preheat on demand propane DHW with electric tank heater triggered from AUX

jtdiesel65 · March 2021

Hi,

I'm over panelling and am looking at putting in a water heater in front of my on demand heater. AUX would likely be off a classic. Max inlet temp is 140 for the on demand so I think I'm all set there. But, I'm wondering about the best way to go about this. I put in two 10/3 lines from my battery shed to house a couple years ago(80-100ft). I have a breaker panel in the shed and in the house. My thought was to wire it to the shed panel and have the relay switch it on in the shed. Is there a better way?

Is there a problem in the situation where aux output would toggle on and off frequently such as with cloudy days?

Also, I'm wondering if I should be thinking about putting DC elements (48v) in the heater and just running dc to the unit from the shed. If I did that, I would have to figure out something for a thermostat since the thermostat that comes with an AC heater probably would not be usable. Ideas?

thx

northernsun · March 2021

I have a similar setup with the Midnite Classic, it works quite well. Just run your Aux line (12v) through the thermostat and you'll have no problems. The thermostat will control the SSR and not the current to the heater. I've found that you need to put significant waits and delays to prevent short cycling.

JBoyKey · March 2021

I dump my panels to a 30 gallon pre-hot water heater, not battery - higher voltage to cross that long rum - 10 167w panels 5s2p about 100v @ 15amps under load to a 240v 6500w element in the bottom of heater, have one 140 degree cutoff thermostat for just in case, it's never tripped and water is at 100 degrees before entering house 40 gallon water heater. Have run it all day alot and is a perfect dump load. these 10 panels also feed secondary controller to my batteries.

preheat on demand propane DHW with electric tank heater triggered from AUX

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