[Equest-users] Questions regarding Heating Coil sizing for 3.65.7175

Fri Sep 27 13:18:01 PDT 2019

Nick and Bill, I am doing another energy model and have had some time to try some iterations to solve my heating coil sizing questions. I have discovered that the PSZ heating unit EDB\EWB temperature changes when the "DOAS attached to"  variable is "MIXED AIR" instead of "CONDITIONED ZONES". The file marked 219-057 Kessler Base DE (G.WE7) SV-A&C shows the heating coil size for a gas furnace/DX unit with a HX with "CONDITIONED ZONES". The file marked 219-057 Kessler HX Mixed LessUnitFan (G.WE7) SV-A&C shows the heating coil size for a gas furnace/DX unit with a HX with "MIXED AIR". The heating coil EDB for the first is 72 F and the heating coil EDB for the second is 65 F. I would think they should be the same since both heating coils are compensating for the same outdoor air load regardless whether the outdoor air is mixed within the unit , "MIXED AIR", or mixed within the space, "CONDITIONED ZONES".

I believe the 65 F EDB heat unit size is closer to reality rather than the 72 F EDB heat unit size. The heating energy consumed by both energy models is close enough in value for me to believe that heating energy consumption is being accounted for correctly in both models even though the heat coil sizing is different. See 219-057 Kessler Base DE BEPS and 219-057 Kessler HX Mixed LessUnitFan BEPS.

I would just use the DOAS HX with "MIXED AIR" option except that the PSZ fans cannot run in "intermittent" mode with this option. The only option available for PSZ unit "intermittent" fan mode is DOAS HX with "CONDITIONED ZONES".

In conclusion, I would still like to know:

  1.  Where can I view the heating unit EDB\EWB for PSZ units shown in SV-C?
  2.  How can I manipulate the heating unit EDB\EWB for PSZ units shown in SV-C?

I have concluded that the Airside Summary Design Heating Capacity value does mistakenly add the SV-A HEATING CAPACITY and the ADDITION RATE so I will just ignore it.

If anyone knows the answer to the questions above, please respond.

Kathryn Kerns
Systems Specialist
BCE Engineers, Inc.
| Ph: 253.922.0446 | Fx: 253.922.0896 |

From: Equest-users <equest-users-bounces at lists.onebuilding.org> On Behalf Of Kathryn Kerns via Equest-users
Sent: Friday, September 27, 2019 8:51 AM
To: Nicholas Caton <Nicholas.Caton at se.com>; bbishop at pathfinder-ea.com
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Questions regarding Heating Coil sizing for 3.65.7175

Nick, thanks for the response. Regarding my questions:

  1.  Question 1: I am also aware of and checked the simulation report file that you show below. If you are correct in that my ZONE HEATING does read 0, then Question #2 becomes more important.
  2.  Question 2: The Design Heating Capacity  in the Airside HVAC Summary does not match the correspond SV-A Heating coil size. The Design Heating Capacity appears to equal the SV-A coil size plus the SV-A ADDITION RATE. Is this some kind of error in the program and was the Design Heating Capacity only supposed to be the SV-C coil size?
  3.  Question 3: I removed the DOA from the model and the SV-C heating coil  EDB temperature reduced from 72 F to 61 F. I still don't know where it comes from or how to manipulate it. Can someone show me where this value originates?
  4.  Question 4: It is possible that the LS-A and B reports showing only the non-ventilation maximum and minimum conditions may not reflect the actual maximum and minimum heating conditions for the zone and that is why the Heating Furnace Design Day Peak occurs on 4/8/8 in SV-C instead of 11/29. If so, where is the temperature profile used for this maximum load calculation shown and how do I adjust it?

The point is that I suspect there is something hinky about the heating coil sizing.

  1.  The heating coil size in the SV-A and SV-C reports do not match the Design Heating Capacity  in the Airside HVAC Summary. The Design Heating Capacity appears to be equal to the SV-A coil size plus the ADDITION RATE. Why is this? Is this an error in the program? Is it supposed to be the heating coil size shown in SV-A?
  2.  The SV-C heating coil size is based on an EDB/EWB temperature derived from where? 72 F is an unreasonable EDB for a heating coil size. If the heating set point is 70 F (which it is in this model) and we have a night setback of 55 F, which we do in this model, and outside air pouring in through a 50% sensible heat exchanger in the early hours of the morning, the lowest possible temperature the heating coil is going to see is not 72 F.  Where does this heating coil EDB\EWB temperature come from and how can I view it and manipulate it?

Kathryn Kerns
Systems Specialist
BCE Engineers, Inc.
| Ph: 253.922.0446 | Fx: 253.922.0896 |

From: Nicholas Caton <Nicholas.Caton at se.com<mailto:Nicholas.Caton at se.com>>
Sent: Thursday, September 26, 2019 10:32 PM
To: Kathryn Kerns <kathryn.kerns at bceengineers.com<mailto:kathryn.kerns at bceengineers.com>>
Cc: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: RE: Questions regarding Heating Coil sizing for 3.65.7175

Hey Sorry for the delay in my response - I (and perhaps a number of others who might otherwise see & respond) am attending the building energy conference this week in Denver.

Here's my take:

  1.  To distinguish/understand addition rate vs heating rate, I would refer you to the following resource, from which I'm highlighting a page addressing and explaining the SV-A report in further detail.  Note I personally reference this PDF as a primary/starting resource anytime I too am unsure of the nuances/meaning of specific SIM outputs:

[cid:image001.png at 01D5752E.F8DEBCF0]

[cid:image002.png at 01D5752E.F8DEBCF0]

That you have zonal heating set to 'None' is in fact reflected in the zeroes under heating rate (in the provided attachments).  I think you may constructively consider ADDITION RATE (and its counterpart EXTRACTION RATE) to be indicators from the LOADS portion of the simulation run, used to inform the autosizing for the whole systems auto sized airflow capacity (which you haven't specified).

