Author Topic: Need some guidance on what I need  (Read 1594 times)

R1pilot

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Need some guidance on what I need
« on: September 15, 2017, 11:22:31 AM »
Hi,

I am a little lost here. I wanted to order the Home Pro model along with a couple of spyders to monitor individual breakers. After thinking that I knew what I wanted, I realize I don't. The questions I have are:

1. If I order one of the spyders with the 60A donuts and use it on 230V breakers, can I only check 4 breakers or 8? I assume I need one donut per pole.

2. Same as above but with the 20A donuts and a single pole breaker, do I need one donut or two per breaker?

3. Is there any disadvantage to ordering all 60A donuts and using some on 20 and 15A breakers? Do I lose accuracy?

Thank you!

pfletch101

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Re: Need some guidance on what I need
« Reply #1 on: September 15, 2017, 01:46:49 PM »
Hi,

I am a little lost here. I wanted to order the Home Pro model along with a couple of spyders to monitor individual breakers. After thinking that I knew what I wanted, I realize I don't. The questions I have are:

1. If I order one of the spyders with the 60A donuts and use it on 230V breakers, can I only check 4 breakers or 8? I assume I need one donut per pole.

Most (at least most domestic) 230V loads are symmetrical - the current drawn from each of the two 'poles' is the same. Under these circumstances, you only need to monitor one 'side' and double the measurement to get the total current draw. The Spyder setup page allows you to do this quickly and easily. You almost never need to measure both sides separately.

Quote
2. Same as above but with the 20A donuts and a single pole breaker, do I need one donut or two per breaker?

On a single phase circuit you are guaranteed (unless something very bad is going on!) to have the same current flowing in the live and return wires - you only need to monitor the (live) wire from the breaker.

Quote
3. Is there any disadvantage to ordering all 60A donuts and using some on 20 and 15A breakers? Do I lose accuracy?

Unlike the main MTU/CT combos, which are linear to and through zero current, the Spyder channels show zero power at and below a non-zero current which depends on their 'rating'. The readings  on channels with 20A CTs drop to zero at a lower current than those on channels with higher rated ones. For best results, therefore, you should use 20A CTs for all the 115V circuits that you want to monitor except those rated at more than 20A (which are very unusual in domestic setups).

Correction added 2/23/2018: for others reading this thread, my original message said that the maximum current for each 'side' of a dual '240V' breaker would be half the nominal rating of the breaker. A subsequent discussion in another thread has made clear that this was and is incorrect. A dual breaker trips when the current on either 'side' exceeds the breaker rating, so that the CT rating for one 'side' should normally still be based on the breaker rating, unless there is reason to believe that lower currents will normally be seen on it.
« Last Edit: February 23, 2018, 10:36:18 AM by pfletch101 »
Peter R. Fletcher
TED Pro Home - main MTUs monitoring utility and PV Solar feeds; 2 Spyders monitoring selected individual circuits

R1pilot

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Re: Need some guidance on what I need
« Reply #2 on: September 15, 2017, 02:59:54 PM »
Thank you Peter, that makes perfect sense.

I am glad I asked before I made the plunge.

R1pilot

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Re: Need some guidance on what I need
« Reply #3 on: September 15, 2017, 06:34:14 PM »
OK, just placed the order. Had to remove the panel cover as I did not know whether I had copper or alum wires. I ordered the mixed spyder setup with the home pro TED.

Get ready for plenty of questions once it arrives  ;D

Thanks again!


lundwall_paul

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Re: Need some guidance on what I need
« Reply #4 on: September 24, 2017, 02:05:29 PM »
You should enjoy the TED Pro. I have one without the Spyder. My last month projected bill was off 33 cents. I find that fantastic. Typically it is off $10-20 I also find that great as our rates here in NH are the second highest within the 50 states. Our meter is typically read on the 18th of the month. If the 18th falls on a weekend it gets read either on the Friday before or the Monday after so that impacts projections. The bottom line is I really enjoy the TED pro. I use a wireless display and monitor real time costs.

