Inverter Remote On/Off Problem

[Steve_switch]

I have a Residential home build solar project that is off grid. I recently purchased a Samlex PST-3000-24 inverter am try to control the On/Off power switch to this unit with a remote mounted relay. In the Owners Manual page 44, a diagram shows the 4 position Terminal Block, showing 3 methods to operate this inverter remotely.

I set up my relay as shown in figure 8.2(a) first. At first it operated as expected, the inverter turning on when the relay contacts closed and off when the relay contacts opened. After operating fine switching on and off just like advertised for as long as I chose to have it on, I started to notice my inverter turn on without the relay energizing. So I double checked my relay circuit, then triple checking for good measure. I didn't find a problem in my relay circuit. My relay is located about 3 feet from the inverter.
So I thought well maybe the connection between pins 1 and 2 on the Samlex was super sensitive. I'll try method 3 shown in figure 8.2(c). Using my 24v batteries supplying the DC input into the PST-3000. I connected the Positive Terminal of the battery, through a 1 amp fuse, to my NO relay contacts, and into pin 3 as shown. I had a similar outcome as the first connection method. The connection seemed to work as my relay would control the inverter On/Off power. Then I again began to notice a seeming flicker of the Inverter power on LED, then off again, happening without the relay being energized. This almost seemed as if there is a bad connection somewhere in my circuit. I double and triple checked every connection. I didn't find a bad connection. Lastly, I connected the remote On/Off shown in the method in figure 8.2(b), I made all connections as shown, and even before I could make the connections to my relay, the inverter turned on. I stopped right there.
what the heck is happening here. I have a call into Samlex, they have not returned my call. Can anyone shed some light on this issue?

 

[Steve_switch]

Is it that maybe I posed this issue in the wrong forum. My project really is experimental so maybe I should have put this inquiry in 'General Discussion and Brainstorming' or 'General Troubleshooting Help' or maybe something else. Could anyone suggest another venue maybe.

 

[v_green57]

Sounds like it may be tripping due to a load kicking in that the inverter has to handle, which would cause a momentary drop in battery voltage. Or perhaps the opposite happening due to MPPT sweep of your CC.

Temporarily use a separate battery to power the on/off ckt. and see what happens.

 

[Crowz]

I agree on the trying a separate power source to trigger it to see what happens. A separate battery would be ideal.

 

[Steve_switch]

Thank you v_green57, and Crowz, I did exactly that and came to the conclusion that the problem is in my relay circuit itself. I designed my relay trigger circuit myself and didn't use an opto-isolator in it. I am supposing that because of the lack of isolation the output on my Arduino is drifting. I have ordered a dual 5v opto-isolated relay board, and will try it out. Here is a photo of the dual relay trigger circuit installed. I have some other sketch issues to work out before I can report on the results.

 

[Steve_switch]

Well the results are, that I still have a problem. I have a sketch running on the Arduino Mega that allows me to set both the Turn On set Point and the Turn Off Set Point. I am using a High on the Mega pin 5 to energize one of the Songle mini relays shown in my photo above. This relay contact completes the remote switch between pin 1 and pin 2 of the remote terminal connection on the front of the Samlex PST-3000-24 inverter, which seems to work well at making the inverter start.

The problem seems to be that the Samlex PST-3000-24 inverter will shut off, then it seems to flicker on and off erratically. There doesn't seem to be a constant period for the flickering. It's not a fast flicker. It acts as if there is a bad connection. I'm afraid to turn my back on it to let it run on automatic pilot. So I don't. I place the inverter power switch into the off position, so that it cannot be operated by the remote terminal, until I can get back to troubleshooting.

The wires connecting the Normally Open contacts of the relay to the Remote Terminal of the Samlex PST-3000-24 inverter is about 5 feet. I wonder if those wires might be picking up radio noise and causing the inverter to trip on and off every few seconds? So to test that out I thought, if I physically move the little relay board closer to the inverter, I could make those wires much shorter. I'll try this.

 

[Crowz]

I would try a mechanical switch at the relay box. This way you can "force" a known good power signal to come from the relay location. If it works then the relay itself may be bad and "bouncing" in place of a firm engagement. At least that way you will know its mechanical and not a signal issue from the distance its away from it.

 

[v_green57]

What Crowz said.

Relay contacts "bounce" and toss all kinda EMI back into connected circuitry. So does the relay coil - when you de-energize it, the mag field created by the coil collapses and throws a reverse spike back at things.

The coil issue is usually dealt with by connecting a diode across the coil in reverse polarity of normal operation. It shorts out the backward spike.

Contact bounce can be snubbed with capacitors. Try .01uF ceramic disc at twice the working voltage. If that doesn't help, go to 0.1uF.

The relay coil itself is basically an antenna. I suppose it could be picking up on stuff in an EM rich environment. But one would think the designers of the relay board you're using would have accounted for that.

 

[OffGridInTheCity]

I also use remote relays to turn my SGP and AIMS inverters on/off by voltage levels. I use their external on/off ports BUT I've recently had to repair both units and noticed that the main on/off switch on the metal case really is just a simple switch with 2 wires.

The Samlex is likely the same - so perhaps you can wire directly to the main on/off switch on the inverter case. Leave the switch in the off position and let you're relay close the circuit. If the main on/off switch doesn't work......

 

[Steve_switch]

I did what Crowz suggested and installed a manual switch. I have attached 3 photos. The 1st(080113.jpg) is a photo of my control board with the dual relay board setting on it. At the bottom, just to the right of center is the mechanical switch that replaced the relay on the right. In the photo (080218.jpg) is a view of the front of the Samlex PST-3000-24 inverter with the switch in the open position, and the inverter has its power switch in the EXT Switch position. The inverter is off. Photo (080243.jpg) is a view of the front of the inverter with the manual switch turned on.
I manually turned on the inverter at 8:11am this morning. At 8:35am the inverter shut off by itself and began to flicker. There was no contact with the switch at all. I suspect that there is something internal to the inverter causing this. I'm open for suggestions, but I think I'm going to have to call Samlex back. I had already called them about this, and their response was that, "remote contact between pins 1 and 2 does turn the inverter on".

 

[Crowz]

That seems to confirm its the inverter and not your switching of it.

 

[Steve_switch]

I called Samlex, got an RMA# from them in an email. I shipped the unit back to Samlex today. Maybe I'll get a new inverter out of this or they'll fix it.

 

[Crowz]

I called Samlex, got an RMA# from them in an email. I shipped the unit back to Samlex today. Maybe I'll get a new inverter out of this or they'll fix it.

This the way.

Couldn't resist the quote. Sounds like the best possible outcome all the way around. Congrats !