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2014

How to wire water heater thermostats

Listed below:
Non-simultaneous Dual element,
Single element 240Volt
Single element 120Volt
Off-peak thermostats
Redundant thermostats
Two water heater
Simultaneous
3-phase non-balanced
AO Smith bulletin: Thermostat wiring diagrams
 Rheem thermostat and element wiring diagrams
Bradford White thermostat and element wiring including 3-phase, single phase etc
American water heater thermostats and troubleshoot
State water heater thermostat and element wiring
Marathon thermostat and element wiring
Craftmaster thermostat wiring
Whirlpool 2012 electric water heater thermost wiring
3-phase electric water heater service manual

Resource pdf files:

Buy thermostats
Water heater thermostats at Amazon
Upper and lower thermostats

Buy generic upper and lower thermostats

Buy/ for residential 90-150 degree F:
Water heater thermostats at Amazon
Shorter style 89T33 thermostat kit at Amazon
Example Camco dual-element thermostat at Amazon
Buy/ 3 phase water heater thermostat 120-180 degree F
Camco 120F to 180F thermostat (commercial grade only)
Camco 180F lower thermostat (commercial grade only)
Residential water heater is not rated for more than 150F
More about 3-phase lower on page

Best to replace both thermostats.

There is no guaranteed way to test themostats.
If thermostat is sticking, then test includes rotating temperature knob which can temporarily unstick thermostat. So bad thermostat appears to work correctly.

NON-simultaneous water heater thermostats


See larger

Residential dual-element water heater

Both elements are never 'on' at same time unless tank is wired for other purpose (see owners manual). This is called 'non-simultaneous operation' since both elements are not 'on' at same time.

Either upper element is 'on' or lower element is 'on,' or both are off.


Resources:
How residential water heater works
Troubleshoot electric water heater
See inside main breaker box
Water heater pilot light
3-phase water heaters
Convert 3-phase water heater to single-phase

Test upper thermostat
Adjust temperature using screwdriver
How to adjust temperature/ gas and electric water heaters
How to replace thermostats
water heater element

Wires attach to either screw on element:

Resources:
How to test elements
How to replace elements



Larger image

Upper thermostat operation/ dual-element tank

Upper thermostat controls operation of water heater
ECO (reset button)
Upper thermostat is main controller <> it turns on upper element until top 2/3 of tank reaches temperature, and then sends power to lower thermostat. Lower thermostat heats bottom 1/3 of tank, and turns on and off to maintain tank temperature during standby hours when no hot water is being used.
Reset button
Resources:
How residential water heater works
How to replace thermostats on electric water heater
How to replace thermostats on gas water heater

Troubleshoot electric water heater
Troubleshoot gas water heater
Buy thermostats
Water heater thermostats at Amazon

See larger

Types of upper thermostats/ dual element tank

All designs work same way.
AO Smith thermostat appears on far left: Operation is identiacal to any brand thermostat, except L2 and T1 screws are not present, and thermostat uses less space, and thermostat cannot be broken apart to make separate ECO and thermostat.

Buy thermostats
Water heater thermostats at Amazon
Take apart thermostats

How to make lower thermostat using upper thermostat

If water heater has foam insulation, then replacing lower thermostat with ECO protected thermostat may not be easy.
Take apart upper thermostat and make new lower thermostat that will work for the specific two-water heater diagrams shown above.

When not to use:
Do not remove ECO protection on upper part of tank.
On simultaneous and single-tank off-peak water heaters, the ECO is require for lower thermostat operation.
ECO protects you in case of overheating and is required for safe operation of water heaters.

