LAARS Rheos+ RHHV - Install and Operating Manual - Manual (Page 29)

LAARS Heating Systems Page 28
another 20-25°F (11-14°C) (when at high fire), and
it leaves the boiler at 160-165°F (71-74°C). This hot
water is then sent to the system.
If the water at the inlet of the copper heat
exchanger is 140°F (60°C), or higher, the water will be
allowed to flow through the copper heat exchanger and
directly to the outlet of the Rheos+, and there will be a
20-25°F (11-14°C) temperature rise between the inlet
and outlet of the unit, when the unit is at high fire.
The by-pass mixing control displays the mixed
water temperature, which is the temperature of the
water that is sent to the copper heat exchanger. This
temperature setting is locked and cannot be changed in
the field.
By pressing and holding the two buttons on the
left of the mixing control for at least 3 seconds, the
user will access two available menus.
The first menu allows selection of the temperature
units. Pressing the two left buttons for at least 3 seconds
displays “Uni” on the screen (for units). Then “°F” is
displayed. Press the up or down arrow on the control to
change from °F to °C, or °C to °F. When the preferred
selection is displayed, press the enter (bottom left) button.
The control will then display “Add” for the second
menu. If no more buttons are pushed, the control will
automatically return to the temperature display mode.
changed. This setting will be the best suited to most
Rheos+ installations.
Fast: Switch 4 to ON position and all others
to OFF. If the rate of system recovery to setpoint is
sluggish with the control set to medium, the “Fast”
setting may be an improvement. The “Fast” setting
will only be used when the rate of change at the sensor
is very rapid. In most cases, this setting is too fast for
the Rheos+.
5.6 Mixing System and Control
The Rheos+ has an internal mixing system
that ensures that the condensation does not occur
on the finned copper heat exchanger, with boiler
return temperature down to 70°F (21°C). This
system, that consists of automatically actuated
and linked valves, is set up at the factory, and is
non-adjustable. The return water goes through the
stainless steel heat exchanger, then to the mixing
system (see Figure 7).
If the water at the inlet of the copper heat
exchanger is less than 140°F (60°C), water from the
outlet of the copper heat exchanger will be directed
back to the inlet of the copper heat exchanger, and will
mix to bring the inlet water up to 140°F (60°C). Once
through the copper heat exchanger, the water picks up
Control Parameters:
Setpoint = 120°F / 49°C
Differential = 15°F / 8°C
Offset = 15°F / 8°C
Throttling Range = 5°F / 3°F
Minimum Output = 25% (Factory Setting)
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
Differential
Offset
Note: As shown, if the offset is set the same as the differential, the throttling range is outside the differential range.
The only time the Rheos+ will be above 25% fire is when the temperature drops below the setpoint's differential.
Line with arrows represents what happens after the Rheos+ achieves 120°F/49°C during a call for heat. It will cool to
105°F/41°C, and will re-energize at 25% of full fire.1°C.
Rheos+ Inlet Temperature
%
of
Full
Fire
Range
Figure 16 - Control Parameter Possible Interference