Stay safe.
Turn main breaker OFF
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How
to wire Tankless electric water heater Stay safe. Turn main breaker OFF |
| 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 |
 EcoSmart Buy: EcoSmart tankless Resource EcoSmart manual |
 (image shows tankless with pigtail attached) Rheem tankless Buy: Rheem tankless Resource Rheem manual Breaker size chart General troubleshoot .pdf |
 Atmor point of use Buy: Atmor tankless Resource Atmor manual |
 Stiebel Eltron Buy: Stiebel Eltron tempera Resource Steible manual |
 Eemax/ point of use Buy: Eemax tankless Resource Eemax manual |
 Chronomite/ point of use Buy: Chronomite tankless Resource Chronomite manual |
| Step 1: getting started | |
 Breakers should never be hot to touch. Do not install tankless electric if main box is overheated. Warm or hot breakers will destroy the service panel (main breaker box) |
Test
if electric service panel is adequate for tankless: A) Open following link to do the Stress-Test on main breaker and service panel: Stress test Why do the stress test? It's your money. Breakers are rated by amps. Tankless pull a lot of amps. Flow of amperage causes heat. Heat is the enemy of electric. Overheated main breaker trips ... or gets loose over time, melts busbar connection, and destroys service panel or breaker box.  Example
#1: if you have 150 amp main breaker, the maximum load is 80%
or 120 amps for 'continuous operation.'
Exceeding 80% on a continual basis will cause main breaker to get warm
and then cool and then get warm again ... eventually shorting out and
melting the busbar. Example #2: if you
have 200 amp main breaker (or 200 amp service), maximum load is 80% or
160 amps. So if you add
whole-house tankless requiring 120-180 amps, you probably need up-size
to 250+ amp service depending on other household loads such as freezer,
pool pump, oven etc.
B) Each tankless has an amp rating. C) Add amps from tankless to service panel stress-test. To Figure amps for tankless: Read label on side of tankless for Volts and Watts. Divide watts by volts to get amps. So if volts are 240V, and watts are 9000, then 9000 divided by 240 = 37.5 amps. A 9000 watt tankless might have two 4500 watt elements, and both elements might or might not activate each time, so actual amp draw off the main breaker can vary depending on incoming water temperature, thermostat setting etc. D) If electric service is too small for expected load, then install new 'electric service' (breaker box and drop wire from power company). Call power company, or local electrician. Or if skilled and local codes allow, have the meter pulled and install new panel yourself ... if incoming wires are correct gauge. Wire gauge chart Or use ordinary tank-type heater and save money, and headaches How to increase amount of hot water |
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Look
at rating
plate located on side of unit Read the manual 1) Look at electrical rating plate showing voltage and wattage Look at product spec
sheet.
2)
Consult
Tankless manual if availableFailure to follow
installation steps in manual will void product warranty
3)
Warranty Caution:However, few manuals show how to wire the unit The warranty covers
defects in manufacturer's workmanship, but does not
cover DIY
installation or electric wiring errors.
Resource
Overview of installation steps |
| Step
2: If tankless
has factory-connected pigtail (wire that is already connected to
tankless) Do not undersize wire and breaker. Larger breaker and wire are ok, and run cooler and save money. |
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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 |
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 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. 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  |
 Screws on main breaker are HOT at all times Even when main breaker is OFF, both screws are HOT Only if meter is PULLED are these screws safe to touch |
What size
breaker and wire should you use? 240Volt ratings: 7.7 Kw= 7600 watts / 40 amp breaker/ 8 gauge wire 9.6 Kw = 9600 watts/ 50 amp breaker/ 6 gauge wire 11.5 Kw = 11500 watts/ 60 amp breaker/ 6 gauge wire 13.4 Kw = 13400 watts/ 70 amp breaker/ 4 gauge wire 16.3 Kw = 16320 watts/ 85 amp breaker/ 3 gauge wire |
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Example
shows 3 wires connected inside tankless Electricity supplied by 3 separate wires from 3 breakers Total electric consumption for typical tankless electric is 96 to 120 amps. Before installing tankless electric, look at main breaker on household service panel. If main breaker is 150 amps, then it is max-ed out carrying this tankless load. Breakers are rated safe maximum at 80% Main breaker 150 amps x 80% = 120amps safe maximum Tankless electric water heaters consume large amount of electricity This is because electric elements cannot heat water as fast as natural gas or propane gas. Tankless electric water heater will cost more to operate than ordinary tank-type electric water heater. This is because so much energy is wasted trying to heat water as it passes quickly in pipe. To reduce energy consumption, add a tempering tank to preheat incoming cold water, keep thermostat setting low, reduce consumption, lower water pressure, add low-flow shower heads. If water moves too slowly through the pipe, tankless may not activate |
Step #4 Inside Main Breaker box |
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Screws on
main breaker are HOT at all times Even when main breaker is OFF, both screws are HOT Only if meter is PULLED are these screws safe to touch |
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Example three
