Rinnai I Series Technical Bulletin

Technical Bulletin 158 - I-Series Boiler with DHW Recirculation
PURPOSE: To announce the I-Series Condensing Combi Boiler offers DHW recirculation and to explain
how DHW recirculation works, the different recirculation modes, and how to configure the boiler for
DHW recirculation.
I-Series Condensing Combi Boiler Models: i060C, i090C, and i120C

DHW Recirculation Facts:

•
Recirculation circulates hot water through the plumbing system, so hot water is always available in
whatever part of the house that the consumer may need it.
•
Recirculation requires an external recirculation pump. For pump sizing, reference the "DHW
Pressure Drop and Flow Curve" in the Boiler Installation and Operation Manual.
•
An optional 24V timer can be used to set the time intervals and duration of recirculation (an
example timer is the Intermatic® MIL72ASTUZ-24).
•
Two recirculation modes are available: Dedicated and Crossover:

Dedicated Mode:

•
The plumbing system includes a dedicated hot water
return line.
•
Recirculation technology in the boiler decides if the
pump will turn on based on time intervals and DHW
setpoint temperature.
•
How the recirculation pump works:
−
The pump turns ON and runs until the DHW
return water temperature is within 6°F of the
setpoint temperature, or for 20 minutes,
whichever occurs first.
−
The pump stays OFF based on the DHW setpoint
temperature (as outlined in the table below).
DHW Setpoint
140° 135° 130° 125° 120° 115° 110° 108° 106° 104° 102° 100° 98°
Temperature (°F)
Typical Pump OFF
Intervals (Minutes)
Note: Rinnai strongly recommends installing insulation to the hot water and dedicated return lines
to decrease the amount of heat loss.
9 10 11 12
Cold water
Home includes dedicated hot water
and cold water lines.
14 16 19 20
Hot water
22 24 26 28
TB-158
7/2019
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