Author Topic: Adding a solar MTU  (Read 3827 times)

bdmsb

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Adding a solar MTU
« on: September 30, 2011, 06:35:51 PM »
I've been using TED 5000. I am installing solar panels. Do I only need to add another MTU/CT set to monitor everything? I suppose that would mean I'd double the X10 data on the house wiring and double my problems with other X10 devices coming on spontaneously.

rotus8

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Re: Adding a solar MTU
« Reply #1 on: September 30, 2011, 06:48:50 PM »
Without adding anything you will still monitor the net usage & generation by your house. If you want separate monitoring of the solar production you will have to add another MTU and CTs. You can probably solve your X10 problems with carefully placed filters.

bdmsb

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Re: Adding a solar MTU
« Reply #2 on: September 30, 2011, 07:07:12 PM »
My main problem with X10 is that we use it for irrigation valves. TED turns them on in the middle of the night. The "noise" I need to eliminate is TED. It's not clear to me how to use the filters to keep TED out of the irrigation valves, without making it difficult to turn on the valves remotely when I want to.

rotus8

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Re: Adding a solar MTU
« Reply #3 on: September 30, 2011, 09:16:11 PM »
You need to add a filter to isolate the part of your electrical system that includes the X10 from the part that feeds the TED. The easiest is to get a filter to create a sub-circuit that feeds both the Gateway and the MTUs. A single filter may be used only connecting the black wire of the MTUs, leaving the red unconnected; you have to set the MTU as 120v in Footprints setup. This same filtered circuit should also supply power to the Gateway.

bdmsb

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Re: Adding a solar MTU
« Reply #4 on: October 01, 2011, 03:32:20 AM »
My solar installation was completed today. The Edison meter is running backwards. TED still claims I'm using 2.1 Kw, when the solar panels are generating 3.4 Kw. The TED data is wrong. My approximate actual usage is probably 2 Kw, so TED is not registering the solar input. The transformers are clipped on the main conductors coming down from the Edison meter, the solar inverter is hooked into a breaker below that. Any thoughts?

rotus8

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Re: Adding a solar MTU
« Reply #5 on: October 01, 2011, 04:28:32 AM »
You should set your MTU1 to Adjusted Load. The simple setting takes the absolute value so all readings are positive.

bdmsb

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Re: Adding a solar MTU
« Reply #6 on: October 01, 2011, 04:58:24 AM »
I set the MTU to Adjusted Load and the data reads inverted. As the sun goes down, the reported use goes DOWN, not up. When the oven came on, the reported use spiked DOWN. This is with Dashboard.

Since I have written my own graphing program, I modified it to subtract every reading from zero, so a reading of -5000 watts is reported as +5000 watts. This seems to allow my own program to read correctly. The oven spikes the meter up, and as the sun is going down, my use is going up.

Is there no setting for one MTU that will work with solar panels and read correctly? Is there some other setting I have to change?

bdmsb

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Re: Adding a solar MTU
« Reply #7 on: October 01, 2011, 06:51:46 PM »
Duh .... sorry to be stupid. I didn't know the standard setting of the MTU reported absolute value. The solar installer must have flipped the CTs but it went unnoticed until I changed the MTU to "Adjusted Load". I expect when I flip the CTs around all will be fine.

rotus8

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Re: Adding a solar MTU
« Reply #8 on: October 01, 2011, 11:59:03 PM »
Yup. You can either flip both CTs, Exchange them keeping the same orientation, or swap the MTU red and black wire connections, each will reverse the sign.