  1.  I apologize, but after re-reading #2 a few times I'm unclear on what specifically is being asked.  Please rephrase =).
  2.  I suspect the 74F stat in your project is the calculated net result of the return air in the heating design day to the furnace after considering the system coil leaving temperature, internal heat gains, and whatever may exist for heat losses in the space(s) served.  In a system NOT involving a DOA, I would intuitively expect this to reflect the mixed air temperature (return + OA), but in your case a DOA is covering the ventilation it appears so I think perhaps MA = RA?
  3.  Once again, I think the detailed sim output reference provides some clues.  It's fair to note that there isn't an entry (at the time of this writing) in that PDF resource for some of the newer (?) reports like SV-C for coil sizing, but pay mind that the 'S' in the SV-C report indicates it's reporting from the SYSTEMS portion of the simulation run, which follows and builds upon the LOADS portion of the simulation ('L' in LS-A).  That context helps with interpreting the paragraph I've boxed in the following snip:

[cid:image003.png at 01D5752E.F8DEBCF0]
                I'm curious if in your model you might find a matching (or a third) time and date stamp when checking the 'Standard' LS-A over the DESIGN DAY LS-A.  Regardless, it would seem apparent that the SV-C report is incorporating OADB conditions in your weather file whereas the LS-A you provided a snippet of is relying upon your DESIGN DAY inputs & sizing ahead of the listed effects introduced in simulation including ventilation loads, motor heat, plenum light heat...

I hope that makes some headway into clearing the air!

Nick Caton, P.E., BEMP
  Senior Energy Engineer
  Schneider Electric of North America
  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:image004.png at 01D5752E.F8DEBCF0]

From: Kathryn Kerns <kathryn.kerns at bceengineers.com<mailto:kathryn.kerns at bceengineers.com>>
Sent: Thursday, September 26, 2019 3:57 PM
To: Nicholas Caton <Nicholas.Caton at se.com<mailto:Nicholas.Caton at se.com>>
Subject: FW: Questions regarding Heating Coil sizing for 3.65.7175

________________________________

Nick, I haven't heard back from anyone so there is probably no clear answer. Do you know how to contact anyone responsible for eQuest's latest revision that might be able to answer these questions? I would really like an answer to Question #3 about where the heat capacity sizing EDB\EWB comes from. It really doesn't make any sense. I know the HX is not providing the EDB\EWB listed, around 72 F. It should be more like 55 F.

Kathryn Kerns
Systems Specialist
BCE Engineers, Inc.
| Ph: 253.922.0446 | Fx: 253.922.0896 |

From: Kathryn Kerns
Sent: Tuesday, September 24, 2019 4:43 PM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: FW: Questions regarding Heating Coil sizing for 3.65.7175

Everyone, I seem to have sent the message without the files. See attached.

Nick, thanks for calling.

Kathryn Kerns
Systems Specialist
BCE Engineers, Inc.
| Ph: 253.922.0446 | Fx: 253.922.0896 |

From: Kathryn Kerns
Sent: Monday, September 23, 2019 1:10 PM
To: Equest-users <equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>>
Cc: Joshua Wood <joshua.wood at bceengineers.com<mailto:joshua.wood at bceengineers.com>>
Subject: Questions regarding Heating Coil sizing for 3.65.7175

Everyone, I have been  looking at the SV-A and SV-C reports for eQuest 3.65.7175 and I am confused. I have a zone with a typical PSZ furnace/DX with no reheat HVAC system related an auxiliary gym space.

The heating parameters are defined in the attached files called 218-112 Totem Base1 PSZ Furnace,DX, NoReheat Parameters and 218-112 Totem Base1 PSZ Furnace,DX, No Reheat HTG Parameters.

The resulting 218-112 Totem Base1 PSZ Furnace,DX, No Reheat SV-A & SV-C file (see attached) shows a Heating Furnace sized at 89.28 kbtu/hr using a 74.83 F EDB and a 90 F LDB. There is a heat exchanger present 0.5\0.5 Sensible\Latent. (see  218-112 Totem Base DOA SV-A attached)

The resulting 218-112 Totem Base1 PSZ Furnace,DX, No Reheat Airside HVAC Summary (see attached) shows a Heat Design Capacity of 58.0 Btu/sf. Multiply 58.0 by 3384 sf (area shown) = 196 kbtu/hr Design Capacity.

There is a big difference between 82.28 kbtu/hr  and 196 kbtu/hr. Curiously, the difference appears to be equal to the -107.03 kbtu/hr , the Zone ADDITION RATE shown in SV-A

The questions are:

  1.  What does the ADDITION RATE represent and why does it show up as ZONE HEATING value when ZONE HEATING is defined as "None"?
  2.  Why does the ADDITION RATE shown up in the Airside HVAC Summary as part to the Design Heating Capacity when the corresponding SV-A Furnace Size does not include this value?
  3.  How is the Heating Furnace Design Capacity  EDB\EWB temperature calculated? Is there a value that gets set in the input file somewhere? If so, where?
  4.  Why does the Heating Furnace Design Day Peak occur on 4/8/8 in SV-C when the LS-A (see attached) shows a maximum load date of 11/29?

These are probably questions only the eQuest staff can answer. Does anyone know how to contact them?

Kathryn Kerns
Systems Specialist
BCE Engineers, Inc.
| Ph: 253.922.0446 | Fx: 253.922.0896 |

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