Run the flood through by hand
One 130 gallon flood at 8.345 lb per gallon is 1,084.9 pounds of water. Cooling it from 60 °F to 32 °F takes 1,084.9 x 1.00 x 28 = 30,376 Btu. Freezing it takes 1,084.9 x 144 = 156,218 Btu. Chilling the new ice from 32 °F down to 22 °F takes 1,084.9 x 0.49 x 10 = 5,316 Btu. The three add to 191,910 Btu, and the middle term is 81 per cent of it.
That is 16 ton-hours of refrigeration for one lap of the machine, and it is why a plant that looks generous against the standing load starts to labour on a tournament Saturday when the floods come every forty minutes.
Standing load against flood load
With the defaults, the standing gains are 225,000 Btu/h — 18.8 tons — and fourteen floods add 2.69 million Btu across the day, which averages 112,000 Btu/h. So on a busy day the resurfacer is a third of the total refrigeration work. On a quiet day with three floods it is a tenth. Neither is a small number and neither is the whole story, which is why the page asks for the floods rather than assuming them.
Why the ceiling is usually the biggest gain
Ice radiates to whatever is above it, and a warm dark ceiling radiates back. The default puts 90,000 Btu/h in that line, forty per cent of the standing load, and that is the number a low-emissivity ceiling is bought to move. It is also the gain that changes most between buildings, which is exactly why it is a field and not a constant.
What this cannot know
It cannot tell you whether your plant is big enough. It reports a ratio between the capacity you typed and the load you typed, and both of those come from documents this page has never seen. It has nothing to say about what happens inside the plant room, and it will not help you get a number by going in there — capacity comes off a submittal, and everything else in a plant room is the refrigeration contractor's work.
Questions people ask
Why does freezing take so much more energy than cooling?
Because the molecules have to give up the energy that lets them move past each other, not just slow down. That is the latent heat of fusion, and for water it is around 144 Btu a pound against about 1 Btu a pound for each degree of cooling. A hundred and forty four degrees worth of cooling, at no change in temperature.
Where do I get the gain figures?
From the mechanical engineer who did the load calculation for the building, or from your own instrumented measurements. This page deliberately has no defaults it stands behind — the numbers in the fields are placeholders and every one of them varies by more between two buildings than anything a web page could guess.
Is the refreeze time it gives me realistic?
Only as realistic as the delivery share you put in. At 100 per cent it is the arithmetic floor, which nobody hits. Time three refreezes on your own sheet and set the share so the page matches what your stopwatch says.
Can I use this to size a plant?
No. Sizing a refrigeration plant for a building is engineering work with design conditions, diversity, part-load behaviour and code requirements this page does not touch. It reports two numbers you supplied against each other.
Why is warm fill water expensive?
Every degree above freezing is another Btu a pound the plant has to remove. Filling at 140 °F instead of 60 °F adds 80 Btu a pound, which on a 130 gallon flood is 86,800 extra Btu — about 45 per cent on top of the whole flood. Hot floods are used for a reason, but the reason is not free.