VRF/VRV PowerPoint on Modeling

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Paul and the rest of the user group,

The attached presentation was a great tool to both confirm and improve our
approach for modeling VRF. I do have a follow-up question/problem that
arose during the excel work (Slides 33 and 34 of the presentation).

*Question:* Has anyone ever followed this approach and found out that the
results from the hourly report are significantly different than the "monthly
and annual energy consumption by enduse" reports that eQuest generates?

*Step-by-step explanation of my process:*
I created an hourly report exactly as in the presentation with the electric
input to both heat and cool for every system in the facility along with an
hourly report for the building as a whole. When I add up the heating energy
and cooling energy of the individual systems, it equals the heating and
cooling energy for the whole facility, so far so good.

Next, we looked at this heating and cooling energy and compared it to the
"monthly and annual energy consumption by enduse" report that eQuest spits
out. These numbers were not in agreement. For example, according to the
hourly reports, the electricity used for space heating is 18,615 kWh while
the space heating electricity in the "monthly energy consumption by enduse"
report is 10,930 kWh. Big difference.

In some modeling programs (cough, Trace), I've seen heat pumps output the
combination of their energy in either space heating or space cooling and not
differentiate (which appears to be happening in eQuest as our space cooling
energy is going up in the winter with the VRF system... and the building is
definitely in a heating-dominated climate and has little internal space).
The combination of the hourly report heating and cooling energy was 74,224
kWh and according to the "monthly energy consumption by enduse" report, the
combination is 64,330 kWh.

I tried adding in the "HP Supp" energy and some other uses from
the "monthly energy consumption by enduse" report to no avail. I've had
another eQuest user check my excel calculations and my hourly reports and
they seem to be in good working order.

Any guesses, suggestions, strong reactions?

Gregory Raffio's picture
Joined: 2011-09-30
Reputation: 0

Hi Gregory,

It's hard to comment without seeing your .inp and .pd2 input files and
without knowing exactly what reports you are looking at, e.g. SS-A, SV-A,
BEPS, etc. My first thought, however, was to wonder if you are looking at a
system report that doesn't include the ventilation load. Some eQUEST reports
do and some do not. It would require investigation to determine whether that
is the case and since, again, I don't know what exactly you're looking at,
I'm not up for it. You might check the documentation about what's in
reports, look on the DOE2 website or Google it, to see for yourself.

That's a start anyway.


cmg750's picture
Joined: 2010-10-05
Reputation: 0

Sorry, Carol, but I think we're on different pages. That's fine, its really
easy for Q&A to misfire via e-mail. Its very likely that my original
question set was a bit too scattered.

Let me try to simplify

- Using the hourly report methodology from the presentation, we obtained
the electricity use for space cooling and space heating for the entire
building, and each individual system.
- eQuest outputs many standard reports such as "Monthly Energy Use
Consumption by Enduse", "Annual Peak Demand by Enduse", "Monthly Utility
Bills - All Rates", etc.
- These reports reflect the information shown in the BEPU and other
common eQuest reports from the detailed results.
- For example, the BEPU report and the "Monthly Energy Use Consumption
by Enduse" report have the same #'s for space heating and space cooling
electricity, as we would expect
- These standard eQuest output reports reported VERY DIFFERENT numbers
for space cooling and space heating compared to the numbers derived from the
hourly reports.

I'm really just putting feelers out there to determine if:

1. If anyone has encountered such a mis-match before (regardless of
system type, just a general "hey modelers, has anyone seen this before"_
2. If anyone has ever followed the hourly report methodology from the
presentation and done the double-check that we did and had agreement between
eQuest's reports and their excel calculations
3. If anyone has run across heat pump heating and cooling energy being
reported oddly (such as all its energy use being reported as cooling when
there is obviously roughly a 50%-50% split)

Gregory Raffio's picture
Joined: 2011-09-30
Reputation: 0


Yes, I have encountered the scenario you mentioned in item 3 below. It seems on
occasion, eQuest is reporting VRV heating energy as cooling. I had a model
where I created multiple hourly report blocks to verify that the spaces were not
above set-point in the winter when the simulation file was reporting heat pump
cooling energy use, which actually was heat pump heating energy use.

Might be the problem is that we are modeling the VRV system as PVVT systems,
which they are not.

I have created custom curves for the Daikin VRV system, and it reduced energy
usage about 3% below the standard eQuest heat pump curves. This is in addition
to the spreadsheet analysis of the simulation heat-cool energy as outlined in
the BSUG slide presentation of April 15, 2009.

Paul Diglio

Paul Diglio's picture
Joined: 2011-09-30
Reputation: 400