LAARS Mighty Therm LO-NOx PW (Sizes 500-1825) - Install and Operating Manual - Manual (Page 9)

Mighty Therm Lo-NOx Page 9
pressure should be at least 15 psi (102.2 kPa) above
the water vapor pressure corresponding to the elevated
water temperature.
Heating boilers are not suitable for open systems
unless the supply water temperatures are kept below
180°F (82°C), and a minimum of 5 psi (34.1 kPa)
static head is maintained at the boiler.
3.2.3 Hot/Chilled Water Systems
When a boiler is connected to an air
conditioning system where the same water is used for
heating and cooling, you must prevent chilled water
from entering the boiler When changing such a system
from cooling to heating, allow the chilled water to
circulate through the building, after the chiller has
been turned off, for a period long enough for the water
to warm up to at least 105°F (41°C) before the water
flows into the boiler. It is equally important to prevent
hot water from entering the chiller. The system shown
in Figure 8 is suggested to make sure the system water
is neither too hot nor too cold when a changeover
takes place. When a boiler is connected to heating
coils located in air handling units (where they may be
exposed to refrigerated air circulation), install a flow
control valve or other automatic means to prevent
gravity circulation of chilled water through the boiler.
Chilled water in the boiler will create condensate on
the boiler tubes. Boilers installed in violation of the
foregoing may void the warranty.
Figure 9. Primary-Secondary Plumbing.
Boiler Circulation
Pump
Cold Water
Make-Up
System Pump
12"
Max.
12"
Max.
12"
Max.
12"
Max.
Thermometer
Temperature
Sensor
Globe Valve
Check Valve
Pressure Reducing Valve
w/Fast Fill Bypass
Expansion Tank
with Air Scoop and
Auto Air Vent
3-Way Valve
Valve
Pump
LEGEND:
Boiler circuit piping must be equal to or larger than
boiler water connection size.
Boiler circulation pump sized for flow through
boiler.
Dotted devices indicate alternate locations.
WARNING: This drawing shows suggested
piping configuration and valving. Check with
local codes and ordinances for additional
requirements.
Purge
Valve
3-Way Valve No. 1
Change-Over
(Heating and Cooling) 3-Way Valve No. 2
To By-Pass
Both Heater and
Chiller
To
System
From
System By-Pass
To Boiler
and
Chiller
From
Boiler
Valve Motors
2-Pos
3-Wire - 24V
115/24V
Transformer
DPDT Manual or Automatic
Change-Over Switch
DPDT - Set at Change-Over
Temperature
Clock Timer
Auto-Resetting
Set at 15 Minute SPDT
Suggested Wiring Diagram For
Tempering System Water at
Changeover From Heating To Cooling
Figure 8. Boiler-Chiller Installation.
From
Chiller
3.2.4 Combined Space Heating/Potable
Water Heating Systems
When using the Laars boiler as a source of heat
for a combined space heating/potable water heating
system, be sure to follow the instructions of the space
heating system.