First, thanks to Jason for the heads up! Taking credit for premium
efficiency transformers is a pretty novel idea in my circles.
I'm re-directing this response/discussion to eQuest-users as I'm
applying this in eQuest and have found a snag along the way...
After coming up with and creating a custom TRANS-LOSS-FPLR curve using
manufacturer data, I hop over to create a new meter to assign this to.
The default transformer size field starts off blank, as transformer
losses are not normally modeled. After entering the transformer size
(225kVA) on the first screen, I immediately encounter the following
dialog:
[text includes: "Range Checking Violation: Value must be > 1"]
Hmm. This seems odd... the text files for TRANSFORMER-LOSS and
TRANS-LOSS-FPLR both indicate this value should be a fraction of the
Transformer size representing the maximum loss (therefore < 1). In my
example, the 225kVA transformer has a maximum loss (at full load) of
3,898VA, so I was expecting TRANSFOMER-LOSS should be 3898/225000 =
0.01732. Regardless, I haven't entered anything in that field yet... so
clicking Cancel to proceed, I return to the following:
Hmm.
The error appears to result from the "Loss:" field being unpopulated. I
cannot however input the Loss ratio (clouded "n/a") for the custom curve
to be applied against! The field ignores anything I type when
highlighted...
Okay so saving and exiting, I navigate the .inp to add TRANSFORMER-LOSS
there:
"Step Down Meter" = ELEC-METER
TYPE = BUILDING
TRANSFORMER-SIZE = 225
TRANSFORMER-LOSS = .01732
TRANS-LOSS-FPLR = "Custom Xfrmr fPLR"
..
Starting eQuest back up, the following error is generated in BDL -
(eQuest proceeds to open and overwrite .01732 with a zero):
*13249* "Step Down Meter" = ELEC-METER
*13250* TYPE = BUILDING
*13251* TRANSFORMER-SIZE = 225
*13252* TRANSFORMER-LOSS = .01732
*ERROR**************************** ======
****************************************************
*ERROR*****VALUE NOT BETWEEN 1.0000 AND 1.5000
*13253* TRANS-LOSS-FPLR = "Custom Xfrmr fPLR"
Here's where I throw up my hands! What interpretation of
TRANSFORMER-LOSS results in a value that would always fall between 1.0
and 1.5?
On a related note: I've read through all the help files regarding
electrical meters (I think)... Once this is meter up and running, can
anyone suggest any method for applying a specific subset of electric
loads (say, only plug loads) to this new meter with the transformer
losses defined?
NICK CATON, E.I.T.
Hi everyone,
My head is still spinning from the posting a few days back regarding
transformer losses... I'm about ready to conclude this is one of those
"not really fully implemented" features, but I hope I'm missing
something...
Simple question:
* You're modeling a 300kVA transformer which loses 7,500W at
full load conditions. Put another way, its efficiency at 100% loading
is 97.5%.
* TRANSFORMER-SIZE = 300
* TRANSFORMER-LOSS = ?
My reading and re-reading of the DOE2 documentation (copied below) has
led me to believe TRANSFORMER-LOSS = 7.5kW/300kW = .025, or 2.5%.
If you simulate an hour with a 300kW (100% part load) draw, the
calculated transformer loss would be, by my understanding:
(TRANSFORMER-SIZE) x (TRANSFORMER-LOSS) x (TRANS-LOSS-FPLR value) =
300kW x .025 x 1.00 = 7.5kW
This interpretation is consistent with the following default/range info
for TRANSFORMER-LOSS:
As eQuest appears to simultaneously caution against values >1, but also
requires an input between 1.0 and 1.5 (when doing a BUILDING/SUB-METER
meter - UTILITY appears unaffected by this behavior), I think either the
help files or the program is flat-out wrong. Is TRANSFORMER-LOSS really
truly a ratio, as in: (300kW+7.5kW)/300kW = 1.025? This seems
incongruous with both the TRANSFORMER-LOSS and TRANS-LOSS-FPLR help
entries (copied below). Entering a value >1 like this does pop up a
caution as the default/range entry above suggests.
Whatever interpretation of TRANSFORMER-LOSS is corrrect, the eQuest
interface needs work, as both the spreadsheet and detailed-window views
round any input figures to the nearest integer (0,1,2... etc),
preventing one from using a value like either 1.025 or 0.025. I have
found entering TRANSFORMER-LOSS values like .025 in the parametric
interface does work however. Modeled electric consumptions fluctuated
up/down as I anticipated with the interpretation that TRANSFORMER-LOSS
should be a number < 1. Entering values manually in the *.inp has given
me mixed results - eQuest will sometimes spit out a BDL error upon
opening the file and overwrite the value with a zero or remove the line
- behavior is sporadic and may be related to experimenting with
already-developed models.
I hope someone else has dived into this and can comment as to whether
this is truly a useable feature at this point. I think it is
functional, but it sure is a headache - the interface behaving this way
makes me concerned I'm misunderstanding something...
Here are entries from the help files I'm referencing:
TRANSFORMER-LOSS
The fraction of output power that is lost at the transformer at full
load conditions (full load is equal to TRANSFORMER-SIZE).
TRANS-LOSS-FPLR
Takes the U-name of a curve that gives the multiplier on
TRANSFORMER-LOSS as a function of the part load ratio (current hour load
on the meter divided by TRANSFORMER-SIZE). The transformer loss is
calculated hourly as
(TRANSFORMER-SIZE) x (TRANSFORMER-LOSS) x (TRANS-LOSS-FPLR
value)
The load is the sum of that due to all directly connected equipment and,
for TYPE = UTILITY and BUILDING, other ELEC-METERs. The default curve is
linear from 0.1 at zero load to 1.0 at full load.
NICK CATON, E.I.T.
This might help....
Vikram Sami, LEED AP
Thanks Vikram - my head has stopped spinning and I'm in a much more
mellow state of mind =).
If anyone wants to take a crack at the remainder of my posting, I'll ...
just be mellow yellow
NICK CATON, E.I.T.
I'd have something to add to my conversation with myself this week
regarding transformers:
Whenever the developers can find some time to take a look at this - I
think a great feature (if possible) to round out modeling transformers
in eQuest would be to add a pull-down at the meter/transformer
definition screen to select either a zone to assign the transformer a
location: 'zone' or 'outside,' exactly as we do with water heaters. The
result of selecting a zone would be similar: the transformer losses
would be added to that space as an hourly sensible heat gain. Of
course, unless I'm missing something I think priority should be placed
on the issues I'm outlining below: fixing eQuest's behavior with the
inputs.
Also, way-way down there I asked a tangent question about how to assign
internal loads to specific meters/transformers, and I totally understand
that bit now...
Have a great weekend everyone! Why, thank you Nick - you are a scholar
and a gentleman! You are too kind! Cheerio...
NICK CATON, E.I.T.