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  #1  
Old 12-09-2016, 04:56 PM
steveb steveb is offline
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Default Appliance pull temporarily shutting down Inverter

Hello!

Forgive me if this the wrong sub-thread to post this question. But here it goes:

I have a 24v solar/hydro setup on my farm. For the first time, we bought a real fridge running on electric—we used camper fridges with propane before—and I got us an 80w fridge.

The inverter we have is a Voltcraft SWD-1200/24v, capable of handling a 2400w peak. The batteries we have are a small bank only 2 x 12V-290Ah AGMs.

The hydro power is provided by a 24v truck alternator, with its own regulator—it stops producing when the batteries are full. The solar is also 24v 11amp direct to the batteries with a Xantrec controller.

But what keeps happening is, about 3–4 times per day, almost every day at the same exact time even, this new fridge will turn on and its pull will trigger the protective auto-shut off on the Inverter, and the inverter stops working. This "brown out" goes for about 1–2 seconds, then the inverter snaps back on, and then the fridge gets it power (and all the rest of the devices we have plugged in).

So I'm assuming it is the compressor, on the fridge, which is actually rated at something much higher than the 80w on the fridges energy consumption sticker. But could a fridge compressor produce more than 2400w pull for a split second? Or is it something else I should look for in my system? The fridge actually comes "on" far more than 3–4 times per day, but when it does these other times, my inverter takes it like a champ.

Thanks in advance for some advice.

-Steve
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  #2  
Old 12-10-2016, 11:34 AM
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Hmmm.. During the "Day".. Maybe the solar is pushing the battery charge voltage to the upper limits of the inverter?

If all is good during the night, monitor the battery voltage provided by the hydro and monitor during the day when the solar is producing. Is the voltage going higher during the day?

Being the battery is charging constantly with the hydro, the solar controller will still go through its phases. (Ramp, Bulk, and Float) The Bulk setting allows the battery to go above the Float voltage setting for a period to assure full charge. Perhaps the Bulk voltage setting in the solar controller is a little high?

Also be aware of your loads to the inverter during the day. Perhaps the added day loads and the fridge is pushing the inverter to its limits..

Is the fridge a new load? Had the fridge been working for a period and then the issue started? In this case, I'd look at the battery..

Just some thoughts..
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Old 12-10-2016, 11:53 AM
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"This "brown out" goes for about 1–2 seconds, then the inverter snaps back on, and then the fridge gets it power (and all the rest of the devices we have plugged in)."

Another theory would be you don't have enough battery. The sudden demand is kicking the hydro on to compensate for the sudden voltage drop and supplying enough to regain operation. I assume the alternator produces more current than the solar?

At night, the hydro is boss and has the ability to cover the sudden demand. During the day, the solar is boss, I assume the day time battery voltage is a tad higher than at night, taking the hydro out of the loop. During the fridge surge, the battery voltage drops low enough to kick the hydro in to assist. The voltage increases, the inverter normalizes, the hydro then monitors the voltage and keeps things running..

If this is the case, you need more battery..
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  #4  
Old 12-11-2016, 09:40 AM
steveb steveb is offline
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Hello 12vman! Thanks for replying.

From what I can tell, this issue is present equally in the daytime or nighttime—if anything, the issue is "worse" at night, when the hydro is the only power source.

I wasn't clear about this earlier.

I was thinking I need to do a test, and that is to spend an evening WITHOUT the hydro supplying power, and see if the batteries can hold the system together when the fridge "pulls" electricity.

I had considered that it was the hydro, actually, somehow overreacting to the demand of the compressor of the fridge, and the near-instant energy change is what makes the Voltcraft inverter protect itself. The Inverter can handle up to 32v power, before it shuts down to protect itself.

With my Xantrec controller, I am using the thermostat addition that monitors the battery warmth, in order to auto-adjust the Bulk and Float. From what I can tell, everything is within good specs (as my system was running good for 2-3 years before the fridge came into it, obviously, I'm rather confident the fridge is the issue, though maybe its use coincides with aging batteries, or, just a too small of a battery bank in general (my greatest worry...)).

My batteries are going on 4 years old now, which I had hoped was only midway through their life cycle, being AGMs. It is also possible that over the years, they were mistreated, as in, over drained (though not when I was on the watch!!).

