New setup hardware list help please

Getting Started
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Hi all, forum newbie here…

So I want to get to grips with my power usage at last… Always been a heavy domestic user and since moving to a larger property in the countryside, things are even worse… Top that with a new ground source heat pump installation (3 phase 15KW) last winter and I’m pushing 30,000 KW consumption per annum!

I’m also potentially having some power issues in the house (single phase) which may or may not be load related.

The power supply to the property arrives in the garage, the garage is connected to the house from a networking perspective, so network connectivity shouldn’t be an issue.

Currently the 3 phase supply has a consumer unit which feeds the Heat Pump and then one of the phases is passed over to the previous single phase boards for the rest of the house purposes.

There are 4 consumer units running on the single phase, 1 for the garage / garden, 1 for the utility / outside lighting, 1 for the basement (air con plus home control stuff), 1 for the ground / 1st floor.

As a starter for ten, I’d like to monitor the four consumer units, they are all fed from a cupboard in the garage with fused isolators. Presumably this is the best place for me to attach the CT sensors as it’s centralised.

Can you please advise which hardware would be best for this? I’m happy to use either the web EmonCMS or host locally (I have a NAS server with Docker facilities).

I’m a programmer by trade, although getting long in the tooth, predominately a Windows software developer (I know), so not very good on Linux / A N other, but have good networking skills and a logical brain!

We are also installing 25KW of solar panels in the next 2-3 weeks, so will want to monitor this in due course, currently we are looking at the Sunny TriPower STP 25000TL-30 so will want to be able to read data from this.

Ideally, I will want to look at the usage on each distribution board and potentially help to balance the 3 phase more than it will be currently.

I see that the EmonPi is an all inclusive box and maybe ideal for a RasperyPi / Linux novice, but I can’t help but think that out of the box I already need more sensors and there is probably a more suitable combination?

Just to be clear, I will happily purchase more units to start focusing in on the culprit energy usage, so will want to be able to add more “sub” sensors if that makes sense.

Thanks for any help in advance.

Cheers, Barry

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You clearly have a fairly complicated arrangement there. The first point is, from what you describe, I wouldn’t consider it to be a three-phase installation, but three separate installations that happen to be on different phases. That’s because at present, I can’t identify a true 3-phase load, except possibly the heat pump - is that correct? But I might change my mind on that point.

The first question: where and how will the new PV installation feed into your existing set-up?

The second is, can you clarify how your three phases are shared amongst the consumer units?

I think the next question is, although you only want to monitor each C.U. as an entity, what else might you want to monitor in the future?

I think from what you’ve already written that an emonPi probably isn’t the best choice, more likely your “base” unit will be an emonBase (essentially the same thing, but without any monitoring inputs, its there purely to handle, store and display the incoming data), with data coming from several emonTx “sensor nodes”.

You might want to look at the Iotawatt. Although it is factored by our shop, I have no personal knowledge of this item, so I am unable to give an opinion as to its suitability.

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Hi Robert,

many thanks for your reply.

It’s fairly unusual compared to your typical single phase household, that’s for sure. So firstly, you are correct, there is only 1 true 3 phase load, the heat pump. Prior to the heat pump, we only had a single phase supply which (obviously) ran everything.

There are 4 single phase consumer units, all fed from a single phase of the three phase supply. All the 3 phase meters etc were fitted to the opposite side of the garage to the single phase wiring. The electricians then effectively connected the L1 phase over to the original location that the incoming single phase supply was connected, so from the perspective of the rest of the wiring, nothing has changed other than the single phase utility company meter has been removed.

There is one more complication, but we can ignore it for now, in that we also have a backup generator covering the single phase supply to the house. Ultimately, I think the generator backup is going to become redundant hopefully, once we have battery backup in years to come.

So to confirm, all the consumer units are on the L1 phase, however, I am prepared to review and adjust this, partly because we are having some problems with sensitive equipment and that following a review by UK Power Networks, whilst we are “in tolerance” for supply, it is very marginal under high draw scenarios. Their recommendation at this time is to spread some of the house load across the 3 phases. The simplest approach to this would be to move two consumer units to the other two phases. Ideally, I want to identify where the loads are coming from and the time of day (if there is a pattern) in order to identify which consumer units to move. The only consideration here is that I can only backup one phase with the generator, so I will need to consider where I need cover most.

I will want to monitor other items in the future, so will want to add more sensor nodes. I’m not 100% sure what this will be yet. There will be things like a hot tub, pond pumps / heating, air conditioning and possibly some other future plans, so expandability will be a requirement. I am however conscious that whilst I am very interested in this project, that once things have been engineered to a point where they are optimised within achievable limits, that much less time will be spent looking at usage, but I think without investing in the monitoring, I will not be able to achieve an optimal setup.

