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The previous sizing methods assume that the icemaker will run continuously 24 hours a day. This total utilization of the icemaker
gives the customer the most cost effective way of producing the required ice. It also requires the bin to be properly sized or the cus-
tomer will run out of ice.
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The example below shows how two operations can have very different usage patterns, yet still require the same size icemaker.
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Using our formula - 2,800 lbs. wkly. usage ÷ 7 days x 1.2 ("safety factor") = 480 lbs. ice/day
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SIZING STORAGE BINS
When ice is used in equal amounts 7 days per week, as in our convenience store example, the storage bin can be sized to
match the production capacity of the icemaker. Each day approximately 500 lbs. will be produced and 500 lbs. will be used.
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Some people think that to size the bin they need only match the bin to the highest day's usage. This will not always work
and often results in a customer running out of ice. If we had used this method for the restaurant example above, we would
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have specified an 800 lb. bin. On Friday, the restaurant would have used 700 lbs. of ice, leaving 100 lbs. in the bin. With
Saturday's production of 500 lbs. we would have only 600 lbs. in the bin — and we would need 800 lbs. — leaving us 200 lbs.
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short on Saturday and again on Sunday. The result would be an unhappy customer.
This is the case in our restaurant example. There are three days — Friday, Saturday and Sunday — when the required amount
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of ice exceeds the production capacity of the icemaker (these are called "peaks"). In this case, the bin and not the icemaker should
be sized to take care of these "peak" days.
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The best way to determine the size bin required is to work backwards from the last "peak" day — in this case Sunday. Take the
amount by which each day's usage exceeds the 500 lb. daily production of the icemaker.
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Add the total (700 lbs.) to the daily production figure (500 lbs.) to get the bin capacity required to meet the restaurant's
weekend demand for ice. This method tells us we need at least a 1,200 lb. bin.
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Once you think you know the size of the bin required, you can check your estimate as follows:
Assuming the bin is empty Sunday evening, 500 lbs. will be produced on Monday with no usage, and another 500 lbs. on Tuesday
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for a total of 1,000 lbs. in the bin. Tuesday's usage of 200 lbs. will lower the bin contents to 800 lbs. but with 500 lbs. of production,
the bin will be full at 1,200 lbs. on Wednesday. The same will be true for Thursday. As we enter the weekend peak period on Friday
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we have 1,200 lbs. in the bin from which we will use 700 lbs. This leaves 500 lbs. in the bin, plus 500 lbs. produced in 24 hours for a
total of 1,000 lbs. Saturday's usage of 800 lbs. reduces the ice available to 200 lbs., plus 500 lbs. of production for a total of 700 lbs. -
exactly the amount needed for Sunday's usage.
It's always a good idea to add the same 20% "safety factor" to the bin as we did to the icemaker. This adjusts for the ice voids
and pyramiding that can occur in the bin. In the case of our restaurant, the addition of the "safety factor" means we would look for
a bin with a storage capacity of approximately 1,400 lbs. (1,200 x 1.2 = 1,440). We can see that an icemaker rated at 500 lbs. of daily
product would easily meet the needs of both of the previous examples, provided that the icemaker runs continuously.
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Convenience Store
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Weekly Total
2,800 lbs.
Sunday usage
- 700 lbs. = 200 lbs. over production
Saturday usage
- 800 lbs. = 300 lbs. over production
Friday usage
- 700 lbs. = 200 lbs. over production
Total = 700 lbs. over production
Restaurant
400 lbs.
Closed
400 lbs.
200 lbs.
400 lbs.
200 lbs.
400 lbs.
200 lbs.
400 lbs.
700 lbs.
400 lbs.
800 lbs.
400 lbs.
700 lbs.
2,800 lbs.
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