use of core driers

As always..Best wishes to all !!! Now my question. What is the best advice for deciding when to use a replaceable core dryer? Most of my work for the past 13+years has been service on nightmare units and install of smaller condensers. I am about to replace rooftop condensers...2 for walk-in coolers and 2 for walk-in freezers. The reason for change is age, increased maint. costs and units run on R502. I am switching to R404 except for smallest BTU rated unit. I am using R22 there. When and why should I consider the canister style dryer when doing this larger sized work?. Thanks for any advice. 1 last thing.... I just want to thank the forum and ALL ITS MEMBERS for providing a place where information is shared without " playing games ". We are part of a family of professionals who do the best we can every day but can always use some advice. I have not been a member for that long but I can't remember a single " log on " where I didn't learn something useful and quite a few times I was lucky to be able to share what knowledge I have with someone in need. It's just nice to be able to ask a question without being laughed at or insulted. Again....thank you for being here !!! Have a great day, everyone !!!:):)

When ever you expect large moisture and contaminant content.
After compressor burn out!
After oil type change!!
Plant in heavy use!

Hi FEISTY,

In simple wards, every time you open the system or replace any part in it, you have to change the drier.

After a motor burnout, there is a different core which absorb the acidity in the gas and oil. This core should be change again to a regular core after about 50 working hours. Acidity test for the oil is always useful and if the test is positive, it should be changed as well.

I appreciate the response to my question. Believe me...ever since I ran a counter for HVAC/R parts and equipment to my current position as chief cook and bottle washer of my own comm. refrigeration company...I have always preached" if you open it, filter it ". It still surprises me how many jobs I go on where the last " pro " changed out the compressor but left the 9 year old drier in place. Guess it wasn't in the bid !!! I am just looking for the accepted reason to choose a replaceable core cannister style over a standard style sealed unit. Don't changeout a lot of large rooftop units so wanted some opinion before I quote the job. Systems are clean...no burnouts...just upgrade with change of *****. Didn't know if this type of equip has need for frequent core replacement where isolation valves on each side of can would make " maint " easier. So there you have it. A long question that has a short answer. Thanks again.

Most of the stuff i work on is under 7.5hp so usually i use normal driers on these.
On a few occasions we've had to clean up a system and i've used a core drier, i think it depends on the flow of refrigerant and the amount of desicant the system needs and then balance this against cost and hastle of replacement as to which one you chose.

i would only be leaving it in for system clean up then remove and fit rated drier to system apart from that its like fitting a rolls royce motor in a mini,it works but is not necessary,