Description
Ultra-Low-NOx (ULN) control, designed for power-damper A. O. Smith 2″ insulation (Natural Gas, 5″ W.C.) tanks
The Honeywell/Resideo WT8860B1000 is a factory-style replacement gas control for A. O. Smith ultra-low-NOx water heaters with a 2″ insulation cavity. It’s built for power-damper models, reads tank temperature through an immersion-well NTC sensor, and ships set for a 5″ W.C. natural-gas outlet pressure. The control is self-powered from the pilot’s thermopile—no external wiring required. CS88xx pilot assemblies are designed for use with this control.
Replaces These Models
- Honeywell/Resideo WV8860B1309
- Honeywell/Resideo WV8860B1310
- A.O. Smith 100073010
- A.O. Smith 318618-000
- A.O. Smith 100093970
- A.O. Smith 9007631005
What it Does Well
Direct A. O. Smith ULN Swap (2″ Cavity)
Direct replacement for ULN, power-damper applications with 2″ insulation so you can avoid re-piping or changing brackets.
Integrated Temperature Sensing
Immersion-well NTC probe monitors water temperature (sensor rated to 221 °F / 105 °C) for accurate control and high-limit protection.
Water Temperature Limit
Sensors provide a fail-safe mechanism that can control water temperature limit (Temperature Cut-Out [TCO]) function.
Self-Powered Design
Runs on thermopile output from the standing pilot. No 24-V supply or batteries.
Quick Diagnostics
Front status LED provides flash codes that speed troubleshooting and cut repair time.
Key Specifications
| Gas Type | Natural gas |
| Regulator Setting | 5.0 in. W.C. outlet pressure (ULN) |
| Insulation Size | 2″ insulation A. O. Smith ULN tanks |
| Fit | Upright mounting for power-damper models |
| Temperature Details |
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| Power Source | Thermopile heated by the pilot flame (no external power) |
| Connections | ½ in. NPT inlet × ½ in. inverted-flare outlet (right-angle body pattern used on OEM applications) |
