eQuest - FCU - how to make it cycle

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Hi All,
Does anyone know how to make a FCU cycle ON/OFF based on the zone
thermostat setting? I tried choosing the "Fan on mode" to be
intermittent in the Fan->Flow parameters tab. When I make the fan to be
intermittent, fan is cycling but the supply CFM is no more a constant
volume. It is varying the supply CFM. I observed this in the hourly
report.

ASHRAE standard 90.1 requires the fan to cycle to meet the loads during
unoccupied hours. How everybody model this in eQuest when you have a FCU
system?

Any suggestions is greatly appreciated.

Regards,

Yuvaraj Saravanan, PE

Yuvaraj Saravanan's picture
Joined: 2011-09-30
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HI folks -

Anyone have any luck with responses from LEED/USGBC - So painful- No
call backs, no response to emails - server is painfully slow - for no
incentives

BOY what do you get ? - how can you sell this to a client is cost way
too much and what do you get a plaque - how about putting that money

Into PV or more insulation or design - lets get real here - I do
understand their roll in the game BUT-

Bevan Walker

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Yuvaraj,

I believe the "intermittent" mode is the correct way to model this.

When you look at the hourly reports it appears that the fan coil is varying the airflow rate. However, I believe eQuest is calculating the percentage of the hour that the FCU operates and then calculates an average airflow during that entire hour. Say the FCU has a constant volume airflow capacity of 500 CFM, but during one hour it only cycles on for a third of the hour. I believe eQuest would then report this airflow as 166 CFM for that hour in the hourly report.

Hope this helps.

If you disagree please let me know.

Sincerely,

Mark Prince

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This question is about setting the efficiency of the budget case
domestic hot water heater for modelling purposes. In 90.1-2004,
Section 11.3.2 (b) is states "All HVAC and service water heating
equipment in the budget building shall be modeled at the minimum
efficiency levels, both part load and full load, in accordance with
6.4 and 7.4.

7.4 refers to Table 7.8. A small gas heated storage tank has an
efficiency of 0.62-0.0019V EF. Where EF is the energy factor. From
what I can find there is no single formula to convert EF to thermal
efficiency. So what would you model the budget case efficiency at in
DOE2.1e for this example?

Thanks for any insight you can give.

Chris Jones, P.Eng.

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I believe a cycling type of fan shuts off when the space temperature falls below the Throttling Range you assign for the particular mode (Heating or Cooling) you are in. For example, a cooling thermostat of 72?F and a throttling range of 4?F yields a high limit of 74?F and a low limit of 70?F. When you fall within this range, I believe the fan should shut off (if you choose the Fan Intermittent mode).There should be no airflow.

But now I am unsure if ALL SYSTEMS allow fan cycling..I believe you can with a fan coil.

The other responder is correct in that eQuest deals in hourly chunks, and a fan may only be on part of an hour, thus a lower CFM, but in reality, the same CFM for only part of the hour.

John R. Aulbach, PE, CEM

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http://www.pnl.gov/main/publications/external/technical_reports/PNNL-16031.pdf

The above paper might have the answer for you (page 35). Let me know if it
works out. I have not really tried it.
-Rohini

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Jay Burch at NREL has developed an approach to calculate the thermal efficiency and the tank heat loss coefficient from the published energy factor test results. It's quite elegant and we use the approach all the time in our consulting projects. I can send you the algorithm if you'd like to use it.JeffJeff Thornton President - TESS, LLC 2916 Marketplace Drive - Suite 104 Madison WI 53719 USA Phone: 608-274-2577 Fax: 608-278-1475 E-mail: thornton at tess-inc.com Web: www.tess-inc.com
----- Original Message -----From: cj at cr-jay.caSent: Wed, September 24, 2008 13:38Subject: [Bldg-sim] Modelling service water heater

This question is about setting the efficiency of the budget case domestic hot water heater for modelling purposes. In 90.1-2004, Section 11.3.2 (b) is states "All HVAC and service water heating equipment in the budget building shall be modeled at the minimum efficiency levels, both part load and full load, in accordance with 6.4 and 7.4. 7.4 refers to Table 7.8. A small gas heated storage tank has an efficiency of 0.62-0.0019V EF. Where EF is the energy factor. From what I can find there is no single formula to convert EF to thermal efficiency. So what would you model the budget case efficiency at in DOE2.1e for this example?Thanks for any insight you can give.
Chris Jones

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Hello All,

I used eQuest 3.61b to modify a file created from eQuest 3.61. I am trying to open this modified file in eQuet 3.6 again and I get the following error.

Does anyone have any prior experience with this?

Any help very much appreciated.

Thanks, Shruti

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Joined: 2011-10-02
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Mark,
I don't disagree with you. You may be right. But is there any
documentation which says it is how equest reports the supply air
flow-rate?