Cheers.
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  #5  
Old 12-13-2016, 07:48 PM
MichaelK Male MichaelK is offline
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I would also suggest that the batteries are too small, especially if they are already 4 years old. A second, related issue is how much amperage can move from the batteries to the inverter. What is the size of the wire connecting the batteries together to the inverter? Too thin wire might have enough resistance that it won't allow the current required to get to the inverter, causing it to shutdown.

Now about the required current, motors that operate under load typically have a starting current substantially higher than their running current. For example, the running current of my well pump is 10amps, but the starting current is 37-38 amps, almost 4X the running current.

To actually measure this you need a meter that can accurately measure "in-rush" current. A generic clamp meter is not fast enough to give a reading for the first few miliseconds of operation. Here's an inexpensive meter that I've bought called the Uni-T216 clamp meter. I've compared this meter side by side with a Fluke meter costing 5X as much, and they agree with each other to within less than 1%.
http://www.ebay.com/itm/UNI-T-UT216C...oAAOSw4shX~1s1

Be aware that a clamp meter will only work properly if you clamp it over one or the other of the AC wires. If you for example clamp it over the cord running to the electrical outlet, the two wires back and forth cancel each other out, and you get a zero amperage reading.

A line splitter like this is designed to allow you to plug any standard appliance into it and then clamp the amperage without cutting any insulation.
http://www.ebay.com/itm/New-Craftsma...0AAOSwtnpXi8c8
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  #6  
Old 12-14-2016, 09:02 AM
steveb steveb is offline
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Hello MichaelK,
Thank you for the additional response.

I'm using a cable 2 m/25 mm² cable, which is made specifically for the Voltcraft inverter (it has come precrimped on the ends). It is rated for length and thickness for the capacity of the inverter.

I also have a digital clamp meter, link you have linked. I have not used that to measure the amps, however, I do have a Watt meter between the fridge and the inverter, which I was using to see if the fridge was pulling more Watts than the inverter was rated for.

What I've measure, as a High Watt pull, is 2145 watts. Now, my inverter is supposed to be able to handle peak pull of 2400w. But I've also seen on site with my own eyes the inverter momentarily shutting down when the fridge only called for 750w (I noticed the meter calculate this).

One other question: could my batteries be too cold? Besides being too old/tired?


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Old 12-14-2016, 09:53 AM
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Quote... "One other question: could my batteries be too cold? Besides being too old/tired?"

Where do you have the batteries installed? Are they in a climate controlled room/area? Cold batteries are less efficient..

If the charge conditions hasn't always been the best for the batteries, (and considering the age) they may have lost some capacity..

IMO.. I would have at least double the battery that you currently use..
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  #8  
Old 12-14-2016, 12:15 PM
steveb steveb is offline
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My batteries are installed in a stone building, which houses the hydro system and the solar (an old mill). I use foam insulation around the batteries in the colder months, as well, the charge controller has a thermostat device on the batteries, to help with managing Bulk/Float.

Charging has never been an issue, even with the new fridge.

I would love to double the battery capacity. But it always comes down to money.
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Old 12-15-2016, 09:33 AM
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My charging condition statement was in reference to your quote in post #4..

"My batteries are going on 4 years old now, which I had hoped was only midway through their life cycle, being AGMs. It is also possible that over the years, they were mistreated, as in, over drained (though not when I was on the watch!!)."

Also, if the temperature of the battery isn't near 70 degrees F, they will be less efficient. (Perhaps as much as 20% less)
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Old 12-15-2016, 02:51 PM
blackpowderbill Male blackpowderbill is offline
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Default test it

If this wasn't suggested already:
I'm no expert on inverters
I'd get the amp meter out .
Get set up ,unplug the fridge, wait a few minutes for your system to settle down.
Then plug the frig in to see what it is drawing on start up.

Also if your system is OK even accounting for old or clod batteries.
Look at the frigs power wire. I've noticed that many appliances are coming with less than desirable power cords.
AND check the outlet as well.

