Weekly digest #4: price changes in copper

Copper prices moved again this week

COMEX copper closed the week around $4.80/lb, up roughly 6% over the last 30 days. Distributors have pushed through two price sheet revisions since mid March, and most supply houses are quoting for 48 hours max. If you bid a job three weeks ago on THHN, your margin is already thinner than you think.

Aluminum building wire held flatter, with most 600V XHHW-2 prices moving less than 2%. That spread matters when you are sizing feeders and services where aluminum is permitted under NEC 310.12 and 310.14. The code has not changed. The economics did.

What is driving it

Three factors are stacking. Chilean mine output is down against forecast, LME warehouse stocks are sitting near multi year lows, and data center demand for large gauge copper keeps pulling supply from the residential and light commercial channel. Expect continued volatility through Q2.

Jobsite impact is uneven. Pipe and wire projects with long runs of 3/0 and larger are taking the biggest hit. Resi service changes and small commercial tenant fitups are seeing 3 to 8% material creep. MC cable assemblies have lagged the raw copper move by about two weeks, but the catch up is coming.

• THHN/THWN-2 #12 stranded: up roughly 7% in 30 days
• Bare copper ground #6 and #4: up 9 to 11%
• 500 kcmil XHHW-2 copper: quotes valid 24 to 48 hours only
• #2 AL SER and 4/0 AL SER: relatively stable

Bidding and change orders

If your standard contract does not have a material escalation clause, add one this week. Tie it to a published index like COMEX or to your primary distributor's price sheet. Define a threshold, usually 5% movement from bid date, and a documentation method. Vague language gets argued. Specific language gets paid.

For work already under contract, pull your open POs and lock pricing where you can. Some supply houses will hold a number for 30 days if you commit to a release schedule. Others will not. Ask before the next revision lands.

Tip from a Local 3 foreman in Queens: photograph the distributor price sheet the day you bid. Attach it to the estimate PDF. When the GC questions a change order four months later, the timestamped sheet ends the conversation in about 90 seconds.

Where aluminum makes sense, and where it does not

NEC 310.12 covers the standard 83% ampacity rule for aluminum service conductors in dwelling units. NEC 110.14 still governs terminations, and you still need listed AL9CU or CU/AL terminations where applicable. None of that changed. What changed is that the break even point on feeders moved further toward aluminum, and more ECs are running the numbers on 400A and 600A services.

Things to check before you switch a spec:

1. Panel and disconnect lug ratings, verify AL9CU or dual rated
2. Conduit fill under NEC Chapter 9 Table 1, aluminum is larger OD for same ampacity
3. Torque specs, use a calibrated torque screwdriver or wrench, NEC 110.14(D)
4. Anti oxidant compound per manufacturer instructions
5. Local amendments, some AHJs restrict aluminum in specific occupancies

Do not substitute on branch circuits serving 15 and 20A receptacles without thinking it through. Most jurisdictions and most inspectors expect copper there, and the labor savings are not worth the callback risk.

Grounding and bonding, watch the theft exposure

Higher copper prices mean more copper theft. Ground bars pulled from service equipment, GECs cut at meter sockets, and lugs disappearing from rooftop units. NEC 250.64(B) requires GECs to be securely fastened and protected where subject to physical damage. On occupied sites and service yards, walk the grounding path before you sign off for the week.

If you are doing temporary service for a project in a high theft area, consider running the GEC in conduit for its full length even where not strictly required. The code minimum and the practical minimum are not always the same number.

Tip: tamper resistant or breakaway ground clamps on exterior rods near alleys and parking lots. Costs a few dollars more. Saves a truck roll.

Quick field checklist for this week

Five things to do before Monday:

• Review any bid still sitting open past 14 days, confirm or revise
• Pull open POs for copper heavy jobs, lock pricing where possible
• Check your standard contract for an escalation clause, add one if missing
• Recount copper inventory on trucks and in the shop, secure it properly
• Talk to your top two distributors about 30 day pricing holds on committed work

Code does not bend when commodity prices move. Your estimating and procurement should. Keep citing NEC 310.12, 310.14, 110.14, and 250.64 correctly, and keep the paper trail tight on everything you quote this quarter.