Single element 120 Volt or 240 Volt residential water heater

Same thermostat used for both 120V or 240V / For correct voltage of water heater, look at label on side of tank
    Upper Thermostats
Single-element thermostat         Dual-element thermostat
2 screws on right side           3 screws on right side  
See Larger   
       
You CAN use dual-element thermostat for single-element tank
You CANNOT use single for dual tank
                 

Single element thermostat/ 120V or 208V or 240V

Same thermostat works for all voltages
Screw numbers are 1 thru 4
Single-element is identical to dual-element thermostat, except all dual-element upper thermostats have 3 screws located on right side.
You can use dual-element thermostat for single-element tank
You cannot use single-element thermostat for dual-element tank, un;ess tank is being rewired for redundant and simultaneous operation.
Wiring illustrations:                
    American thermostat                    American thermostat wiring
See Larger 240 Volt single                            See Larger 120 Volt single

Off -peak water heater thermostats

See more OFF-peak options
Off peak with two water heaters
Off peak 120Volt
Off-peak thermostat wiring

Purpose of off-peak ... save energy during peak electric prices.  
> Upper thermostat operates normally to keep top 2/3 tank hot.
> Lower thermostat heats bottom 1/3 of tank when ordered by off-peak meter or timer

Compare:
Off-peak water heater thermostats
Ordinary water heater thermostats

1. Lower thermostat replaced with ECO-protected thermostat identical to upper thermostat. ECO safety red reset cuts off power when water in tank reaches dangerously high 150-180F

2. Upper thermostat: Red wire is moved L4 to T4. Color of wires can be different.

3. Black wire from lower thermostat does not connect to upper thermostat T4 screw

4. Black wire from lower thermostat runs to top of water heater for connection to off-peak meter, or off-peak timer

5. 240 Volt potential exists between yellow wire and each black wire at top of water heater

See Off-peak operation sequence

Ordinary tank wiring
Larger image
Tork DTU timer Off peak operation
Larger image

Tork DTU timer OFF peak

Wire water heater so lower part of tank is OFF during peak price times.
Less hot watger is available.
Tank is cooling during peak price, and probably will not run unless hot is drawn from tap

How to wire Tork DTU timer
How to wire thermostats
How electric water heaters work
EH40
Off-peak water heater timer

Off peak water heater timer

Lower thermostat receives power only when timer orders > Upper thermostat receives power full time

Resource:

How to wire off-peak water heater to timer

Sequence showing off-peak operation

Off peak water heater sequence
Larger image
OFF-Peak Non-simultaneous operation.
Lower element turned OFF during off-peak.
Upper element keeps top of tank hot
Less hot water is available.
When off-peak ends, normal NON-simultaneous operation resumes.

Redundant thermostats

Only lower element operates


Step 1:
Remove blue and yellow wires from upper thermostat
Step2:
Move black wire from terminal T4 to terminal T2
Tighten screws very tight against copper wire.
Step3:
ECO protected thermostat must remain at top of tank to protect against overheating event.
Redundant thermostat

Upper element is disconnected.
Lower element heats tank.
Water heater responds immediately when cold water enters tank.
Can possibly cause more stacking events

Both thermostats control lower element.

When upper part of tank cools, the lower element turns ON. Hot water rises.
When lower part of tank cools, lower element turns ON.
ECO-protected thermostat must be kept at upper part of tank to avoid overheating event that can damage or rupture tank, cause scalding, release of hot water through TP valve and distill chemicals out of the water.


Cold enters lower part of tank through plastic dip tube.
Homeowners should check with plumber before altering water heater wiring. See insurance data on water heater failure

Redundant thermostats control 2 water heaters
Two water heaters Additional tank in series to double available hot water at peak times
See wiring option below
Read about two water heaters
Reduntant thermostats - two water heatersLarger image Redundant thermostats control 2 water heaters

Purpose:
Add additional tank so more hot water available at peak times, without adding additional wiring.

Heater #1 must be satisfied before power is sent to heater #2.
Heater #2 may not fully heat before heater #1 needs to turn ON again. This will happen IF water heater is poorly insulated or hot water is drawn from heater #1 or incoming water is very cold.