EVFan

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Re: Need some guidance on what I need
« Reply #5 on: October 14, 2017, 04:13:44 PM »
This is Great!! Sorry to hammer at this but if I'm understanding this in order to monitor (2) 240V 40AMP circuits (2 circuits for 2 EVSE to charge cars) I would only need 1 TED Home Pro as I could put 1 CT on one circuit and the other CT on the second circuit. Is that correct? Then in the software just double the numbers? Would I need 2 MTUs? All the examples put CT's on the main power source and quite frankly every time I open up the panel and do something with the mains I need many drinks afterwards!! Sounds like I don't need to touch that. While I'm at it I have solar panels but they aren't connected to the house. They send all power to the grid thru a separate meter. I'm assuming that has no affect on the PLC communication?   

pfletch101

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Re: Need some guidance on what I need
« Reply #6 on: October 14, 2017, 07:53:18 PM »
If you literally only want to monitor your EV charging loads and don't care about what the rest of your house is doing, then you could probably get away with a Ted Pro setup with a single MTU and a regular pair of CTs. You would have to assume that the EVSEs draw the same current from both 'sides' of their 240V feeds (almost certainly true within the margin of error of the device) and put one CT on one side of each. Once they were correctly oriented, the indicated power would be half the total drawn by the two EVs together. You would not be able to distinguish between the two of them - you would know that power was being drawn, but not by which one or (if both were running) how much by each.

My recommended way of just monitoring the two EVSEs - again, if that is literally all you want to do - would be to get two MTU/CT sets, put the respective CT pairs on both sides of the two EVSE breakers, and call them both 'Load'. The power flux would read correctly, and you would be able to distinguish between the two.

My real recommendation would be to bite the bullet - if necessary with the help of an electrician - and install a single MTU/CT set to monitor your Utility Mains and a Spyder to monitor not only your EVSE circuits but also half a dozen other loads of your choice.

The way you have your PV system set up will not cause problems - TED will just ignore it.
« Last Edit: October 14, 2017, 07:56:43 PM by pfletch101 »
Peter R. Fletcher
TED Pro Home - main MTUs monitoring utility and PV Solar feeds; 2 Spyders monitoring selected individual circuits

EVFan

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Re: Need some guidance on what I need
« Reply #7 on: October 15, 2017, 09:20:00 AM »
Thanks for your advice! Very much appreciated. As I pondered what I'd like to do the Spyder sounds like a better idea. I would like to know the draw of each EVSE also clothes dryer, the kitchen the garage and some other circuits. Just one last question. Why monitor the main? My utility has a website that allows me to look at what I'm consuming. It is not realtime but then again I'm more interested in history than any point in time. Am I missing something or do most people that buy TED systems not have a utility supplied website?

pfletch101

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Re: Need some guidance on what I need
« Reply #8 on: October 15, 2017, 04:37:32 PM »
You're welcome! There are a number of reasons for monitoring the main feed:
1) Historically, that's the way (and much of the reason) the original versions of TED were developed, at a time when few or no utilities offered convenient ways for the customer to keep track of his/her power usage other than by manually reading the meter. Prior to the TED Pro, too, there were few effective ways of monitoring longer term usage at the breaker level, so you had to look at overall usage and try to break out major loads by turning them on and off and/or looking for patterns.
2) While an increasing number of utilities are offering consumers finer-grained ways of tracking their usage, I think most still only do this (for most customers) at the monthly bill level. Smart meters too, which allow much more fine-grained local monitoring, are only starting to roll out in many areas. As someone generating solar power on a feed-in tariff basis, you are a special case, and you may well be benefiting from web technology whose primary purpose is to support that - I don't think that what you may be seeing is available to the majority.
3) An increasing number of utilities are rolling out more complex demand- and/or time-of-use-based billing systems. These can be very good for the energy-conscious consumer, but, to make the best use of them, one needs real-time usage data so that one can use power (or not!) when it is beneficial to do so.
4) Utilities make mistakes! I am currently fighting my utility about a small but significant overcharge going back some years resulting from a systematic calculation error that I would not have picked up if I didn't have (and look at) my own detailed records.
Peter R. Fletcher
TED Pro Home - main MTUs monitoring utility and PV Solar feeds; 2 Spyders monitoring selected individual circuits