LAARS Mighty Max VW (Sizes 320M - 400M) - Installation, Operation and Maintenance Instructions - Manual (Page 6)

Page 6
LAARS Heating Systems
NOTE: The heater and all other gas appliances
sharing the heater gas supply line must be firing at
maximum capacity to properly measure the inlet
supply pressure. Low gas pressure could be an
indication of an undersize gas meter and/or
obstructed gas supply line.
8. Do not exceed the maximum inlet gas pressures
specified. Excessive pressure will result in
damage to the heater's gas controls. The
minimum pressures specified are for gas input
adjustment.
9. The correct differential gas pressure is stamped
on the rating plate. The regulator is preset at the
factory, but may need adjustment for altitude per
Section 3.
10. Before operating the heater, test the complete gas
supply system and all connections for leaks using
a soap solution.
CAUTION
Since some leak test solutions (including soap and
water) may cause corrosion or stress cracking,
rinse the piping with water after testing.
ATTENTION
La commande d’allumage fonctionne sur un
courant de 120V. Pensez-y lorsque vous travaillez
sur le chauffe-eau et prenez soin d’éviter tout
contact avec des pièces branchées sur le courant
qui causeraient une électrocution, conduisant à des
dégâts matériels, aux blessures voire à la mort.
2.7 Water System Piping
2.7.1 Water Chemistry
Laars equipment is designed to be used in a
variety of water conditions. The water velocity in the
heat exchanger tubes is kept high enough to prevent
scaling from hard water, yet low enough to avoid
erosion by soft water. The water in 95 percent of the
urban centers in the United States is compatible with
this equipment, but in some areas a water supply will
contain a large quantity of scaling chemicals or the
water may be extremely soft or erosive. In rare
situations the water will contain both scaling
chemicals and erosive chemicals such as calcium or
sodium chloride. These conditions may be caused by
well water or a nearby pumping station, and the
particular condition may not be characteristic of the
entire city water system.
NOTE: It is possible to have hard and soft water in
the same city. Check with the local water company.
If an installer sees damage to any water handling
equipment at the installation site, it should be repaired
as soon as possible to help reduce maintenance costs.
If there is erosion, resize the pump to reduce water
velocity before the tube ruptures. If scaling is bad, set
up a heat exchanger tube-cleaning maintenance
schedule to prevent heat exchanger tube cracking and
wear. Not fixing the condition may cause serious
damage to the heater and the water system.
Scaling is a layer on the inner surface of the heat
exchanger tubes which restricts the flow of water.
Scale can be any color or texture, smooth or rough,
granular or amorphous. Erosion is usually identified
by pitting, cavitation, ridges and “islands” on the inner
surfaces of the heat exchanger tubes. If this is caused
by extremely soft water, or a water softener in the
system, the internal copper surfaces will be very
shiny. Other chemicals, such as chlorine or chlorides
in the water, will cause dark patches of erosion.
NOTE: Laars does not warrant heat exchangers
damaged by scaling, corrosion, or erosion.
2.7.2 Water Piping
Minimum inlet water temperature is 120°F
(49°C).
VW heaters are intended for heating large
volumes of water at constant flow rates, usually for
storage in a tank. Heaters in this type of application
are sometimes called circulating water heaters.
Figure 5 shows the VW heater with tank and two
pumps. One pump (recirculation) only circulates the
hot water through the building plumbing. The other
pump (heater) circulates water between the tank and
the heater. This heater circulating pump is essential for
proper operation of the heater (see Section 2.7.5).
The heater circulating pump must be sized to
provide enough flow to prevent damage to the heat
exchanger, and must handle the hardness or softness
of the water being heated. Generally, hard water must
be pumped at higher velocity; however, soft water will
erode holes in the heat exchanger tubing if pumped
too fast.
The Mighty Max VW heater comes standard
with copper tubes, but in areas where the water supply
is soft or corrosive, the heat exchanger should be
factory ordered with cupronickel tubes. Consult the
Figure 4. T-Fitting Sediment Trap Installation.
Gas Supply
Inlet
3 in.
(76mm) Min.
Cap
Nipple
To Equipment
Inlet
Tee
Fitting
OUT OF
PRODUCTION