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How to wire off-peak water heater thermostats

Homeowner should check with plumber/electrician before altering water heater wiring
Altering wiring will void product warranty. Tip: Don't call water heater manufacturer and report that your installation is out of warranty.

Off-peak option 1: Rewire thermostats for peak operation

Off-peak thermostat wiring

240 Volt potential exists between L3 yellow wire and each L1 black wire

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 only when ordered by off-peak meter or timer

Off-peak water heater

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 L3 yellow wire and each L1 black wire at top of water heater
Resource:
How to connect timer to off peak water heater
See Off-peak operation sequence
How to wire thermostats
AO Smith wiring diagrams
See all electric water heater thermostat wiring diagrams

Tork DTU timer Off peak operation
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Tork DTU timer OFF peak

Wire water heater so lower part of tank is OFF during peak price times.
Less hot water is available.
Tank is cooling during peak price, and probably will not run unless hot is drawn from tap
\
Buy:
DTU40 at Amazon

Resource:
How to connect timer to off peak water heater
How to wire Tork DTU timer
How to wire thermostats
How electric water heaters work

off-peak water heater timer
EH40 off-peak water heater timer

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


Resource:
Compare box-type water heater timers
How to connect timer to off peak water heater

How to wire off-peak water heater to EH40 programmable timer
Buy:
EH40 at Amazon

Resource:

EH40 off-peak water heater timer
Off peak water heater sequence
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Off-peak option 2: Add another water heater to store hot water

 ...so more hot water available at usage time
Add timer to either water heater -or- both water heaters
Two water heaters Install tanks in series:
Cold water enters heater #1 and then feeds into heater #2.

Wiring goes in reverse order:
Wire from circuit breaker arrives at heater #2, and then goes to heater #1 (as shown diagrams below)

IF WATER HEATER HAS FOAM INSULATION the wiring may not be possible without drilling hole to drop additional wire into lower part of tank.
This action will void water heater warranty.
Remember, for water heater to work correctly, the thermostats and element must be covered with insulation or thermostat will misread temperature.
Reduntant thermostats - two water heatersLarger image
Add timer to either water heater or both water heaters

Redundant thermostats control 2 water heaters
Set upper thermostats at lower temperature than lower thermostats

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

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:
1) Power  from circuit breaker arrives at ECO-protected upper thermostat on heater #1
2) ECO protection 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-simultaneous 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.
Resource:
Read about two water heaters
Two water heaters 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 generally 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.
Resource:
Read about two water heaters

Add timer to either water heater or both water heaters
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
Resource:
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.

Resource:
Larger image
How thermostats work
How to wire thermostats
Take apart thermostats If water heater has foam insulation, then replacing lower thermostat with ECO protected thermostat may not be easy.
Take apart most upper thermostats 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.

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
Resource:
See basic water heater circuit

Water heater timer for two water heaters
Both water heaters have same schedule & turn on-off at same time

More box-type water heater timers
Control 2 water heaters Control 2 water heaters

Each water heater can have different 7-day schedule

10 gauge wire and 30 amp breaker run cooler.
30 amp circuit breaker and 10 gauge wire for water heater runs cooler with less energy loss. Breaker box lasts longer.

Different wiring:
For two 4500 watt water heaters, you can use one 40 amp breaker and 8 gauge wire to bring power from breaker box to the first timer.

For two 5500 watt water heaters, you can use 50 amp breaker and 8 gauge wire
Resource:
Water heater timers
EH40 water heater timer
Things you can do to increase amount of hot water

9 ways to save with water heater

Off-peak option 3: Re-wire circuit from 240Volts to 120Volts

.... for homes with reduced consumption

How to wire water heater for 120 Volts Re-wire water heater circuit from 240Volt to 120Volt.
Not correct option in homes with several people

Wires inside water heater are NOT changed.
Reduce electric consumption by heating water more slowly.
Water heater will not 'recover' as quickly. Instead of heating 20 gallons hot water per hour, tank will heat about 5-10 gallons per hour.
Physics has not changed: it still takes same Kwh to heat 1 gallon of water. This option is for low-consumption homes, in areas that have peak electric pricing.

Inside breaker box:
Move black wire from 240V breaker to 120Volt circuit breaker rated for correct amps.

Move white wire from 240V breaker to Neutral busbar where ground wire connects.
Some breaker boxes have separate Neutral busbar where white wires are connected.
Resource:
Read more about this option

Back of thermostatThermostat sits flat against tank wall so temperature reading is accurate and water heater is protected from overheating

Access doors and insulation must be put back over thermostat to avoid higher water temperatures than desired set point, which leads to overheating, which will trip ECO reset.
Resource:
Read how electric water heater works

ECO energy cut off turns off power to water heater when temperature reaches 150-170
Resource:
Read troubleshooting steps
Resource:
How to install electric meter on water heater

Adding a timer that turns water heater off during peak price is easy way to solve peak-price problem
Resource:
Compare water heater timers

Aube CT241 phone controllerControl appliances/ water heater over the phone.
Aube CT241
Uses old fashioned plug-in phone cord
Buy:
At Amazon

Resource:
Manual
Contactors
Adding home energy system is more expensive option.
Automated home energy system can regulate all appliances during peak pricing. Basically same as adding programmable timer to each appliance.
Difference is more control tweaks available with home energy system. For example, instead of turning heat OFF and water heater OFF, the system can decide to run one or the other so both do not operate at same time.
Example system: Brayden Energy Sentry
    Water heater elementChange elements to lower wattage for slower heating
Good for homes with lower consumption and homes with peak electric pricing

Resource:
How to replace element
3-element tank from Giant Water Heater & Hydro-Quebec
Manual & specs
Product manual
Elk remote control contactorElk remote control contactor (relay)

Works on 120Volt.
Plug into outlet.
Relay works with automated hardware.
Rated up to 60 amps.
Buy:
Elk relay contactor at Amazon

Resource:
Elk-9200 manual
Grasslin Ecosave
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Grasslin Ecosave UK/ European

230volt mains timer from UK
24 hour repeat timer with off-peak and boot features
13 amp maximum x 230 volts, means 2900 watt element maximum

Resource:
Grasslin manuals
Sell sheet/ pdf
Ecosave manual/ pdf
Intermatic CA3750
Larger image

Control water heater or pool pump with telephone or computer

How to wire Intermatic CA3750

Control water heater with Z-wave

Intermatic CA3750 contactor module
Contactor controlled by remote Z wave
5-year warranty/ 30 amp

Buy:
Intermatic CA3750 at Amazon
Vera3 at Amazon

Resource:
How to wire and set up CA3750
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