Bosch default output temperature is 120°F. Residential cap is 140°F. Commercial override extends to 180°F with installer enablement.
Why 120°F is the default
- Scald safety: 120°F causes third-degree burn in 5-10 minutes. 140°F does it in 5 seconds
- Energy: every 10°F above 120°F adds 3-5% to gas use
- Heat exchanger longevity: higher setpoints accelerate scale formation
How to set on Greentherm
- Controller: up/down arrow buttons. Range 100°F to 140°F residential
- Home Comfort app (9999 SE and select 9900): slider interface
- Commercial override (above 140°F): requires installer to enable via service menu
Greenstar combi — DHW vs heating temperatures
Greenstar combi units have TWO temperature settings:
- DHW output temperature — same rules as Greentherm (100-140°F)
- Heating supply temperature — separate setting, 130-180°F. Outdoor reset modulates based on outdoor temp
Tronic POU temperature
Tronic POU mini-tanks have a dial on the unit (typically marked A/B/C or numeric). Default factory setting is 120°F. Range typically 90-150°F (verify model-specific limits).
When to deviate from 120°F
- Dishwasher needs 130-135°F: raise unit to 135°F + install thermostatic mixing valve (TMV) at fixtures for 120°F delivery
- Legionella concerns in larger homes with infrequently-used fixtures
- Recirculation loop temp loss — long loops drop 5-10°F; raise source to compensate
- Commercial sanitation: 180°F required for high-temp dishwasher sanitation rinse
Common temperature problems
- Water not hot enough at setpoint: scale on heat exchanger. See descaling
- Lukewarm at start of draw: cold-sandwich on Greentherm without recirculation
- Temperature swings during draw: low gas pressure or modulation issue
Bottom line
120°F unless a specific use case forces higher — then use a thermostatic mixing valve to deliver 120°F at fixtures. For Greenstar combi, the heating-supply temperature is a separate setting with its own optimization rules.