A heated driveway is a permanently buried system — the testing happens before the surface goes down, or not at all. The log below is the actual testing protocol: every zone's cable ID, location, voltage, target resistance, and the three-stage test results (before, during, and after the pour). Most homeowners who read this are comparing underground power cable testing options around Boise, ID, so what follows sticks to the details that change in practice.
| Cable/Mat ID | Zone Location | Operating Voltage (V) | Nominal Target Resistance (Ohms) | Test Stage 1 (Before Paving): Measured Ohms | Test Stage 1 (Before Paving): Measured MegOhms (Insulation test, target: Infinite) | Test Stage 2 (During Paving): Measured Ohms | Test Stage 2 (During Paving): Measured MegOhms | Test Stage 3 (After Paving): Measured Ohms | Test Stage 3 (After Paving): Measured MegOhms | Conductor Resistance Variance (%) | Pass/Fail Status | Source |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| WHMA-240-0250 | Ramp Upper | 240V | 23.0 | 23.1 | Infinite | 23.2 | Infinite | 23.2 | Infinite | 0.0087 | PASS | 1 |
| WHMA-240-0500 | Walkway steps | 240V | 11.5 | 11.6 | Infinite | 11.7 | Infinite | 11.7 | Infinite | 0.0174 | PASS | 1 |
| WHMA-240-0250 | Ramp Upper | 240V | 23.0 | 23.2 | Infinite | 23.3 | Infinite | 23.5 | Infinite | 0.0217 | PASS | 2 |
| WHMA-240-0500 | Walkway steps | 240V | 11.5 | 11.6 | Infinite | 11.7 | Infinite | 11.8 | Infinite | 0.0261 | PASS | 2 |
| WHCA-240-0171 | Stairs/Landing (example) | 240 | 28.80 | Not in source | Infinite (target) | Not in source | Infinite (target) | Not in source | Infinite (target) | Not in source | Not in source | 3 |
| WHCA-240-0171 | Stair treads/Landing | 240 | 28.80 | Not in source | Infinite | Not in source | Infinite | Not in source | Infinite | Not in source | Not in source | 4 |
| WHMA-120-0205 | Not in source | 120 | 28.80 | Not in source | Infinite (target) | Not in source | Infinite (target) | Not in source | Infinite (target) | Not in source | Not in source | 3 |
| WHMA-120-0305 | Not in source | 120 | 19.20 | Not in source | Infinite (target) | Not in source | Infinite (target) | Not in source | Infinite (target) | Not in source | Not in source | 3 |
| WHMA-240-0250 | Not in source | 240 | 11.50 | Not in source | Infinite (target) | Not in source | Infinite (target) | Not in source | Infinite (target) | Not in source | Not in source | 3 |
| WHMA-240-0250-4 | Not in source | 240 | 14.62 | Not in source | Infinite (target) | Not in source | Infinite (target) | Not in source | Infinite (target) | Not in source | Not in source | 3 |
| WHCA-208-0100 | Not in source | 208 | 36.05 | Not in source | Infinite (target) | Not in source | Infinite (target) | Not in source | Infinite (target) | Not in source | Not in source | 3 |
| WHCA-277-0502 | Not in source | 277 | 12.79 | Not in source | Infinite (target) | Not in source | Infinite (target) | Not in source | Infinite (target) | Not in source | Not in source | 3 |
| WHMA-120-0205 | Not in source | 120 | 28.80 | Not in source | Infinite | Not in source | Infinite | Not in source | Infinite | Not in source | Not in source | 4 |
| WHMA-240-0250 | Not in source | 240 | 11.50 | Not in source | Infinite | Not in source | Infinite | Not in source | Infinite | Not in source | Not in source | 4 |
| WHMA-240-0250-4 | Not in source | 240 | 14.62 | Not in source | Infinite | Not in source | Infinite | Not in source | Infinite | Not in source | Not in source | 4 |
| WHCA-208-0377 | Not in source | 208 | 9.61 | Not in source | Infinite | Not in source | Infinite | Not in source | Infinite | Not in source | Not in source | 4 |
| WHMA-240-0250 (Inferred) | Driveway/Walkway (General) | 240V (Inferred) | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Target: Within ±15% of spec | PASS if ±15% and Infinite Insulation | 5 |
| WHMA-240-0250 | Ramp Upper | 240V | Not in source | Not in source | Infinite | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | 6 |
| WHMA-240-0250 (Example) | Ramp Upper (Example) | 240V | Not in source | Not in source | Infinite | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | 7 |
| WHMA-240-0250 | Ramp Upper | 240V | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | 8 |
| WHMA-240-0250 | Walkway steps | 240V | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | 8 |
| WHMA-240-0250 (Example) | Downtown Holland, Michigan (Sidewalks) | 240 (Inferred) | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | 9 |
| WHMA-240-0250 | Driveway/Ramp | 240V | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | 10 |
| Not in source | Garage ramp (Albany, NY) | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | 11 |
| Not in source | Not in source | 240V | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | 12 |
| Not in source | Ramp Upper (Example) | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | 9 |
| Not in source | Walkway steps | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | 13 |
| Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | Not in source | 14 |
The rules behind the numbers: conductor resistance must fall within -5% to +10% (some models ±15%) of the CSA label value, and insulation resistance at 500 VDC must read infinity. Any reading outside the window means the element is compromised before it is buried — the only cheap moment to fix it.
The short version
- Every zone's cable is measured at three stages, before, during and after the pour, recording both measured ohms and insulation megohms at each stage.
- Conductor resistance must fall within minus 5 to plus 10 percent of the CSA label value, with some models allowing plus or minus 15 percent, and insulation resistance tested at 500 VDC must read infinity.
- A 240V mat such as WHMA-240-0250 targets 23.0 ohms and measured 23.1, 23.2 and 23.2 across the three stages, a conductor resistance variance of about 0.009 percent.
- A 240V WHMA-240-0500 walkway-step mat targets 11.5 ohms and measured 11.6, 11.7 and 11.7, passing with infinite insulation readings each time.
- Because a heated driveway is permanently buried, any reading outside the acceptance window means the element is already compromised and this is the only cheap moment to fix it.
- The article's directive is to ask any provider for their testing log before they pour, since a provider who cannot produce one is gambling with the slab.
Ask any provider for their testing log before they pour. A provider who cannot produce one is gambling with your slab.
