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lief ryan avatar image

2.7kw array 3kw inverter and 3kw resistive load

this is not strictly a victron question but i hope somebody can help, if i have a 2.7kw solar array and a 3kw inverter with a 3kw resistive load (water heater) will the inverter feed all available power to the heater as the power from the solar array fluctuates?? i know this isn't conventional but i'm trying to figure out a way to use the power from the solar to heat my water when the batteries are full

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3 Answers
svtti123 avatar image
svtti123 answered ·

Yes you can do that with a inexpensive battery charge discharge control borad for your battery voltage and a 30 amp control relay in simple terms if the voltage goes above a battery charged set point the control relay pulls supplying ac to water heat when it goes bellow the low voltage set point its disconnts. If you have any voltage drop at your battery terminals when its loaded this idea fails because your panels have to be outputting near max all the time. Or your control relay will connect and disconnect,connect and disconnect as panels become shaded. Now you have to add a time delay in the circuit that has its own faults how long do you set it for?

A much simpler was is to decrease the wattage of your heating element. My water heater was 1400 watt my water tank was hot in 1 hour I decreased it by 78.57 % to 300 watt now i get a tank of hot water every 3 hrs and gives me 3 tanks of hot water every day. My batterys are charged every night.

How may gallon are you trying to heat and how fast would you like to heat water to what temperature?

I can let you know what size heating element you need?

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I have to add that i have also added the circuit i talked about so on cloudy days i only heat the water when the batteries are full since i dont load the batteries heavy i dont get a voltage drop at the battery terminals i dont get the control relay turning of and on my water heats water when my battery voltage reachs 12.4 shuts off when it reaches 12.0 volts turns back on at 12.4. Sunny days i just bypass the circuit.

Opps turns on at 12.4 off at 12. Volts sorry

jacko avatar image
jacko answered ·

are You talking about a battery inverter like one of victrons or an grid conected inverter? A battery inverter doesn’t fluctuate the output with available solar power, it remains on while the battery is within the working parameters, so say batteries were full it would turn on till the cut off voltage and shut down, as the array is smaller than the heater load this would probably happen quite a lot until the tank was hot. You could make this work by ac coupling your solar and adding in an I-boost or alike with a ct clamp on the live from that inverter that looks at the amount of power being generated and diverts that amount to the heater.

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hi, yeah maybe ac coupling a grid tie inverter with the multiplus might work (with the i-boost device) my only worry with that setup would be efficiency, but it might be worth losing some efficiency to gain better use of the excess power.... food for thought, thanks :)

Pat Davitt avatar image
Pat Davitt answered ·

You have asked a general question, so I will give you a general answer.

Yes, it is possible; but it may not be economically or technically feasible depending upon your level of expertise. There are quite a few posts on this site concerning routing power to "Diversion Loads", which is what you want to do.

Many people are looking into this functionality, hopefully in the future it will become a standard feature.

Pat


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thanks for your reply, i guess my question depends on the characteristics of the inverter, i will have to go ahead and try it, i do have some experience but i have been installing grid tied systems and this is my first off grid installation.