Sequence:
1) Power  from circuit breaker arrives at ECO-protected upper thermostat on heater #1
2) ECO protection might be required on upper part of tank to prevent overheating event since heat rises
3) Typical lower thermostat on heater #1 is replaced with ECO thermostat so power can be transferred to heater #2 when heater #1 thermostats are satisfied.
4) Once heater #1 is satisfied, power goes to heater #2.

Either heater can be wired for redundant or typical non-simulataeous operation.
The key is adding ECO-protected thermostat to lower part of heater #1, and adding wire from lower thermostat so power can be transferred to heater #2.

Water heaters with foam insulation may require long drill bit from home center or fry's to bring wire to top of tank. Be sure insulation and covers are put over thermostats so thermostat not exposed to cool temperatures and cause temperature misread.

Read about two water heaters

Non-simultaneous thermostats control two water heaters
Two water heaters
Larger image

Non-simultaneous thermostats control 2 water heaters

Simultaneous wiring will heat top of tank first.
Redundant will turn ON as soon as cold water enters tank. How electric water heater works

Purpose:
Add additional tank so more hot water available at peak times, without adding additional wiring.

Heater #1 must be satisfied before power is sent to heater #2.
Heater #2 may not fully heat before heater #1 needs to turn ON again. This will happen IF water heater is poorly insulated or cold water is drawn from heater #1 or incoming water is very cold.

Sequence is basically same as above.

Water heaters with foam insulation may require long drill bit from home center or fry's to bring wire to top of tank. Be sure insulation and covers are put over thermostats so thermostat not exposed to cool temperatures and cause temperature misread.

Read about two water heaters

Larger image
How thermostats work
Why does this work?
240volt water heaters have two hot wires from breaker. Each element is permanently connected to one hot wire, and will always test hot for 120Volt to ground.
Thermostat opens and closes second hot wire to element. This action turns element ON-OFF
Basic water heater circuit
Thermostat is either Hot on T2 or Hot on T4, but never both.
Some ECO thermostats are numbered 2 and 4.
So the lower thermostat on water heater #1 will either send power to lower element on heater #1, or it will send power to heater #2.
Water heater #2 will not turn ON unless water heater #1 is OFF
When water heater #1 turns OFF, then heater #2 has 240V power available.

If you cannot rewire water heater:
WHQ4 Water heater timer  WHQ water heater timer

If you cannot rewire water heater because of foam insulation or other factor such as warranty:


Re-plumb water heaters in series, and run additional 30 amp circuit to additional heater. Then put both water heater on a timer
See basic water heater circuit
How to wire WHQ timer and GM40 timer

Water heater timer for two water heaters
Both water heaters turn on-off at same time
More box-type water heater timers

Simultaneous water heater thermostats
California restaurant code requires 9000 watt (9K) simultaneous water heater certified by manufacturer.
They do not allow rewire of residential tank since manufacturer will not certify.
Restaurant must buy commercial simultaneous water heater costing $1500 to $3000
Read Restaurant water heater sizing

Simultaneous water heater wiring/ both thermostats operate independently

Used in large water heaters when elements cannot keep up with demand, or in high demand situations.

Lower thermostat replaced with ECO protected thermostat.
Each thermostat is wired separately.

Additional wire from breaker box required
Each thermostat wired to a separate circuit breaker, since each element draws 4500 to 5500 watts.
Wattage appears on end of each element
Figure wire and breaker size

Turn up thermostat temperature to get more hot water
Ways to increase amount of hot water
Simultaneous water heater wiring

Simultaneous water heater wiring/ both thermostats operate independently

Upper and lower thermostats and elements work independently from each other.
Increased first hour delivery of hot water
Faster recovery time

4500Watt elements, then total wattage is 9000 watts.
Use 50 amp breaker and #6 gauge wire
or two 30 amp breakers and two 10 gauge wires

5500Watt elements, then total wattage is 11,000 watts
Use 60 amp breaker and 6 gauge wire
or two 30 amp breakers and two 10 gauge wires

