LAARS Mighty Therm VW (Sizes 2000-5000) - Installation, Operation and Maintenance Instructions - Manual (Page 8)

LAARS Heating Systems
Page 8
or floor sink. Special attention must be given to
relief valve settings in installations where the
heater is located on the ground floor of a tall
building. In both instances, the static pressure of
the system is elevated, and could cause the relief
valve to leak. Where no special setting of the
relief valve is ordered, the factory will furnish a
125 psi setting. Never reduce the relief valve
opening. If necessary, install the relief valve in a
Tee immediately past the heater outlet.
3. The weight of all water and gas piping should be
supported by suitable hangers or floor stands.
4. Check piping diagrams with local applicable
plumbing, heating and building safety codes.
5. All two-temperature systems using temperature
valves must have forced recirculation in the low
temperature building loop.
6. A check valve installed at the hot water inlet to
the tempering valve will prevent cold water from
being drawn in reverse through the tempering
valve into the hot water.
7. When installing a tempering valve, locate it at
the bottom of the antithermosyphon loop at least
24" high to prevent excessive hot water from
entering the mixed water supply (see Figure 7).
Bring the cold water supply up from the floor to
the valve.
8. Keep thermometer bulbs in moving water. Use
of a bushing will cause temperature readings to
be off 10° or more (see Figure 8).
9. Insulate all pipes containing hot water,
especially in unheated areas. Sizing charts
assume this condition exists. Excessive heat loss
of exposed piping adds to gas consumption and
could result in insufficient hot water during peak
demand periods. If pipes are uninsulated, a
larger heater must be used.
2.7 Water Expansion
When cold water is heated, it expands. If no
water is being used during the heat-up period, the
expanded water will normally back up into the city
mains.
2.5 Electrical Wiring
Electrical diagrams are included with the packet
provided with each unit.
WARNING
The heater must be electrically grounded in
accordance with the most recent edition of the
National Electrical Code and ANSI/NFPA 70 , and in
Canada, follow Canadian Electrical Code CSA
C22.1. Do not rely on the gas or water piping to
ground the metal parts of the heater. Many times,
plastic pipe or dielectric unions isolate the heater
electrically. Service and maintenance personnel who
work on or around the heater may be standing on
wet floors and could be electrocuted by a poorly
grounded heater.
1. Check heater wiring and pump for correct
voltage, frequency and phase. If the pump circuit
is other than 115V, check to see that the heater is
provided with an appropriate transformer.
2. Wire the heater and pump exactly as shown in
the wiring diagram supplied with the heater.
3. The pump and heater must be electrically
interlocked so the heater cannot come on unless
the pump is running.
4. All field installed electrical safety devices and
all field installed devices (draft switches, relays,
timers, outdoor temperature reset devices, etc.)
can be connected to the heater wiring at points
shown in the wiring diagram designated “Field
Interlock.”
2.6 Water Piping of System
1. Be sure to provide valves at the inlet and outlet
to the heater so it can be readily isolated for
service.
A butterfly or similar type of valve is
recommended.
2. The pressure relief valve must be installed in the
tapped opening provided in the heater header, or
on the "T" connection on the heater outlet side,
with its outlet piped but not fastened to a drain
Hot
Water
Hot
Water
Storage
Tank
Floor
Automatic
Tempering
Valve
Cold
Water
Tempered Water
24"
Figure 7. Tempering Valve Installation. Figure 8. Thermometer Bulb.
Right Wrong