Weil-McLain is the heritage US boiler brand — over 140 years in the market, historically dominant in cast-iron hydronic boilers. Their ECO Tec line competes directly with Lochinvar NOBLE/KNIGHT in the condensing combi segment.
Side-by-side
| Lochinvar NOBLE / KNIGHT | Weil-McLain ECO Tec | |
|---|---|---|
| AFUE | 95% | 95% |
| Turndown | 10:1 | 5:1 to 7:1 (lower) |
| Heat exchanger | Stainless fire-tube | Stainless fire-tube |
| Heat exchanger warranty | 5-yr NOBLE / 10-yr KNIGHT | 10-yr (residential) |
| Sizing range | 85-199 MBH | 110-220 MBH |
| Heritage | 1919 (Lochinvar) | 1881 (Weil-McLain) |
| Parent company | AO Smith | SPX Technologies |
Where Lochinvar leads
- Better turndown (10:1 vs 5:1-7:1) — maintains comfort at low loads better, fewer short cycles
- Smaller sizing (WHN85 at 85 MBH) for compact homes
- Cascade-friendly controls for multi-unit installs
- SQUIRE indirect ecosystem tightly integrated
- SMART TOUCH controls regarded as more user-friendly for contractors
Where Weil-McLain leads
- Brand heritage — Weil-McLain installs are widespread; legacy contractor familiarity
- 10-year heat exchanger warranty standard (matches KNIGHT, beats NOBLE)
- Larger top-end sizing (220 MBH) for very large homes
- US manufacturing in Indiana
- Existing Weil-McLain installs — easier brand continuity for contractor service
When existing Weil-McLain matters
Many older homes have Weil-McLain cast-iron boilers (Gold series, Series 88, etc.). Contractors who serviced them often default to Weil-McLain ECO Tec for replacement. If you have a strong relationship with a Weil-McLain contractor, that may be the deciding factor regardless of feature comparison.
Turndown matters in mild weather
10:1 turndown means the unit can fire as low as 10% of rated input. 5:1 turndown bottoms out at 20%. In mild outdoor conditions (spring, fall), 5:1 turndown leads to short-cycling — fire on, satisfy quickly, off, repeat. This shortens heat exchanger life and wastes fuel. Lochinvar\'s 10:1 is a meaningful advantage in moderate climates.
Which to choose
- Mild climate + want longest part-load efficiency: Lochinvar (turndown advantage)
- Existing Weil-McLain contractor relationship: Weil-McLain
- Smaller home (need 85 MBH size): Lochinvar KNIGHT WHN85
- Largest residential (220 MBH): Weil-McLain
- SQUIRE indirect pairing planned: Lochinvar single-brand
Bottom line
Both established US-distributed boiler brands. Lochinvar wins on turndown ratio (key for mild-climate efficiency) and SQUIRE ecosystem. Weil-McLain wins on heritage and contractor familiarity in markets with deep Weil-McLain history. Contractor preference often decides.