wewire2;Happy to assist you with the CAD Query.
Let me know how the LOADCALC Application works out - along with which CAD App' you choose.
BTW, Try Ebay; you might find an AutoCAD Package for a good price.
If it is not too late, I could send you a copy of my Panel Schedule Workbooks (Excel Spreadsheets), so you may compile the Panel Schedules in an Industry-Standard "Looking" format, and the Architect will be able to Attach the Schedules to the relevant Plan Sheets' CAD Files.
Send an E-mail message to me at the following address:
ENGINEER AT SETELECTRIC DOT NET
- remove the spaces between words, along with the following changes:
- Change "AT" to "@",
- Change "DOT" to "."
Lastly, per the Cold Boxes:
For my designs, all Equipment is figured as to be running coincidentally - i.e.: 100% (no diversity)... unless otherwise stated - such as redundant systems, etc.
There will be certain events, which the Condensing Units will stop - such as when design target temperature is achieved, or Defrosting.
Keep in mind, the Target Design Temperature will be affected by normal activity, such as:
- The frequency of usage by the Staff (opening lift and man doors),
Along with Heat Burden factors - Including:
- Staff bringing in "Room Temperature" foods,
- The "Box Exterior Ambient Temperature",
- Heat dissipated from in Box Lighting and Under Floor Heating,
- Box Insulation Leakage.
Most important to mention will be the type of Defrosting used on the Evaporators (Air units).
Air Defrost is the lowest load type.
Air Defrost is simply keeping the Fans running, without the Refrigerant being "Re-Condensed". Ambient Air flows across the Evaporator Coils, thereby achieving Defrost
(The Evaporator Fans are run continuously, but the Condensing Unit stops).
This will occur per "Zone" for something like 15 minutes per each hour (verify with Refrigeration Designers).
Air Defrost is typically used in "Coolers" with Ambient Design target temperatures of 40ºF and higher.
________________________________________________________
Electric Defrost uses Resistance Heaters for Defrosting the Evaporator Coils.
As with the Air Defrost technique, the Refrigerant stops being moved (Condensed) while the Air Unit is in Defrost Mode.
The Fans
May or
May Not be operating, while in Electric Defrost Mode.
Normally, the Total Heaters' Load of Electric Defrost will be equal to, or +10% of the Condenser Motors' FLA + the Evaporator Fans' FLA combined.
With an Electric Defrost system, the rated FLA normally represents the Defrost Load, which is commonly the Highest value.
Electric Defrost will occur in an "opposite time" with other Evaps in the Box.
Examples:
1: Freezer Box with (2) AUs (Air Units):
AU1 runs in COOL Mode for 1 Hour; AU2 is in DEFROST Mode at same time.
Next Hour, AU2 runs in COOL Mode, while AU1 goes in DEFROST Mode.
2: Freezer Box with (4) AUs (Air Units):
AU1, 2 and 3 run in COOL Mode; AU4 is in DEFROST Mode at same time, and Defrosts for 30 Minutes.
When AU4's DEFROST Mode has timed out, it goes into COOL Mode with AU2 + AU3, while AU1 takes on DEFROST Mode for 30 minutes.
When AU1's DEFROST Mode has timed out, it goes into COOL Mode with AU3 + AU4, while AU2 takes on DEFROST Mode for 30 Minutes.
When AU2's DEFROST Mode has timed out, it goes into COOL Mode with AU4 + AU1, while AU3 takes on DEFROST Mode for 30 Minutes.
... Pattern repeats as needed.
________________________________________________________
Hot Gas DefrostThis is the Recycling of the "Un Condensed" Refrigerant, used for Defrosting the Evaporators' Coils.
Liquid Solenoid valves are used to run the Hot Gas "Back" through an Evaporators' set of Coils.
The Condensing Unit's Compressor Motors are always running during COOL Mode and DEFROST Mode.
Defrost Scheduling matches the Schedule for Electric Defrosting, shown above.
___________________________________________________________
___________________________________________________________
Since the Cold Boxes (Cold Rooms) you will be designing around will be less than 400 Square feet, the Systems will most likely be derived from either (1) or maybe (2) Condensing Units.
Each Condensing Unit _SHOULD_ be driving the Evaporators associated with it, so the Nameplate Values will reflect the Highest Total Load - Condenser Motors + Fan Motors -vs- Defrost Load.
*** If the Freezers are "Cabinet Freezers" or "Case Freezers", everything changes per what I have listed above!
The above text denotes "Walk-In Freezers" or "Warehouse Freezers", sized for at least One Person to enter the Box, close the Door, and perform a given Task.
Cabinets / Cases are Pre-Made Units, which work independently, and _MAY POSSIBLY_ be figured with a diversity factor.
Since there are so many variables, the choice in design must reflect the Equipment and Environment together.
For a simple suggestion, I would suggest figuring all at 100% coincident Loads (all running at the same time, for up to 179 Minutes).
Figure the Unit with the Highest MCA at 1.25 × the MCA, and the remaining (8) Units at 1.0 × the MCA.
Use this on the Branch Circuits + the Load Calcs.
If you need more, feel free to contact me.
-- Scott
