Filling In the Capacity Column of an Equipment Schedule
A mechanical schedule names each unit in tons, because that is how manufacturers organise their catalogues and how the plans get marked up. The capacity column underneath, the selection software and the submittal that comes back from the supplier all speak BTU per hour. Every line of the schedule therefore carries the same number twice, in two units.
What the Schedule Needs the BTU/h Figure For
Matching capacity to the block load
Setting the design airflow
Sizing chilled water flow
Reading performance tables
Working Down the Schedule Line by Line
A schedule is a repetitive document. The trick is getting each capacity right without reaching for a calculator between rows.
Enter the nominal tonnage from the tag
Type 7.5, 12.5 or 62.5 — decimals are ordinary in unitary sizes, and a comma is accepted in place of the point for anyone working on a European keyboard layout.
Drop the BTU/h into the capacity cell
The copy button gives the number alone, with no unit and no thousands spacing, so it lands in a schedule cell or a selection form already formatted the way the software expects.
Reverse it to check a submittal
When a supplier returns 118,000 BTU/h rated against your 10-ton line, press the swap button (↔) for BTU/h → TR and read 9.83 tons — the honest figure behind the nominal size.
Switch the right-hand unit for a foreign catalogue
Selecting kW on one side turns the same tonnage into the figure an imported air handler or a European chiller datasheet is written in, without leaving the page.
Packaged Unit and Chiller Sizes with Their Air Volumes
Standard catalogue capacities as they appear on a schedule, with the exact BTU/h behind them and the design airflow at the customary 400 CFM per ton.
| Equipment | Nominal capacity (TR) | Total capacity (BTU/h) | Airflow at 400 CFM/ton |
|---|---|---|---|
| Single-zone unit, small retail bay | 3 TR | 36,000 BTU/h | 1,200 CFM |
| Packaged unit, restaurant dining room | 5 TR | 60,000 BTU/h | 2,000 CFM |
| Constant-volume unit, office suite | 7.5 TR | 90,000 BTU/h | 3,000 CFM |
| Packaged unit with economiser | 10 TR | 120,000 BTU/h | 4,000 CFM |
| Two-compressor packaged unit | 15 TR | 180,000 BTU/h | 6,000 CFM |
| Variable-volume roof unit | 25 TR | 300,000 BTU/h | 10,000 CFM |
| Air-cooled scroll chiller with air handler | 40 TR | 480,000 BTU/h | 16,000 CFM |
| Screw chiller serving an air handler bank | 100 TR | 1,200,000 BTU/h | 40,000 CFM |
The airflow column is a starting point rather than a rule: 400 CFM per ton suits general comfort work, humid coastal jobs are often designed nearer 350 so the coil pulls more moisture out, and dry climates or spaces dominated by lighting and equipment heat can run 450. On the water side that 100-ton chiller needs roughly 240 GPM at a 10 °F range, which is what sets the header diameter.
Habits That Save Time on a Long Schedule
Tonnage and BTU/h track each other as you retype
Both fields are live, so running 3, 5, 7.5 and 10 through the left box produces a whole column of capacities without a single click in between.
Back-check a supplier's rated capacity
The swap arrows turn a certified BTU/h figure into decimal tons, which is how you catch a machine that is really 9.6 tons wearing a 10-ton badge.
Every unit a datasheet might use
The searchable dropdowns hold kW, W and BTU/min alongside tons, so an imported chiller sheet and a domestic schedule can be reconciled in one place.
Values that paste into selection software
Copy hands over the digits with no unit and no separators, which is exactly what a capacity field in a selection program or a spreadsheet expects to receive.
Equipment Schedule Queries
Why does a nominal 10-ton unit not deliver exactly 120,000 BTU/h?
The tonnage in the model number is a size class. Certified capacity is measured at the AHRI test conditions — 95 °F outdoor air, with 80 °F dry bulb and 67 °F wet bulb entering the coil — and lands wherever that particular coil and compressor combination lands, commonly within about 5 % either side. Schedule the certified figure at your design ambient, not the badge.
Where does 400 CFM per ton come from, and when should I move off it?
It falls out of roughly a 20 °F supply air temperature difference across a coil handling a typical mix of sensible and latent heat. Move down towards 350 CFM per ton where humidity control matters, because colder, slower air condenses more moisture, and up towards 450 in dry climates or spaces dominated by lighting and equipment heat.
How much of the scheduled BTU/h is sensible capacity?
Total capacity splits into a sensible (temperature) part and a latent (moisture) part, and the sensible heat ratio gives the share. Comfort equipment typically sits between 0.75 and 0.85, so a 10-ton machine rated 120,000 BTU/h total at an SHR of 0.78 offers about 93,600 BTU/h of sensible cooling. Compare that against the sensible half of your load, not the total.
Can I size refrigerant lines and water pipe straight from the tonnage?
Only as a first pass. Split-system line sets come from the manufacturer's table for that model, capacity and equivalent length — a nominal 3-ton run commonly uses 3/4 in suction with 3/8 in liquid, a 5-ton 7/8 in suction — and long runs or a large vertical lift change the selection. Chilled water pipe is sized from flow rather than tonnage: take 2.4 GPM per ton at a 10 °F range and choose the diameter that keeps velocity in the sensible band.
How do compressor stages affect the capacity I can actually schedule?
A 15-ton machine built from two independent circuits does not give you any value you like between zero and 180,000 BTU/h — it gives roughly half and full, so the first stage is around 90,000. Four compressors produce quarter steps, and a variable-speed lead compressor fills the gaps continuously. Where a space spends most of the year at part load, the number of steps matters more than the headline tonnage.
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