hey refer guys
ok went to the job tonight (last call) walk in cooler (beer)
its the first time i ever been to this job
it has 2 mismatched evaps, a 2 fan evap with a 1 h/p cond. and a 3 fan evap with a 2 h/p cond.
2 different stats for the same cooler
cooler is 25 wide x 8 length x 7 foot ceiling,
anyway the 2 hp comp. has wasted valves and its old, i am gonna replace the condenser
i am probably gonna wire a relay to turn both compressors on and off at the same time thru 1 controller
maybe i will slap a 1 minute delay between both stages for $hits and giggles
or is there a different way anyone else would do it?
my second thought was turning one stat (the bigger condenser) a few degrees lower than the other
what option would you guys use, and can you see any advantages or disadvantages one way or the other
I would go with one controler with at least 1 min or longer delay on bigger
unit.just my 2 cent's
The advantage of turning both compressors on/off at the same time would be better defrosting during the off cycle. It is very difficult to get two stats to work in sync, one of the units is going to run (and ice) more. I wonder, though, why there are two units to begin with. Is there something about the construction or loading that might cause one end to overcool if both units run at the same time? If that is a concern, I would use an electronic stat on each unit so they can be set on the exact same setting with no guesswork.
I like to use these controllers. Very reliable and accurate and you can program each set of contacts seperately.
Me, Id have them both on/off at the same time unless the 2 Hp could handle the load all by itself and the 1 hp could be for heavy usage periods/quick pull down.
If the box needs all 3 Hp then why bother with a few degrees colder as the capacity of the 2 hp is at its minimum at temp and will run longer to get the box down those few more degrees, ie unneccesary wear on the comp.
Every day that goes by is another day that you could have done what you intend to do tommorow.
The times I see this an interior wall was removed. The smaller is usually a freezer that makes a better cooler. What direction are the fans blowing with relationship to the 25 ft. wall ?
If You Can Dodge A Wrench You Can Dodge A Ball
heres a thought, since one comp is trashed, why not resize for the correct hp comp and not have to peice meal the controls,defrost and you end up with a better system and a happier customer.
good question air.. Ive actually been wondering about this.. As i picked up a few new stores and 3 of them have walkins with 2 condensing units , one evap per condensing unit and a stat for each.. Yet to work on any of them but was wondering the best way to go.. so lets hear it guys
i have always run them as 2 totally independent systems usually one stat set 2-3 degrees colder than the other. time clock defrost pump down system. have never had a defrost problem and i usually run my beer walk-ins 33-34 degrees. usually switch the lead- lag units once a year or so.
Like the post before me, keep one unit running for lower energy costs. Keep the second stat 3-4 degrees warmer
Aire Serv of SW Connecticut- Gas heat, dual fuel and central a/c systems installed and serviced
Sounds like this might be a display cooler with glass doors? Evaps mounted along the 25' wall?
Originally Posted by Airmechanical
If so, I design many display boxes with two systems, although normally the same HP. I'd probably leave them on separate t'stats. One side of the cooler glass doors might be used more often than the others. The load will vary from one end to the other. Or it could have been an add on. Are the evaps mounted evenly along the wall or is at a after thought cluster?
thanks for opinions guys, evaps are running the length of the cooler (not one on each end)
If you are replacing one of the condensing units already, you may want to consider sizing a unit that will take care of the whole load and run one condensing unit for both evaps. (depending on how hard it would be to re-pipe the coils and how old the 1 h.p. cond. unit is).
Originally Posted by nwrscold