LAARS Mighty Therm VW (Sizes 2000-5000) - Installation, Operation and Maintenance Instructions - Manual (Page 9)

Page 9 Mighty Therm Volume Water Heaters
Size
Water
Cat.
Flow
Rate
(GPM)
Head
Loss**
(ft.)
plumbed to avoid putting strain on the pump
casing.
2.9 Tank Installation
1. Be sure the floor is structurally capable of
supporting the tank when it is filled with water,
and is waterproof.
2. The tank should be placed so that manholes,
inspection covers, nameplates and drain valves
are accessible.
3. Be sure the tank is suitable for the water in the
system. Some water is corrosive and requires a
protected tank with a special lining.
4. If the tank is glass lined, it should be equipped
with a suitable magnesium anode. It is a good
practice to replace the anode when it is
approximately 50% used. The factory warranty
on a glass-lined tank will be void if a satisfactory
anode is not in place at the time of a failure or if
it is consumed by cathodic action.
5. Make sure the tank connections in the heater-
tank circulating loop are the proper size as listed
in Table 4. If tappings are smaller than the
Temp. Rise
Across
Heater (F)
Indoor Outdoor
A water pressure reducing valve installed in the
incoming cold water line may act as a check valve,
and prevent the expanded water from backing up. This
will result in a pressure rise in the heater, which will
be relieved by the pressure relief valve. If the relief
valve pops frequently, a mineral deposit may build up
on the valve seat, causing a leak.
The following suggestions may solve the
problem:
1. Replace the installed water pressure reducing
valve with a suitable valve having a back-flow
port. These valves allow water to flow
backwards when the pressure in the system
exceeds the pressure in the mains.
2. Install a check valve around the pressure
reducing valve which will permit reverse flow.
This will permit the expanded water to back flow
into the mains.
3. Install an auxiliary small relief valve set at 25 psi
less than the main relief valve. The valve must
be piped to a drain, and may require occasional
cleaning. It will bleed off the expanded water,
and protect the main pressure relief valve from
becoming fouled.
4. Install a properly sized expansion tank.
2.8 Pump Installation
A suitable pump must be field installed on
Model VW heaters to provide circulation between the
heater and the storage tank. The pump must be sized
to avoid an excessive temperature rise and to provide
correct flow for the existing water hardness
conditions. The specification in the following table
include allowances for 30 feet of piping and normal
fittings between the heater and the storage tank.
IMPORTANT:
Check the oil level in the pump before starting. Oil
the pump every 3 months. Fill the bearing assembly
to lower level of the overflow vent. Add 5 or 6 drops
of oil to front and rear of motor. Use 20W non-
detergent oil. Pumps located in very hot or dusty
locations should be oiled once a month. Self-
lubricating pumps do not require oiling.
1. Install the heater in a cool location to avoid
damage to the pump, accidental tripping of a
thermal switch if one is installed, and scaling in
the heater.
2. The pump must be accessible for lubrication,
inspection and service.
3. If the pump is designed for floor mounting,
install it securely on concrete block or pad at
least 6 inches above floor level. This will
prevent flooding of the motor when the floor is
washed. Be sure that floor mounted pumps are
not suspended from piping, and that piping is
Soft 100 4.2 33 –
2000 I Normal 150 9.0 22 –
Hard 200 15.0 16 –
Soft 100 4.5 40 35
2450 I Normal 150 9.7 27 24
2200 E Hard 200 16.0 20 18
Soft* 200 6.1 25 22
3050 I Normal 150 11.0 34 29
2800 E Hard 200 18.0 25 22
Soft* 200 6.3 29 25
3500 I Normal 150 11.0 38 34
3200 E Hard 200 19.0 29 25
Soft* 200 6.7 33 29
4050 I Normal 150 12.0 44 39
3600 E Hard 200 20.0 33 29
Soft* 200 6.9 37 32
4500 I Normal* 180 17.0 41 36
4000 E Hard 200 21.0 37 32
Soft* 200 7.2 41 36
5000 I Normal* 180 18.0 46 40
4500 E Hard 200 22.0 41 36
I = Indoor E = Outdoor
* These heaters are single pass.
** Pressure drop includes loss through 30 feet of pipe and
normal fittings when heater is installed with storage tank. Pipe
and fittings are assumed to be 4".
Table 4. Pump Performance Requirements.