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#190621 - 11/27/09 07:29 AM metering a subfeed
pdh Offline
Member

Registered: 01/20/05
Posts: 354
I'm building a new data center for a new company. I'd like to add power metering for the actual computer rooms. I am trying to get a subpanel put into, or just outside of, each computer room (one is built now, but only the 120V convenience outlets are installed). My idea is to meter the feed to the subpanel. What I'm looking for is what kind of metering equipment could be used that can provide data to a computer to record power usage. It will be my own computer software collecting, archiving, and analyzing the data. System is 208Y/120. A few single phase 208V UPS systems were already ordered before I started here. I'd like to have minute-by-minute power usage readings if possible. I will be running this data center, not just building it.

Any ideas of equipment that could be installed ahead of a subpanel to do this? Or should I just have the power run through a CT cabinet with shorted CTs pre-installed ready to use (to select actual reading equipment later)?

I don't yet have all the specs on expected power usage because it won't even be known how big this could get for maybe another year.

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#190623 - 11/27/09 08:39 AM Re: metering a subfeed [Re: pdh]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
Google for "E-Mon D-Mon." I'm certain they have what you want.

Inatallation is typically at the panel, with the metering connected to the panel with a short nipple. You put the ct's around the feeders in the panel itself.

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#190646 - 11/28/09 03:42 PM Re: metering a subfeed [Re: renosteinke]
Davep Offline
New Member

Registered: 11/14/09
Posts: 3
Loc: Canada
http://www.theenergydetective.com/index.html

Check out this company's products. I have used one of their earlier ones for years (240 volt single phase) to monitor instantaneous demand, daily kwh, max kw anytime during day. The current donuts are split type so easy to install. It uses power line carrier to get signal from panel to remote monitor. The two current donuts feed a transmitter which is connected to a breaker. You need to get on the same phase leg as the transmitter for the remote monitor to work. I think their latest products will deal with 3 phase and also provide a data feed to a PC for your own software or spreadsheet to massage. The cost and ease of use dwarfs most commercial metering arrangements.
Dave

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#190648 - 11/28/09 06:41 PM Re: metering a subfeed [Re: Davep]
pdh Offline
Member

Registered: 01/20/05
Posts: 354
Are there any disadvantages to using a split core CT, such as accuracy?

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#190649 - 11/28/09 06:46 PM Re: metering a subfeed [Re: pdh]
pdh Offline
Member

Registered: 01/20/05
Posts: 354
I didn't see any three phase capability for The Energy Detective. That's a definite must ... as is the ability to feed data continuously to my Linux server running my software. The E-mon products look interesting, but I can't get at details, yet, since some of their PDFs are not working on Linux.

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#190650 - 11/28/09 07:58 PM Re: metering a subfeed [Re: pdh]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
PDH:
I've installed numerous E-Mon's over the years; can't say much 'bad' things about them. All were used for revenue purposes. Read the documentation at E-Mon as to accuracy. Most were manually 'read' for billilg purposes, later ones were installed with modem interconnect to a Windows based PC.

Also, Square D has a similar offering. And another system I installed a few times was 'Power Logics'.
_________________________
John

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#190652 - 11/28/09 08:38 PM Re: metering a subfeed [Re: HotLine1]
pdh Offline
Member

Registered: 01/20/05
Posts: 354
They do offer Windows based software. But I need to automate the gathering and processing of the data (and this is not for revenue purpose), and that needs to be done on Linux. It is possible that they use a proprietary or maybe even encrypted data format to send to a computer to force they use of their own software. Many companies are known to do that even if they give their software away. I'll be giving E-mon a phone call or sending them some email after the holidays, to see what they can tell me, and suggest a specific product.

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#190654 - 11/28/09 10:10 PM Re: metering a subfeed [Re: pdh]
Davep Offline
New Member

Registered: 11/14/09
Posts: 3
Loc: Canada
I guess I was premature on the Energy Detective but it sounds like a 3 phase product is in the works.

Q: Are there any other versions of TED?
A: We are working on a 3-phase unit for commercial applications, as well as a 240v 50Hz version for non-North American use.

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#190662 - 11/29/09 08:01 AM Re: metering a subfeed [Re: Davep]
pdh Offline
Member

Registered: 01/20/05
Posts: 354
Digging deeper into E-mon, though without being able to read some of their PDFs, yet (need a new PDF reader and the latest one from Adobe goes into a CPU loop) ... I see some installation procedures that involve some keys related to computer/LAN use. That strongly hints at encryption keys and a possible lockout of all software other than their own. I'll still be contacting them as soon as I can.

I was looking at what Eaton (Cutler-Hammer) has. Their approach seems to be limited, as well. They do offer "computer access", but digging deeper, this seems to be limited to a web browser accessing their device to get daily revenue numbers manually. They probably have something else; this is likely their marketing people focusing on "executive perspective".

Haven't checked Square-D / Schneider, yet. Probably should also check other big companies like ABB, GE, etc, as well as more Googling to find smaller ones.

I'm still focused more on what I need to ask for in the electrical installation that will be proceeding forward in the next couple weeks, including location of panels, and space (whether in the branch panel, or in a separate enclosure) for the CTs. The original plans were apparently drawn up by one of the contractors based on UPS specs, with no real idea of what we are actually doing here. Things are rolling and I don't want to slow it down too much. So what I need to do now is just making sure that the electrical work that will be done "real soon now" won't have to be replaced. Maybe that is as simple as adding to the specifications that we need space to add CTs for the computer room feed and maybe also for branch circuits.

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#190664 - 11/29/09 09:19 AM Re: metering a subfeed [Re: pdh]
pdh Offline
Member

Registered: 01/20/05
Posts: 354
More on the Eaton devices. They do support a CSV export. But this has to be done manually through a Java-enabled web browser. It also has intervals no smaller than 5 minutes. I need at least as small as 1 minute and I need to get that data into my software within a minute after the interval ends. Their metering device, and the web service is includes, does provide a lot of features for what I call "review analysis". That might be useful. But the automation I'm planning does not seem to be doable with Eaton's equipment. Of course, I will call them up to see what more is really possible at the engineering level.

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