What hardware for 400A + 2x200A service?

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Hello! Doing some investigation and happened to find IoTaWatt and am really looking forward to having some solid data in terms of my power needs - at some point in the future I’ll be looking to add solar power generation to the mix (but that’s not any time soon).

I have a new house, and was fairly hands on in terms of the specifics of what was installed electrically - we have 400A service from the street, and from the exterior 400A panel, it comes in to two 200A subpanels (each next to one another). I still have several open spaces for new circuits, but off hand don’t have an idea of how many individual breakers I’d need (I can do an accounting of it later, because I know a few of the double pole breakers are large, about 60A).

Enough rambling, let me see if I can compose a few (more) succinct questions:

  1. What type of sensors would I need for the mains? Just one that handles 400A, or two that each handle 200A? How do those work together if separate?
  2. Being that I have multiple panels, I assume I can have a single base unit in between both panels, and organize the bevy of low voltage wires entering each panel?
  3. Being that there’s only 14 inputs for individual circuits, what is used to join multiples together (I am certain I have more than 7 circuits in each panel)?
  4. Assuming larger circuits (like 60A) need higher amperage sensors.
  5. Where do the circuit sensors clamp to, around the hot leads? How does that work for double pole breakers with two hots, do they require multiple sensors?
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That is an impressive amount of capacity. You must have a lot of high powered loads. I would suggest taking a step back and think about what questions you want to be able to answer?

Today everyone has the easy ability to collect WAY more data than they will ever need or be able to do anything about. I know. I have been collecting data for decades. Most of it is ephemeral and not very valuable, but (and this is the reason I keep doing) sometimes it is really valuable to be able to see how long a problem has been going on.

Here’s an example related to Iotawatt. A few weeks ago I was looking at my Grafana dashboard and noticed the main power utilization was high. This is not unusual, since I have a standard-ish electric water heater at the barnyard. But, the high utilization stayed higher longer than usual. I took a closer look and the culprit was the heat pump water at the house. I looked at its history and it was using the element (s) a lot. Since I have it on efficiency mode, it should only turn the element on if the tank is below 65°F (turns out to make it less likely for people to complain they also turn the top element on if the top is below 105°F). Clearly, something was wrong. Since I have a background in computer science, the logical thing to do was reboot the water heater (that is what the manual says too :grinning:).

Had I not been watching, I would not have noticed that my water heater wasn’t working right. It was still “working”, but using about 2X the energy.

So, there is a LOT you can learn by measuring just the mains. Start there. If you provide pictures you will get better help selecting CTs. If you want to combine the two panels (to only use 2 of the 14 inputs) you will need (4) 400A CTs to be sure to not overdrive the inputs. If you can access the cables before they split to the two panels, you could use (2) 400A and the same 2 inputs.

I would then put CTs on the big energy consumers. I have the following measured:

  • Main A
  • Main B
  • Barn A
  • Barn B
  • Furnace
  • HPWH
  • Other WH and well pump
  • Heated floor
  • Some kitchen circuits
  • Some other circuits

I actually have 2 Iotawatts and have been thinking about a 3rd. I don’t really need it, but it would make some things easier.

The furnace data is moderately interesting. It looks my blower motor sometimes used the wrong speed.

The dishwasher circuit helped me understand the problem when my dishwasher had what looked like a reason to replace it. Couldn’t find one I liked well enough, so decided to try and fix it. Since it was already broken, unlikely to be able to make it effectively more broken.

The heated floor data is also interesting. So far I like it too much to want to turn it off, but it costs a lot more than I originally estimated. Since the heat goes into the house, it isn’t really wasted (or so I tell myself).

Remember that this is just a gateway to more data collection. As far as I know there is no 12-step program for data collectors (or even hoarders) :wink:

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Thanks for the really helpful suggestions and context. Since I’m still really early on in the planning phase, I guess my first inclination was “data for all the things” - since the house is new I have questions about what uses power, and how much. But taking a more surgical approach may actually work well.

So I’m assuming as long as my mains are covered, I can do some simple maths with the circuits I know are directly monitored, vs the ones that aren’t?

I’ll have to dig in more to see what exactly can be done with IoTaWatt before I go get anything.

You also mentioned using multiple base devices - is it frowned upon to have the device outside of the elec panels, with low voltage wires entering, so any measurement must occur within the panel?

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The correct answer is that you need to check with the AHJ (Authority Having Jurisdiction Definition: 715 Samples | Law Insider).

Generally, the Iotawatt is not suitable for putting in the high voltage environment of an electrical panel. Take a look at the pictures from the installs that other people have posted on this site to get ideas. All of the ones I have seen have had the Iotawatt outside of the main panel. There have been different techniques to get the CT signals outside of the box. The CTs have high voltage rated cable, but most extensions do not.