Other thing is, I am having a continously operating exhasut fan and
outside air fan (24/7) and intermittently operating FCU. Attached is the
hourly report. In this case I have a 100 cfm exhaust and outside air. If
you are right then I dont understand how the ratio of OSA/supply air
flow-rate is reported. Can you give me your insights?

Regards,
Yuvaraj

Yuvaraj Saravanan's picture
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Yuvaraj,

I'm unaware of any documentation that would support my theory. This is just my gut feeling.

As for your hourly report, I believe the OA/SA ratio is being reported as 100 CFM divided by whatever the average hourly flow was. Anytime the average hourly flow is less than 100 CFM it simply reports it as 100%. The odd thing is that any hour the FCU doesn't cycle it reports the ratio at 90.9%. ???????? I can not explain this.

Something that does concern me is that it may appear that eQuest is only modeling the 100 cfm of ventilation/exhaust air when the FCU is cycling. If you want to make sure your results are accurate I would suggest doing the following:

1.) Serve the zone with the FCU only. The FCU will take care of cooling/heating load in the zone.

2.) Find a dummy zone (unconditioned zone) within your energy model and constantly ventilate/exhaust that zone with the 100 CFM. Be sure to use some wide t-stat ranges so you don't have any unmet heating/cooling load hours and don't waste any energy on reheat.

By separating the FCU from the ventilation, in this way, your energy calculation should be pretty accurate. Granted, the 100 CFM of ventilation air is probably helping cool your zone some, but I'm guessing from your hourly report that the ventilation is shutting down when the FCU shuts down. This should be more accurate.

Hope this helps.

Sincerely,

Mark Prince

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Hello, I am looking for any information anyone has on utility rates in Mexico for the following cities. Mexico CityMaridaMonterey If anyone has the utility rates for these locations or who to contact for said information, I would be most appreciative! Thank you all, Robert Salcido
---

V. Robert Salcido, P.E., LEED AP

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In my experience, there is no descending compatibility between 3.61 and
3.6.

You'll probably need to reverse back to 3.61.

______________

Demba Ndiaye

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Hello Shruti,

I quickly checked into opening eQuest files in previous versions and I found
a similar error. What I did to remedy the problem was simply remove the
strings of text that were causing the error.

*I can tell you what I did but I am open to other suggestions from the
board.*

The *.pd2 file that your error refers to is a text file and you can open it
in any text editor.

1. Make a backup copy of the *.pd2 file.

2. Open the file in a text editor

3. Find row number 24 (as your error message refers to)

a. It should look like the following text:.

ProjTreeType[1] = 1

ProjTreeID[1] = 10040000

ProjTreeLabel[1] = "Site Data"

b. It seems that the newer versions of eQuest use this "projecttree"
notation and the previous version do not.

4. Therefore, delete these rows of text and save the file.

5. Try to reload the file in the previous version and it should load.

If this doesn't work you will still have your backup file you made in step
one. Good luck and tell me if this helps.

Joel Travis, LEED AP

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Hi Rob,
You should be able to get the electricity rates from the following
website. But you should know Spanish to interpret the rate structures.
http://www.cfe.gob.mx/es/
Regards,
Yuvaraj

Yuvaraj Saravanan's picture
Joined: 2011-09-30
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The following is a message I composed a little while ago addressing this
topic for another user -
-------------------
There is no simple 1-2-3 method to convert files from a newer version of
eQUEST to be run in an older one because the critical question is - what
properties or symbol selections are written to the PD2 file that are
valid for the later version but not in the earlier version. There may be
no errors, or there may be many.
v3.61e was distributed back around 5/07, and a lot has happened since
then (though mostly behind the scenes and related to DEER measure analysis).
Working through all the errors and getting to a point where the project
loads without any errors will NOT necessarily result in the same
simulation results, and may in fact not even enable the simulation to
run w/out further edits. With this in mind, you really need to think
twice about rolling back to an earlier version for any project.

If you DO decide that you need to open a newer version project into an
earlier release...
There are two levels of errors that you may need to contend with -
Wizard/project (.pd2) incompatibilities and DOE-2 (.inp) incompatibilities.

You will be alerted to the PD2 errors first.
Simply trying to open the project file into your v3.61e will likely
result in an error message something like this:
Error Reading File C:\...\
.pd2
Line Number: 39
Column Number: 19
File Format Error

What you need to do is open the .PD2 file up into a text file editor
that reports line/row & column info and see what is written to the PD2
file in this location. In the project file that posted the above error,
line #38 contains:
BDBUpdateReEval = 1
This was a new property added back in 2/08 to facilitate more detailed
project backward compatibility processing. This item could just get
deleted from the PD2, since the property itself is not recognizable in
the earlier release.
Once this line is deleted, you can try to load it again and will likely
get other errors further down in the PD2. In most cases you need to
simply delete those lines and re-open, etc.

Once the PD2 errors are bypassed, the INP will get loaded and you may
find that the new INP contains keywords not supported in the earlier
version. Same iterative method can be used to resolve those errors...

That's the best advice I can offer on this topic.

- Scott

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