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Old 03-20-2023, 12:40 PM   #1
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SW12DEL water heater electrical issues.

Good afternoon folks. So I have noticed that my SW12DEL suburban water heater stopped working when connected to shore power. Propane works fine.
What is interesting is that when I set the multiplus inverter to “inverter only” the water heater starts drawing power from batteries and heats the water.

Is there something that is simple that is preventing the water heater from heating on shore power?
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Old 03-20-2023, 12:55 PM   #2
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Suburban SW12DEL........uses 12VDC to trigger the 120VAC to the element

The 12VDC to the On/Off switch goes to DC Relay located in junction box on side of WH Tank
When that relay closes 120VDC goes to the OEM Switch in outside compartment then to/thru AC set of t-stats to element

Inverter is supplying AC Voltage same as Shore Power would

Do you have a EMS --Energy Management System--- that curtains certain AC Loads if too much is being drawn on Shore power
Water heater & Microwave and/or AC Units etc?

That would be only difference between AC from Shore or Inverter
*Inverter not going thru EMS (Energy Management System)

SW12DEL DC and AC wiring Diagrams Page 11
Figures 10 and 11
I took my Medication today. HAVE YOU?
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Old 03-20-2023, 05:46 PM   #3
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Thanks for the reply.

Everything was working as should until yesterday.
What I did so far.
Bypassed hardwired EMS module (only inverter powers the water heater either way)

Power to on/off switch confirmed
Resistance of on/off switch in “on” position is 0.01
Resistance of on/off switch on “off” position is OL

Power to heating element confirmed
Resistance of heating element is 0.10

Resistance of low and high thermo switch is between 0.01-0.02 on the 120v and 12v side while water heater water temp room temp and breaker off.
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electric, electrical, heat, heater, water, water heater

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