HVACopediaHTP · Boiler · Other
Cascade operation
What happens, in order
- Master sees a heat call from TT contact, DHW sensor or 0-10 V
- Master checks which follower addresses answer on the bus
- Master brings boilers up toward the cascade set point staged by demand
- Firing order rotates after the rotation time
- If the system sensor is missing, all boilers fire together
- System pump runs from the master dry contact
Timings and thresholds
| Item | Value |
|---|---|
| Max boilers | 8 (address 0 to 7) |
| Rotation | 48 h default (0 to 240) |
| Max cascade set point | 190 F |
| Max bus cable length | 200 ft |
Codes you may see during this
Applies to: EL-80, EL-110, EL-150, EL-220, EL-299, EL-399 (N/LP)
More HTP boiler sequences
- Ignition retries and lockout · Ignition
- Central heat call · Heating
- Outdoor reset and warm weather shutoff · Heating
- Indirect water heater call · Domestic hot water
- Pump service mode · Pump/purge
- Standby and over-temperature protection · Standby/shutdown
Related
Take it to the job
Sequences of operation, error codes and tips work offline in the HVACopedia app.
Source: Elite EL-80 N Installation Manual (LP-293), p. 6, p. 63, p. 64, p. 58. Written in our own words; timings can differ by model and software version, so check the manual for your exact unit.
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.