Hello All,
I am new to the whole thing and have basic knowledge. I am reading up as much info as possible but I need some expert advice.
The specifications of the things I am using is provided below
Country of residence: Malaysia (Kuala Lumpur)
emonPi: RaspberryPi.3, emonpiv2.50
emonTx V3
emonsd 03May16
hosted on emoncms
running on ubuntu 15.10 (64 bit)
I want to monitor the energy of my office which has 3 phase supply. I want to monitor lighting load separately, ac load separately and plug load separately. I am going to dedicate each line of the 3 phase to lighting load, ac load and plug load.
My question is, I have one emonPi, one emonTx and 3 CT sensors. Is it possible to achieve my goal? How do I go about it?
with warm regards
Yes, you can do that. But I would not advise it unless the three phases are approximately equally loaded. This might not be important if the loads that you have are relatively small, but it becomes more important when the load on one phase becomes significantly different to the load on the others. Your electricity supplier, or a local electrician, should be able to advise you what is acceptable.
There’s a brief introduction to 3-phase power in Resources > Building Blocks.
The emonTx and the pre-loaded sketch are intended for single-phase supplies only. If you do as you suggest, the emonTx as you buy it will NOT measure real power accurately. If you do not have the a.c. adapter, it will estimate apparent power based on measured current and a nominal voltage of 230 V. You can apply a (fixed) scale factor in emonHub (in your emonPi) to correct for your typical voltage if it is different. If you add an a.c. adapter, you will need to reprogram the emonTx with the 3-phase sketch, and calibrate it, in order to read correctly the real power, or if you only want apparent power, you will need to edit the sketch to send the apparent power to emonCMS.
3-phase emonTxV3 firmware sketch can be found here, it can be uploaded using Arduino IDE :
Thank you Robert.
What would be the best way to separately monitor lighting load, Air con load and plug load if I am using emonPi and/or emonTx
What concerned me with your original proposal was the possibility of having a seriously unbalanced load on your supply, which is bad practice and something the electricity supplier might well object to. Not knowing the supply arrangements (i.e. its capacity to handle the degree of imbalance you might impose), it’s very difficult for me to say what you need to do. The first thing is to decide how you are going to split the loads so that your supplier is happy. After that, we know where the goalposts are and we can design a scheme to provide you with the information you need.
I’m assuming throughout that you need to measure real power. If apparent power is acceptable, then you have a great deal more flexibility.
At present, you’re proposing one emonPi and one emonTx. Together, those give you the capability of monitoring 6 currents, however the Pi is much harder to reprogram than the emonTx, so I suggest you reserve that for monitoring two places on the same phase. That leaves the emonTx and 4 channels, one of which is low-power but that’s easily changed.
If you spread the loads evenly across your 3 phases, it implies 9 circuits: 3 phases with lighting, air con and plugs on each. If you do that, it implies you’ll need at least one more emonTx. But it might not be necessary - it depends on the answers that you get from your supplier.
Sorry I can’t be more precise at this juncture.