If not installed you can install a soft start on the frig compressor. This will help mellow the start up draw.
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Old 12-16-2016, 09:52 AM
steveb steveb is offline
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Hello blackpowderbill,
Thanks for the reply. Can you point me to a soft start device on the internet, so I can inform myself of this option?
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Old 12-16-2016, 12:33 PM
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Thumbs up soft start

Quote:
Originally Posted by steveb View Post
Hello blackpowderbill,
Thanks for the reply. Can you point me to a soft start device on the internet, so I can inform myself of this option?
Hi Steve, I had a link posted in another thread that had wiring details.. Here is a google page link

https://www.google.com/search?q=refi...ir+conditioner
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Old 12-16-2016, 03:26 PM
steveb steveb is offline
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Something like this:

https://www.amazon.com/SCHNEIDER-ELE...2soft+start%22

Which unfortunately costs more than my refridgerator did!
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Old 12-16-2016, 10:30 PM
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Pretty sure you do not need that expensive item. You are just adding a capacitor to provide the starting amp surge. Somewhere on your fridge is a capacitor that you can hook up an addtional one too. The purpose of the "soft" start capacitor is to store extra energy that the compressor uses when it starts, therefore effectively using less amps on start. Thus, it's called a "soft start". Sometimes they are added to central AC units when they get older and are using more amps to start up then the factory installed capacitor can handle. S

The soft start kits come into play when using a generator or in a campground with low voltage due to heavy loads.

This one is $11.25
http://www.globalindustrial.com/p/hv...FRYvgQodfusDHg
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Old 12-17-2016, 07:49 AM
steveb steveb is offline
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Not to be hard-headed about this, but you are listing items referred to as "hard start," which are for compressors that are getting old and need more "juice" to get going, where I though we were discussing the value of a "soft start" device, which actually limits the initial pull from the compressor, so as not to force the inverter to shut down to protect against a surge.

Unless, what you are saying is a hard start capacitor/device is the same thing as a soft start device (which they do not seem to be, to me).

Thanks.
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Old 12-17-2016, 05:45 PM
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I am no expert by no means. Somebody that knows more will most likely chime in. I have been told they are both the same thing. Just different people use different terms. My understanding is you are drawing extra amps at start up and it trips your inverter. I had thought the extra capacitor would provide the extra amps at start up and prevent the shut down.

A hard start kit is basically a start capacitor that has a relay attached to it. Your compressor has 3 winding's on it. The start winding, the run winding, and the common winding. What your run capacitor does is create a phase shift of the incoming power across the start winding so it kind of gives you a sort of 3 phase power, but with only 2 hot legs. This allows the compressor motor to start turning. If you have ever seen a motor that has a bad run capacitor, it will just hum until it trips on the internal overloads. What the hard start kit does is kind of the same thing the run capacitor does, but it discharges a quick pulse of power, usually a second or two, and it get's your compressor up to speed much faster than just a run capacitor.
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Old 12-19-2016, 04:01 PM
blackpowderbill Male blackpowderbill is offline
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Quote:
Originally Posted by steveb View Post
Not to be hard-headed about this, but you are listing items referred to as "hard start," which are for compressors that are getting old and need more "juice" to get going, where I though we were discussing the value of a "soft start" device, which actually limits the initial pull from the compressor, so as not to force the inverter to shut down to protect against a surge.

Unless, what you are saying is a hard start capacitor/device is the same thing as a soft start device (which they do not seem to be, to me).

Thanks.
I have always called the soft start caps. The capacitor stores energy so when the refrig calls for a start it gives the compressor a jolt of stored energy to help the start process.

I've never paid over 30$ and those were for 2 to 4 ton AC/frig units. Some where on the BHM forum I posted a page that list how to install one of these. I could not located it.

Ya know another thought you may have a bad run cap on your frig!?

Do the amp draw like I suggested. Remember to leave the frig unplugged for a while to let the pressure inside to equalize so it does not cause a false hard start. I.E. starting short cycled under high head pressure.
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Old 12-19-2016, 04:12 PM
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Thumbs up YEOW

Quote:
Originally Posted by steveb View Post
Something like this:

https://www.amazon.com/SCHNEIDER-ELE...2soft+start%22

Which unfortunately costs more than my refridgerator did!
NO OMG nah
Like this http://www.globalindustrial.com/p/hv...sk3BoCIMzw_wcB

http://www.jimdow.com/jimdow/sales/d...orOverload.htm

Now you have to look at your unit and see what hp the compressor is. It may not even be listed . I usually take the voltage/watts, amp and do a rough calculation to get me close.

AND you can install these on furnace blower motors too.
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