HELP!! Dual Element Thermostat Settings

[Rags13]

For residential purposes, I have a Rheem Marathon Light Duty (MELD105-FTB) 105 gallon electric water heater that is wired with #6 gauge AWG on a 60 amp circuit. It is configured to operate both upper & lower heating elements simultaneously.
I am confused by how to set the upper and lower thermostats. There are no numbers - just a dial with "low" "med." and "high". The manual states that the upper thermostat set at "Med" will be 110 degrees and the bottom thermostat set at "Low" will be 110 degrees (see photo). The plumber who installed the water heater set both thermostats just a bit above "med". According to the manual, that would mean the upper is set to about 120 degrees (approx) and the lower is set to 150 degrees (approx).
My question and confusion is, when dual elements are configured to operate simultaneously, should both thermostats be set to the same setting (in this case, both "med") which results in different temperatures according to the manual. Or, should they be set according to temperature meaning the upper just above "med" for 120 degrees, and the lower set at just above "low" for 120 degrees?
Further confusing this, the manual states that to lower temperature, BOTH thermostats should be turned down, and to increase temperature, it is recommended to increase the lower thermostat only.
Trying to wrap my head around how any of this applies to simultaneous configured elements. Any help is much appreciated!!!

 

[Rags13]

Bump

 

[Sponsor]

 

[Fitter30]

Page 16 and 17
16 shipped set at 120°
17 want to raise the temp just adjust the bottom
Lower the temp lower both stats

manualsfile.com/product/k3zb53gnpol.html#p12

 

[Rags13]

Page 16 and 17
16 shipped set at 120°
17 want to raise the temp just adjust the bottom
Lower the temp lower both stats

manualsfile.com/product/k3zb53gnpol.html#p12

Thanks for the reply. My problem is, the plumber who installed it changed both settings from the 120 degree factory setting. I have no starting point now to follow those directions.

 

[Bgard]

most water heaters are wired so that if the top element is on, the bottom element cannot come on, the reason for this is that the water temperature stratifies to the top of the heater, the water in the upper portion of the tank is warmer than the lower portion, it is presumed that when the top element turns off the hot water demand has stopped, since the lower portion of the tank where the cold water enters may still be cooler than the top,the lower element can now come on to heat the tank back to set point. When a new demand for hot water starts, the lower portion of the tank becomes cooler first, the top element is still off so the bottom element is able to come on, up to the point when the upper portion of the tank starts to cool down, then the top element comes on to try to maintain the setpoint outlet temperature. During small hot water demand cycles the top element may not need to come on. Both elements can be wired to come on together, but unless there is a long high demand the outlet temperature will Most likely be significantly higher than the setpoint. The two thermostats also have different on/off differentials.

 

[Rags13]

most water heaters are wired so that if the top element is on, the bottom element cannot come on, the reason for this is that the water temperature stratifies to the top of the heater, the water in the upper portion of the tank is warmer than the lower portion, it is presumed that when the top element turns off the hot water demand has stopped, since the lower portion of the tank where the cold water enters may still be cooler than the top,the lower element can now come on to heat the tank back to set point. When a new demand for hot water starts, the lower portion of the tank becomes cooler first, the top element is still off so the bottom element is able to come on, up to the point when the upper portion of the tank starts to cool down, then the top element comes on to try to maintain the setpoint outlet temperature. During small hot water demand cycles the top element may not need to come on. Both elements can be wired to come on together, but unless there is a long high demand the outlet temperature will Most likely be significantly higher than the setpoint. The two thermostats also have different on/off differentials.

Thank you for the info

 

[Fitter30]

most water heaters are wired so that if the top element is on, the bottom element cannot come on, the reason for this is that the water temperature stratifies to the top of the heater, the water in the upper portion of the tank is warmer than the lower portion, it is presumed that when the top element turns off the hot water demand has stopped, since the lower portion of the tank where the cold water enters may still be cooler than the top,the lower element can now come on to heat the tank back to set point. When a new demand for hot water starts, the lower portion of the tank becomes cooler first, the top element is still off so the bottom element is able to come on, up to the point when the both elementsupper portion of the tank starts to cool down, then the top element comes on to try to maintain the setpoint outlet temperature. During small hot water demand cycles the top element may not need to come on. Both elements can be wired to come on together, but unless there is a long high demand the outlet temperature will Most likely be significantly higher than the setpoint. The two thermostats also have different on/off differentials.

This water heater is for light commercial. 105 gallon with 12.1 kw total between two elements 50.4 amps. Page 12 under 240vac 1 phase out of the factory their wired sim.

User Manual Rheem MELD105-FTB 240 VOLT 12 KW - 28 pages | manualsFile

Rheem MELD105-FTB 240 VOLT 12 KW Manual Online. Download or read online manual, installation instructions, specifications, pictures and questions and answers

manualsfile.com

 

[John Gayewski]

What's the question again?

 

[Rags13]

What's the question again?

My question is, when dual elements are configured to operate simultaneously, should both thermostats be set to the same setting (in this case, both "med") which results in different temperatures according to the manual. Or, should they be set according to temperature meaning the upper just above "med" for 120 degrees, and the lower set at just above "low" for 120 degrees?

 

[Fitter30]

Did you read post 3.

 

[John Gayewski]

Did you read post 12?

There is no post 12