Piping Components - Smith XWH 150 Instruction Manual

SCALDING
This water heater can deliver scalding temperature water at any
faucet in the system. Be careful whenever using hot water to avoid
scalding injury. Certain appliances such as dishwashers and
automatic clothes washers may require increased temperature
water. By setting the thermostat on this water heater to obtain the
increased temperature water required by these appliances, you
may create the potential for scald injury. To protect against injury,
you should install a mixing valve in the water system. This valve
will reduce point of discharge temperature by mixing cold and hot
water in branch supply lines. Such valves are available from the
local plumbing supplier.
Figure 56. Scald Warning Label Located on the Appliance
The following chart (Table 21) details the relationship of water
temperature and time with regard to scald injury and may be
used as a guide in determining the safest water temperature for
your applications.
Table 21. Approximate Time / Temperature Scald Chart
APPROXIMATE TIME / TEMPERATURE
RELATIONSHIPS IN SCALDS
120°F
125°F
130°F
135°F
140°F
145°F
150°F
155°F
WATER CHEMISTRY
NOTE: The required temperature rise and the standard
circulating pump are sized based on the heating of potable water
with a hardness of 5 to 25 grains per gallon and a total dissolved
solids not exceeding 350 ppm. Consult the manufacturer when
heating potable water exceeding these specifications. Heating
of high hardness and/or high total dissolved solids water may
require a larger circulating pump, and a revised temperature rise
specification based on the water chemistry of the water to be
heated.
Water with a hardness of less than 5 grains per gallon will usually
have a pH which can be aggressive and corrosive causing
non-warrantable damage to the pump, and associated piping.
Corrosion due to water chemistry generally shows up first in the
hot water system because heated water increases the rate of
corrosive chemical reactions.
More than 5 minutes
1 1/2 to 2 minutes
About 30 seconds
About 10 seconds
Less than 5 seconds
Less than 3 seconds
About 1 1/2 seconds
About 1 second

PIPING COMPONENTS

WATER HEATER SYSTEM PIPING
Water heater system piping MUST be sized per the pipe
requirements listed in Table 22. Reducing the pipe size can
restrict the flow rate through the water heater, causing inadvertent
high limit shutdowns and poor system performance.
CHECK VALVES:
Field supplied. Check valves are recommended for installation
as shown in Figure's 57 thru 60.
WATER HEATER ISOLATION VALVES:
Field supplied. Full port ball valves are required. Failure to use
full port ball valves could result in a restricted flow rate through
the water heater.
ANTI-SCALD MIXING VALVE:
Field supplied. An anti-scald mixing valve is recommended when
storing domestic hot water above 115°F.
UNIONS:
Field supplied. Recommended for unit serviceability.
TEMPERATURE AND PRESSURE RELIEF VALVE:
Factory supplied on water heaters. The T & P relief valve is sized
to ASME specifications. Storage tanks may require additional
valves depending on local codes.
TANK SENSOR:
A. O. Smith supplies a tank sensor. The tank sensor must be
installed in the tapping provided in the lower 25% of the storage
tank to achieve proper operation. As shipped from the factory,
the tank sensor is in the literature package shipped with the unit.
Placing the sensor in the tapping provided on the storage tank
will improve temperature response and prevent short cycles of
operation.
Table 22. Water Heater Pump Applications / Recommended
Temperature Rise
WATER HEATER PUMP APPLICATIONS
Model *Pipe Armstrong
Size
1-1/4" E8
150
1-1/4" E8
200
2" E17
285
2" E24
400
2" E22
500
2" E22
600
2" --
700
2" --
800
NOTE: Pump sizing and flow requirements are based on 45 feet
of piping, 4 - 90° elbows, and 2 - fully ported ball valves.
37
Grundfos Flow Loss Temp
Rate
(FT/
GPM) HD)
UP 26-99 16 16.6 18°F
BF
UP 26-99 21 11.8 18°F
BF
UP 43- 30 17.1 18°F
100 SF
UP 43- 39 21 18°F
110 SF
UP 43- 53 26 18°F
110 SF
UP 43- 53 26 22°F
110 SF
TP 40- 63 32 22°F
160
TP 40- 67 31 24°F
160
Rise