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How
to wire Tankless electric water heater Stay safe. Turn power OFF FYI; Manufacturer's literature and side-by-side research shows whole-house tankless electric, for average family of 4, costs $100 more per year to operate vs ordinary tank-type heater. Large research file |
 Ahhhhggg .. I have to read |
 EcoSmart Buy: EcoSmart tankless Resource EcoSmart manual |
 Rheem tankless Buy: Rheem tankless Resource Rheem manual Breaker size chart |
 Atmor Buy: Atmor tankless Resource Atmor manual |
 Stiebel Eltron Buy: Stiebel Eltron tempra Resource Steible manual |
 Eemax Buy: Eemax tankless Resource Eemax manual |
 Chronomite Buy: Chronomite tankless Resource Chronomite manual |
 iHeat Buy: iHeat tankless |
 Titan Buy: Titan tankless Resource Titan manual |
 Bosch Buy: Bosch tankless Resource Bosch manual |
| The trick for
solving which tankless might be to decide how much hot water is needed
.... To calculate: take a routine bath in the 100 gallon bathtub ... get out of tub, but don't drain ... use a 1 gallon bucket to empty the tub to get actual amount of water used for bath .... it will be less than 100 gallon ... suppose it's 80 gallons... then calculate percentage of hot to cold .... Typical bath temperature will not be higher than 104° Next, measure temp of full hot water coming from tank ,,,, suppose it is 128°... then the percent of hot to cold is 81% of the total gallonage in tub ... round up to 85% of the 80 gallons needed is Hot ... or 68 gallons of hot needed to fill tub. Next measure temperature of incoming cold water at outdoor tap using cooking thermometer etc... suppose in winter it's 40° and summer 60°F. That means the tankless must be able to raise 68 gallons of hot water from 40° to 128°, or a 88° degree rise in temperature... Next look at spec sheet for each type of tankless unit to see what each model can deliver. The incoming cold water is the weak point for using tankless heaters... Resources: Average-temperature-of-shallow-ground-water.html Tempering-tank.html |
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| Step 1: get started | |
 Do not install tankless electric if main box is overheated |
Test
if electric service panel is adequate for tankless: 1) Stress-Test main breaker and service panel: Main breaker stress test 2) Rule of thumb: Exceed 80% on main panel causes main breaker to start getting warm. Over time, the breaker gets weak, and overheats on busbar, damaging panel. Example: 150 amp service, maximum load 80% = 120 amps. For tankless unit requiring 50-60 amp breaker, you might need larger service. Do the stress test. Example: 200 amp service, maximum load 80% = 160 amps. For whole-house tankless requiring 120-180 amps, you need up-size to 250 amp service ... depending on other loads such as freezer, pool pump, oven etc. 3) To Figure amps:: Read label on side of tankless for Volts and Watts. Divide watts by volts to get amps. 4) Add amps from tankless to service panel stress-test: Main breaker stress test |
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Failure to follow steps in manual can void product warranty 1) Look at electrical rating plate showing voltage and wattage or -Look at product spec sheet. 2) Consult Tankless manual if available 3) Warranty Caution: The warranty covers defects in manufacturer's workmanship, but does not cover DIY installation or electric wiring. Resource Overview of installation steps |
| Step 2: If tankless has factory-connected wire | |
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Factory-connected
wire/ or pigtail attached to
tankless Read rating plate on side of unit for amps and watts. Connect wire from breaker and factory pigtail inside octagon box using wire connectors This type of tankless will have 1 heating element. Resource How to select and install correct wire connector Select correct wire and breaker size How to wire 240Volt outlets |
| Step 3 Look inside tankless unit for wire connections | |
 This Example shows tankless supplied by 1 wire  Wires can be black-black, white-black or black-red Ground wire is required Tankless MUST be grounded Resource: Color code for wire |
Single
240Volt has L1 and L2 L1 L2 means 240 volt with 2 Hot wires Use 1 circuit breakers  1) Look for single block with L1-L2 terminals where you will install wires under screw plate -or- look for 2 wires where you will connect with wire connectors Single wire cannot be split apart to connect to multiple terminals. 2) Look at rating plate on tankless to determine total watts 3) Scroll down to see wiring examples for breaker Resource How to select and install wire connector 2 wire 240Volt has 2 sets L1 and L2 Single wire cannot be split apart to connect to multiple terminals. Single wire cannot be split apart to connect to multiple terminals. Use 2 circuit breakers  Example:Rheem RTE27: use two 60 amp breakers, and two 6 gauge wires 3 wire 240Volt has 3 sets L1 and L2 Single wire cannot be split apart to connect to multiple terminals. Separate wire needed for each set L1-L2 terminals Use 3 circuit breakers  |
| End page 1: Go to Page 2: select wire and breaker size Page 3: connect wires to main breaker panel Page 4: Connect tankless to subpanel |
