Suburban water heater

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morganwes

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Jun 5, 2017
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My suburban water heater works on LP but not on 120 volt ac. Checking the power with a meter, I get 120 volts to ground from either terminal of the element. Putting the test lead on either terminal of element to any point on the high temp / temperature switches will show 120 volts. Turning the power switch off will turn off the power.
The schematics show power from switch to thermal cutouts and then to the element with the white wire going back to complete the circuit. In actual readings, it appears that the power from switch goes directly to the black wire on element. The thermal cutouts show they complete the circuit back to the electrical panel. There appears to be something open between the element and the thermal cutouts. The trailer is a 2014 Coachmen Catalina 293 RKS.

Anyone with an idea?
 
Sounds like it's very possible the element is toast. Someone may turned on the power before the tank was full of water. unless I'm reading your post wrong.
 
A "toast" element would be either shorted or open. If open, you won't have 120v on both terminals. Shorted, however, should trip a breaker somewhere unless maybe the element is shorted halfway down its length. Try an ohms measurement (with power off). Should be about 10 ohms. Less than that indicates a partial short, which will result in low heat.

Is there any indication of heat when power is on? Does the tank wall get warm near the element? Or at the PT relief valve? Are you sure the thermostat is switching power to the element as needed?

Service manual: http://bryantrv.com/docs2/docs/subsw.pdf
 
the circuit is open between the element and the thermal cutouts. Element reads 10 ohms. Voltage from black wire on element to ground = 120. voltage from white wire on element to ground is 120. voltage from element to thermal cutouts is 120. By reading voltage through the element, and the element is at 10 ohms resistance, the element appears to be good. The voltage between the element and the thermal cutouts indicates that there is an open circuit from the white terminal on element to the cutouts.

Am I missing a switch somewhere that completes the circuit? I do not have a manual on the unit. I can not find another switch.

Help!!
 
I'm confused, so let me re-cap: The white wire is the neutral and goes back to the load center; the high limit cut-off and the thermostat are one unit and on the black wire. You say you measured 120v on both black and white terminals to ground, but how did you do that if the circuit is open? Are you saying that you have 120v to a separate meter ground, but no 120v between the black terminal and the white terminal otherwise? That would mean the neutral is open (disconnected) somewhere. There should be no switch or relay on the neutral, but it may well go through a junction box somewhere.
 
Click on the link below, then look on page 9. It shows a wiring diagram.

http://waterheatertimer.org/pdf/Suburban_Water_Heater_Service_Manual.pdf

If you are reading 120 volts ac to ground on both the black feeding the element and the white leaving the element, I would say you have an open neutral between the element of the water heater back to the panel.
 
My drawing shows the black wire from switch to thermal cutouts then to element with the white wire returning to neutral buss. This would be correct if proper wiring methods were followed.
The circuit appears to go from the switch located next to element direct to the element black wire. The white wire should go back as neutral; however, it does not complete the circuit so must be open at some point. The contacts on the thermal cutouts do complete the circuit if putting a meter between element and cutouts.
Is there a way that I can gain access to the wiring without pulling the water heater? There is a problem with the wire that should bring power to the thermal cutouts before going to the element and then the neutral.
I am a Master electrician with more than 50 years in the trade (still learning new things until I retire) but never took on an RV wiring issue. I suspect that someone worked on this unit before and crossed the wiring in a panel someplace. Any help on gaining access to the wires is appreciated.
 
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