Oversizing breaker and wire runs cooler and is more efficient

Off-peak
Connect lower thermostat to timer and convert water heater into off-peak operation.
Water heater companies are integrating their products with future smart-grid. Except they are installing electronic thermostats. Consider whole house surge protection
Whirlpool's (American/ AO Smith water heater) new 'energy smart'

The era of generic off-the-shelf parts is coming to an end quickly as companies try to boost sales by using proprietary parts that must be ordered from them.
SO buy extra parts and water heaters now.
Change water heater temperature using timer
Larger image

Change water heater temperature using GM40 timer and simultaneous wiring

Not necessary to increase wire or breaker size for this diagram
Use timer for two different temperatures on electric water heater.
Applies to GM40 timer and Tork DTU timer and GE 15207 timer etc


Either upper thermostat and element have power or lower themostat and element have power. But not both at same time.

Install ECO-protected thermostat for lower thermostat.
Both upper and lower parts of tank are ECO-protected from overheating
Rewire tank so upper and lower parts are separate.
Use GM40 timer to switch power between lower and upper parts of tank.

Normal operation, the lower thermost and element receive power and keep tank at temperature set point. Upper thermostat and element have no power.
This is called 'redundant' water heater operation. This technique for heating tank more rapidly after cold water first enters tank.

When timer activates, power to lower part of tank turns OFF. Power to upper part of tank begins. Upper thermostat is set for higher temperature.
Since tank is at regular temperature, the higher setting means upper element will turn ON and begin heating tank to higher set point.


Use this technique to heat water very hot for laundry cycle.
Disadvantage: The lower part of tank will cool rapidly as new cold water enters tank, so this technique is good for making short-term batches of hot water.
Whirlpool energy smart wiring
Larger image

Whirlpool energy smart with electronic thermostat


Resources
Whitlpool energy smart features and information

3-phase

480 Volt timer
Larger image

Timer for 3-phase water heater

208, 240, 277, 480 etc
See 3-phase timer wiring

Or convert 3-phase non-balanced to single phase show below
3 phase non-simultaneous water heater
Larger image

3-phase non-simultaneous

Unbalanced

Both elements are never ON at same time.
Always use ECO-protected thermostat on upper and lower
Elements will heat with any applied voltage
Each element has volts and watts listed on side.
Volts squared divided by watts = correct ohm rating to test if element is good.
3-phase water heater service manual

Buy commercial grade 3-phase thermostat for 3-phase non-balanced water heater
Camco 120F to 180F thermostat with reset button at Amazon (commercial grade only)
Thermostats for residential water heater 90F to 150F at Amazon

Identify unbalanced water heater: it looks just like ordinary tank-type heater and does not have metal large box with contactors attached to front of unit.
3-phase balanced water heater has large box attached to front of unit.
 
Unbalanced means that 1 leg of the three phase carries greater load than other two legs. So this is just ordinary single-phase water heater except few wires moved so there is a 3-wire connection on top of unit. Difference is that 3-phase non balanced will usually have larger wires and breaker and elements.

Unbalance water heater uses ordianry 2-pole element and thermostat, except thermostat can be rated for 40 amps at 240Volts, and 30 amps at 480 volts
Ordinary hardware store thermostats are rated 30 amp at 240V.
3-phase thermostat at Amazon
40 amp 240V thermostat at Amazon
pdf file see page 7

Balanced load, means all three legs carry equal load.
Balanced water heater uses element with connections for 6 wires.
Illustrations for balanced: see lower on page
Wire water heater for 3-phase
Larger image
Another image slightly different wiring: larger

3-phase simultaneous

Unbalanced.

For example:
L2 50 amps, L1 and L3 29 amps, depending on each element etc

Compare with non-simultaneous shown above: Move Red wire from T4 on upper thermostat to L1 on upper thermostat
Either element can turn ON, as temperature varies top and bottom of tank
Always use ECO-protected thermostat on upper and lower
Elements will heat with any applied voltage
Each element has volts and watts listed on side.
Volts squared divided by watts = correct ohm rating to test if element is good.

