wire water heater thermostat How to wire water heater thermostats

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2024
Upper and lower thermostats
thermostat temperature range
Buy residential upper and lower thermostats

Thermostats are interchangeable/ each works with your water heater
89T is discontinued/ replace with Apcom or Therm-o-disc

Buy 90-150° F for residential tank:
Rheem UV11698
Rheem SP11698
Camco 08163
Aprom / 110-150°
Water heater thermostats
Camco thermostats
More thermostats
Test upper thermostat
Adjust temperature using screwdriver. Typical residentail range 115-130°F
Typical bath shower is 104°/

All settings are approximate.
Higher temperatures risk scald.
Commercial water heater thermostatsCommercial only
... upper and lower thermostats

Buy  120-180 degree F
Rheem SP8293 upper / 110-170°
Camco 08314 lower / 180°
Rheem SP8295 lower / 110-170°
Camco 08304 upper/ 180°
Apcom WL6190 Upper 130-160°F
Apcom WH9C lower 135-180°F
Apcom WL6200 Upper 135-180°F

Residential tank thermostat is rated 90-160° F
Residential tank is NOT rated for pressure and temperature of 170-180° water.
Only use 180° F thermostat on commercial water heater that is rated for high temperature

Thermostats are rated for Single phase and 3-phase-non-balanced water heaters up to 480 Volt
Resource
How to change 3-phase water heater to single phase
Read more about 3-phase water heater
CAMCO-therm-o-disc-thermostats.pdf
Commercial-and-residential-electric-water-heater-thermostats.pdf
Electric-water-heater-thermostat-troubleshoot.pdf
Therm-o-disc-59T-66T-thermostat-Bulletin.pdf
All brands of thermostats are interchangeable

$48
for 2 low density 240 Volt 4500 watt elements/  + Upper and lower thermostat


Buy LOW density kit:
Apcom plumbers pack Amazon
110°-160°
Resource
How to replace elements

$35 for 2 high density 240 volt 4500 watt elements + Upper and lower thermostat

Apcom thermostats
Buy HIGH density kit:
Apcom plumbers pack Amazon
110°-160°
Resource
How to replace elements


Low density elements might last longer in hard water 
$45 for 2 high density 240 Volt 4500 watt elements/ + Upper and lower thermostat

Therm-o-disc thermostats
Buy HIGH density kit:
Therm-O-disc high density plumbers pack
Therm-O-disc high density
Therm-o-disc high density / copper element
90°-150°
Resource
How to replace elements
water heater element
Wires attach to either screw on element:
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
Water heater cover
Larger image
Thermostats must sit flat against tank, and be covered with insulation

Without insulation, thermostat is exposed to room temperature and will misread temperature and cause overheating.

Thermostat must sit flat against tank wall to read correct temperature. Wiggle thermostat. Check that bracket is not rusted and loose.

Steel cover should be reinstalled.

Plastic protector should be snapped over thermostat if available



Ordinary residential tank has
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.

Buy thermostats from my affiliate links
Water heater thermostats at Amazon

Resources:
How to replace thermostat
How residential water heater works
Troubleshoot electric water heater
See inside main breaker box

Two water heaters
Larger image
Non-simultaneous thermostats control 2 water heaters

Purpose:
 Add additional tank so more hot water is available at peak times, without adding additional 30 amp breaker.

Both heaters are never ON at same time.
Only when Heater #1 is fully heated will power be sent to Heater #2.

When Heater #2 is receiving power, then Heater #1 is not heating. But if Heater #1 needs to start heating again, then Heater #2 will turn OFF.

Heater #2 may not fully heat before Heater #1 needs to turn ON again.

Tip: Adding extra wire to heater #1 may require long drill bit to bring wire to top of tank. Be sure insulation and covers are put over thermostats so thermostats are not exposed to cool temperatures and cause temperature misread.
Buy 
72" drill bit from Amazon
Fish bits

Resource/ more wiring options:
Two water heaters/ with more wiring options

Footnote:
240 volt has circuit 2 hot wires. Water heater thermostats only turn off 1 of the 2 Hot wires going to elements.
This means each element has 1 Hot wire that turns ON-OFF, while the other Hot wire has live power at all times ... and this is why elements will test live 120 Volt to ground at all times.
Turn off breaker before working on water heater.
Resource
Basic water heater circuit

Take apart thermostatsSee larger
How to make 3 terminal 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.

Do not remove ECO red reset protection on water heater.

