Remote CT to control GTI export limit 250 feet (~75 meters) away

I understand that’s the case in Spain (or parts of).

That’s not much of an issue. 5500 Watt immersion type water heater elements are widely available
and very affordable over here. Common ratings are 1.0, 1.5, 2.0, 3.3, 4.5 and 5.5kW. There are probably others as well. Those are the ones I’ve seen on shelves in several shops.

I ran one of Robin’s diverters into a 55 gallon drum of water dump load until I got my net meter.
It took about 9 months to get it. Robin’s diverter did the job very well. The only thing I had to do was top off the 55 gallon drum as needed.

I’ve heard about Spain, but I meant in the US. That was why I asked him which state he was in
as well as mentioning that I’m in the US too.

Hi Bill,

I should’ve provided more detail rather than say export was not allowed. It’s not allowed in my case because I do not have an agreement with the local utility. Those agreements end up costing many thousands that I’d rather spend on storage. My GTI’s are anti-islanding and I do not plan to export, so in effect I’m not tied to the local utility.

I’m in Arizona, our utilities are quite strict about feeding back to the grid and even with an agreement, if we do feed back to the grid, the utilities give us very little for our KWH’s.


I hear ya there, Brother. The town I live in (SW Oklahoma, pop ~900) gouges its resident 13 cents per kWh no matter what they pay for the energy. They give me 95% of their avoided cost (wholesale rate)
(gee, I wonder why they call it avoided? :grin:) which varies from 4.5 to 7 cents per kWh.

Any IEEE 1547/UL 1741 approved GTI will be anti-islanding.

If he can use 333mV CTs, Magnelab says of their CTs:

Q-What is the maximum length of black and white lead wires?

A-The current passing through thestandard lead wires of the Magnelab current sensors very low, therefore, there is insignificant voltage drop due to the length of lead wires. In practice, the units have been tested up to 7,500 feet and the output voltage and phase angle shift were withinthe listed specifications.

Frequently-Asked-Question-on-Magnelab-Standard-Series.pdf (54.4 KB)

Bill, that’s extremely helpful guidance/advice. I also reached out to Dent Instruments too: Extending the Leads on Your DENT Current Transformer - DENT Instruments

Wish I would’ve found that link before posting here, but on the bright side, I’ve stumbled across what seems to be a great community here!

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That advice (Magnelab & Dent) will be true for any c.t. with its output at rated current in the milliamps (up to say 100 mA) region. It won’t hold true for 1 A & 5 A c.t’s - not that users here are likely to see those - unless you use the appropriate cable and the c.t. has a v.a. rating to overcome the voltage drop.

Correct Robert, a dump load would be in addition to, not in lieu of an extended CT run, but I do like the idea of a dump load too, as the weather here is perfect (at least by my standards) during our winter (33 degrees North) where it is currently cloudless and headed to a high of 68F (20C) so my panels, even with the small array I currently have connected, produces far more power than I use during the day and I don’t yet have enough battery storage to consume all that excess power, so a winter dump load sounds like a perfect solution.

During the summer, a dump load isn’t needed because I will consume 100% of my solar production and still consume quite a bit of power from my local utility provider. The weather here is great during the winter, but summer is oppressively hot - daytime temps routinely reach 115 (46C) and sometimes several degrees hotter with nighttime temps that drop to a wonderfully unpleasant 99 or 100 degrees F. Those oppressive temps require considerable cooling during the day (my office is here in my home - even pre-COVID) and almost as much during the evenings so that we can sleep comfortably. Our average July usage is 140KWh per 24 hours, so as you might imagine, I can consume everything my small 7,200 watt array will produce.

I’d need the dump load outside the home for (at least) two reasons:

  1. I already have a fairly high efficiency hybrid heat pump water heater

  2. even with panels set to 80 degrees to provide the greatest output during the summer months, I’m still producing at least 3,000 watts more than I consume during daylight hours, so I suspect a continuous 3,000 watts into my water heater for almost six hours each day would cause the water to boil and possibly launch it into LEO.

Anyway, thanks again Robert and Bill, I appreciate the guidance.



I used a 55 gallon drum with a 5500 Watt immersion heater along with one of Robin’s diverters.
At the time, my system was about the same size yours is now. I had no problems dumping all of the excess energy to the drum of water. Had to top ‘er off more when it was sunny, but other than that,
it worked like a champ. Robin’ diverters can work with more than one dump load.

from my experience noise is not a problem as long as you avoid crossing other high electrical lines in the house. if you want if you have weatherized CT’s (or make the ct weatherized) you can put your CT’s out side the house and run a the cat5/6 from there directly . the most important thing to eliminate noise is to maintaining the twisted pair of the cat cable and I bundle up the pairs so that the line drop is reduced

Actually, crossing them is what you want to do, if there’s no other choice. (at a 90° angle) What you want to avoid is running them in parallel with the mains wiring. Of course, the best thing to do is route them away from the mains wiring, but that’s not always possible/practical.

yeah I really meant avoiding high power lines altogether or maintaining some distance from them :wink:

if you want there is s Robin’ diverters or you can use my version based on the oem’s tx shield and an uno ( preferable wemosD3) which also does multiple SSR dumps as well, but can also configure to handle multiple relay loads as well which in the summer for me it turns on my air conditioning, my electric utility car charging and now my recently added electric car ( a chevy volt - as I live pretty remote and there no infrastructure for pure electric cars out here)

You folks are great.

