Permanent master slave GTIL2

Doin it

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Some possible useful info: I got 2 2000w gtil2s wired to separate 240v breakers then to one 240v breaker in the main panel. I am using a limiting cable I made that has 2 ct clamps (one for each phase-wire) and 2 connectors (one for each inverter).
I am trying to have one inverter stay primary-master every time and the other slave every time. At the moment either inverter could be master or slave depending (I think) on which inverter is more responsive at the time.
The reason Im trying to accomplish this: I can then install batteries to be the power supply to only the slave inverter. Then the master inverter will supply whatever it can from straight solar and then batteries are only used when first inverter can not fully supply the loads. This would prolong the lifespan of the batteries and also allows the batteries to stay full more often. Also this would allow an offgrid inverter to be installed in line with the slave and not be in line with the master which can be beneficial for several reasons. Any help will be greatly appreciated. The pic is what Im trying to accomplish.
image_ylijlg.jpg
 
Running both GTI's in parallel at the same load level would extend the life better.

Create a common DC voltage from both solar outputs to the battery and GTI's

Running GTI1 to maximum and then switching on the second would seem to be a lot more problematic due to the way the limiter signal changes the output (i.e. you could not just simply isolate the limiter signal from unit 2) or maybe it just is as simple as removing the limiter signal. Simplest option, disconnect the DC input to GTI2 and switch on/off based on the DC current going into GTI1.

Personally I would have both solar charge the off-grid battery and then have both GTI units powered from the battery this way solar output drops caused by clouds could be leveled out with the batteries, unless you want to retain the battery output just for outages.
 
Was hoping to have one inverter directly connected to pv so it could handle most of my loads thrunoutbthe day and not have to use the second inverter (connected to batteries) very often during the day and then use second inverter at night once first inverter has no more pv. Therefor extremely prolonging the life of the batteries due to not using the batteries most of the time due to master inverter supplying for most of the loads during the day


What u said about switching the slave on and off based on dc current sounds promising...but I just found out that when one 240v inverter is the only inverter turned on-connected to the cts and it is covering all the loads that it slightly backfeeds but the system doesnt backfeed when having the second inverter connected even if that inverter isnt supplying power...so I need the second-slave inverter atleast powered up at all times
 
slightly backfeeds - the GTIL unit uses a few W on standby so this could be just an additional load cancelling out the export ?

I read (or seem to remember) that someone opened up a GTIL and adjusted the calibration for the CT, unless it was a different inverter. Maybe the first unit just needs calibrating for the CT.
 
But using the dc current of the first-master to turn on the second inverter wouldnt work during clouds...
Yeah the slight backfeed happens (Error on electric meter) when second inverter is turned completely off and first inverter is covering all loads.. So it might be the power draw of the second inverter that keeps the system from back-feeding,,,but thats only a few watts which could be enough to stop the backfeed I guess...something tells me that the second inverter somehow (when powered up and splitting the ct cable by paralleling another connector) allows more power to be supplied by the grid...Im also thinking about putting a 1% resistor in the ct cable instead of the 10% resistor that came with the cable, should maybe stop that backfeed..
U also said about opening up the inverter and calibrating it to the cts..the cts are the cts that come with the inverter...I guess the slight backfeed is just due to the cts supposedly only allow the grid to supply like 7w when the inverter is supplying all of the loads...this is to low of a number and can easily be off by a few watts therefor backfeeding slightly. When both inverters are powered up the inverters show minimum of like 50w combining what both inverters screens say...I think the grid feeding this 50w is safer to not backfeed anyways
 
1%, 5%, 10% is just the error of accuracy of the Ohm rating, not what the actual Ohms(resistance) is.
 
Right so I figure if the ohm rating for the inline resistor is closer to its actual rating then maybe it would be more accurate then it could help send a more accurate signal to the gtil
 
It was probably calibrated with the resistor that is there. So changing it, you might need to have it recalibrated. That's my guess anyways, which could be wrong. So, meh
 
A 100-Ohm resistor "could" have the following values:
1%: 99 - 101 Ohm
5%: 95 - 105 Ohm
10%: 90 - 110 Ohm

So during factory configuration, they would calibrate the unit based on what the "actual" Ohm is of that resistor. This would be done by sending a preset current/voltage through the sensors/device and checking the devices readouts. Then adjust the device to match the known values. This calibrates the unit to use "that" resistor.
Changing the resistor could actually make the unit not calibrated anymore. And obviously the higher the Ohm rating, the wider the range.
Also, the resistor in the CT cable is probably a "burden" resistor and is irrelevant during actual operation. That's the way it is with my clamp on CT sensors. The burden resistor is there to make sure there is no accidental overload of the sensor when it's not plugged into the unit with the possibility of the core being saturated and give the unfortunate person who touches the bares wires a nasty zap.
 