| Use only 600 volt wire. Lamp cord, extension cords are not rated 600 volt. Use copper wire only. Aluminum wire is fire risk and should be avoided or installed by professional. 30 amp breaker use 10 gauge / 120-240 volt 30 amp outlet can be installed on 30 amp breaker only/ use 10 gauge wire ... cannot be connected to 15-20-40 amp breaker.  Orange/ #10 gauge wire, with ground ... 30 amp capacity. Safe maximum: 30 x 80% = 24 amps. Buy: 10-2 gauge/ 30 amp 10-3/ 30 amp Southwire electric tools |
Yellow
12 gauge 20 amp 120 volt 20 amp outlet can be installed on 20 amp breaker, but not 15 amp breaker/ use 12 ga wire. ... cannot be connected to 30-40 amp breaker. 1  Yellow/ #12 gauge wire, with ground ... 20 amp capacity. Safe maximum 16 amps. Buy: 12-2 gauge/ 20 amp 12-3/ 20 amp NMB is house wiring UF is underground Rolls of stranded wire HOOK UP Wires |
White
14 gauge 15 amp 120 volt 15 amp outlet, AFCI, GFCI, timer, switch etc can be installed on 15 or 20 amp breaker. Never connect 15 gauge wire to 20-30-40 amp breaker.  White/ #14 gauge wire, with ground ... 15 amp capacity. Safe maximum 12 amps. Buy: 14-2 gauge/ 15 amp 14-3/ 15 amp NMB is house wiring UF is underground |
| 50-60
amp breaker use 6 gauge / 240 volt 50 outlet can be installed on 50 amp breaker only  Buy: 6-2 wire Southwire electric tools NMB is house wiring UF is underground |
40-50
amp breaker use 8 gauge / 240 volt 40 amp outlet can be installed on 40 or 50 amp breaker only  Buy: 8-2 wire Southwire electric tools NMB is house wiring UF is underground |
  Copper ground wire. Every device, load, metal enclosure etc must be grounded. Ground wire must be continuous throughout installation, never switched on-off, never used as a Neutral wire. Generally ... use same size as other wire in circuit Buy: 12 gauge copper ground wire Ground wire Green ground wire Ground pigtails Ground rods/ ground clamps at Amazon |
 Non metallic flexible cables must carry ground wire, but do not have hazard of short circuit causing injury from shock. Armored steel cable can be used as a grounded connection, and will protect wires from damage. Metal can be energized from an insulation failure. All conduit ...metal, plastic ... flexible and rigid ... must be attached to structure, and attached to enclosures, boxes. Movement, damage and deterioration are major cause of electrical failure. Buy: Non-metallic flexible conduit Power whip Armored cable Southwire armored cable cutter Pull boxes |
 Electrical tools must be insulated. Always best to disconnect power, but insulation failure, lack of proper grounding, grounded neutral, lack of GFCI, out-of-code wiring, generator operating without transfer switch, and other problems still pose a risk to anyone working on electric power ... even when breaker is off. Buy: Electrician tools kits KLEIN TOOLS Tools kits IRWIN tools KNIPEX Telephone cable knife Low Voltage Mounting Bracket for Telephone |
 600 volt 12 ga Stranded wire ot THHN wire is good for conduit with multiple wires ... but stranded cannot be installed under screw terminals on outlets, switches, timers etc without risk ... of heat causing splayed strands ....that come loose ... and begin to arc. Connect stranded to short piece of solid copper wire, and attach solid to screw terminal. Do not solder residential or commercial wiring. Project wire, extension cords, thermostat, bell and automotive wire are not rated for residential or commercial wiring. Only wire maked 600 volt can be used for permanent household wiring. Buy: Southwire 600 volt stranded wire Rolls of stranded wire HOOK UP Wires |
 Protect wiring from damage Use nipper instead of pliers or screwdriver for removing staples (and nails). Do not damage cable or wires inside cable. -Code says: Cable SHALL BE secured without damage to the outer covering. NEC sec. 336-15 Buy End cutting nippers at Amazon |
  Electrically insulated tools When removing insulation from wire, do NOT score or put cuts on surface of copper wire. Doing so increases resistance and heat on wire and creates possible weak point. Buy tools: KLEIN TOOLS Wire strippers at Amazon Electric Wire Stripping Machine Linesman pliers Utility knife at Amazon |
 Multimeters Voltage is tested across two separate wires. Ohms or resistance is tested across both ends of same wire. Amperage is tested along one or two points on same wire. Buy: Analog multimeter Multimeters at Amazon Klein multimeter Electric testers at Amazon Clampmeter for testing amp flow on line |
 GFCI circuit breaker A GFCI circuit breaker will protect all boxes on circuit. Circuit must be grounded. Ground wire must be continuous and connected to each piece of equipment. White wire on circuit breaker must be connected to Neutral busbar inside the breaker panel. Buy GFCI circuit breakers |
Push down 1" wide Push down breaker Plug-in breaker Buy single-pole: Choose from 15 to 60 amp Eaton CL series Siemens 15-60 amp Single-pole tandem breaker Tandem breakers |
Push down 2" wide Push down breaker Plug-in breakers Buy double-pole: Choose from 15 to 125 amp Choose from 15 amp to 200 amp Eaton CL series circuit breaker Siemens circuit breaker Double pole GFCI |
 Larger image of 240 Volt subpanel Image of 120V-240V subpanel |
240
Volt Subpanel
