The Dimming Directive Two Days Before Rough-In
You are pricing a tenant fit-up: 1,850 m2 of office, 42 recessed 2x4 LED troffers, 12 ceiling occupancy sensors, 3/4 in. EMT, 120 V circuits from an existing 120/208 V panel with 14 spare poles. Your takeoff was built from the architect's reflected ceiling plan. Two days before the electrical rough-in the owner's representative hands you a written directive: the 42 troffers must become 0-10 V dimmable and must be controlled in four zones from wall stations, not by the occupancy sensors alone. The ceiling has changed from lay-in T-bar to Type X drywall, so the fixtures need new supports and the dimming conductors must leave the fixture boxes through a different wiring method. Your labour rate is $92/h, 0-10 V cable is $0.68/m with an average of 18 m per fixture and 10 % waste, commissioning is 8 h at $110/h, the dimming terminations add 0.35 h per fixture, and overhead and profit is 15 %. The general contractor says: "just do it and invoice at the end - don't slow the schedule."
1. Quantify and price the change order. Show the arithmetic line by line so the owner's rep can follow it.
Read the worked answer
Labour - dimming terminations: 42 fixtures x 0.35 h = 14.7 h x $92/h = $1,352.40
Material - 0-10 V cable: 42 fixtures x 18 m = 756 m; add 10 % waste = 831.6 m x $0.68/m = $565.49
Commissioning: 8 h x $110/h = $880.00
Subtotal: 1,352.40 + 565.49 + 880.00 = $2,797.89
Overhead and profit at 15 %: 2,797.89 x 0.15 = $419.68
Change order total before tax: $3,217.57
Explicitly excluded from this number, to be quoted separately or by RFI:
- Four zone wall stations and any dimming controller or power pack, which were not in the directive and are not in my material figure.
- New fixture supports and drywall ceiling adaptation - that is a ceiling change, not an electrical one, and if I supply the supports it is a separate line.
- Additional labour for the alternate wiring method for the dimming conductors if the drywall ceiling forces a different raceway or cable.
- Any fixture replacement cost if the specified troffers are not 0-10 V capable; verify the model number before ordering.
State the exclusions on the face of the change order. An unpriced scope is how a $3,200 change order becomes an argument.
2. What in this directive is genuinely extra, what was already yours, and what do you do about "just do it and invoice at the end"?
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Genuinely extra (owner-directed change):
- Converting 42 fixtures to 0-10 V dimmable, including the additional dimming conductors and terminations.
- Four-zone wall station control and the associated control wiring.
- Re-commissioning and re-labelling of the panel schedule and lighting control sequence.
Already in your contract, do not charge twice:
- The 42 troffers, the 12 occupancy sensors, the EMT, the 120 V circuits, and the standard fixture whips.
- Rough-in labour for boxes and conduit already priced - the dimming cable is additional, not the entire circuit.
- The originally specified ceiling support method, which changes only if the ceiling type genuinely changed after tender.
"Just do it and invoice at the end": decline politely and in writing. Verbal direction on a scope change is unenforceable, and "invoice at the end" means the owner's rep will dispute the number after the work is in the ceiling and there is no leverage left. The professional route is:
- Acknowledge the written directive and confirm receipt the same day.
- Issue the priced change order with exclusions, and a stated validity period.
- Request written authorization to proceed before ordering the dimmable fixtures - lead time is the real schedule risk, so say that explicitly.
- Offer to release the non-controversial portion (dimming cable pathways) on a time-and-material basis with a not-to-exceed figure so the schedule does not slip while the paperwork clears.
That protects the schedule without giving away the pricing.
3. What documentation and technical issues do you flag before this change order is signed, including the 0-10 V wiring itself?
Read the worked answer
Documentation:
- RFI for the fixture cut sheet. Confirm the specified troffer is 0-10 V dimmable and identify the dimming protocol (0-10 V analog, or a digital protocol). If the fixture is not dimmable, the change order price changes completely.
- RFI for the ceiling change. Get the Type X drywall detail in writing, with the support method and who supplies the supports. This is the largest unpriced risk in the directive.
- Marked-up drawings and a revised panel schedule showing the four zones, the wall stations, and the new circuit assignments. The original schedule no longer matches the installation.
- Written confirmation of who owns the dimming controls (owner-furnished vs. contractor-supplied), because the wall stations are excluded from your price.
- Closeout documents: updated as-builts, lighting control sequence, and commissioning records - these are contract deliverables and they are what the owner will use to operate four zones.
Technical - the 0-10 V wiring:
- 0-10 V dimming conductors are typically a Class 2 circuit under Section 16. They must be kept separate from the Class 1 power conductors, or the installation must be reclassified using Chapter 3 wiring methods and the appropriate conductor insulation and separation. Confirm with the manufacturer's instructions and the AHJ before pulling dimming conductors in the same raceway as the 120 V circuit.
- Do not run the dimming pair in the same conduit as the power conductors without that decision being made explicitly and documented.
- Voltage drop and polarity matter: reversed 0-10 V polarity gives a fixture that dims backwards or not at all, and long control runs with cheap cable cause flicker at the low end.
- Label the zones at the panel and at each wall station, and record the control sequence so the commissioning hours are not spent rediscovering it.