Compound or Multiplex Racks? Evaporative or Air Cooled Condensers?
What equipment do you prefer?
Compound OR Multiplex?
Most of the Compound systems that I've worked on were also multiplexed.
Now, you've also got to decide if you want to compound internally or externally.
Actually, compound compressors, in the market refrigeration that I've seen, are mostly a small niche item and are being phased out.
Compound is Multiplex, just compound cooled. So here we refer to Compound as being a compound cooled multi plex rack and Multiplex is almost any other rack. Does that make a little sense? Anyways, only WallyWorld has Compound Racks around here.
Originally Posted by MechanicallyInclined
Compound is often a Carlyle 06CC compressor. Internally compounded by a series of headers installed routing suction gas into 2 heads, out, through the motor barrel and into a final head before it is discharged.
I've seen these before.
I've also seen a rack where 6 compressors (single stage 06D) pump into a high stage consisting of 3 single stage compressors (also single stage 06D). This is called an externally compounded system.
Given my preference, I'd opt for a single stage rack simply because R-22 is phasing out and R-22 is the main reason that we used compound compression in the first place.
As I recall, multiplex was a term coined by Hussmann back in the 1960's for systems with multiple circuits. They were usually parallel compressor racks but could also refer to a single compressor, multi-circuit "rack" unit they made back then.
Compound systems to me are generally two-stage systems, although there could be more than just two stages. They can be either internally compounded or externally compounded.
As for air-cooled vs evap condensers, I think for systems in the typical supermarket the air-cooled makes the most sense. Larger systems need evap condensers just due to the higher condensing capacity requirements. Air-cooled condensers don't get much beyond 120 "nominal" tons sizewize.
Originally Posted by icemeister;14979171[COLOR=#ff0000
Only you would be old enough to remember them.
Continental used to build me 300, 400, and 500 ton air cooled
Doesn't anyone do that any more? No one builds them that big?
I used to use 300 or 400 nominal-ton air cooled condensers on 200 HP low temp chillers - to compete with water cooled. Some jobs didn't have the water for towers and so forth. I just set the fan controls to maintain a 90-100º condensing temperature.
Originally Posted by icemeister
The conventional view serves to protect us from the painful job of thinking.
When transcritical CO2 racks start moving more south we may see a smaller evap cond resurgence!
Originally Posted by icemeister
Sig removed by mod. G-Rated site
Always been a fan of the Hussmann TD system....as shown in my photo.
Carrier 5H compressors, and Evap condensers in areas where climate (humidity) favors them....providing their maintained.
What was the oil mgmt system used with the Hussmann TD? I ask because there are several stores with a similar setup; 2 comps for LT, 2 for MT and 2 for HT...all on common piping and one receiver. There isn't a separator but there is a reservoir. From the reservoir it feeds the 2 LT comps, which are the only comps with oil floats. (I haven't 100% verified this next part) There is piping hooked up to the sump of the LT comps (to the right of the oil floats) for the overflow to feed the next 2 comps, which are the 2 MT's. The 2 MT's do not have oil floats but do have the same overflow piping. That piping feeds the next 2 comps, the 2 HT's. The overflow piping from the HT comps feed back to the reservoir. See attached.
Originally Posted by bunny
EDIT:As I typed this I realized there cannot be overflow from the LT comps with correctly functioning oil floats. Hmmmm.
Last edited by smilies; 01-13-2013 at 10:13 PM.
In answer to your question Smilies:
The original Hussmann TD system didn't have an oil separator, oil reservoir or oil level controls on the compressors.
The oil system consisted of two 7/8" equalizer lines between the crankcases of compressors operating at the same pressure (1 for oil level equalization and 1 for pressure equalization), and cap tubes piped from the oil pump discharge of the high stage compressors to the crankcases of the low stage compressors. The idea was that the low stage compressors were constantly pumping oil into the high stage compressors, with the cap tubes feeding oil back to the low stage compressors.
I don't recall ever seeing any compressor oil level issues.
The system in your photos is the Raley's (or Farm Fresh or Big Y) modified and modernized version of the TD and probably has a more conventional oil system.
I'm not familiar with the early Hussmann TD designs, but their systems in the mid-1980's did have oil separators and floats:
I believe the earlier versions of the TD, as well as Husmann's 2-stage "Big System" and the later single stage "New System" oil management was primarily oil & gas equalization. The oil floats were first introduced by Refrigeration Research in the 1970's, as I recall.