for Tankless electric ***White Neutral wire is not needed for 240Volt breakers. Ground wire arriving from main panel can be connected to busbar at top of subpanel, or install a separate ground busbar lower on panel. Keep ground wires away from Hot connections and Hot busbars. Sometimes it is easier to add ground busbar near bottom of subpanel so ground wires can be kept away from Hot connections. Illustration shows how to install subpanel for adding more breakers to main panel With tankless electric, install 150amp breaker/ replace any 2-pole breaker close to top of panel Use 2/0 wires with 150 amp breaker 2/0 copper wire between main panel and subpanel, up to 100 feet. Install 3 40-amp breakers in subpanel to supply each of three 240Volt #8 wires going to Tankless. Read nameplate on Tankless for watt rating. #8 wire for 240Volt loads up to 7680 watts Use 50 amp breaker and #6 wire for 240volt loads above 7680 and less than 9600 watts For example tankless with single wiring terminal, might require 9600 watts or more Resources: How to install subpanel *Neutral wire is not needed if subpanel is NOT going to have 120volt breakers. Place subpanel within eyesight of Tankless to avoid disconnect requirement Disconnect lets electrician cut power to Tankless unit. Disconnect is for safety. Electrician or homeowner knows for certain when power is OFF. Never touch leaking water heater or wet water heater unless power is OFF Never run water pipes directly above tankless where leaking and condensation can drip on water heater. If tankless flooded, disconnect power and replace water heater |
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Option:
Install meter on 120-240V subpanel ***White Neutral wire not needed for 240Volt breakers. Neutral wire only necessary for 120Volt breakers Illustration shows Neutral wire in event you want a 120V-240 subpanel Meter will read all voltage that passes to subpanel Buy: New and used electric meters Buy subpanel: Main lugs at Amazon Siemens 125 amp/ 8 space at Amazon Siemens 125 amp/ 12 space at Amazon Resources: How to install electric meter on water heater or subpanel How to get electric service |
| Step #5 Power cut-off -or- disconnect | |
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DisconnectElectrical Code may require disconnect at Tankless unit, if Tankless installation is not within view of main breaker boxCall local electrician for specific local code Buy non fused safety switch: 60 amp 2-pole safety switch Pullout Disconnect at Amazon< Fusable pullout disconnect 2-pole 30 amp non-fusable safety switch/ power cut-off 2-pole 60 amp non-fusable safety switch Shop AElectronic parts |
| Step #6 Protect with surge protector | |
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Whole
house surge protector Tankless electric water heater is not protected from surge Appliances, water heaters, timers, circuit breakers are not protected from surge Most appliances today have electronics. Few of these appliances are protected from surge Water heaters the plug into outlet are not protected from surge Homeowner insurance might have appliance exclusion. Read policy Water heater warranty does not cover surge event. Protect 120V and 240V circuits with whole house surge protector Resources: How to wire whole house surge protector Intermatic IG1240RC3 whole house surge protector/ pdf |
| Other considerations: | |
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Think
about freezing temperatures Locate tankless in naturally warm location Tank-type heaters are warm full time. Tankless will only heat with water demand. Add tempering tank to passively preheat incoming cold water. Add power to tempering tank in winter. Some tankless will not activate if incoming temperatures exceed set point.  Buy Reliance water heaters Resource: How to wire under counter water heater |
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Water
pressure should not exceed 80 psi Connect pressure gauge to spigot For example 200 psi Rain Bird P2A or 100 psi Brady BTG 100 Use pressure reducing valve and expansion tank on incoming cold water line Buy: Water pressure gauge Temperature-pressure gauge Safety Equipment for Professionals Industrial and scientific Amazon Resource Clogged water lines/ Low water pressure |
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Tankless
cannot be exposed to more than 11 grains hardness in water Efficiency will decline within months. Parts such as pressure sensor will fail within 2 years De-liming will not prevent failure Warranty does not cover failure due to water problems Buy: Hard water testing kits Resources: Bradford White side-by-side study Water softener research pdf |
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Delime
tankless yearly Buy project materials Tankless flushing kits Tankless service valves Submersible pump Filter washers at Amazon Washing machine hoses at Amazon Deliming will not restore full efficiency. Read research Resource: How to delime tankless water heater Maintain water heater 2012/ pdf |
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Clean
water filter monthly Warranty does not cover failure due to water problems Resource Read typical maintenance pdf |
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Tankless
recirculation Resource How to install Tankless recirculation |
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Recirculation systems |
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