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Have a Smiths VK4252 rod thermostat for a hot water cylinder. The thermostat is marked "D" and "S". Which of these is the supply/active and the other the supply/feed to the element?

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  • Water Heaters Master
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S is source from the mains, D is distribution to the coils

Posted on May 05, 2013


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SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

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Posted on Jan 02, 2017

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SOURCE: no hot water

If the water does not heat, then you have to troubleshoot to find the problem. With a voltmeter determine if 240VAC is actually getting to the water heater. Take care here - a defective circuit breaker can give a false 240 volt reading - check for the 240 volts across the upper element (i.e. when the 240 volts has a live load on it, not just an open circuit test).
Also, remember, the upper element has priority over the lower element, and if the water is cold, the upper element will try to turn on and this locks out the lower element (only one element is allowed to heat at any given time). The lower element comes on ONLY after the upper thermostat is satisfied. Therefore if the upper heating element is burned out you will never get any hot water. If you suspect this, TURN OFF THE POWER TO THE HEATER and take a resistance check of the upper element.

Posted on Nov 17, 2008

  • 5568 Answers

SOURCE: limited hot water

Some checks are surely possible but PLEASE make sure that the 220VAC is absolutely shut down.
In a home we built in 1977, circuit breakers were improperly marked and I, with decades of experience, believed I had turned off the power to our water heater only to find that it was still 'hot' and blew away a screwdriver tip before thinking to check across terminals to see if the voltage was in fact OFF.
You may have the same problem I had twice over ~30 years; that the lower heating element is open/failed. These typically will gather a coating of mineral deposits and eventually be unable to transfer their heat to water fast enough to avoid overheating and failing.
The limited hot water comes from the fact that the thermostat is checking for temperature at the exit point of the heater; the top. The thermostat turns on both elements but with only the top one still working it heats 10-15% of the tank capacity and then shuts off.
With your meter set to the lowest Ohms scale (typically 200 Ohms), measure across the element terminals. You should measure pretty much a short since the elements have an extremely low resistance; on the order of 10-20 ohms, if you measure anything that goes 'off-scale' on the 200 ohm range (normally blinking), the element is shot.
Don't forget to drain the tank before pulling out the element!      
If you are in the US, near any city, check your white pages for: Johnstone Supply or check their website to see if one is near you.You will pay 1/3-1/2 hardware store prices for the replacement element - buy two, store the second one. They are 'wholesale' to the trade but have never been refused.
If you don't feel like wading through their extensive website, you can take the element with you and they can give you what you need.

Posted on Jan 25, 2009

  • 408 Answers

SOURCE: Rheem Hot Water Cylider Thermostat keeps tripping

Sounds like you have a faulty thermostat.  This is the unit that detects the water temperature, and if it is not where it is set, will kick the switch to allow electricity to flow to the elements you replaced. The thermostats are relatively cheap and if you have the knowledge to change the elements, changing these thermostats should not be a problem.

Posted on Mar 07, 2009

  • 659 Answers

SOURCE: not enough hot water

Makes you feel good to save some money right? Have a great day!

Posted on Apr 10, 2009

  • 9 Answers

SOURCE: 12-year old Rheem residential single-thermostat


Posted on Sep 08, 2009

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Symptom: water gets too hot, before and after thermostats are replaced, burn mark and insulation swelling/melting on non-common wire from upper element to upper thermostat, and the breaker trips.

Double check the thermostat connection and setting; if it persists, I would add a pipe hugging thermostat connected to a shunt trip for the heater elements.

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My hot water heater is 6 yrs old should i change the elements or replace the water heater

Replace elements and thermostats
Check the anode rod

If anode is replaced, then tank will not rust.
This maintenance will keep electric water heater is good operating order indefinitely.
You never need to replace electric water heater if water pressure is kept below 80 psi, and anode is good and keeps tank from rusting.

