 almost 2 to 1 ;-)

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI