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27Part No. 550-141-935/0602
To pipe tankless heaters:
1. Size piping no smaller than heater inlet and outlet.
2. Automatic mixing valve must be installed. See Figure 26.
Follow manufacturer’s instructions to install.
3. Flow regulating valve must be installed. Size according
to continuous draw of heater. See Table 10. Follow
manufacturer’s instructions to install.
4. Operating control with small adjustable differential
scale is recommended. Install in temperature control
tapping in heater plate.
5. Multiple tankless heaters (see Figure 26):
a. Use cold water supply header with individual risers
to each heater. Size header by increasing one pipe
size for each additional heater.
b. Use hot water outlet header with individual risers
to each heater. Size header by increasing one pipe
size for each additional heater.
c. Do not pipe multiple heaters in series.
6. In hard water areas, soften cold domestic water supply
to heaters to prevent lime build-up.
Table 10 Tankless Heater Ratings
Figure 26 Tankless Heater Piping
Tankless
heater model
Continuous draw
(no recovery period)
GPM
Inlet and outlet
tappings
78-24 6.5 ¾"
Pipe tankless heaters10
Hot water can scald!
• Consumer Product Safety Commission and some states recommend domestic hot water
temperature of 130°F or less.
• When installing an automatic mixing valve, selection and installation
must comply with valve
manufacturer's recommendations and instructions.
• Water heated to a temperature suitable for clothes washing, dish washing and other sanitizing
needs will scald and cause injury.
• Children, elderly, infirm or physically handicapped persons are more likely to be injured by hot
water. Never leave them unattended in or near a bathtub, shower or sink. Never allow small
children to use a hot water faucet or draw their own bath. If anyone using hot water in the
building fits this description, or if state laws or local codes require certain water temperatures at
hot water faucets, take special precautions:
— Install automatic mixing valve set according to those standards.
— Use lowest practical temperature setting.
— Check water temperature immediately after first heating cycle and after any adjustment.