WayneW
Senior Member
Nope, the current is the same in the whole wire path.
New Brultech Energy Monitoring Model (ECM-1240) due in 2009
- Thread starter sic0048
- Start date
Doesn't matter, but if using summing CT's on one channel make sure the polarity is correct. The install of the split CT's are ideal if you have the main circuit breaker at the meter socket outside and CT install is in the main panel. With the Main off you can do your work safely enough in the panel with it dead (always test first).
Keep in mind, if the main breaker is in the panel be VERY careful as the incoming conductors to the main breaker are still energized. Most if not all residential pole top transformers are only fused on the primary side so there is a lot of arc flash energy available at the main breaker. A good visual check of the incoming conductors first to make sure the terminations are clean, tight, and that the conductor insulation is not dry or brittle before trying to move wire around to install the CT's.
If there is any evidence of water or rust on the breaker or in the panel (which is common for service entrance cable), or if you are at all concerned about doing yourself, do NOT attempt to do the install yourself, consult an electrician it's not worth it!
And yes, nylon tyrap or tape the CT conductors together and exit the panel through a knockout with a bushed connector.
In order to keep everything organized, I started a new thread for the Brultech Homeseer Plugin, and moved all related posts to that thread. If I forgot to move a post, let me know please.
All of our SPLIT CTs are now UL/c listed. We still have older stock of the same CTs (without the label). Please specify UL/c listed when ordering.
The MicroCTs are in the process of being UL/c listed. All material used to manufacture these are UL listed.
We now have stock on everything. We will be posting the new packages on our site later today and shipping tomorrow. If anyone is in a hurry for their order, we can ship using a courier, however, you may get charged for brokerage costs at you end from the courier. This is why with typically use Express Post. You may want to check with your courier to make sure.
At this time, we cannot provide a cocoontech special. We are still ramping up this product and until we fully automate our assembly, calibration and testing procedure, the additional labor is really cutting into our margin. We will give a special price to cocoontech members having purchased an ECM-1220, although we haven't yet established what that discount would be. Once we get streamlined, we can look at a cocoontech deal.
Paul
Paul,
2 Questions:
(1) How would you like orders submitted that are not packaged items today? Contact you or Sales? Or best-effort on the site with comments? Specifically, I would like to order:
* A+/200 with the -2 MicroCT's for Aluminum
* Y Split-60 to go with this (sub panel)
* Additional pack of 4 -2 MicroCT's
(2) Is this unit capable of dealing with a 240Y (open delta) residential feed? We discussed this back in September but the 1220 wasn't capable of handling this. I realize I can't get a perfect reading because of 2-transformer setup and single voltage reference, is there a way to use 1, 2 or 3 CT's in a series configuration with the appropriate resistors & multiplier to get close? (5 Ton A/C unit for those interested)
Thanks,
Jay
2 Questions:
(1) How would you like orders submitted that are not packaged items today? Contact you or Sales? Or best-effort on the site with comments? Specifically, I would like to order:
* A+/200 with the -2 MicroCT's for Aluminum
* Y Split-60 to go with this (sub panel)
* Additional pack of 4 -2 MicroCT's
(2) Is this unit capable of dealing with a 240Y (open delta) residential feed? We discussed this back in September but the 1220 wasn't capable of handling this. I realize I can't get a perfect reading because of 2-transformer setup and single voltage reference, is there a way to use 1, 2 or 3 CT's in a series configuration with the appropriate resistors & multiplier to get close? (5 Ton A/C unit for those interested)
Thanks,
Jay
In the 3-phase configuration of which the "open delta" is a specific case, the mains voltages are shifted by 120 degrees wit respect to each other. Therefore, it is impossible to calculate power using only one voltage channel as is done with the split phase configuration where you can pretend that each leg has the same voltage and just sum up current transformer outputs. If you attempted the same with the open delta, your power reading would be about 25% lower for resistive loads.
Clarification please...
Impossible in a 3-phase configuration (ie, A/C unit) or impossible in my 120/240V panel that services the rest of the house because the phase-phase in that panel is 120 instead of 180? If you are talking about the 120/240V panel then wouldn't I have a high neutral current because it is completely unbalanced? (I don't)
In the case of the A/C unit - it would be an independent channel and I'm looking for a "close" measurement - be it 1 ct * sqrt(3) or other factor, or 3 summed with a multiplier.
Thank you for the guidance.
