General IRC UPC Unions req'd within 12in. . . . . . . . . . . . . . . . . . . . .[2801.3] {609.5}
Full-bore water valve only . . . . . . . . . .F-p12, F-p13 [2903.9.2] {605.2}
Hot and cold pipe insulated within 5ft. . . . . . . . . . . . . .[n/a] {energy}
Insulate hot water recirculating pipes . . . . . . . . . . . .[energy] {energy}
Min. R12 integral (no blanket) . . . . . . . . . . . . . . . . .[energy] {energy}
Electric req's in-sight or lockable disconnect . . . . . .[T4001.5] {NEC422-31b}
Flue (also see termination clearances--page 22)
Draft hood or barometric damper in appliance space [1802.1] {521}
Min. height 5ft. above draft hood . . . . . .[1804.2.3,2426.6.6] {517.2}
Only one draft hood . . . . . . . . . . . . . . . . . .[1801.1,2425.5] {501.0}
No single-wall in cold space . . . . . . . . . . . . . . . . .[2426.7.6] {514.3}
Access & Working Space Working space by firebox 30in.x30in. min. . . . . . . . .[1305.1] {511.5}
Must be able to remove water heater . . . . . . . . . . .[1305.1] {511.0}
Min. door size 24in.x30in. high OR . . . . . . . . . . . .[1305.1.2] {511.1}
Trap door 22in.x30in. {30in.x30in.} OR . . . . . . . .[1305.1.3,4] {511.3}
Passageway min. 24in. wide,solid floor, max. 20ft. long . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [1305.1.3,4] {511.3,4,5}
Location
Prohibited in bedroom, bathroom, clothes closet or area open to same
except direct-vent or electric appliance . . . . . . . . . . .[2005.2] {509.0}
Over framing req's watertight pan w/1in. {win.} drain [2801.5] {510.7}
In garage--burner/heating element must be 18in. above floor .
Water can scald on contact at temperatures as low as 110°F
Water changing state from liquid to steam expands over 1,600 times
Water at sea level atmospheric pressure boils at 212°F
Temperature relief valves are set at a maximum of 210°F
Pressure relief valves are set at a maximum of 150psi
Under pressure, the boiling temperature of water goes up
At 150psi, water boils at 358°F
The thermostat in a water heater shuts off gas when the temperature needs have
been satisfied. If the thermostat fails, the water heater could have a continuous
rise in temperature and pressure (from expansion of the water). The temperature
and pressure would continue to rise until the pressure exceeds the pressure
capacity of the tank (300psi). In the instant the tank bursts, the superheated
water boils and expands with explosive force. The superheated water turning
to steam turns the water heater into an unguided missile.
To prevent these catastrophic failures, water heaters are required to be protected
for both excess temperature and pressure. Usually, the means of protection is
a combination temperature and pressure (T&P) relief valve.
Site/Underground
Approved plans & building card on site . . . . . . . . . . .[105.7] {114.2}
Equipment listed and installation instructions on site [1401.1] {302.1}
Energy conservation report . . . . . . . . . . . . . . . . . . .[1101.2] {energy}
Forced-Air Furnace
IRC UMC Not open to bedroom or bathroom, EXC. . . .[1701.4, 2406.2] {304.5}
Direct vent or elec. furnace OK bedroom or bath . . .[2406.2X] {304.5X}
OK to access attic or crawl equip. through bedroom closet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [2406.2] {304.5X2}
OK in br. closet if tight door w/closer & outside combust air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [2406.2X5] {304.5X5}
Furnace room-passageway min. 24in. wide . . .F-m4 [1305.1.2] {307.2}
Work space 30in. deep to height of unit or min. 30in. [1305.1] {307.2}
Total space must be 12in. wider than furnace (exc--replacement furnace) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-m4 [1305.1.1] {304.7}
Combustion chamber--6in. min. to closed door . . .[1305.1.1] {304.7}
Return >10ft.min. from combustion . .F-m4 [1602.3X2,2440.5-4X] {404.1.X3.3}
Receptacle req'd within 25ft. . . . . . . . . . . . . . . . .[3801.11] {306.3}
Underfloor
On slab {min. 3in.} above grade . . . . . . . . . . .[1305.1.4.1] {304.8}
Suspended furnace min. 6in. above grade . . . . . . .[1305.1.4] {304.8}
Passageway--22in. {30in.} x 30in. or manu. spec. .[1305.1.4] {307.4}
Access door max. distance 20ft. to equip. . . . . . . .[1305.1.4] {307.4}
Switch at entrance for light at appliance . . . . . . .[1305.1.4.3] {306.4}
Attic
Access--22in. x 30in. (or dimension of appliance) [1305.1.3] {307.3}
Max. distance from opening 20ft. . . . . . . . . . . . . .[1305.1.3] {307.3}
Solid floor from access door min. 24min. wide . . . .[1305.1.3] {307.3}
Min. 30in. deep platform in front of firebox . . . . . .[1305.1.3] {307.3}
Upright furnace req's 5ft. headroom . . . . . . . . . . . . . . .[n/a] {307.1}
Lighting outlet switched at access door near furnace .. . .[1305.1.3.1] {306.4}
Books based on 2006 IRC, UMC, & UPC; 2005 & 2008 NEC; 2007 CBC, CPC, CMC & CEC with references to changes from prior editions. Books are published by The Taunton Press Inc. Code Check Copyright 2009 • Code Check is a registered trademark of the Taunton Press, Inc., registered in the U.S. Patent & Trademark Office
MECHANICAL 
