Extending CT leads

[mroch]

I am trying to extend my CT's leads by about 25'. Ben and others have said on other threads that people have done this successfully before. For me, just having the wire connected to the GEM, even if it's open on the other end, causes the GEM to read about 50W and 2A when configured as an M-40.

I've seen in other threads that I can mess with the CT "type" to try to calibrate it. I can't find anything about what I should actually set it to, though. If I set it to something like 10, it reads 3W, 0.2A, if I set it to 60 it reads 20W, 0.8A, with no load. And turning on a load (e.g. a 60W bulb) makes no difference, the readings don't change.

So, it seems like it's not able to read the CT at all, and the wire itself is interfering. Is this something I can calibrate away, or do I have to drill a hole in the outside of my house to move the GEM closer to the panel?

[Teken]

I am trying to extend my CT's leads by about 25'. Ben and others have said on other threads that people have done this successfully before. For me, just having the wire connected to the GEM, even if it's open on the other end, causes the GEM to read about 50W and 2A when configured as an M-40.

I've seen in other threads that I can mess with the CT "type" to try to calibrate it. I can't find anything about what I should actually set it to, though. If I set it to something like 10, it reads 3W, 0.2A, if I set it to 60 it reads 20W, 0.8A, with no load. And turning on a load (e.g. a 60W bulb) makes no difference, the readings don't change.

So, it seems like it's not able to read the CT at all, and the wire itself is interfering. Is this something I can calibrate away, or do I have to drill a hole in the outside of my house to move the GEM closer to the panel?

Hello,

Please advise what type of wire are you trying to use to extend the CT? If using CAT5e / CAT6 cabling have you tried to double up the pairs to help reduce the resistance?

Also you should not adjust the CT Type until you have confirmed just the CT is fine. This will give you a base line to reference to and others like me to track. Keep in mind there are four things that can be done to help fine tune the GEM. In no specific order are the following and should be done with great care and understanding some of the changes are global in nature.

1. Adjust the PT Transformer
2. Insert a jumper wire into the channel impacted by noise.
3. Adjust the CT *Type* based on a known load while using an accurate true RMS DMM.
4. Adjust the *Current Constant* value.
5. Verify the CT you have is programmed correctly and is (NOT) set to 240 VAC doubling.
6. Verify the CT is in fact plugged into the correct PJ in the GEM's terminal block.

[mroch]

Thanks for the help. I tried with a 50-pair cat5 trunk cable (100-conductor, in twisted pairs), about 25' long. Each conductor is 24 AWG.

Then I tried a 10' cat6 (23 AWG) which was about half as bad (I can try to get better numbers if it's necessary), which makes me think it's linear in the length of the cable and that there wasn't much difference between the cat5 trunk and normal cat6.

I doubled up the cat5, and it helped some but not enough so I'll still need to calibrate. Plus I need 31 pairs, so I can't afford to double them all up.

What do the CT Type and Current Constant values mean? When I adjust them, what am I changing?

[mroch]

Data point using the doubled-up cat5:

no load: 44W @ 3.30A -- actual current (per Klein CL2000 meter): 0A
144W load: 220W @ 3.8A -- actual current: 1.52A

Edit: also, the GEM matches the meter on both voltage and current on a non-extended run (on a different channel), so if the Current Constant and PT adjustments do what I think they do, I think they're already correct.

[Teken]

Data point using the doubled-up cat5:

no load: 44W @ 3.30A -- actual current (per Klein CL2000 meter): 0A
144W load: 220W @ 3.8A -- actual current: 1.52A

Edit: also, the GEM matches the meter on both voltage and current on a non-extended run (on a different channel), so if the Current Constant and PT adjustments do what I think they do, I think they're already correct.

Hello Mroch,

Can you state what the line voltage is with your Klein meter at the PT Transformer outlet and what the GEM indicates in the live tab window.

Next, can you take a small, medium, large load and indicate using the default CT length what the readings are seen by the GEM. Then, compare them to the Klein meter for all three (known loads) so we can compare.

Next, take a small piece of CAT5e / CAT6 cable and cut a small jumper wire and reference page 5 at the very bottom of my install thread. The link is in my signature below which also offers insight to many of the adjustments I outlined above.

Do not change the *Current Constant* or any other value until you posted them up here for reference. As a side note I have several CT's exceeding 50 feet and none of them have shown such a large variance.

What method are you using to terminate the wires to the existing CT's?

[mroch]

Can you state what the line voltage is with your Klein meter at the PT Transformer outlet and what the GEM indicates in the live tab window.

Klein: 123.7V
GEM: 122.2V

Next, can you take a small, medium, large load and indicate using the default CT length what the readings are seen by the GEM. Then, compare them to the Klein meter for all three (known loads) so we can compare.

Will come back to this in a future comment if necessary, see below.

Next, take a small piece of CAT5e / CAT6 cable and cut a small jumper wire and reference page 5 at the very bottom of my install thread. The link is in my signature below which also offers insight to many of the adjustments I outlined above.

I added a jumper to the doubled-up cat5 and got a 6W/0.1A reading when the lights are off, and 183W/1.50A when two 72W incandescent bulbs are on. 1.5A exactly matches what the Klein says. The 6W when off could very possibly be from my Zigbee light switches.

So the jumper seems to have dramatically helped! Going to try a couple more.

What method are you using to terminate the wires to the existing CT's?

http://www.homedepot.com/p/Ideal-Yellow ... /100036034

[Teken]

If you're sure the Klein tool is accurate change the PT Type up / down until you're as close as possible.

Once that is done monitor the two for about 2-5 minutes and see if they correlate well to one another.

Please keep in mind when you placed the jumper wire into the PJ in the terminal block the power value should be given with just the CT in place so we can have a baseline. Once known you can extend the wire in 5 feet increments to see what variance there is.

It should be noted the wire you use should be copper and not cheaper CCA CAT5e/ CAT6 cable that is all over the inter webs.

As it has higher resistance and you will find the twisted pairs not properly isolated with the barrier strip.

The connector you showed is perfectly fine to use.


Ideals are peaceful - History is violent

[ben]

Jumper looked to filter out most of the noise.

It looks like there's still a little bit of noise being picked up by the CT line (shown by the amperage). Turn the breaker off and adjust the CT Type until the amperage reaches/is close to 0. Then compare it again to against your meter when back on.