Inverter Grounding

[jeffy104]

SO for grounding I’ll have a relay controlled conductor joining one of the inverter outputs to the neutral in the panel. That should do it.

[Mike90250]

The sure sine is a beast of an inverter. It needs that 100A input fuse to be able to deliver a surge without blowing the fuse.
And yes, the 3A 240V fuseholder is a odd duck tor try to find, they are about $1 in bulk, why they could not include one in the box, and instead risk folks not using one, or using a 32V one from the auto parts store is beyond me.

[jeffy104]

The inverter came today. Testing resistance between the 12v input negative lug and the ground lug shows open/no circuit. Reverse leads same result. I would say that this inverter weighs as much as a half dozen or so of the units from the big box outfits.

[bcroe]

But the 3A fuse is in the 120V AC output. Can't use a cheap automotive 32V rated fuseholder

Right, choose the part rated for the ap. Del City is great for battery stuff, but they do have
some high voltage fuse stuff. Bruce Roe

[Mike90250]

But the 3A fuse is in the 120V AC output. Can't use a cheap automotive 32V rated fuseholder

[bcroe]

So now I’m searching for the fuse holder for the output ac line on the inverter. Can anyone point me in the right direction to a fuse holder that I can connect 12 AWG wire to? It’s only a 3 amp fuse but the instructions say to use #12 wire so I was hoping to find one that would work.

For lower voltage wiring stuff, I rely on DEL CITY in Milwaukee. Bruce Roe

[jeffy104]

Thanks. I was able to order one. VERY hard to find item. Hard to believe it’s not included with the inverter.

[Mike90250]

From DigiKey.com
https://www.digikey.com/product-deta...302-ND/8119218 600v rating 25A 12awg $2

[jeffy104]

So now I’m searching for the fuse holder for the output ac line on the inverter. Can anyone point me in the right direction to a fuse holder that I can connect 12 AWG wire to? It’s only a 3 amp fuse but the instructions say to use #12 wire so I was hoping to find one that would work.

[jeffy104]

Yes, the inverter will run the pump but only if I’m not home and only if the power is out. If I leave, the inverter will be powered up but not powering anything but itself. The output of the inverter is wired to the relay on a normally closed contact so when the grid is on, this contact is open and the output of the inverter goes nowhere. When the relay loses the 24vac from the grid powering the coil, the inverter is connected to the the same ac duplex receptacle that the grid is connected to, but the grid has now been disconnected from the outlet so there can be no backfeed to the panel. After triple checking and checking the drawing again, I assembled the circuits in the shop and it proved out with the DMM. This receptacle will not be used unless I’m not home, and it will be on it’s own breaker which will be turned off 99.99999% of the time. It’s not needed when I’m home. I hadn’t planned on a switch between the battery and the inverter. The inverter gets 12v to it’s own switch 100% of the time but it’s turned off 99.99999% of the time. There is a certain order to the things which are done to bring the inverter into play with the special relay-controlled receptacle and I’ll have to leave written instructions for myself so I don’t screw it up and fry something. There will be a switch between the transformer and the coil on the relay because the relay doesn’t need to be running 99.99999% of the time- just when I leave. I do need to find out why the inverter people want a 100 amp fuse on a 300w unit. Not thinking I followed their instructions and bought 100 amp fuses for the holder. THAT does not make any sense to me now that I’ve had time to think about it. Still waiting for the inverter to arrive for Sunking’s resistance test. I am thinking I may just bite the bullet and run a new ground rod for the inverter but I just get the feeling that somehow it should be on the same ground rod as the panel. I’m still wondering about that. Thanks again for following along.

[Mike90250]

Sunkings method, running the pump 100% of the time off the inverter, needs no relay. But the inverter is now 100% in charge. If it fails, so does the pump.

But you really need to wire the relay properly if you use it to alternate between Grid and Inverter. And does that same relay also engage the 12V for the inverter ? And be sure to try it first.

If the grid fails, and the relay switches over, the inverter now has a load and is being powered up from a cold start. Some inverters do that fine, some won't

[jeffy104]

