For all you California electricians out there have you run into this? Dry type transformers 600 volts or less manufactured after (I don’t remember the exact date) February 2003 must meet a certain energy efficient standard. Apparently someone did a study and found that most transformers of this type are lightly loaded and waste lots of energy. These transformers are a pretty significant cost increase compared to there standard counterparts. This has thrown the GC on the job I am presently doing into a tail spin. The job has dragged on for about a year without starting. Lots of design issues and money issues with the owner. The GC is on a GMP and when they found out there will be a significant cost increase due to this they went through the roof. The bids they have accepted and wrote letters of intent for (no contracts written yet) were turned in between September and November of last year. All were done under the assumption that contracts would soon follow and equipment orders finalized. Well, all this time has passed and no contracts yet! Now when they do finally write the contracts and we can write PO’s to the switchgear suppliers we will have to buy energy efficient models. This of course is a change order. Multiplied by the two other electrical contractors on site. Anyway, I just wondered if anyone else has run into this.
You cannot define energy savings without defining the load profile (current versus time).
There are two types of losses in a transformer core (steel), and windings (conductor). Core losses exist for as long as the transformer is energized. Winding losses exist based on the amount of current flowing through the transformer. Ignoring everything else, due to I^2xR, a transformer loaded to %50 will have only %25 of the winding losses of a fully loaded transformer.
Now using some daily values for an office: 12hr @ 100A, 4hr @ 50A, 8hr @ 0A
Pick a standard loss 75KVA transformer 480-208Y/120, FLA-208A, full load winding loss-2700W, core loss-450W; an energy savings design 75KVA FLA=208A, full load winding loss-1,350W, core loss-585W: and a standard 45KVA, FLA-125A, full load winding loss-1,620W, core loss-270W.
Applying the load profile Total Energy lost KWHr = (Core losses X 24hr) + ((actual load/full load)^2 X winding losses X HR)
Standard 75KVA Total losses = 18.42KWHR Energy Savings 75KVA Total Losses = 18.08KWHR Standard 45KVA Total Losses = 19.96KWHR
Results: A lightly loaded transformer is inherently energy efficient.
[This message has been edited by JBD (edited 03-24-2003).]
Re: Energy Efficient Transformers#23648 03/24/0303:29 PM03/24/0303:29 PM
In roughly the 15-300kVA range for low-voltage drytypes, there are three “grades” or temperature-rise ratings for transformers: 150°C, 115°C and 80°C, with the idea that lower operating temperature yields, I guess, lower losses. As mentioned, transformer efficiencies are based on no-load [iron] losses and load [copper] looses. It’s not hard to imagine the CEC again trying to legislate laws of physics.
Re: Energy Efficient Transformers#23649 03/24/0307:41 PM03/24/0307:41 PM
I read about this awhile back. The document(s) is(are) located at the California Energy Efficiency Website - same main page as the link which Bjarney has embedded.
It's one of the "typicals" in the context of commonly encountered "Title 24, Part 6 / Energy Conservation Compliance", which all of us here in California are well aware of.
This one I believe was proposed for introduction into the next version of the Non Residential Compliancy Designs (currently used version is August 2001).
Be sure not to read the disclaimer wrong! As it states at this time, only Transformers Manufactured after February, 2003 will be required to conform to the reduction of "lossy true power", but until the Non Residential Design Manuals specifically target a new Design to use ONLY these listed Transformers (would be CEC Default then), they are not mandatory - only optional. Also, your project was (is) originally dated at least in the early months of 2002, or easilly back in 2001, so unless this item was specified on the originally proposed (bid on) plan set, and this same plan set was stamped "Approved", plus accepted by the City's plan checking division, it carries this project's compliance minimums. If this set was rejected by plan check, and a new revision set was issued, which (finally) was accepted and stamped "Approved", that plan set would be the compliance minimums. It should have been given to all Contractors and if prior proposals had been made on the old set, all Contractors should have been allowed to revise their bids with these "Extras" where the plan check revisions affected a given Contractors' Installation.
This certain Design Issue has been kind of sitting around idle, in the minds of the CMP of the California Energy Compliance Commission for some time now! (have been reading about "Future Ideas To Possibly Include Transformer Efficencies" for about 10 years so far!). In wake of that sweet "Rolling Blackouts" scenario, the Efficency Standards have been highly revised. Looks like they have decided to "Get Serious" about all Equipment's Efficencies + Efficacies, hence the references to the Transformer.
IMO, it's a good thing that should have been done long ago! I do not feel any remorse for having designed Lighting systems which use Energy "Wisely". The Equipment used for Lighting gets more Efficient each year, plus winds up being more pleasing!
As long as the CEC Compliance Standards do not target in anyway "Making Money For Certain Manufacturers", or push only a single "Device Idea" that is simply an issue to raise Money for "Certain Individuals/Corporations", than I support the energy conservation design standards. If they cross the line, then I will oppose everything!
Before stepping down from the Soapbox, I must say that there has been a very noticable change - in the good direction - of lighting equipment's output, consumption and the coupled effect of reduced Smog. Looking back to the mid 1980's, everyone was use to "Bi-Level" or "a/b" switching of lights. Then they were tossed the "Slave/Master" design concept for lighting fixtures. This was met with confusion and anger, but quickly became accepted by the trades (commercial).
Since the days when Slave/Master equipment was introduced, I have been continuously impressed and pleased by the quality of output light at a reduced consumption.
Scott " 35 " Thompson Just Say NO To Green Eggs And Ham!
Re: Energy Efficient Transformers#23650 03/24/0310:26 PM03/24/0310:26 PM
Thank You Scott, I am tracking it down from another angle too. Apparently Square D feels that they cannot sell a standard transformer in California manufactured after March 1st 2003. I am trying to find out on what basis they make that claim. I will post back with any info.
Re: Energy Efficient Transformers#23653 03/26/0308:50 PM03/26/0308:50 PM