Safety
ECO will trip at 170°F and protects you and protects the tank in event of overheating, and is required for safe operation of heater. Ordinary residential steel water heater tanks are rated for 150°F, but engineered to withstand rupture up to 300°F, assuming tank is not rusted. TP valve releases water at 210°F which is highest temperature allowed for any type water heater, to protect from violent steam explosion that will completely destroy home.

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


You can use ordinary upper thermostat for either single-element or double-element tanks.

Thermostats that are missing the T4 screw, or 3rd screw located on right side, are made for single-element tank only.


Manual

Wiring illustrations for single element water heater:

240 volt and 120 volt
Same thermostat for any voltage up to 480V

Off -peak water heater thermostats
Off-peak thermostat wiringSee image
Off-peak
Purpose of off-peak
Save energy during peak electric prices.

How it works
> 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 vs
Ordinary water heater thermostats

1. Lower thermostat is replaced with ECO-protected thermostat identical to upper thermostat. ECO safety red reset cuts off power when water in tank reaches dangerously high 170°F

2. Upper thermostat: the Red wire is moved from L4 to T4, so lower thermostat and element can only receive power if upper part of tank is heated. Color of wires vary.

3. Black wire from L1 on lower thermostat does not connect to upper thermostat T4 screw.

4. Black wire from L1 on lower thermostat runs to top of water heater for connection to output fom off-peak meter, or off-peak timer.

5. At top of tank, Black L1 and Yellow L1 come from the same leg on 240V breaker, and the Black Hot 2 comes from other leg on 240V breaker. See image

Resources:
See Off-peak operation sequence
See more OFF-peak options

Tork DTU timer Off peak operation
Larger image
Intermatic GM40/ DPDT 40 amp/ 7-day programmable timer used for 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
GM40 timer
Resources:
How to wire GM40 series timer

EH40Off-peak water heater timer
EH40/ 30 amp/ 7-day programmable Off peak water heater timer

Lower thermostat receives power only when timer orders > Upper thermostat receives power full time
Buy:
EH40 at Amazon
30 amp timers

Resource
How to wire off-peak water heater to timer
Simultaneous water heater thermostats
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

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
9000 watt water heater
Simultaneous DC water heater Simultaneous DC water heater
Read how to convert AC water heater to DC/ high voltage
Convert AC water heater to DC/ low voltage



Meter on water heater

The Kwh meter is din rail mounted inside enclosure.
Records billable power usage in Kwh. Multiply by rate you pay per Kwh to get monthly/ yearly cost of running electric water heater.

Buy
Bomain power meter
Ketotek power meter
240 volt pass through Kwh  meter
2T2502GA beige plastic enclosure
2T2500GA grey plastic enclosure
din rails

Resource:
Enclosures
Figure volts amp watts for water heater
Simultaneous water heater wiringSimultaneous 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 Tork TU, Tork DTU, Intermatic GM40 40-amp/ 24-hour repeat cycle timer with 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 thermostat and element have power. But not both at same time.
Buy:
Tork TU 40 amp 24 hour repeat cycle timer
Tork DTU 7 day programmable timer
Intermatic GM40 timer

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 thermostat 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.

CA3750 off-peak water heater
Two 30 amp breakers required
Larger image

Z-wave contactor: 
1) Off-peak water heater  
2) simultaneous water heater 
3) change water temperatures 
4) water heater timer 
Set different scenes to utilize all 4 choices
Resource:
How to set and wire CA3750 Zwave contactor

Resource pdf files:

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 thermostat wiring
3-phase electric water heater service manual
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.





Check with plumber before altering water heater wiring.
See insurance data on water heater failure

Water heater valves
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

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-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
wire water heater thermostat How to change wiring / foam-insulated tank
Rewire foam insulated tank
Drill through top of tank near wiring cavities
Keep drill bit near outer edge of tank shell

Buy
36" drill bits
Fish bits
Resource:
How to re-wire electric water heater
WHQ water heater timer If you cannot rewire water heater because of foam insulation or other factors 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
Both water heaters turn on-off at same time

Resources
WHQ4 Water heater timerSee basic water heater circuit
How to wire WHQ timer and GM40 timer
Water heater timer for two water heaters
More box-type water heater timers
3-phase water heater thermostats
Convert 3-phase balanced to 3-phase non-balanced for residential use has moved to another page
Resource:
3-phase water heater
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/ shown on 3-phase water heater
Resource:
3-phase water heater
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 ordinary 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.
Buy
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.
Resources
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
3-phase water heater information has moved to another page
Resource:
3-phase water heater

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