Jay
Jay,
My understanding is that your house gets a three wire (two phases and the neutral) open delta feed. The AC unit is connected to two phases. The rest of the house is more or less distributed between the two phases. Is that correct ?
If so, your panel voltage is probably 120/208 (sqrt(3)*120) volts rather than 120/240 and the AC unit gets 208 volts. In the open delta systems, the neutral current is rather high due to grossly unbalanced phases. For example if you have perfectly balanced 50Amp resistive loads on two phases, the neutral current would also be 50 Amp. However, you said that it is not the case. There are several possible explanations:
o You did not measure the neutral current correctly (unlikely). Did you measure the current directly on the mains neutral wire where it enters your house ?
o You have a separate 120/240 ordinary residential feed in addition to the open delta feed for your AC.
o You have a real three-phase feed, your AC has a three phase motor, the house loads are distributed between three phases and your imbalance is not substantial.
Whatever your arrangement is, if the phase shift is any other than 180 degrees as measured against the neutral, I do not think Brultech can measure power using only one voltage sensor for obvious reasons. As I wrote before, with the 180 degrees shift, you just assume that the voltage amplitude is the same for the unmeasured phase and drop the sign (which would be negative if you multiply by the "wrong" voltage). You cannot do the same for the 120 degrees phase shift.
Theoretically, they could have separated their current channels into two (or three for a real three-phase power feed) banks, measured single phase voltage, assumed that the voltage amplitude is the same for all the phases and the angle is perfect 120 degrees, and introduced the 120 degrees shift into their power calculations. It would raise however the messy question: how do you know what phase your load is connected to before assigning a current channel to a specific CT ? Besides, it would probably be easier, more precise and not much more expensive just to measure directly the real phase voltage without such assumptions, but with remaining messy questions of figuring out what phase feeds what load !
We can take this offline since this isn't directly related, unless others are interested and have a similar (odd) configuration.
A Picture that Paul found that represents the voltages/legs correctly is below. My feed from the pole is 3 phases (A/B/C) and Neutral. HOWEVER the picture is showing a single transformer but the pole is using a 2-transformer setup with #1 feeding the A/C legs 120/240/neutral and #2 feeding B which is 240 to A, 240 to C and 208 to neutral. I am running the air conditioning compressor using all 3 legs 240 leg/leg - no neutral.
"3 phase 4W Delta-connected. This illustration shows a three-phase, four wire, delta-connected secondary. There are 240 volts from phase to phase. The midpoint of one phase winding is grounded to provide 120V A/N and 120V C/N. Between B/N, however, the voltages is 208V. This is referred to as the high leg."
OK, so you have case 2: three-phase delta source/load for the AC motor and the conventional 120/240 split phase for the rest.
I am afraid you cannot measure the AC load with Brultech although you can measure the rest of the house, of course.
If you had a three-phase four-wire star (Y) configuration you could assume a perfectly balanced supply/load and measure power with a single watt meter, but you have a delta configuration that does not have a neutral (the "neutral" depicted on the diagram is not a three-phase neutral but just the secondary coil midpoint that creates 120/240V split-phase configuration) so you cannot do that.
It can be shown that in order to measure three-phase power, balanced or otherwise, only two watt meters are needed. Then, total power would be algebraic (signed) sum of their reading. Of course, it is rather expensive and I believe Brultech does not give the power sign, only the absolute value.
As I said before, you could also recover phase voltage from line voltage programmatically assuming perfectly balanced delta, calculate power for one phase and multiply by three, but it would need firmware modification.
So it seems, that the real solution would be to provide an additional voltage channel as well as signed power output. Then, you could use such meter in any kind of configuration.
Not sure that this means anything, but yesterday I went to the Brultech site to order and noted the the "A" and "B" packages didn't have [add to cart] options available. Tonight they do.
However, the status pages still shows them not in stock.
Jay
vc1234 - Thank you for the assistance.
However, the status pages still shows them not in stock.
Jay
vc1234 - Thank you for the assistance.
So, I have to ask, does anyone have an ethernet version of the 1240 running with any software? So far, it sounds like the people that are writing interfaces to the 1240 are depending on COM port. However, from the documentation, I don't believe there is a COM port when you use the Etherbee or Etherport? So, if you go the network route, is there or will there be any software that will work with it?
Thanks,
Jesse
Thanks,
Jesse
hucker
Active Member
I don't think that is right. I have an box with Zigbee support but have been using the COM port for all my testing. I asked the question when I bought this version because I knew I wouldn't be using the radio stuff quite yet.