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Newly installed Hott Rod in 6 gal RV water heater only heats to lukewarm. Has been on for 12 hours. Outside temperature is 60 degrees

Hott rod is 120Volt AC.
Check voltage supply for undervoltage, or reversed polarity, or tripped breaker.
Check that electric thermostat is set to 120 degrees.
Rotate thermostat temperature adjustment back and forth and see if you can hear water heater working.
Thermostats can be bad, or stick.
Check the ECO red reset button is not tripped out.
If tank was not full of water before power was applied, the element will instantly burn out.
Use continuity tester across bare element screws to see if element is good. Or use multimeter and test across bare element screws shows 29 ohm for 6 gallon, 18 ohms for 10 gallon.
More resources at Hott Rod, for troubleshoot and contact.

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Whirlpool hot water heater puts out overly hot water

1) Make sure factory-supplied insulation and cover are reinstalled over thermostats, or cooler room temperature causes thermostat to under-approximate tank temperature, and this causes overly hot water.
2) Replace both thermostats.
Sticking thermostat can seem to act normally when tested, but when left alone it sticks, causing runaway overheating.

More resources:

Oct 03, 2012 | Water Heaters

1 Answer

Hi i have a atwood 22.7 litre water heater model mpd93754 . IT ignites heats water, but wont shut off when it gets too hot. could you please help solve this problem . many thanks rod baker.

Gas control valve thermostat might be bad.
The copper cylinder located on back of gas control that sticks into water is the thermostat.
If thermostat is not reading correct temperature, then gas might stay lit.
Usually the gas control will sense overheated water and trip the ECO so no gas will flow to burner.
In any case, the gas control valve is replaced.

Open following links to see typical manuals, service manual, parts link, and other resources:

Jul 28, 2011 | RTO Atwood Water Heater - 6 Gal LP

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Smelly black discharge from hot water every so often seems like a chemical reaction with well water and what heats the water in the tank. When turn off power and let the hot water sit for awhile there is...

Turn off water heater and flush it out. Hook hose up to hose bib on water heater.Close valve on hot water side.Run hose outside or into a drain.Open valve where you hooked up hose and let run 20 to 30 minutes to clear out tank.I would recommend putting a filtering system on the line going into the tank.This should clear up the problem.If not you have to have the anode rod replaced,depending on the age of the water heater.If you want to learn more about the anode rod,google anode rod ,it will bring you up to a site that will explain to you what it is. You will have to go to a plumbing supply store to find one.

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Why is my Rheem water heater making a "hissing" noise?

It is boiling the water. Turn it down. Look on the side and remove the small cover to expose the thermostat Turn it counter clock wise to reduce heated water temp.
There may be two.
After an hour or so test the hot water and see if you can keep your hand in the flow of all hot water. If it
is so hot it will burn you it is still too hot. 170 is hot enough. That is slightly painful and will cook the skin

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1 Answer

I have a six month old Reliance 40 gallon water electric heater,The thermostats keep shutting the heating rods down, leaving only cold to lukewarm water, no matter how much I adjust the thermostat readings...

1) Try changing both thermostats. Thermostats are frequently defective. Don't change 1, change both, using generic parts from hardware or home center or plumbing supply.
Be sure to put-back insulation and cover over thermostats so they are not exposed to cooler air and cause misread of tank temperature.

2) Next step would be complete 30 minute troubleshoot, that would isolate the problem and give understanding of water heater operation.

Add a comment for more free help.
Also take advantage of fixya phone service.
For a price, expert speaks with you over phone while you work on heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

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The reset button has popped for the last 3 nights and I have reset it each morning. It doesn,t do this during the day when water is being used. Also the water is scalding hot with the temperature setting...

replace immediately!!!

replace both upper and lower thermostats. not just the upper that is giving the trouble. after you replace them, make sure to set them both to the same water temp markings, they will opperate more efficiently.

Aug 15, 2010 | Reliance & 50gal Electric Water Heater

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