SQUIRE is Lochinvar\'s indirect-fired water heater line — storage tanks heated by an external boiler via internal heat exchanger coil. No burner, no flue, no gas connection to the tank itself. For boiler-heated homes, often the highest-efficiency DHW path.
The two SQUIRE families
SIT — Glass-Lined Standard
- SIT040 — 40-gallon
- SIT065 — 65-gallon (volume size)
- SIT080 — 80-gallon
- SIT120 — 120-gallon (large residential / light commercial)
10-year residential / 5-year commercial tank warranty. Magnesium anode rod standard. Glass-lined steel tank.
SSU — Stainless Steel Premium
Lifetime residential warranty / 10-year commercial. No anode rod required (stainless). Best for very hard, aggressive, or chloride-heavy well water where glass-lined would corrode.
How indirect works
Hot boiler water circulates through a coil inside the tank. Heat transfers from the coil to the domestic water in the tank, which is then drawn at fixtures. The boiler does the actual fuel-burning for both space heat and DHW. See indirect vs tank comparison.
Specs
| Model | Capacity | FHR (with 180°F boiler) | Warranty |
|---|---|---|---|
| SIT040 | 40 gal | ~180 GPH | 10-yr residential |
| SIT065 | 65 gal | ~240 GPH | 10-yr residential |
| SIT080 | 80 gal | ~280 GPH | 10-yr residential |
| SIT120 | 120 gal | ~360 GPH | 10-yr residential |
| SSU45 | 45 gal | ~200 GPH | Lifetime residential |
| SSU80 | 80 gal | ~300 GPH | Lifetime residential |
FHR scales with boiler output. A 200 MBH boiler dramatically boosts FHR vs an 85 MBH boiler.
Pairing with boilers
- NOBLE / KNIGHT heat-only boilers (not combi) — natural pairing
- NOBLE / KNIGHT combi — usually redundant since combi already produces DHW; indirect added only for high simultaneous demand
- Other-brand modulating-condensing boilers — Lochinvar SQUIRE works with any mod-con
- Cast-iron atmospheric boilers — works but inherits the boiler\'s 70-80% efficiency. Consider boiler upgrade alongside SQUIRE install
Sizing for the home
| Household | Recommended SQUIRE |
|---|---|
| 1-2 person | SIT040 or SSU45 |
| 3-4 person | SIT065 |
| 4-5 person | SIT080 or SSU80 |
| 5-6 person / large fixtures | SIT120 |
Install
See install guide. Key: boiler-loop circulator (Taco 007 / Grundfos 15-58), DHW priority wiring, tempering valve downstream of tank, T&P relief, anode rod accessible (SIT only).
SIT vs SSU — which to choose
- SIT (glass-lined): standard pick, $400-700 less than equivalent SSU, requires anode rod maintenance, 10-year warranty
- SSU (stainless): premium pick, lifetime residential warranty, no anode rod ever, ideal for aggressive water (well water with high chlorides, sulfates, or low pH)
For most municipal-water installs, SIT is the right answer. For well water and known-aggressive water, SSU is worth the premium.
Bottom line
SQUIRE is the most-efficient DHW for boiler-heated homes in heating-dominant climates. SIT065 is the volume residential pick; SSU45 or SSU80 for premium installs and well water. Combined with a 90%+ mod-con boiler, you have the highest year-round DHW efficiency available outside of heat pump water heating.