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RELAY TO SHUT DOWN SECONDARY INVERTER USED TO POWER MY A/C IN A BATTERY LOW VOLTAGE CONDITION

Sycamore

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Jan 25, 2020
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60
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40th and Plum (Plum Fu** in the middle of nowhere)
My application is solar. I needed a relay to sense my battery voltage and if it drops to a certain voltage have a relay shut down or disconnect my inverter. The inverter is separate from my main house inverter. It's function is to power a Mr Cool Universal central air conditioner or a electric water heater. When the suns out my inverter solar charger charges at a higher voltage than the batteries are when the sun goes down. So I want the AC or Water Heater to be run by the Inverter at 53.5 volts or above. When solar is removed the batteries drop to 53 volts which is the settled voltage on my 48 volt LiPo4 system. So the relay is the 48V/220V model which I will set to 53.5 volt under voltage thresh hold to trigger the bottom relay section to open turning off my inverter. My concern was if it engaged and closed the relay again would there be a loop as the A/C Inverter when turned on would pull the voltage down again. WELL there is a "hysteresis" setting! Had to look that one up, lol. That is basically the spread when it engages or disengage again. It has a range of 0.1-30V on the 48V model with a default of 2.0V. I can set it at say 0.3 to have the relay reset at 53.8V or wherever I like it. On top of that there's a manual, auto and auto timed reset. So it can auto reset on those parameters or I can have it auto reset with a timer buffer of 0-.999 seconds (17 minutes). The manual says the power on delay and the reset delay is the same thing. You can also set a delay time (same range) for the activation of over or under voltage. The other question I asked and the seller answered is are the relays independent of the input, and they are. Also the relays, 2 of them are independent of each other...nice!
I was going to power a 80A 240V AC DPDT relay to disconnect the L1/L2 240V power out of the inverter to the A/C but after talking to Ean of Watts247 I am going to simply wire the relay in parallel with the inverters on/off switch. In parallel I can turn off the inverter switch and let the relay do the work or if I want to bypass the relay simply turn the inverter switch on. Turns out even if the inverters off the solar charger inputs from the panels to charge the batteries remain active.

RELAY: https://www.amazon.com/SVR1000-Prot...763H/ref=cm_cr_arp_d_product_top?ie=UTF8&th=1

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Restart delays are very important with refrigeration equipment to prevent hot starts. I assume many advanced AC controls have this built in. I do have concerns when the differential voltage is quite low. Any startup usually drags down the voltage for a time. This timer also has an undervoltage delay which should be set for a fairly long time to prevent false trips. I assume you have also done that. That module seems quite suitable to the application.
 
Restart delays are very important with refrigeration equipment to prevent hot starts. I assume many advanced AC controls have this built in. I do have concerns when the differential voltage is quite low. Any startup usually drags down the voltage for a time. This timer also has an under voltage delay which should be set for a fairly long time to prevent false trips. I assume you have also done that. That module seems quite suitable to the application.
Your correct on the delay. I was thrilled to see the delays up to almost 17 minutes and especially the hysteresis settings as I was concerned with cycling. This relay is available in 240 input also and could be used to prevent under/over voltage coming out of the inverter. I believe this inverter the "Growatt 5000ES" can keep the voltage in range. My concern was if I ran it battery-less the effect cloud cover etc. would have on output. I imagine it could be done with proper settings to prevent damage to the A/C. When it's not running the A/C it will be routed to the electric water heater. Here's an interesting page on wiring a switch to your water heater for 120/240 operation. "https://www.electricaltechnology.org/2020/02/toggle-water-heater-120v-240v.html". My goal here is to fully utilize the solar. My batteries (60kWh") are fully charged by 10 am after only 2 hours of sun. Currently my 24 hour load is only 25 kWh. That's with 4500 kWh of panels on the E side and the same on the W side of my shop roof. The inverter has 2 4Kwh solar inputs. Just reroofed the house and have 40 250 watt panels that will go up there primarily for the A/C and water heater. Haven't had to fire up the generator since the original 9 kWh went up.
 
Your correct on the delay. I was thrilled to see the delays up to almost 17 minutes and especially the hysteresis settings as I was concerned with cycling. This relay is available in 240 input also and could be used to prevent under/over voltage coming out of the inverter. I believe this inverter the "Growatt 5000ES" can keep the voltage in range. My concern was if I ran it battery-less the effect cloud cover etc. would have on output. I imagine it could be done with proper settings to prevent damage to the A/C. When it's not running the A/C it will be routed to the electric water heater. Here's an interesting page on wiring a switch to your water heater for 120/240 operation. "https://www.electricaltechnology.org/2020/02/toggle-water-heater-120v-240v.html". My goal here is to fully utilize the solar. My batteries (60kWh") are fully charged by 10 am after only 2 hours of sun. Currently my 24 hour load is only 25 kWh. That's with 4500 kWh of panels on the E side and the same on the W side of my shop roof. The inverter has 2 4Kwh solar inputs. Just reroofed the house and have 40 250 watt panels that will go up there primarily for the A/C and water heater. Haven't had to fire up the generator since the original 9 kWh went up.
I am trying to learn how to use this to control my pool vacuum cleaner. Basically I have a small shed with 1.1kw of solar panels and 2.4kwh of battery. I want to shut off the pool vacuum cleaner if the lifepo4 battery is low and before the bms shuts it off.

Can I wire this to a switch that then goes on to feed the gfci outlet? I could also try to use this to control my inverter as the Cotek sk-1500 does have a remote option.

I have never done something like this, but I am excited to learn. I did find this video which showed me what a relay is.

I am assuming I wire my 24v DC battery + and - to the a1 and a2 of the relay

On the load side, however I am somewhat confused. When I wire a light switch, I connect the black line wire of my 12/2 romex ac to the two poles of the switch. In this relay, however, do I wire the white neutral wire to the common side of the relay? Based on the wiring diagram, I can choose either side if I want it on or off at rest.
 
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