# Rheem Water Heater has me stumped!

Discussion in 'Water Heater Forum, Tanks' started by lizzydog, May 5, 2009.

1. ### lizzydogNew Member

Joined:
Mar 28, 2009
Heater 3yrs old
electric
30 amp double pole breaker
120 volts each leg breaker
120 volts each wire at heater
new thermostat
new elements
120 volts each side thermostat
120 volts each side of top and bottom element
reset pushed
NO Hot Water
Help

Thanks
lizzydog

2. ### jimboPlumber

Joined:
Aug 31, 2004
Location:
San Diego
Measuring each leg of a 240 volt circuit, to ground or neutral, will throw you off. You never know when you are reading across an open.

You need to see 240 across the two terminals of an element. If it is not 240, it will not heat....period. Something is open.

Joined:
Oct 7, 2005
Location:
.
Try turning the breaker all the way off and then, all the way back on. Check the top 2 scews of the top thermostat at the same time and you should have 240 volts.

5. ### ThatguyHomeowner

Joined:
Aug 27, 2008
Occupation:
A bounty hunter like in "Raising Arizona"
Location:
MD
Each 4500w element should read 240Â²/4500 = 13Ω.
Voltages measured with respect to ground?

Joined:
Oct 7, 2005
Location:
.
12.80 you rounding?

7. ### jadnashuaRetired Defense Industry Engineer xxx

Joined:
Sep 2, 2004
Occupation:
Retired Systems engineer for defense industry.
Location:
New England
Well, few meters out in the field can read that accurately, plus, the resistance will be different than that when cold verses energized...but, close enough.

Don't try measuring resistance with the power on unless you like sparks and value the meter (the fuse should blow, but you never know).

8. ### ThatguyHomeowner

Joined:
Aug 27, 2008
Occupation:
A bounty hunter like in "Raising Arizona"
Location:
MD
That I be.

There is also Significant Figures, which is a little harder to 'splain.

120 could mean between 119.5 and 120.4 [3 significant figures] or it could mean 115 to 124 [two significant figures] in which case the '0' is just a placeholder. I took it to mean two figures and so the answer should be the same number of figures. Since the 120 varies by Â±5% or Â±10% this is plenty close.

We nerds get around this by using scientific notation, so 1.20 x 10Â² is 3 figures and
1.2 x 10Â² is 2 figures and 1.20000 x 10Â² is 6 figs.

Last edited: May 5, 2009
9. ### CassPlumber

Joined:
Nov 12, 2005
Location:
Ohio
WoW...were trying to fix a water heater not fly to the moon....

10. ### ThatguyHomeowner

Joined:
Aug 27, 2008
Occupation:
A bounty hunter like in "Raising Arizona"
Location:
MD
Rum does that to me

11. ### lizzydogNew Member

Joined:
Mar 28, 2009
Rheem waterheater has me stumped

Thanks for all the information. The new 30 amp double breaker was bad.

lizzydog

12. ### hjModerator & Master PlumberStaff Member

Joined:
Aug 31, 2004
Occupation:
Plumber
Location:
Cave Creek, Arizona
heater

WHO measures resistance? If the element has 240 volts and the amperage is ZERO the element is bad. It it reads in the neighborhood of 18 amps it is good. AND both leads have to read the same amperage.

13. ### ThatguyHomeowner

Joined:
Aug 27, 2008
Occupation:
A bounty hunter like in "Raising Arizona"
Location:
MD
Nah, he's on first

I figured more people have ohmmeters than clamp-on ammeters and more people prefer to make unpowered measurements.

240v/18A = ~13Ω.

Last edited: May 9, 2009
14. ### RedwoodMaster Plumber

Joined:
Dec 15, 2007
Occupation:
Service Plumber
Location:
Connecticut
I test like HJ does...
Seems to work for some reason...

15. ### ThatguyHomeowner

Joined:
Aug 27, 2008
Occupation:
A bounty hunter like in "Raising Arizona"
Location:
MD
What's also is in your favor is that a water heater element doesn't fail in many different ways.

I doubt that the element resistance changes in value and it's unlikely that the resistance element shorts to the grounded element tube because of all that ceramic insulator packed in there, so your choices for resistance/current flow are 13 Ω/18A or infinity/zero.

It's pass/fail.

16. ### RedwoodMaster Plumber

Joined:
Dec 15, 2007
Occupation:
Service Plumber
Location:
Connecticut
Oh elements do short to ground.

17. ### ThatguyHomeowner

Joined:
Aug 27, 2008
Occupation:
A bounty hunter like in "Raising Arizona"
Location:
MD
In that case troubleshooting by CB is easy!

The ratio of failing by opening to failing by shorting is, would you say, 90/10? 60/40?
I don't fix enough of these to offer odds.

18. ### RedwoodMaster Plumber

Joined:
Dec 15, 2007
Occupation:
Service Plumber
Location:
Connecticut
Not always.
Lets say the short occurs at the center of the element.
The element will coninue to work normally without popping the breaker however, since only one side of the power is switched by the t-stat the element will continue to heat on 120 volts after the t-stat shuts off.

The hot water if not used will end up being quite hot...

This is the reason for checking both wires to the element for amperage to make sure they match.