CT consumption extension

What I said here:

Current Transformer or CT wires

And from page 12 is the true recommendation: Consumption meter lead wires can be extended to be installed in panels away from where the lQ Gateway is located. These wires may be extended to a maximum of 1.5 Ohms per wire and 3 Ohms for both wires end to end. Appropriately rated, 0.75 mm2 to 1.5...
forums.mikeholt.com

You don't need twisted pair. (I suppose you could make it carefully with a drill if you really had the time and space, but not necessary.)

For 200ft you might want to just use 14awg THHN, as it will give you a little more accuracy and is readily available. I've also used 18awg TFFN lot (stuff I get is crosslisted as MTW so it's fine for wet locations). I've also used that Enphase control cable, which is the same number and guage of conductors.

don_resqcapt19 said:
Just changing the voltage rating of the conductor does not permit you to run what appears to be a Class 2 circuit with line voltage conductors.
Click to expand...

I mean that's techically true, but using a Class 1 or higher rated method is fine. So upgrading from something like 300V rated CL3R to 600V THHN does, in fact, permit it.
 
jaggedben said:
What I said here:

Current Transformer or CT wires

And from page 12 is the true recommendation: Consumption meter lead wires can be extended to be installed in panels away from where the lQ Gateway is located. These wires may be extended to a maximum of 1.5 Ohms per wire and 3 Ohms for both wires end to end. Appropriately rated, 0.75 mm2 to 1.5...
forums.mikeholt.com

You don't need twisted pair. (I suppose you could make it carefully with a drill if you really had the time and space, but not necessary.)

For 200ft you might want to just use 14awg THHN, as it will give you a little more accuracy and is readily available. I've also used 18awg TFFN lot (stuff I get is crosslisted as MTW so it's fine for wet locations). I've also used that Enphase control cable, which is the same number and guage of conductors.



I mean that's techically true, but using a Class 1 or higher rated method is fine. So upgrading from something like 300V rated CL3R to 600V THHN does, in fact, permit it.
Click to expand...
And yes your post were you talked about that is the same I posted in. First post was very informative
 
Ya but I wanted to save a buck lol
That was for 14 gauge also—— not 10 like I wanted—- but technically enphase says 14 is good for about 350 feet so I’ll probably use it—— only thing it’s a cable called is/os and I got to fiqure out what that is never seen it before


That only twisted pair at 600volt mg supply house can get—
 
jaggedben said:
I suppose you could make it carefully with a drill if you really had the time and space, but not necessary.
Click to expand...
To make a twisted pair that will not try to untwist itself you need to reverse twist the individual wires as you twist the pair.
 
AC\DC said:
Retarded question and as soon as you give the answer, I’ll be like oh , but why does the twisting direction matter?
Click to expand...
When you twist the pair one way while twisting the individual wires the other way the individual wires are not twisted but just go around each other. If you don't do this the pair will try to untwist itself.
 
AC\DC said:
O that if your adding pairs of twisted to a make like a 14-4 twisted pair correct— I can see that
Click to expand...
When rope is made they have the same thing to contend with. I have seen rope making machines where the individual twines are twisted one way by planetary gearing while the bundle is twisted the other. This must be done or the rope will come apart every time you cut it.
 
Last edited:
Are extra long CT wires often part of these installs? Seems like really questionable design choice by enpahse,
In other systems (not related to PV/ESS but used CT's) the CT's have like a short twisted pair 5 amp secondary ~0.333 VAC signal from a CT to a little DIN rail converter box that converts it to industry standard 2-wire loop powered 4-20mA.
output from that converter box goes back the PLC or data logger, your still running shielded cable but its small and manageable like so:
CT --> CT wire (short) --> media converter -> 4-20mA or RS422 long run--> PLC
Just my 2cents enphase should offer direct CT input and 4-20mA or RS422 input or something industry standard like that.
 
tortuga said:
Are extra long CT wires often part of these installs? Seems like really questionable design choice by enpahse,
In other systems (not related to PV/ESS but used CT's) the CT's have like a short twisted pair 5 amp secondary ~0.333 VAC signal from a CT to a little DIN rail converter box that converts it to industry standard 2-wire loop powered 4-20mA.
output from that converter box goes back the PLC or data logger, your still running shielded cable but its small and manageable like so:
CT --> CT wire (short) --> media converter -> 4-20mA or RS422 long run--> PLC
Just my 2cents enphase should offer direct CT input and 4-20mA or RS422 input or something industry standard like that.
Click to expand...
Yeah, I hear you, but it's a trade off I think. For the majority of installs where the combiner is within CT-lead length of the main panel that converter would be an extra cost, extra SKU for logistics (more cost), and extra box on the wall for the customer. (Solaredge was like that last I worked with them, they used a white-labeled WattNode meter and it was more often annoying although sometimes a savior.) It's maybe 10% of installs where CTs need to be extended so they get stuck with slightly lower accuracy in exchange for saving everyone else some margin.

Also on the newest generation product where the meter collar does the consumption monitoring, the functionality you describe is incorporated into the meter collar, so it's an even smaller slice of installs (the partial home backup ones) that might need CT extension. (They're using CAN bus not RS-485, but I don't think that matters to your point.)

Keep in mind this is designed for residential market. In commercial I think the approach you advocate is a no brainer.
 
Twisted pair for CTs was used in switch gear wiring so the pairs could be traced through out the gear.

There is no practicle reason for making twisted pair when dealing with 5A secondaries.
 
Last edited:
You must log in or register to reply here.
Top