Yes. That’s exactly what I’m making here. Exactly. Batteries maintained by a charger which I will run only when needed- which will be hardly ever. An inverter ($277) to make the ac. And then the heart of the system- the relay. Without the relay all this work and expense is worthless. It has to do the work of switching ac sources all by itself. The inverter has dip switches on it and by setting them a certain way, the inverter can be programmed to have a standby mode. When the inverter senses a load of 8 watts or greater, it supplies ac output. Unfortunately, I’m pretty sure this won’t work for the computer that runs my pump but the flip side is that this pump will be on the grid 99,999999999% of the time. It just won’t be used much at all. I can also set voltage thresholds with the dip switches. I tested the relay today (no inverter yet) and it works perfect. It puts the voltage where I want it when I want it there and there’s no back feed from the grid to the inverter or from the inverter to the grid. I just used the grid in place of the inverter because the inverter is still in transit from amazon. I know I’m using the relay as a transfer switch and it works exactly the way it needs to but I’m waiting to hear that under no circumstances should this be done. In the mean time when I have contacts that are either N/O or N/C (normally open- normally closed) voltage can only flow where there is a circuit and is blocked where there is none. I’ll test it to see how long the system supplies useable power to the pump and adjust battery capacity. I also have to find out what the minimum voltage is for the computer/pump. There is also power consumed when the inverter is on but in a no-load state and the amount of power consumed is made up for by the
charger. Dip switches control when the inverter shuts down due to low battery. I’m still waiting on the inverter so I can test resistance. I have a friend who has the exact same system and he doesn’t even have stand-by power. His system blew last year when the power failed and the sun was out. When the power fails here, and the sun is out, I start my generator. I told him I could install the same thing at his house once I figure this out but have since changed my mind and can only offer to show his HVAC man what I have done here and under no circumstances will put this in his house. In the mean time I can only suggest he get a generator. Some day I’ll have a auto stand-by generator and all this will be moot. LOL Thanks again for your reply.

[Sunking]

It has a plug in cord which powers a small computer and some sensors and the computer runs the pump.

Oh gosh this is easy then. You may not like the idea at first, but is how it is done. Basically you are going to make a Dual Conversion UPS, or I like to call them Poor Mans UPS. Sounds complicated but Stupid Simple.

AC Powered Battery Charger > Battery > Inverter.

That is all there is to it. Only real trick is sizing the Battery Charger and Battery. The Charger is sized to charge the battery in 12 to 16 hours, plus the load. Where you start is by first determining the Run Time. By that I mean how many hours you want it to run before the battery is exhausted. To do that you need to know how many watts the load is times the hours you want it to run. So say you device uses 100 watts and you want to run 10 hours. 100 watts x 10 hours = 1000 watt hours. This leads us to determining both the Battery Capacity and Charger Size

Since this is a UPS we can get away discharging down to 80% DOD. It will be a rare event it is ever running on batteries. 99% of the time on commercial power. So to account for 80% DOD and 90% efficiency the battery capacity Watt Hours x 1.4 / Battery Voltage. So 1000 Watt Hours x 1.4 / 12 volts = 117 Amp Hours. So would be looking for a 12 volt 120 to 150 AH battery in this example.

Charger size in this example is stupid simple to calculate C/10 where C = Battery Amp Hour Capacity. So say you buy a 120 AH battery means you need a 12 Amp Charger. There is some wiggle room so you are looking for a 10 to 15 amps Float Charger.

It is a much better option, more reliable, cost less, and battery will last much longer than doing this with Solar. To do this with Solar would require a battery 4 to 5 times larger, requiring a large solar panel array and a large expensive charge controller.

He is an idea on cost. To build yourself a UPS with a Charger and Battery. less than $300.

Want Solar? To start you are looking at a 800 to 1000 Watt Panel System so there goes $2000 down the drain, another $600 for the Charge Controller, plus a monster sized $500 battery Easily $2500 to $3000 or roughly 10 times more upfront initial cost, and since you will cycle your batteries daily means a lot more frequent battery replacement of a battery 4 to 5 times larger.

So you might want to rethink this and build you a UPS. Will get you where you want for a whole lot less money and simple to use. Just unplug your gizmo, plug the charger in it place, plug your Gizmo in the Inverter and call it done. .

[jeffy104]

I looked into that. I mistakenly call the relay solid state. I should have said “enclosed”. I looked at the relay board and assumed solid state but the click sound it makes should have told me it was mechanical. Some relays I have here are exposed and clunky looking but they only turn things on and off and aren’t involved in switching ac sources. The funny thing is that there are other people that have the same problem I have but it’s hard to track down any info. I asked the installer about power failures when he was here and he said the biggest problem anyone had was the “main” computer (on the boiler) switching from English to German. He also said that as far as the solar part of the system goes, some people use a battery and an inverter. I’m sure I was correct in thinking he was talking about a backup which required you to be home to use it. And that’s where this can of worms comes from. I appreciate all the input I’m getting here- all you guys are a great resource for “secret” information. Thanks.

[Mike90250]

Beware the sold state relay (SSR) They are extremely sensitive to Kickback voltages, even with DC lines. And you must slam them on HARD and slam them OFF. never a "gentle transition", that's when they start overheating and fry in a second.
So read up on "Snubbing Circuits" for SSR's