LAARS Mighty Max VW (Sizes 320M - 400M) - Installation, Operation and Maintenance Instructions - Manual (Page 7)

Mighty Max Volume Water Heater Page 7
local factory representative or Laars factory for
additional information.
2.7.3 Pressure Buildup in Water System
The water utility supply meter may contain a
check valve, back flow preventer, or water pressure
reducing valve. This will create a closed water supply
system. Contact the water supplier or local plumbing
inspector on how to control this situation.
During the heating cycle of the heater, the water
expands creating a pressure buildup in the water
system. The pressure and temperature relief valve may
discharge hot water under these conditions, causing a
loss/waste of energy and a buildup of lime on the
relief valve seat.
NOTE: Do not plug the relief valve.
There are two methods to prevent the water
heater pressure relief valve from discharging hot water
in a closed water system:
1.
Install a pressure relief valve on the cold water
supply line. Make sure that the discharge of this
valve is directed to an open drain and protected
from freezing.
2. Install a properly sized thermal expansion tank
on the cold water supply line.
2.7.4 Temperature and Pressure Relief
Valve
For protection against excessive pressure, the
water heater is equipped with a pressure relief valve.
When the water heater is connected to a separate
storage vessel, a temperature and pressure relief valve
must be installed on the storage vessel. The
temperature and pressure relief valve must be design-
certified by a nationally recognized testing laboratory
that maintains periodic inspection of listed equipment
or materials, in accordance with the requirements of
the standard for Relief Valves for Hot Water Supply
Systems, ANSI Z21.22 / CSA 4.4.
The temperature and pressure relief valve must
have a BTU/h (kW) capacity rating that is greater than
the BTU/h (kW) input of the water heater. The
temperature and pressure relief valve must be marked
with a maximum working pressure not to exceed the
maximum working pressure shown on the rating plate
of the water heater, or the maximum working pressure
of the separate storage vessel, whichever is the lower
pressure. The temperature and pressure relief valve
must have a maximum working temperature not to
exceed 210°F (99°C).
Do not place any shutoff valves between the
temperature and pressure relief valve and the storage
vessel.
The relief valves discharge water in large
quantities should circumstances demand.
The discharge pipe:
1. Must not be connected directly to a drain. The
Discharge pipe must terminate 6 inches (152mm)
above a floor drain or external to the building. If
the discharge pipe is not directed to a drain or
other suitable means, the water flow may cause
property damage.
2. Must not be smaller than the pipe size of the
relief valve.
3. Must be of material capable of withstanding
210°F (99°C) without distortion.
4. Must be installed to allow complete drainage of
both the relief valve and discharge pipe.
5. Must not have any valve between the relief valve
and the end of the discharge pipe.
Do not thread, cap, plug, or block the end of the
discharge pipe. Do not install a reducing coupling or
other restrictions in the discharge pipe.
WARNING
Hot water can scald! Hot water can produce third
degree burns in 6 seconds at 140°F (60°C) and in
30 seconds at 130°F (54°C).
ATTENTION
Au moment de l’entretien des commandes, mettez
des étiquettes sur tous les fils avant de les
débrancher. Des erreurs de câblage peuvent
causer un fonctionnement inadéquat et dangereux.
Vérifier que tout fonctionne bien après votre
entretien.
Manually operate the relief valves at least once a
year. To prevent water damage, discharge pipe must
terminate at an adequate drain. Standing clear of the
outlet (discharge water may be hot), lift and release
the lever handle on the relief valve to make the valve
operate freely.
2.7.5 Pump Requirements
Table 5 specifies water flow rates for the
Mighty Max VW heaters, and the pumping head
required for typical piping configurations. Table 5
allows for 30 feet (9.1m) of piping and typical
fittings (see Figure 5). Piping with a shorter length or
larger diameter may reduce the head requirement and
pump power consumption. Contact a Laars
representative for assistance.
The correct flow rate can be verified by checking
the temperature rise of water as it passes through the
heater. To check the temperature rise, measure the
difference in water temperature between the heater
inlet and outlet to determine flow. For example: If a
Size 320M VW heater is installed and normal water is
used; the inlet water temperature is 160°F (71°C); the
outlet water temperature is 171°F (77°C). Then there
is a 11°F (6°C) degree temperature rise. Per Table 3,
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