3-phase simultaneous current load

Heavy-duty commercial water heaters:
Balanced 3-phase
Commercial electric water heater troubleshoot
Commercial electric water heater part diagnosis
3-phase electric water heater manual
single-phase non-simultaneous
Larger image

Convert 3-phase non-balanced water heater into single-phase water heater

3-phase converted to single phase non-simultaneous

Unbalanced


Compare with non-simultaneous shown above: Move Yellow wire from L3 on upper thermostat to L2 on wiring connections
Connect single-phase power to L1 L2
3-phase wire size chart


Ordinary electric water heater can run on any voltage (excluding volt/amp ratings below amount needed to heat tank of water, for example typical 12 volt battery will not heat tank of water).
Resistance elements are like light bulbs. Any voltage will work. Less voltage means dimmer bulb. Read more in section below.

Voltages include single-phase, split phase, and 3-phase residential/commercial voltages with either 50 or 60 Hz.

You can also rewire tank as if it is ordinary non-simultaneous
See image
convert-3-phase-to-single-phase
Image shows general idea: BUT 3-phase balanced Tank can be wired for single phase without removing contactors/ open .pdf to right.
Convert 3-phase balanced to single-phase
3-phase balanced water heaters have contactors that turn elements on-off.
Generally 3-phase balanced water heaters have box attached to front of heater to hold contactors
While 3-phase non-balanced and single-phase water heaters do not have box attached to front of water heater.

AO Smith 3-phase to single-phase conversion instructions/ .pdf
Convert-3-phase-water-heater-to-single-phase / pdf

How to install light duty commercial electric water heater
How-to-install-commercial-electric-water-heater /pdf
Repair and Service 3-phase balanced electric water heater  (24Mb download/ huge file)
At AO Smith - click literature tab
3-phase water heater manual

Image of amp rating chart/ jpg

Assumes 4500 watt element rated for 240V
Element wattage and voltage printed on end of each element
How to identify and replace element

Wattage drops when voltage is reduced
See water heater label showing difference between 208V - 240V
Resistive loads such as light bulbs and elements will burn less hot when voltage is reduced. Examples: ordinary household dimmer for incandescent bulbs, or power brown-out when household voltage is reduced
Formula for 240-to-120V:
.25 x 4500 watts = 1125 watts

3 phase water heater elements
Larger image

Balanced and unbalanced element wiring

3 phase water heater elements
Balanced means equal draw across all three Hot legs in 3-phase circuit
Unbalanced draws power from 2 legs for one element, and 2 legs for other element, so one leg is constantly ON when thermostat calls for demand. Other two legs alternate depending if power is on upper/lower element.

Balance heat element has 6 wires, and 3 heating loops
Elements will heat with any typical voltage

3-phase heating element
Loss of phase or failure of one element in 3-phase Delta circuit will reduce wattage output by 33%. Result 3/0 open delta
Loss of phase or failure of one element in 3-phase Wye circuit will reduce wattage output by 50%. Result 3/0 open wye.
3-phase thermostat wiring

Example 3-phase thermostat wiring

Thermostats open-close 3-pole contactor
Contactor opens-closes power to element(s)
water heater electric meter

Electric meter on water heater

How to install electric meter on electric water heater
Gas and electric water heaters Support the economy:
Buy water heaters  from my associate links:

50 gallon Gas water heaters at Amazon
40 gallon gas water heaters at Amazon
50 gallon Electric water heaters at Amazon
40 gallon electric water heaters at Amazon
Hybrid / heat pump/ water heaters at Amazon

Resources:
How to install gas water heater
Troubleshoot gas water heater
Troubleshoot electric water heater
box timers Compare box timers
programmable timer Compare programmable timers
Countdown timers Compare countdown timers
Compare power packs

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