Need suggestions to prevent inverter overload by limiting the load

[crn]

I have a solar powered off-grid cabin. I am using two 120 volt AC pumps (one for fresh water and one to pump the septic outflow up a hill to the drainage field). The previous owner put in a 3500 watt inverter, because each pump runs at about 1000 watts, and has a considerable start-up surge: if they come on at the same time the draw is considerable.
If I could figure out how to prevent the two pumps from running at the same time, I could use a smaller inverter. Does anyone have any suggestions on setting up a switching system that would give priority to the water pump, allowing it to interrupt the septic pump when the water pump's pressure switch activates? In other words, a setup that would allow only one pump to run at a time, with priority to the water pump?

 

[Diysolar123]

a you could use a relay (AC contactor) that cuts off power to the secondary when the primary is running.
You would control this with a current sensing switch(normally close for your case), something like this:

Amazon.com: AC Current Sensing Switch Adjustable Current 0.2~30A Flameproof ABS Self-Powered Sensing Switch Users Manual(Normally Open): Industrial & Scientific

Amazon.com: AC Current Sensing Switch Adjustable Current 0.2~30A Flameproof ABS Self-Powered Sensing Switch Users Manual(Normally Open): Industrial & Scientific

www.amazon.com

 

[pollenface]

A DPDT relay?

 

[crn]

a you could use a relay (AC contactor) that cuts off power to the secondary when the primary is running.
You would control this with a current sensing switch(normally close for your case), something like this:

Amazon.com: AC Current Sensing Switch Adjustable Current 0.2~30A Flameproof ABS Self-Powered Sensing Switch Users Manual(Normally Open): Industrial & Scientific

Amazon.com: AC Current Sensing Switch Adjustable Current 0.2~30A Flameproof ABS Self-Powered Sensing Switch Users Manual(Normally Open): Industrial & Scientific

www.amazon.com

Thank you for your expertise! I didn't expect the solution would be so straightforward, and inexpensive.

 

[crn]

A DPDT relay?

I looked up "DPDT relay" and found a very informative site (https://www.electroschematics.com/dpdt-switch-relay/), so thanks, with this reply and Diysolar123's, I feel I'm on the right track.

 

[pollenface]

Yeah I had to google it as well

 

[efficientPV]

I don't know your exact circuit. You could use two relays with the coil across each motor. Use the normally closed (when off) to interrupt the control line or power to the other motor. First relay on wins.

This is the simplest cheapest way, just two relays, and avoids necessity of buying two current sensors.

 

[GSXR1000]

are the pumps close to each other.. and what voltage controls the switch function

 

[AI6MK]

I have a solar powered off-grid cabin. I am using two 120 volt AC pumps (one for fresh water and one to pump the septic outflow up a hill to the drainage field). The previous owner put in a 3500 watt inverter, because each pump runs at about 1000 watts, and has a considerable start-up surge: if they come on at the same time the draw is considerable.
If I could figure out how to prevent the two pumps from running at the same time, I could use a smaller inverter. Does anyone have any suggestions on setting up a switching system that would give priority to the water pump, allowing it to interrupt the septic pump when the water pump's pressure switch activates? In other words, a setup that would allow only one pump to run at a time, with priority to the water pump?

Hi,

I had a similar problem with a well pump and a booster pump in our pumphouse. If the well pump was operating and the booster pump started (inrush current), there was insufficient capacity in my LV5048 to supply the power.

I used a DPDT relay with a 240V coil. I connected the 240V coil to the booster pump motor and the well pump to the NC, normally closed, contacts. So when the booster pump is on, it also activates the relay and prevents the well pump turning on.

I was concerned that I might have to add a delay to make sure the system was break-before-make, but in practice I didn't need to.
Regards,
Brian