A 12-sheet chiller replacement, taken off in 14 minutes and checked line by line
Three mechanical contractors bid this public job. Their prices were $75,153 apart. Here is what Aginera read from the same drawings — and what a reviewer had to fix.
14 min
12 sheets, 137 rows
18 / 20
new-work lines matched the drawings
277 LF
new pipe and duct measured to scale
12.2%
spread between the 3 bids
Why a replacement job is a hard test
On a new building, everything drawn gets priced. On a replacement, most of what is drawn stays: the existing ductwork, the existing hot water system, the tank the new piping ties into. The takeoff has to separate the new chiller, air handler, pumps, valves and sensors from everything tagged existing, and pick up scope that only appears in a keynote — “base bid to include four new balance dampers” — or a controls points list.
That is also where bids drift apart. The three contractors who bid this job were $75,153 (12.2%) apart on the same drawings. A takeoff does not set a contractor’s price, but a missed keynote or an existing unit priced as new moves it — and checking for that by hand on every bid is what estimators run out of time to do.
Every new-work line, checked against the drawings
Every new-work line read against the 12-sheet set by hand: equipment schedules (M601), plan keynotes and tags (M102), piping diagram (M701) and controls (M703). 18 of 20 matched. The 2 that did not are shown in red with the reason — both are existing equipment drawn on the piping diagram for connection.
| Item | Qty | Sheet | Checked against | Result |
|---|---|---|---|---|
| Air-cooled scroll chiller, 38.4 tons, digital scroll, unit-mounted disconnect(CH-1) | 1 EA | M601 | M601 chiller schedule (CH-1, 38.4 tons, notes 1–3) | ✓ |
| Multizone air handling unit, 10,000 CFM, supply-fan VFD with integral disconnect(MZU-1) | 1 EA | M601 | M601 air handling unit schedule (MZU-1, 10,000 CFM, note 2) | ✓ |
| Dual-duct mixing damper, triple V blades, 9 zones(MZD-1) | 1 EA | M601 | M601 multizone damper schedule (MZD-1, 9 zones) | ✓ |
| Outside air damper, 48" x 48", opposed blade, fail closed | 1 EA | M601 | M601 control damper schedule (OAD 48" x 48", fail closed) | ✓ |
| Return air damper, 24" x 40", opposed blade, fail open | 1 EA | M601 | M601 control damper schedule (RAD 24" x 40", fail open) | ✓ |
| Chilled water expansion tank, 23 gal, 125 psi(ET-2) | 1 EA | M601 | M601 expansion tank schedule (ET-2, 23 gal) | ✓ |
| Chilled water control valve, 3-way mixing, 82 GPM, Cv 62 | 1 EA | M601 | M601 control valve schedule (CCV, 82 GPM, Cv 62) | ✓ |
| Pre-heat control valve, 3-way mixing, 12 GPM, Cv 42 | 1 EA | M601 | M601 control valve schedule (PHCV, 12 GPM, Cv 42) | ✓ |
| Re-heat control valve, 2-way, 25 GPM, Cv 11 | 1 EA | M601 | M601 control valve schedule (RHCV, 25 GPM, Cv 11) | ✓ |
| Chilled water circulator, ECM, 82 GPM, 30 ft head, 2.1 HP(CWP-1, CWP-2) | 2 EA | M601 | M601 chilled water pump schedule (CWP-1, CWP-2) | ✓ |
| Balance dampers, 14" x 12", in the nine zone supply ducts (base bid quantity per keynote M10) | 4 EA | M102 | M102 keynote M10: base bid includes four 14" x 12" balance dampers | ✓ |
| Zone temperature sensors, one per zone Z1–Z9 (keynote M08) | 9 EA | M102 | M102 keynote M08, tagged in all nine zones | ✓ |
| VFD for the new supply fan SF-1 | 1 EA | M102 | M601 AHU schedule note 2: supply fan VFD with integral disconnect | ✓ |
| Supply registers, double deflection, 29½" x 12" face (per schedule) | 2 EA | M102 | M102 plan: register tag A shown twice; M601 GRD schedule | ✓ |
| Air separator, chilled water loop | 1 EA | M701 | M701 piping diagram: air separator | ✓ |
| Y-strainer with blow-down, chilled water loop | 1 EA | M701 | M701: one "Y" strainer with blow-down drawn on the chilled water loop | ✓ |
| Duct smoke detectors on the new AHU, return and supply | 2 EA | M703 | M703 control diagram: two SMK duct smoke detectors | ✓ |
| DDC control points for the new AHU (from the points schedule) | 30 EA | M703 | M703 AHU DDC control summary, points 1–30 | ✓ |
| Chilled water buffer tank | 1 EA | M701 | Existing to remain, not new work: the drawing labels it EXT. and keynote DM02 keeps the existing volume tank. | ✗ |
| PRV and auto-fill assembly, ¾", chilled water make-up | 1 EA | M701 | Existing to remain, not new work: drawn in grey existing linework on the piping diagram. | ✗ |
277 LF measured where there was a scale
12 new pipe and duct runs on the enlarged mechanical-room plan (½″ = 1′-0″), each with its size and system — chilled water, heating hot water, spiral supply duct.