Stephen, I just found your post about extending CT’s, I’m going to use two cat5e UTP that are buried in PVC all the way to the container (I didn’t know UTP was an option before today). I’ve got five cables running out there to the container, and I only need one to get internet service out there, so borrowing two of the five will not cause issues. Can I simply combine all eight conductors from one “cable” to act as a single conductor, or should I use four from one cable and combine those with four from the other cable? I assume the second method will reduce noise even more, but that’s just an assumption, so guidance is appreciated.

I will have to run the cables parallel to the primary supply lines into the house because they will be in the same 3” conduit that leads to the attic from the main breaker panel outside the house (yes, for some odd reason, here in AZ and also in many parts of CA, the panels are outside the home - I don’t love it, but I’ve not owned a home in either state with the primary box inside the home). From that point onward, I can keep the two cables away from other sources of interference / induced current.

Background: I have five cat5e runs leading to the container from the edge of my home simply because the dirt in arizona is difficult to dig up (when it’s dry, the soil is almost like rock - check out caliche to see what I’m talking about) , so I rented a trencher and if I was going through all that trouble, I wanted to have extreme redundancy in the event one of the cables failed, I’d have plenty of spares to leverage. That’s why I can steal two of those UTP cables for the CT’s.


as I mentioned earlier it is the twisting of the pairs that reduce the noise. I would only try for now one cable I am sure it will suffice. if you are not familiar with cat five cable twisted pairs consist of a solid colour wire and a striped wire of the same colour . there are green/ green stripe, orange/orange stripe, blue/blue stripe and brown/ brown stripe just put together all the solid colour wires together as one lead and all the stripe wire together as the other lead for the CT… the cable itself should have enough redundancy as it has 4 separate strings of wire in the one cat cable if you want to do two cat cables you still have to put all the solids together and all the stripe wires together from both cables to reduce noise

I’ll run both to the box, but initially connect only one of the cat5 cables. I’ll let you know if everything works as expected. It’ll have to wait for the weekend.

Thanks again

I must emphasise, don’t do that. If I understand you correctly, it could make it a lot worse, not better. As Stephen says, the noise immunity comes from the twists - in effect each half-twist is a loop that picks up interference - and the next half-twist picks up the same but in the opposite sense. So the interference cancels itself.

If you do use two cables, you’re likely to make one big loop that will pick up loads. Use just one. Cat 5 cable loop resistance is ≤0.188 Ω/m, so using even only one pair, you’ll have a series resistance of 14.1 Ω. Depending on your c.t., I doubt that this will worry you. (Two pairs in parallel will reduce it to 7.05 Ω, etc.) But you, or rather your GTI, is really only interested when the current is close to zero anyway, so the volt drop arising from the cable resistance won’t matter, because it too will be close to zero anyway. So while I don’t think there’s a need to use all the pairs in one cable, it won’t cause a problem if you do.

I have it working with six CT clamps and six separate wires running 320 feet (about 97 meters)

I was not able to run the wires through my attic, not because of any interference, but because I was unable to access the far corner of the house to run those attic wires into the distribution panel.

When I gave up on that approach, I rented a trencher (Ditch Witch) from Home Depot ( like Kingfisher if you live in Europe) and trenched 310 feet (the excess cable brings that to 320 feet) and picked up direct burial CAT6 ( Cat6e Shielded Ethernet Cable 1000FT Outdoor Direct Burial Gel 23AWG Pure Copper) on Amazon. I twisted the 4 striped conductors and the 4 solid conductors together giving me two conductors per cable run and 12 conductors total (six cable runs x 2). Each CT has two conductors which were connected to the two conductors in the cat6 cable and then connected at the other end, to the small connector on the Grid Tied Inverter. Six cable, six CT’s and six inverters. I’m told I can run more than one inverter from each CT, but I’ve not tried yet.

It works perfectly, the inverters pick up the CT signal a few seconds after they come on-line each day. 3 of the inverters are on L1 and the other three backfeed L2 - each shows approximately the same current within about 8 watts - which seems pretty good for something so cheap.

I appreciate the helpful guidance from everyone.

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