Rinnai Circ-Logic — Learning-Mode Recirculation Explained

Circ-Logic is Rinnai's adaptive recirculation firmware available on the Sensei RX and Sensei+ (RUR) series. It runs the built-in recirc pump only when needed — saving energy compared to always-on schedules.

Three modes

• Learning Mode — Circ-Logic watches your hot-water usage for 14 days and builds a profile of typical draw times (morning showers, evening dishwashing). After the learning period, the pump runs in 10-30 minute windows before predicted draws.
• Schedule Mode — manual time windows you set in the ControlR app or controller. Example: 6-8 AM, 5-7 PM.
• On-Demand Mode — pump runs only when you press a wireless button installed at the farthest fixture. Maximum efficiency.

How learning works

The unit logs every hot-water draw — time, duration, GPM. After 14 days, it correlates draws to time-of-day and day-of-week. By day 21, the pump pre-heats the loop 10-20 minutes before your typical morning shower. The model updates continuously — schedule changes (new baby, work-from-home shift) reflow within a week.

Settings you can override

• Maximum daily runtime — cap at 2 hours/day to prevent the pump running excessively on irregular usage
• Quiet hours — block pump activity during night hours (the pump itself is quiet, but the burner cycling is audible to light sleepers)
• Vacation mode — pause Circ-Logic; pump won't run for the duration set

Performance compared to schedule mode

Field testing by Rinnai (and corroborated by Building America Solution Center studies on adaptive recirc): Circ-Logic uses 30-50% less gas than always-on, 10-20% less than fixed schedule. The savings come from skipping unnecessary pump runs on days when usage shifts.

Energy use ballpark

• Always-on recirc: $25-50/month additional gas in a typical 2,500 sq ft home
• Fixed schedule (2 windows/day): $10-20/month additional
• Circ-Logic learning: $5-12/month additional
• On-demand button: $1-3/month additional (when used)

Setup

1. Confirm the unit is Sensei RX (RX130/180/199) or Sensei+ (RUR98/199)
2. Verify the return line is plumbed (with check valve) and the pump is hydraulically commissioned
3. Open the ControlR app → Recirculation → Mode → Learning
4. Set Quiet Hours and Max Runtime preferences
5. Let it run for 14 days without manually overriding

Comparison to other brands

Navien's similar feature is "HotButton" — also learning-mode but with less mature firmware. Rheem's RTGH series doesn't have a true adaptive option; it's schedule-only. Circ-Logic is the most mature adaptive recirc in the residential tankless category as of 2025.

Bottom line

If you have a Sensei RX or Sensei+, switching to Learning Mode after the first month is free energy savings. See our general recirculation guide for unit selection and plumbing options.