50 amp 240Volt breakers Use 50 amp breaker with 6 gauge wire No difference if all 3 breakers are on same side of panel, or on different sides. You want to balance the loads on your breaker box ... so each busbar (blue and black in illustration) is delivering same amperage as other .... any 240 volt breaker is automatically balanced because the double breaker draws off both busbars. Requires 250 amp service and 250 amp main breaker. Footnote: if double breaker is rated 50 amp, then both wires off the breaker are delivering 50 amp (not 25 amps each wire). Resource Wire size chart Main breaker Stress test Buy: Circuit breakers at Amazon |
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Double
check wire size and distance
100'-150' etc requires larger diameter wire Some sources say the cut-off is 50' ../ not 100' ... a oversized breaker and wire are OK, and run cooler with more efficiency ... but wire MUST match breaker ... and both breaker and wire be rated for the amp draw from tankless. 240 volt/ each breaker greater than 7.7 Kw= 7600 watts / 40 amp breaker/ 8 gauge wire greater than 9.6 Kw = 9600 watts/ 50 amp breaker/ 8-6 gauge wire greater than 11.5 Kw = 11500 watts/ 60 amp breaker/ 6 gauge wire 13 Kw = 13400 watts/ 2 60 amp breakers/ 6 gauge wire Resource: Select correct wire and breaker size |
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 Larger image of 240 Volt subpanel Image of 120V-240V subpanel |
240
Volt Subpanel
for Tankless electric ***White Neutral wire is not needed for a 240Volt subpanel. Resource: How to wire subpanel 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 |
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| 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 Amazon - Industrial Electric Products |
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| Step #6 Protect with surge protector | |
 Whole
house surge protector/ protects every 120-240
volt circuit.Most appliances, timers, computers etc have electronics today. Few are protected from surge ... unless your 120 volt computer is plugged into Type 3 plug-in surge protector strip ... that jumps the gap to ground wire instead of absorbing or suppressing. A 240 volt tankless cannot be protected with a Type 3 surge strip like 120 volt loads. For
whole house protection, install Type 1-2 surge protector that absorbs
or suppresses surge event. Install either inside the panel in double
slot closest to main breaker ... or connect the Type 1-2 to a dedicated
double breaker located closest to main breaker. Big screws on main
breaker are hot at all times, een when main breaker is off.
Homeowner insurance might have appliance exclusion. Read policy240 volt hardwired Type 3 can be installed directly at the tankless unit ... or at 240 volt HVAC etc. Any circuit can have multiple surge protection. Double, triple protection per circuit is fine. The closer the surge is located to load, the better it protects. Water heater warranty does not cover surge event. Buy: Whole house surge protectors Resources: How to wire whole house surge protector Intermatic IG1240RC3 whole house surge protector/ pdf |
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| Other considerations: | |
| Your money -FYI; Tankless cannot be exposed to hard water. 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 - Tankless heat exchanger is prone to scale build-up, and must be delimed each year. How to delime tankless -Tankless electric can save money for installations such as small point of use hand washing sink vs pulling hot from tank each time .... or vs cost of installing recirculating system. But a small point of use tank is easier to maintain. How to install point of use -Ignore the rabid promotion that 'tankless save money while delivering endless hot water' ... promising to suspend laws of physics to supply hot water without using energy. The laws of physics are still in force, despite all beliefs to the contrary, and if incoming water is too cold then tankless cannot keep up, unless you buy a unit rated with enough wattage. Some mauals have a chart that shows the curve based on water temps. See chart -Very few service resource are available for tankless heaters ... gas or electric. Parts are not generic, and are expensive to purchase. Service folks in your area might not be trainned on your brand heater ... ... tankless are generally the least environmentally friendly heaters, with the offer to 'throw-in-landfill when no longer functioning' recycling and repurposing strategy. -In all cases, tankless will have more operational issues than ordinary tank-type heater. Ordinary tank type heaters can be maintained to last forever, are not susceptible to surge and can usually be fixed DIY. |
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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/ 50 psi is best Connect pressure gauge to outdoor spigot ... check neighbors spigot Use pressure reducing valve and expansion tank on incoming cold water lines Buy Water pressure gauge Temperature-pressure gauge Safety Equipment for Professionals Industrial and scientific Amazon Resource Clogged water lines/ Low water pressure TP valve releasing hot water |
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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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Buy Electronic parts Industrial supplies Tools and home improvement Home and garden Hayward pool Pentair pool Southwire electric |
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Buy
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Resource: Compare box timers DPDT timers Intermatic Control water heater w/ Z-wave |
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Recirculation systems |
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