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CT reads negative, is my gateway wired wrong?

Odobo

Member
Feb 16, 2021
28
16
USA
My powerwall is not discharging during peak time (cost saving mode, 20% reserved), so today I logged into the gateway installer mode and see if I can find anything wrong.

When I got to the metering page, I see Meter 1 CT1 and CT2 are both reading negative W, when I click on the Flip check box, a info screen pops up and say "A negative power reading may indicate the CT is installed backwards or on the wrong phase."

on the gateway installation manual pg 34, it says "– This Site meter may be used when the Grid connection is at the Supply terminals." Does this mean my gateway is wired wrong? (either the 2 incoming wires or the CT)

could that cause my powerwall to not discharge during peak hours because they are reading negative value?
 

h2ofun

Active Member
Aug 11, 2020
2,180
336
auburn, ca
My powerwall is not discharging during peak time (cost saving mode, 20% reserved), so today I logged into the gateway installer mode and see if I can find anything wrong.

When I got to the metering page, I see Meter 1 CT1 and CT2 are both reading negative W, when I click on the Flip check box, a info screen pops up and say "A negative power reading may indicate the CT is installed backwards or on the wrong phase."

on the gateway installation manual pg 34, it says "– This Site meter may be used when the Grid connection is at the Supply terminals." Does this mean my gateway is wired wrong? (either the 2 incoming wires or the CT)

could that cause my powerwall to not discharge during peak hours because they are reading negative value?
I keep reading about CT's being put in wrong. So how can I avoid this when my installers are putting my gateways in?
 

Laketime

Member
Dec 13, 2020
130
72
LI NY
They reversed the gateway's leads. It's an easy fix if you are comfortable opening the panel, if not they will fix when they come back out.
 

DHevey

Member
Oct 18, 2019
29
23
Bluffton, SC
so, what check/checks should one do BEFORE they leave from an installation?
I think one issue is that many installations get finished at the end of the day, when solar is at a minimum, so it is not possible to see how everything works. The installer may get the app working at 5:00 PM, and everything looks nice, but you may not be producing, charging or discharging, so the only thing that you can see is consumption. This happened to me, so it wasn't until the next day, when the readings were all wrong, that I realized something is wrong, and yes, it was frustrating, because I had to wait for over a week for a tech to come out and repair the problem.

Given this, the very least you should do is make sure that the app is showing consumption in amounts that make sense for your particular case, and don't let them leave until it does. If that is done correctly, it's half the battle.
 
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Laketime

Member
Dec 13, 2020
130
72
LI NY
I think one issue is that many installations get finished at the end of the day, when solar is at a minimum, so it is not possible to see how everything works. The installer may get the app working at 5:00 PM, and everything looks nice, but you may not be producing, charging or discharging, so the only thing that you can see is consumption. This happened to me, so it wasn't until the next day, when the readings were all wrong, that I realized something is wrong, and yes, it was frustrating, because I had to wait for over a week for a tech to come out and repair the problem.

Given this, the very least you should do is make sure that the app is showing consumption in amounts that make sense for your particular case, and don't let them leave until it does. If that is done correctly, it's half the battle.
Exactly. Same thing happened to me- the sun was down when they finished and couldn't tell they were wrong. As I have said it is the easiest thing to correct but some people get skittish when opening a panel box.
 

Laketime

Member
Dec 13, 2020
130
72
LI NY
so, what check/checks should one do BEFORE they leave from an installation?
If the sun is down there isn't much you can do but they usually come back in a day or two to check everything so it is no big deal. The issue is everyone wants to turn their system on the day it is installed but it isn't ready. I think it's a small lack of patience.
 

h2ofun

Active Member
Aug 11, 2020
2,180
336
auburn, ca
If the sun is down there isn't much you can do but they usually come back in a day or two to check everything so it is no big deal. The issue is everyone wants to turn their system on the day it is installed but it isn't ready. I think it's a small lack of patience.
Do the CT's have markings for current flow, and if not, how would they know the direction to use?
 

Vines

Active Member
Jul 20, 2018
1,870
2,185
Silicon Valley, CA
Do the CT's have markings for current flow, and if not, how would they know the direction to use?
More CT fun!

Agree, its a common problem to have the CT on the wrong phase. I would advise against flipping them electronically, as occasionally Tesla does a firmware update that resets the state of that electronic flip.

The CT are marked, so it should be obvious which way they go on, but misphasing is a common problem as well. Measure wire to wire on each L1 to L1 between the gateway and the panel in question. If you have 0v, then you have the correct place to put CT1. If you measure 240V you are phase swapped and need to switch L1 and L2 for that subfeed, or swap the CT.

To prevent this, I'd hire the best installers, and check your app works correctly. If you login to the installer portal and see negative values where there should not be then I'd bring that up.

Installers have a checklist of things like this, and getting all up in their work with your own checklist may not lead to the best results.
 

h2ofun

Active Member
Aug 11, 2020
2,180
336
auburn, ca
More CT fun!

Agree, its a common problem to have the CT on the wrong phase. I would advise against flipping them electronically, as occasionally Tesla does a firmware update that resets the state of that electronic flip.

The CT are marked, so it should be obvious which way they go on, but misphasing is a common problem as well. Measure wire to wire on each L1 to L1 between the gateway and the panel in question. If you have 0v, then you have the correct place to put CT1. If you measure 240V you are phase swapped and need to switch L1 and L2 for that subfeed, or swap the CT.

To prevent this, I'd hire the best installers, and check your app works correctly. If you login to the installer portal and see negative values where there should not be then I'd bring that up.

Installers have a checklist of things like this, and getting all up in their work with your own checklist may not lead to the best results.
Is there any manual with tests, info, diagrams that show how to do this step by step.. Since it seems to get messed up a lot, would seem Tesla would want to have some detailed documentation out there.
 

Redhill_qik

Member
Aug 16, 2020
186
99
South SF Bay, California
More CT fun!

Agree, its a common problem to have the CT on the wrong phase. I would advise against flipping them electronically, as occasionally Tesla does a firmware update that resets the state of that electronic flip.

The CT are marked, so it should be obvious which way they go on, but misphasing is a common problem as well. Measure wire to wire on each L1 to L1 between the gateway and the panel in question. If you have 0v, then you have the correct place to put CT1. If you measure 240V you are phase swapped and need to switch L1 and L2 for that subfeed, or swap the CT.

To prevent this, I'd hire the best installers, and check your app works correctly. If you login to the installer portal and see negative values where there should not be then I'd bring that up.

Installers have a checklist of things like this, and getting all up in their work with your own checklist may not lead to the best results.

I finally (4 months after install) got a Tesla tech out to fix a monitoring issue with the loads that are still in the main panel and not backed up by my Powerwalls. He was here for 3.5hours playing with the Gateway 2 and the CTs. I have no idea what he was doing with the setup, but those loads are fairly accurate now.

One item that he mentioned was that there was a batch of CTs that had the current direction label placed on them backwards and that had caused a number of issues until they caught it.
 

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