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Consumption Guide |
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Consumption Guide |
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This guide should be used for estimation purposes only. There are many variables involved that will effect consumption & heat-leak calculations, but if you follow the step-by-step process below it will approximate figures for estimation purposes.
Step one
Measure the box interior dimensions & calculate the volume in cubic feet.
Step two
Measure or estimate the thickness of the insulation.
Step three
Consult the tables below & find the approximate hourly heat-leak into the box for either a refrigerator or freezer. For a spill-over system, calculate the heat leak for both sides of the box & then add them together.
Refrigerator
Heat leak into box in watts per hour.
|
Cubic volume |
2" insulation |
3" insulation |
4" insulation |
6" insulation |
|
2’ |
20.7 |
17.1 |
13.4 |
12.2 |
|
3’ |
26.8 |
20.7 |
17.1 |
14.6 |
|
4’ |
30.5 |
24.4 |
20.7 |
17.1 |
|
5’ |
34.2 |
26.8 |
23.2 |
19.5 |
|
6’ |
37.8 |
30.5 |
25.6 |
20.7 |
|
7’ |
41.5 |
34.2 |
26.8 |
23.2 |
|
8’ |
45.1 |
36.6 |
29.3 |
24.4 |
|
9’ |
50.0 |
40.3 |
31.2 |
25.6 |
|
10’ |
53.7 |
43.9 |
34.2 |
26.8 |
|
12’ |
59.8 |
51.2 |
36.6 |
31.2 |
|
14’ |
70.7 |
57.3 |
43.9 |
36.6 |
|
16’ |
85.4 |
62.2 |
48.8 |
41.5 |
|
18’ |
87.8 |
68.3 |
59.8 |
46.4 |
|
20’ |
102.5 |
73.2 |
64.7 |
51.2 |
Freezer
Heat leak into box in watts per hour.
|
Cubic volume |
2" insulation |
3" insulation |
4" insulation |
5" insulation |
|
2’ |
37.8 |
29.3 |
25.6 |
22.0 |
|
3’ |
46.4 |
37.8 |
31.7 |
26.8 |
|
4’ |
53.7 |
42.7 |
37.8 |
32.9 |
|
5’ |
59.8 |
48.8 |
42.7 |
36.6 |
|
6’ |
63.4 |
53.7 |
46.4 |
40.3 |
|
7’ |
67.1 |
59.8 |
50.0 |
42.7 |
|
8’ |
72.0 |
65.9 |
53.7 |
46.4 |
|
9’ |
79.3 |
73.2 |
58.6 |
51.2 |
|
10’ |
87.8 |
80.5 |
63.4 |
56.1 |
|
11’ |
97.6 |
87.8 |
69.5 |
62.2 |
|
12’ |
109.8 |
93.9 |
76.9 |
69.5 |
Step 4
Divide the figure found in step 3 by either 100 for a freezer, or 132 for a refrigerator to find estimated run time per hour. For a spill-over system, use the freezer figure.
Step 5
Multiply the figure found in step 4 by either 3.5 for a freezer or 4.5 for a refrigerator to find estimated current draw in amp-hours. For a spill-over system use the freezer figure.
Step 6
Multiply the figure found in step 5 by 24 to find approx. amp-hour consumption per 24 hours
Example
12 cu ft refrigerator box with 3" insulation
Step 3 From tables, estimated heat leak is 51.2 watts/hour
Step 4 Estimated run time per hour = 51.2/132 = 0.38 hours/hour
Step 5 Estimated current draw = 0.38 x 4.5 = 1.74 amp-hours/hour
Step 6 Estimated daily consumption = 1.74 x 24 = 41.9 amp-hours/24 hours
Coastal Climate Control, Inc
P O Box 4535
Annapolis MD 21403
Frigoboat.com