[Bldg-sim] [Equest-users] BEST PRACTICES: Wild Coils

[Melissa Crowe]

Hi Nick

Ah I like "wild coil".   Makes this industry feel much more exciting.

We usually  call it "simultaneous heating and cooling".    And sometimes it is not so much wild as a poor controls design. eg For a given zone the VAV box is  on one thermostat, and baseboard radiation on another.

In eQuest, from my experience,  it really depends on the situation but one thing I have done is:


  *   With the "Cool Control" = Constant,  set  VAV box minimum flow high so that reheat is required to meet set point.  Adjusting DAT and VAV min flow (within reason so as not to throw fan energy out of wack) until the results are reconciled with utility billing.  (Noting that I back into it starting from proper setpoints )

On the fly I can't see how messing with valves (in eQuest) would help.

I usually save infiltration adjustments as suggested by Julien to model poor fan tracking (excess exhaust ,poor building pressurization)

Best

Melissa Crowe, LEED AP, BEMP
mcrowe at cmta.com<mailto:mcrowe at cmta.com>
508-647-9200 x 225



From: Nicholas Caton <Nicholas.Caton at se.com>
Sent: Friday, June 21, 2019 1:37 PM
To: equest-users at lists.onebuilding.org; bldg-sim at onebuilding.org
Subject: [Equest-users] BEST PRACTICES: Wild Coils

Apologies for the cross-post, however I wanted to ask this question from 2 angles and I feel both communities may benefit from the discussion (if I can spark one).

A common reality I've observed with "real-world" hydronic systems is that system coils and baseboard/radiator loops fall into a state coined wild coils.  Rather than modulating flow to maintain a measured supply air or room temperature setpoint, flow is uncontrolled.  A heating or reheat coil for example will end up dumping heat at all times the associated circulation loop is active, independent of its associated system's fan operation, cooling coil activity, or thermostat signals requesting more/less heating.  Occupants in response to wild coils, when they cay, will end up using windows, propping open doorways, plugging in local space heaters / circ fans, and generally suffering in terms of comfort.  In just about every case, this scenario presents a win-win in terms of improved occupant comfort potential in parallel with energy savings potential for whoever is paying the bills.

Causes for this situation I've encountered more than once include:

  *   Manual Control valves left in an open state, with dusty cobwebs suggesting their presence is unknown to the occupants/building operators
  *   Automated valves (electric or pneumatic) which have become mechanically stuck in an open, or partially open position
  *   Automated valves (electric or pneumatic) which are otherwise busted due to upstream pneumatic line/system issues or mechanical failures of the moving parts at the valve
  *   A valve was never designed and/or installed and/or wired up for control in the first place


For all of this however, I have always struggled in approximating the energy and comfort impacts of "wild" coils in my building energy simulations.  Quantifying this impact with some degree of confidence is difficult, but desirable in cases where I am calibrating to existing utility bills (read: always) and/or asserting the utility savings and comfort improvement impact for fixing/addressing such situations.

For the [bldg-sim] family:  Are there any 3rd party tools, models, or other energy simulation platforms with explicit options for evaluating the comfort and energy impacts of wild coil situations?  Is there any research I could be pointed towards exploring this topic?

For the [eQuest-users] crowd:  Can anyone share a best practice or recommendation for simulating this sort of problem-state within a doe2/eQuest model?  As far as I know, the native input options are essentially limited to a pair of "working" coil modulation states: TWO-WAY and THREE-WAY.  Here's an example doe2 reference entry, with language that repeats a couple times over for different scenarios:
[cid:image003.png at 01D52852.0C054940]
I personally have taken different approaches, with none being particularly satisfactory.  These have included introducing process loads onto the loops concurrently with "free" internal energy source definitions to get those losses dumped into the spaces experiencing discomfort.  I have also played with artificially bumping the thermostat schedules around to reflect measured, uncomfortable temperature states...

Any solutions/experiences/shared-commiseration would be very welcome!

~Nick

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

D
M
F
E

913 . 564 . 6361
785 . 410 . 3317
913 . 564 . 6380
nicholas.caton at se.com<mailto:nicholas.caton at se.com>

15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States

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



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