The Iotawatt can do the math to give you something that shows (all) other circuits.

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Actually, devices inside a panel must be certified to a rigorous standard. IoTaWatt is not, and must not be installed inside the panel. There is no prohibition against wires running into the panel as long as they are certified to the applicable voltage. Some local authorities may require that the wires be enclosed or otherwise protected against damage.

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So here’s my dilemma. Being that I have two 200A panels, I didn’t realize each of the 200A CTs were for each of the hots, so with the hardware I have now, I can only monitor total usage from one panel, plus the sums of the other CTs I have.

If I were to get two 400A CTs, I’m assuming I cannot wrap the wire outside of each 200A subpanel, as it includes the aluminum neutral/ground from the exterior panel? With 4 hots, am I left to give up another two CTs in order to get whole service usage monitoring?

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The CT has to (generally) measure a single wire. There are ways to get creative, but generally not with wires that are that big.

A lot depends on the particular panel(s). Sometimes there is access to the wires before they split to go to the individual panels. Pictures always help. Most people starting out want to measure everything in great detail because they have no idea what they really want or what is interesting. This is why I asked you to think about which questions you wanted to be able to answer. Most people’s needs can be handled by a single Iotawatt. You could start there and then if you want more detail get another one. I have two and have considered getting as many as two more to measure everything at just the house. I have considered getting something to get more detail at the barnyard, but the total isn’t so great that the detail would be really worth it.

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It depends what you are capable of doing. If the panels are close enough to run CTs from each to the IoTaWatt, you can put two 400A in each panel and combine them with headphone splitters. That’s an expensive option, especially since you already have two 200A. There is another option. You can use two more 200A and combine them using headphone splitters but you would need to change the burden resistors for those two inputs to 10 Ohm, or use three way splitters and put a 20 Ohm resistor across the third (effectively turning the internal burden to 10 Ohm).

I can change the internal burdens to 10 Ohm if you send me the base unit, or I can provide a couple of 20 Ohm resistors mounted to 3.5mm jacks if you want to go the three way splitters route.

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A lot depends on the particular panel(s). Sometimes there is access to the wires before they split to go to the individual panels. Pictures always help. Most people starting out want to measure everything in great detail because they have no idea what they really want or what is interesting. This is why I asked you to think about which questions you wanted to be able to answer. Most people’s needs can be handled by a single Iotawatt. You could start there and then if you want more detail get another one. I have two and have considered getting as many as two more to measure everything at just the house. I have considered getting something to get more detail at the barnyard, but the total isn’t so great that the detail would be really worth it.

Yeah, thank you for that early piece of advice. Not knowing much, I really did start at the default “measure all the things” - but like you said, that amount of data rarely if ever gets used.

In my specific case, being that we’re in a new house, I actually haven’t even had a completed power bill for the last 4 or so months (power company was finalizing the switch to 400A service, so I had to pay one lump sum bill - all of the kwh was lumped into one pool, so I have no idea what my power usage is actually like). Moving forward though, in addition to total usage (which I will eventually see on my bills), I want to monitor power usage for my geothermal heat pump, and I’m especially excited to get monitoring around its ability to lower hot water heating electricity usage - starting now when the furnace is still pulling heat from the ground, I should get a good baseline, and then lead into the warmer months ahead where the heat pump reverses for AC mode, and will hopefully cut a good portion off of the electricity we use.

I’m going to see if I can’t get 4 200A CTs to use two mains ports with overeasy’s help, and from there do what I can to be more surgical in what I measure, likely holding off on measuring the furnace backup heat strips until next fall.

Without working with the IoTaWatt much, I guess that begs the question of can you keep both the device’s data history of specific ports cleaner, so that they actually belong to “names” (I’m thinking of either disconnecting one CT for cold weather, to swap to another that’s warm, perhaps they stay in the panel year round), or is that something you just have to do in the downstreams, just change the label?

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Without working with the IoTaWatt much, I guess that begs the question of can you keep both the device’s data history of specific ports cleaner, so that they actually belong to “names” (I’m thinking of either disconnecting one CT for cold weather, to swap to another that’s warm, perhaps they stay in the panel year round), or is that something you just have to do in the downstreams, just change the label?

Last paragraph is a bit confusing, I apologize. But say that I used port #11 to monitor… a window AC for the summer. Early October, cold weather well on its way, the AC has long left the window, and I want to switch it to a circuit that will… run a plug in 1500W heater. Will the IoTaWatt only ever track that data as port 11, and it’s incumbent upon me and whatever downstream processes/tools use that data to know that starting on this October date, this is now a heater, and not a window AC?

