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Rinnai · Boiler troubleshooting

Central heating works, no domestic hot water

What is going on

Heating runs but no DHW.

Likely causes

  • DHW program key not on
  • Flow switch not working
  • T3 DHW sensor in plate heat exchanger defective
  • RS100 timer or DHW program not responding
  • Three-way valve not moving to DHW

Check in this order

  1. Switch the DHW program on at the Control Tower.
  2. Check the flow switch for impurities and operation; replace if needed.
  3. Replace the T3 DHW sensor if defective.
  4. If using an RS100, check its DHW timer times and see its instructions.
  5. Check three-way valve wiring; replace the valve motor if needed.

Applies to: E50CRN; E75CRN; E75CRP; E110CRN; E110CRP

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Source: Rinnai E-Combi Series Installation & Servicing Instructions (8U516009 V0116), p.77 (15.4). Written in our own words; check the manual for your exact model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.