The inline burden resistor in the cable sold on eBay is used due to the cts being wired together in series therefor doubling the voltage so the resistor divides that voltage back down to as if only one ct was being used. I believe the inverter would not need to be calibrated just by using a resistor that is more accurate to the ohm its supposed to be. But I guess its possiblr calibration could be needed...I think the guy making the cables just used the 10% resistor cuz its close enough


Korishan a do u know anything about the Iotawatt?
 
CT's have near zero to do with voltage. Think current only and what the current does to the resulting voltage across the resistor.

Current Transformer (primarily to proportionately represent current)

An open circuit CT is a basic transformer, however with a 1 to say 20 (in the case of 50mA per A) so if you have it hooked up to 240V it would try giving out 4,600V and arc out internally, which is why CT's should always have a burden resistor attached (wherever in the circuit) otherwise they will destroy themselves.

CT's are just a massive step up transformers from a voltage perspective.

Just thought this might be useful to point out.


From what I remember there is a small pot (variable resistor) in the GTIL unit, which can be adjusted to alter the power flow for a given CT current, so changing the resistors is probable not required.

IotaWatt I believe has an internal setting / configuration to allow a scaler adjustment to be made to calibrate the CT.


The burden resistor is in the circuit (in the CT or in the equipment) just to convert the current into a measurable voltage. CT's generally do not have burden resistors for safety because becuase this would then have to be taken into account to the rest of the measuring circuit as it would divide the current making component selection more difficult for plug and play electronics.
 
The burden resistor in my case I believe is used to half whatever it needs to half (due to the cts beingwired in series) for both cts to act as one.
 
Correct

Disconnecting the DC line would be the easiest way to turn the second unit off (without hooking up internally) while leaving the 240V side connected. But would still result in a higher battery drawdown.
 
Are u talking about the gtil2


My inverters are 240v, my home power supply is split phase


As for the iotawatt...I need to be able to adjust-calibrate the voltage reference, was trying to figure out if anyone knew if there was an option on the iotawatt for this...I tried asking the iotawatt forum but they wont send me an email to log in
 
Ah, ok, was just looking at the circuit outline.

The calibration for IotaWatt is mentioned in a post somehwere on this site.
 
Can u check out what wolf and I are talking about on advice for gtil inverter post plz to see if u can assist


As for this post I think I figured out to have 2 sets of cts spread far apart (one set to each inverter) to allow first inverter to supply the power loads need and then the second inverter will not see the loads that the first inverter is supplying. Problem is figuring out how far apart the individual sets of cts need to be in order to give the first inverter time to supply the loads so the second inverter doesnttry to supply power for the same load...but still if the first inverter didnt have enough power to supply all of the loads then second inverter would supply those loads butthen when first inverter has enough power to supply the loads Id want the second inverter to allow the first to supply as much as it can and second inverter just supply the rest...so I havnt figured out nothn
 
Check my new feedpack post :p

https://secondlifestorage.com/t-Advanced-Search-multiple-words


You can't separate the CT's out by distance (unless you plan oin putting the second inverter about 8x further than the moon away)

Just wondering if this trick could work, add another burden resistor to the second unit (using separate CT setup for each GTIL). The first unit will respond quicker to changes (as it will see the full load) and should be the primary balancer, while the second unit would only think it is seeing a smaller load change and track to the target load slower.


The way the GTIL's work is they just keep on increasing output (with PID style target tracking) until the CT sees a zero flow, so if ome is trying to get to 1000W and the second thisks it is trying to get to 100W the changes on each unit would be 10x different..

Might work out enough to get 80% of the result with minimal work.
 
Wouldnt that change the total output that the second inverter needs to put out, to cover all loads
 
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