- New heating hot water return branch piping, 1 1/2"9.8 LF
- New heating hot water supply branch piping, 1 1/2"9.8 LF
- New heating hot water return piping, 1 1/4"12.1 LF
- New heating hot water supply piping, 1 1/4"12.1 LF
- New round spiral supply-air duct, 14" diameter20 LF
- New chilled water return piping, 2 1/2"55.1 LF
- New chilled water supply piping, 2 1/2"49.9 LF
- New heating hot water return piping, 2 1/2"40 LF
- New heating hot water supply piping, 2 1/2"35.1 LF
- New heating hot water return piping, 2"15.1 LF
- New chilled water expansion-tank makeup/vent piping, 3/4"7.9 LF
- New round supply-air branch duct, 6" diameter9.8 LF
Flagged, not guessed
The piping diagram on M701 carries pipe sizes but no scale. Instead of averaging a guess into the total, the run returned those 9 runs (361 LF) as low-confidence estimates on the review list, outside the priced total. Part of that diagram is the existing hot water system the engineer marked “shown for reference — not in scope”, which is exactly why it should not be priced automatically.
- 607 LF of existing duct in 19 runs and 16 sizes kept as existing-to-remain, visible for scope but not priced.
- 6 demolition keynotes carried as scope alerts: demolish the existing air handler, chiller, pumps and supply duct, salvage the pressure sensing plate, replace the thermostats.
- Keynote scope picked up: four new balance dampers (M10) and nine zone sensors (M08) — items that appear on no schedule.
What this means for an estimating team
Start from a checked list
The reviewer starts with every schedule item, keynote and points-list line already itemised by sheet, and spends the time on the two lines that need judgment.
See where each number came from
Every row carries its sheet and tag, so a project manager or a second estimator can audit the takeoff without redoing it.
Price it where you already price
Export straight to Trimble/Accubid, McCormick, ConEst IntelliBid, Procore or Excel instead of re-keying quantities.
Run the same test on a set you have already bid
Send us drawings you have estimated. We run them and go through our takeoff against yours, line by line — what matches, what we missed, what we caught. That is the pilot for an Aginera team plan.
Questions
Is this a real customer project?
It is a real public project, not a customer. The State of Missouri publishes its bid sets and bid tabulations, so anyone can download the same 12 sheets and check every number on this page. We use public sets for case studies because we do not publish customer drawings.
How was the takeoff checked?
By hand, against the drawings themselves. Each of the 20 new-work lines was read against the sheet it came from: the equipment schedules on M601, the keynotes and tags on the M102 plan, the piping diagram on M701 and the controls sheet M703. 18 matched exactly. The other 2 were existing equipment drawn for connection that the run listed as new.
What does an estimator still do?
Review. Confirm the two existing-to-remain items, decide how to carry the lengths on the not-to-scale piping diagram, field-verify the balance damper sizes the engineer asked for, and price it. The takeoff removes the counting and the sheet-flipping, not the judgment.
Can we run the same test on our own drawings?
Yes — that is the pilot. Send a set you have already estimated; we run it and go through our output against your takeoff line by line, so you see where it agrees and where it does not before you commit.
Sources: State of Missouri OA/FMDC project R2515-01 drawings (Klingner & Associates, issued March 20, 2026) and the published bid tabulation. Takeoff run 2026-09-22 on the production engine; line check 2026-10-13. See also the full example output and AI HVAC takeoff.
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