here is my problem........
I have 2 different freezer contractors quoting me two different equipment sizes for the same walk in freezer box.
Here is the backstory:
Freezer will be 15x30x8 with floor. 4 inch urethane. 1 60x84 door. The box will need to maintain a storage temp. of -20F for ice cream. Product will enter @ -10F. (200 lbs/day) for the purpose of storage w/ low door traffic.
On to the mechanicals:
This will be a (2) Cond. unit / (2) Evap setup. (separate systems) Both contactors quoted with 5HP Low temp scroll cond. units (Russell # ML0500L44) that are rated at 13200 BTUH @ -30F Suction temp. @ 95F ambient for a total of 26400 BTUH.
The evaporater selection is where it gets tricky! one Co. choose the (Russell # AE46-164B)4 fan / elec. defrost rated @ 15000 BTUH capacity @10 Degree T.D. at a -30 Evap temp. total capacity = 30,000 BTUH (2 evaps) The 2nd Co. chose the russell # AE36-140B which is rated @ 13,300 for a total of 26,600 BTUH at the same specs.

Summary: System 1 Cond. units 26,400
System 1 Evaps. 30,000
=8.8 T.D.

System 2 Cond. Units 26,400
System 2 Evaps. 26,600
=9.9 T.D.

System 1 quote argues that 8.8 T.D. is acceptable with short pipe runs etc. for a freezer.

System 2 quote says that 9.9 T.D. system is more efficient and is better matched. Also that I cant squeeze the extra capacity out of the evaps. if the condensing units cant provide it!

O.K. which is the better designed system?? What are the pros and cons to each, or is it a matter of right and wrong.
I am in Western WA state where the average daily temp is 50F. these are outdoor units.(Box and Cond. units.)
If anyone has the ability to run box load calculations on this set-up please do as I wish to know if they are even sized right for my application.

Thank you for any and all feedback!