We also have a Control4 home automation control system, so we have control of most aspects of the house, I’d love to get to some level of automation where I can trigger events to the home automation system based on monitoring conditions. Not sure what they are yet, but I’m always thinking! Maybe in time, controllable tumble dryer etc to use power when excess is available for example.

The new PV installation is going into a field next to our property, 88 300W panels, ground mounted. I’m not completely clear on how this is connected, but it will be generating on all 3 phases, another reason why we should look to spread the house load across all three phases.

Sorry for the long ramble, hopefully that’s clarified what we have and an insight in what I am looking to do for now (monitor the 4 boards consumption initially so that I can determine how to re-allocate them to the 3 phases).

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  1. As your heat pump is likely to be balanced across the 3 phases (more or less), there’s little point in monitoring each phase individually (combined with other loads yes, but not separately).

  2. If there’s a spare input, the generator can use it. Else I’ll disregard it and the battery, because the battery might well take the d.c. from the panels direct.

  3. You want to monitor the 4 consumer units. That rules out the emonPi (it has only 2 current inputs), so you need an emonBase and for now, one emonTx. That will give you single phase measurement across 3 high current inputs and one low current (but convertible with minimal expertise in electronics - solder in one resistor). You can (not at the same time) load a 3-phase sketch and get approximate power on a 3-phase system (approximate because it can only measure the voltage on one phase, so depending on the voltage balance across the phases, there’s an error in the other two).

  4. Adding more items. The easy way will be one or more emonTx’s, keeping each to one phase. There’s a practical limit to how many, because all share the same radio channel. What the limit is depends on how often you’re prepared to miss readings because one jammed another.

  5. Monitoring the PV - this might be by an emonTx (3-phase), or you might be able to import the data direct from the inverter, if the protocol is published and somebody has written the software to read it. That could be a consideration in your choice of inverter.

I think your starting point is an emonTx, an emonBase and the appropriate c.t’s and a.c. adapter, power supplies, leads etc, and (depending of course on the load on the 4th C.U.) modify the emonTx to have 4 100 A inputs. That will give you the “instantaneous” (at 10 s intervals) load separately on all four, which you can plot against time.

1 Like
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Thanks Robert.

I think that all tallies up with where I’d got to after some late night reading. The only thing I wasn’t sure about was the 4th input being only 20A, but you mention that this can be made 100A with a small change (a resistor), are you able to provide more details?

The overall 3 phase consumption I can get from time to time from the meter reading, that will do as a start for now to ascertain the heat pump usage (by removing the 4 consumer unit usages from the total).

With regards to future EmonTX’s and the possibly wireless crashes, it is not possible to connect them over ethernet or Wifi and remove the radio element? Something for the next one or two units I know, I can see that there are two channels available on the shopping site.

I’ll get an order together for all these bits, I got itchy fingers now!

Thanks for your help.

Cheers, Barry

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The change to input 4 of the emonTx is the burden resistor - this determines the voltage that the c.t’s secondary current generates. It’s the resistor immediately behind the jack socket, and in the case of input 4, it is 120 Ω (22 Ω for the others). There are two holes either end of it for a wire-ended component, so you need to add a parallel resistor to bring the total resistance down to 22 Ω - 27Ω is very close. A 0.5%, 0.1 W would be my preference, but you might need to settle for 1%, and 0.25 or 0.33 W won’t hurt provided the body is short enough.
You’ll also need to change the calibration constant in the sketch, so if you don’t have one, a FTDI programmer needs to go on your shopping list.

Yes it is, you can add the ESP8266 WiFi Adapter for EmonTx to the serial output. Have a read of GitHub - openenergymonitor/EmonESP: ESP8266 WIFI serial to emoncms link

The problem with

is, we don’t have a two-channel receiver for the Raspberry Pi, so WiFi is safer. But the r.f. collisions problem depends of course on how many transmitters you have. The risk doesn’t become serious until you have more than a handful.

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Thanks for all those helpful replies!

Ok, shopping basket is done. I’ve left the programmer off the list for the minute. My gut feeling is that the Utility consumer unit doesn’t have much going through it, there’s a washing machine and tumble dryer out there, and a microwave, but they aren’t typically on together. What will happen if there is greater load, will it just “top out” the reading? I can always get the programmer / etc as my next task in the overall project!

Good to hear that the EmonTX can connect over other methods than the radio, as it’s unlikely future EmonTx’s in the house would reach the EmonBase in the garage anyways.

Looking forward to receiving my order now.

Thanks again.

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It will do that, but there’s also a risk of damaging the ADC input, and it’s not replaceable. So I’d strongly recommend adding the resistor even if you don’t adjust the calibration in the emonTx, you can tweak the numbers when they get into emonhub (part of the software that makes up emonCMS).

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Ahh, ok, will get that sorted then.

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In case I forget, when you come to adding the inputs to emonCMS via WiFi, you’ll need to change the configuration file for emonhub.