[Equest-users] DOAS and Fan Coils

[Nicholas Caton]

Matt,

Well-documented!

It's been somewhat established through a couple threads over the past few months that "convergence errors" can sometimes, if not always, be related to difficulties in the system sizing portion of the simulation, and in those scenarios may be resolved by providing DESIGN-DAY inputs and/or manually specifying coil capacities you are relying on eQuest to auto-size.

You might check this possibility off the list by navigating to your first tab (Project & Site), deleting any design days you see there in the component tree, then importing the attached to see if that has any effect.

I believe references to convergence in the errors can also sometimes be a red herring,  but in this case I'm not seeing some related telltale language in those screen snips.  If you do encounter something to the effect of "MsgBomb call argument: " followed by some number of digits that is something you'll want to document/share as well.

~Nick

[cid:image005.png at 01D515A3.47EDD880]
Nick Caton, P.E., BEMP
  Senior Energy Engineer
  Energy and Sustainability Services
  Energy Performance Contracting
D
M
E

913 . 564 . 6361
785 . 410 . 3317
nicholas.caton at se.com<mailto:nicholas.caton at se.com>
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Lenexa, KS 66219

[cid:image006.png at 01D515A3.47EDD880]


From: Equest-users <equest-users-bounces at lists.onebuilding.org> On Behalf Of Matthew S. Garlick via Equest-users
Sent: Thursday, January 16, 2020 6:41 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] DOAS and Fan Coils

Howdy,

I'm trying to simulate a four pipe fan coil system with a DOAS ERV providing outdoor air in DOE 2.3 and getting some errors I haven't been able to figure out, I'm hoping someone here knows the answer!

The fan coil system runs by itself, connected to a campus CHW and steam loop, though I get the following error in my sim file:

***ERROR***********************************************************************
             Heat-Exchanger: L1West Perim Zn (G.W1)           UA calculation
             failed to converge.

This seems to be a random zone and switches every time I run it. Besides defining OA flow at the zone, there are no other custom inputs at this time on the zone. When I add the DOAS (without the ERV) to the "OA From" field in the fan coil system, I get an aborted simulation and the following errors:

***NOTE************************************************************************
             Convergence issues in Design-Day mode 14
             Hours Slow: 3209;  Hours Failed:    0

***ERROR***********************************************************************
             Heat-Exchanger: HENE Perim Zn (M.ENE16)          UA calculation
             failed to converge.

***ERROR***********************************************************************
             Heat-Exchanger: HSouth Perim Zn (Mb.S22)         UA calculation
             failed to converge.

***ERROR***********************************************************************
             Fatal HVAC simulation errors.

Adding the ERV to the DOAS gets me a new set of errors:

***NOTE************************************************************************
             Convergence issues in Design-Day mode 14
             Hours Slow: 3384;  Hours Failed: 1834

***ERROR***********************************************************************
             Heat-Exchanger: HNorth Perim Zn (M.N17)          UA calculation
             failed to converge.

**WARNING**********************************************************************
             PredictX parabolic solution failed.  Please
             send this input and weather file to program developers      3015
***ERROR***********************************************************************
             Heat-Exchanger: HEast Perim Zn (T.E39)           UA calculation
             failed to converge.

***ERROR***********************************************************************
             Fatal HVAC simulation errors.

Same notes and warnings as before but it adds the PredictX warning around 50 times (I edited the above).

I tried stepping back to DOE 2.2 but of course you can't define a DOAS in that engine and in 2.2 and 2.3 I'm unable to put an ERV on a fan coil system type.

So then, can anyone shine a light on what's going on?


[TBCx]

Matt Garlick, CxA, CEM, BEMP
Building Efficiency Engineer | TBCx

E-mail: msg at tbcxinc.com<mailto:msg at tbcxinc.com>
Mobile: 801-907-5654
Direct: 801-401-9492

324 S. State Street, Suite 400
Salt Lake City, UT 84111
www.tbcxinc.com<https://eur02.safelinks.protection.outlook.com/?url=http%3A%2F%2Ftbcxinc.com%2F&data=02%7C01%7CNicholas.Caton%40se.com%7C76063b4b33a54a126de208d79ae5fa2f%7C6e51e1adc54b4b39b5980ffe9ae68fef%7C0%7C0%7C637148184845936058&sdata=rMYhO7OSmLsV9DMm%2BWLGmKuJkkjU2AmFLw9P%2BkloypU%3D&reserved=0>





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