LAARS Rheos+ RHHV - Install and Operating Manual - Manual (Page 28)

Rheos+ Boiler and Water Heater Page 27
5.5.6 Integration Constant
The proportional control used on the Rheos+ has
internal circuitry that helps to minimize overshoot that
can sometimes be associated with proportional plus
integral (PI) controls. There are three field-selectable
integration constants (slow, medium and fast), and
an off position on the proportional control, which
are selected with the dipswitches on the control (see
Figure 14). In most cases, this setting will not need to
be changed
Off: Switch 1 to ON position and all others to
OFF. Setting the control to the “Off” position puts the
control into proportional only operation. This is not a
recommended setting for the Rheos+.
Slow: Switch 2 to ON position and all others
to OFF. This is the slowest integration constant. It
allows the Rheos+ the most time to reach its setpoint.
In most cases, this is too slow for Rheos+ installations.
Medium: Switch 3 to ON position and all others
to OFF. The integration constant is set to “Medium”
at the factory, and in most cases, will not need to be
46°C and 49°C, the unit will remain at low fire.
Between 38°C and 41°C, the unit will be at full fire.
The throttling range is adjustable between 2°F
and 30°F (1°C to 17°C). The range can be set by
removing the cover of the S350P control and adjusting
the “THROT RANGE” dial (see Figure 14).
5.5.5 Minimum Output Setting
The minimum output setting of the controller is
0% of full fire. However, the minimum output of the
Rheos+ is limited to 25% of full fire by the fan speed
controller, to ensure proper operation of the Rheos+.
If a minimum desired output is higher than 25%, the
setting can be adjusted up by removing the cover of
the S350P control and adjusting the Min Output dial
(see Figure 14). Turning the dial clockwise increases
the minimum output. In most cases, this setting should
be left as shipped from the factory.
100°F
38°C 41°C
105°F
43°C
110°F
46°C
115°F
49°C
120°F
100%
75%
50%
0%
25%
Throttling Range
Differential
Offset
Note: Line with arrows represents what happens after the Rheos+ achieves 120°F/49°C during a call for heat.
It will cool to 110°F/43°C, and will re-energize at less than full fire. The Rheos+ will be at full fire only if the
temperature goes below 105°F/41°C.
Rheos+ Inlet Temperature
%
of
Full
Fire
Control Parameters:
Setpoint = 120°F / 49°C
Differential = 10°F / 5°C
Offset = 5°F / 3°C
Throttling Range = 10°F / 5°F
Minimum Output = 25% (Factory Setting)
Figure 15 - Control Parameter Graph