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The datalog is referenced by input port only, so your options are to keep track of the dates when you repurpose an input so you can know what you are looking at, or upload selected inputs to an external database like influx.

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Changing what you are measuring and keeping all the data is challenging. There isn’t an Easy Button ™ for it. Decide if you really need it, or are just being a data horder. I definitely understand the feeling. I have a refactor of inputs I want to do, but I don’t want to lose the data. I also have a new location I want to upload the data (new instance of InfluxDB). I will probably do all of those at once and start with a fresh data log. But, I have been saying that for over a year now, so not high on the priority list.

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To chime in on the moving CTs between circuits

If you are

  • likely to be moving the circuits you are monitoring and want to distinguish between the old and new readings easily
  • want to display cost not watt hours
  • want a ‘flashy dashboard’ showing several outputs at once

You will need to install influxdb (and grafana for the graphs) on a separate always on machine (or the cloud)

When you move the CT from ‘oven’ to ‘hob’ rename the output accordingly and influx will keep the old data and start collecting the new.

Influx can also collect other info like outside temp (from a suitable source) or brine temp from a ground source heat pump.

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You will need to install influxdb (and grafana for the graphs) on a separate always on machine (or the cloud)

interesting! I’ve actually been working to get emoncms installed on my Unraid machine. I was trying to suss out the difference between emoncms and influxdb, because it seems a lot of folks who use IoTaWatt use it. Are they complementary projects, or competing?

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It’s been years since I tried (and gave up) with emoncms.

I believe that emoncms is an integrated all in one solution (capture data, graph)

Influxdb is a time series database. It just captures an stores data. There was a huge upgrade from 1.6 to 2.x that changed the whole approach to getting data out. 1.6 was sql like, 2.x was json like. I believe the latest builds of the 2.x have the ability to use both query types. I’m still running 1.6. Though have a test instance of 2.x.

Grafana is a visualisation tool. It connects to a data source and has built in query tools.

You can run emoncms in the cloud relatively cheaply - I had more success with that approach but ultimately went with influx and grafana.

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Iotawatt started adjacent to emoncms. That is where I heard about it originally and actually purchased my first one from their store. I have been using emoncms for a decade or so. It is about the same now as it was then. It once was free, but they started charging about a £1/channel/year a few years ago. I got some credit for the Iotawatt purchase which lasted awhile. I was running about 50 channels and it was easier to just leave most of them there. But, I have started to move more stuff to InfluxDB and Grafana. Grafana does dashboards/visualizations really well. But, there is a learning curve.

I wanted local data, not because I am paranoid, but rather because internet goes out here enough and I still wanted to be able to see what was happening.

So, emoncms is designed for energy monitoring and has a passionate following. It has no easy button for local install the last time I looked. It does have instructions, they just are not really simple. All the code is open source so if there is something you don’t like, you could fix it. The visualizations are fairly basic and have a turn of the millennium (at best) feel to them.

InfluxDB is a generic time series database. I like the latest 2.x version. It supports both IQL and flux for the same data. IQL has been around a lot longer so there are examples. Flux much less so. It is more powerful, but with power comes responsibility.

Grafana is a generic dashboard/visualization product. It is very powerful, but is reasonably easy to get started and create beautiful looking graphs.

Using these with Iotawatt requires some thought. There are MANY ways you can choose to use it, which can make it challenging to get started. There are some posts about the various ways people have chosen to save data, but there isn’t a definitive way to do it. Some of it comes down to what insights you want to be able get out of the data. Different configurations will allow some things easier than others. As an example, I am only saving watts for most channels but do save amps and volts for the mains. This allows me to know what my peak amp draw is (so I know if I could ever overload my generator). It would probably be better to periodically generate watt-hour and peak data points to make some graphs easier on the system. With flux some of my queries will time out when I try and get more than 30 days worth of data. With better data, I suspect years would not be an issue. But, 10s resolution data for years is probably not very worthwhile. Being able to quickly view years worth of data and then zoom to the interesting point years later can be very helpful. I do that about once a year or two, when I have a question about some particular sensor (because the data know is confusing and I want to see if it matches what happened in the past).

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ha! I actually opened a few PRs against the project last night. I’m a developer by day, and just so happen to also work with PHP, which is what emoncms is written in, and noticed they probably need a little help in getting the project compliant with PHP8, which is the current iteration.

I also got an Unraid template setup for running a standalone version of it, because I have a home server that I use Unraid for (rather than using enterprise-grade RAID of the HDDs, Unraid is a bit more friendly/cost effective), so if anyone’s willing to give it another go on Unraid it should be fairly simple to get going (once I get the PHP8 kinks ironed out)

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