Sorry to be beating a dead horse...
the attached document has been floating around the boards for awhile in
regards to how an entered EER value in the Wizard gets converted to the
Cooling-EIR value in the Detailed Edit mode, and after doing a few EER
value tests, I can confirm it works...
I've also found in various emails the conversions on the heat pump
heating side of COP and HSPF to Heating-EIR, and those work too after
testing various values in the Wizard...
Heating EIR = (1/(COP*3.413)-0.012167)/((1/3.413)-0.012167)
Heating EIR = (1/((HSPF*0.28+1.13)*3.413)-0.012167)/((1/3.413)-0.012167)
But I just can't get the SEER to EER conversion from the document (EER =
SEER x 0.778 + 1.4) to work. I'm assuming that the converted SEER to
EER value then gets put into the working equation from that PDF of
Cooling-EIR = ((1/EER)-0.12167)/((1/3.413)+0.012167)).
As an example...if you put in a 13 SEER into the Wizard, a 0.2507
Cooling-EIR value is calculated in the Detailed Edit mode, but if you
use the SEER to EER (13 SEER would equal a 11.514 EER) and then the EER
to EIR equations, it says EIR should be 0.2447.
Any help/suggestions would be great...hopefully it's just a math error
on my part.
Josh Greenfield, PE, REP, LEED AP
I also tried it some weeks ago, and could not get it match the Wizard Value. Maybe someone from the development team might help.
________________
Demba NDIAYE
I have the same question as Josh. My value from the wizard is coming out
different from the equation. Even when calculating EER to EIR.
Example:
Wizard = EER 11 = 0.258
Calculation = EER 11 =0 .31 (which actually is the default value in my model
when I fire it up)
Wizard = EER 12.5 =0.2223
Calculation = EER 12.5 = 0.27
Wizard = SEER 13 = 0.2507
Calculation = SEER 13 = 0.296
However in my calculations there is a 0.05 difference from wizard to
calculation. (Obviously missing something) Should I just use the wizard
values and be done with it?
Thanks,
PETER HILLERMANN
>From the eQUEST help file:
COOLING-EIR
The Electric Input Ratio (EIR), or 1/(Coefficient of Performance), for the cooling unit at ARI rated conditions. The program defines EIR to be the ratio of the electric energy input to the rated capacity, when both the energy input and rated capacity are expressed in the same units. This EIR is at ARI rated conditions, i.e., without correction for different temperature or part load.
Note: If you include fan electric energy consumption in your value of COOLING-EIR, then you should set SUPPLY-KW/FLOW to zero (and SUPPLY-STATIC, SUPPLY-EFF and SUPPLY-DELTA-T should be omitted). Otherwise, the supply fan electrical energy will be double counted. For commercial systems the default value of COOLING-EIR includes compressor and outdoor fan energy, but not indoor fan energy. Imbedding the fan energy into the COOLING-EIR is valid only if the fan is constant volume and INDOOR-FAN-MODE = INTERMITTENT; i.e. the fan cycles on/off with the compressor. If the fan runs continuously during occupied hours, or the fan is variable volume, then the fan energy cannot be included in the COOLING-EIR (or HEATING-EIR).
Kelsey Van Tassel
Peter,
If you replace with following to the Cooling EIR calculation in the middle of the page, the values will be correct for the AC EIR calculations.
Cooling EIR = ((1/EER)-0.012167)/((1/3.413)+0.012167) (note the additional parenthesis in the numerator)
EIR = ((1/11)-0.012167)/((1/3.413)+0.012167) = 0.258
This equation is comparable to the EIR equation at the top of the page.
However, when given a SEER, I find a difference in the results.
EER = SEER x 0.778 + 1.4 = 13 x 0.778 + 1.4 = 11.514
EIR = ((1/11.514) - 0.012167)/((1/3.413)+0.012167) = 0.2447, not your Wizard value of 0.2507
Brett Fero, P.E., LEED AP
Brett,
Thank you for the help I know now what my equation was missing. It's the
-0.012167 and the +0.012167 That's why there was a consistent error. Do you
know what that value is representing, because I know the 3.413 is the BTU
conversion?
Thanks,
PETER HILLERMANN
My understanding is that that is ARI fan power input based on 365 watts
per 1,000 cfm with the supply air flow rate fixed at 400 cfm per 12,000
BTUH of net cooling capacity. (365 w./1000 cfm) * (400 cfm/12000 BTUH)
= 0.012167 It is my understanding that this is only applicable to
Systems 1, 2, & 3, which are package units (PSZ), (PHP), and (PVAV),
with built in indoor fans. I don't believe that this is applicable to
all system types. If you have the correct fan input numbers, for your
particular system, then I would think that probably you would want to
input the correct numbers yourself rather than using the Wizard numbers,
to insure correctness. My experience has been that use of default
numbers will many times throw your model off. Of course, unless you
don't have actual numbers to input, and are just approximating your
inputs.
David A. Bastow
David,
You are correct. I have been talking with Brett and the constant is for
system 1,2 and 3 and their the fan power. I have since realized that if you
do not switch into detail mode eventually your model will not be refined and
will probably have larger margins of error. I noticed this in my modeling. I
am comparing real data from another similar building to my model of a new
building so it's giving me a benchmark to check my inputs and outputs. This
is why I'm asking so many questions.
The best thing to do for modeling is as someone mentioned earlier. Have
utility bills of a facility you know the reality of and model towards
getting those results accurate, then apply those techniques to your next
model.
Thanks,
PETER HILLERMANN