[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [EnergyPlus_Support] Re: DX coil psychrometric problems





Sorry, Jim.  I have no idea.  The guys at the helpdesk would transition and run the input file for you and be able to tell, perhaps or be able to lead you?

Or I suppose you could transition and run to see if it has changed.

Linda

At 11:15 AM 8/14/2018, Jim Dirkes jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx [EnergyPlus_Support] wrote:


Thanks, Linda.
I'm using the v8.6 included with Designbuilder. Do you think v8.9 has improved DX coil modeling?

p.s., I'm becoming a champion DX coil bludgeoner, but it's no fun. Normally I don't have so many problems with Actual coil selections, but I think these are over-sized.....

On Mon, Aug 13, 2018 at 2:56 PM, Jim Dirkes < jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

Dear Forum,Â

(excuse cross-posting with UnMetHours)

Although I have had occasional problems with EnergyPlus giving a fatal error due to DX cooling coil sizing problems, most have been associated with autosized coils. I have a project now which uses 11 different rooftop units, all with DX cooling coils. Three of them are giving me fits (problems). So far, I have:
disabled the coil below a specified outdoor temp (<= 65F) using an EMS script
raised the airflow 20% (for improved flow/watt ratio)
reduced the coil rated capacity by up to 50% (for improved flow/watt ratio)
disabled the coil completely (availability = always OFF)Â
The only strategy which works is to disable the coil - and that isn't a very good representation of actual performance :)

The current problem coil has these characteristics:

11,400 cfm VAV fan with minimum flow fraction = 0.7Â
385 MBH / 113 kw rated capacityÂ
single stage coil
The Fatal error looks like: * Severe * PsyRhoAirFnPbTdbW: RhoAir (Density of Air) is calculated <= 0 [-2.69960]. * ~~~ * pb =[98900.00], tdb=[-400.80], w=[9.9866244E-006]. * ~~~ * Routine=Unknown, Environment=STORE 291 - STURGIS (01-01:31-12), at Simulation time=05/16 01:40 - 01:50 * Fatal *Program terminates due to preceding condition.

Can you suggest ways to correct this? Thanks in advance. The rooftop unit uses a digital compressor, which unloads very flexibly. Perhaps I should make the coil multi-stage?


--

James V Dirkes II, CEO / President
The Building Performance Team Inc.
1631 Acacia Dr, Grand Rapids, MI 49504

(alphabet soup of efforts for greater understanding: PE, BEMP, BCxP, LEED AP)

Direct / Mobile: 616.450.8653
jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx

Website l  LinkedIn


Coffee conversation:


You are hereby authorized to make two big mistakes each year, otherwise you will never learn anything.



--

James V Dirkes II, CEO / President
The Building Performance Team Inc.
1631 Acacia Dr, Grand Rapids, MI 49504

(alphabet soup of efforts for greater understanding: PE, BEMP, BCxP, LEED AP)

Direct / Mobile: 616.450.8653
jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx

Website l  LinkedIn


Coffee conversation:

You are hereby authorized to make two big
mistakes each year, otherwise you will never learn anything.












__._,_.___

Posted by: Linda Lawrie <linda@xxxxxxxxxxxxxx>


EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx

The EnergyPlus web site is found at:
http://www.energyplus.net/

The group web site is:
http://groups..yahoo.com/group/EnergyPlus_Support/

Attachments are currently allowed but be mindful that not everyone has a high speed connection.  Limit attachments to small files.

EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the Documentation link and press the &quot;search&quot; button.




Visit Your Group
Yahoo! Groups
PrivacyUnsubscribeTerms of Use

__,_._,___