P.34
Thermometers (Optional)
Thermometers shall be dial or scale type and shall have a metallic body and casing and a
glass lens. The range of measurement shall be not less than 30
o
F to 200
o
F with an
accuracy of +/- 2%. An electronic temperature sensing system may be used in place of
dial or scale thermometers (see below).
Temperature Sensors (Electronic)
An electronic temperature sensing system may be used in place of dial or scale
thermometers. Temperature sensors shall be shall be of metallic construction and have a
maximum temperature rating not less than 200
o
F. Temperature reading may be via digital
readout, LCD screen, internet or other electronic device. The temperatures may be read at
the differential controller screen. The range of measurement shall be not less than 30
o
F to
200
o
F with an accuracy of +/- 2%.
Sensor Wire:
Sensor wire for temperature sensors or other electronic sensors must be no less than
18/2 AWG. Sensor wire must be insulated; in locations where the sensor wire is
exposed to the elements it must be UV resistant and rated for outdoor use.
Piping and Hoses
Piping and Hoses shall be copper tube or corrugated stainless steel with a maximum
operating temperature of not less than 220
o
F and maximum working pressure of not less
than 125 psi.
Pipe Insulation
Pipe insulation shall have a maximum operating temperature of no less than 220
o
F. All
pipes shall be insulated to R2.6 or greater, typically this will require a wall th
ickness of ¾”
or greater. When located in exposed areas, pipe insulation shall be protected with a UV
resistant coating or jacket.
Auxiliary Water Heaters
The auxiliary water heater shall be listed by an accredited listing organization.
The acceptable range of water heater sizes and capacities are listed in the table below. The
specific auxiliary water heater selected for a system should be adequately sized to meet the
full hot water load at the residence taking into account the delivered hot water temperature;
the mains cold water temperature and the expected hot water usage as per standard water
heater sizing guidelines.
Type
Storage Volume
Minimum Power Rating
Electric Tank Water
Heater
30
–
240 gallons
2,400W to 9,000W
Gas Tank Water Heater
30
–
240 gallons
10,000Btu/h to
200,000Btu/h
Tankless Gas Water
Heater
na
95,000Btu/h to
200,000Btu/h
Appendix A
