# Question about VRF Condensing Unit Inputs

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Good afternoon,

I'm looking to better understand the Condensing Unit inputs in eQuest 3.65
(build 7175) using DOE 2.3.

My project has two (2) 12 Ton condensing units (same capacity) serving
approximately 40 zones.

I'm trying to better understand the following inputs (and how they relate):
"Num system (multiplier)", "Max cap/system", and "Cooling Capacity".

Per the screen capture below, is the Max cap/system input the maximum
cooling capacity of each condensing unit? So in my case this would be 12
Tons?

How (if at all) does this relate to the cooling capacity and heating
capacity specified under Cooling Performance and Heating Performance
(circled in the image below)...is that again the capacity per condensing
unit? If so, is this a redundant input to the Max cap/system input
specified above?

Additionally, can someone provide an example of when the "Num systems
(multiplier)" input would exceed 1?

[image: image.png]

Thanks in advance for any help.

---

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Joined: 2012-01-23
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Hi Chris,

I don?t see why you can?t model each unit and connect them to the terminal units. I?ve attached an example model file. The user-entered values are going to take priority over default values. You can right-click on the cell to read more about the input and it?s relationships with other inputs.

[cid:image001.jpg at 01D7A4A6.78F44600]

[cid:image002.jpg at 01D7A4A6.78F44600]

[Table, calendar Description automatically generated]

_______________________________________________
Ethan Seaman
Sustainable Design Analyst
SMMA
t: 617.520.9288
www.smma.com

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Chris,

To answer your questions, I am starting with DOE definitions for these
inputs:

1.

Number systems (multiplier): number of separate VRF systems that are
represented by the condensing unit. This is effectively a multiplier on the
outdoor unit that represents multiple identical VRF systems. All systems
are assumed to be equally sized.
2.

Max cap/system: maximum rated cooling capacity of one VRF system
represented by the condensing unit.
3.

Number outdoor units: number of outdoor units that are networked
together to serve a set of indoor units. All units are assumed to be
equally sized.
4.

Cooling capacity: total rated cooling capacity of the condensing unit.
If Number outdoor units or Number systems (multiplier) is greater than 1,
then the Cooling capacity is the total of all VRF systems defined for the
condensing unit.

Cooling capacity = [capacity of one unit] * Number outdoor units * Number
systems (multiplier)

Now, as per my understanding of these definitions, number systems
(multiplier) and max cap/system represent the inputs for VRF units (PVVT
and/or DOAS) modelled separately whereas number of outdoor units and
cooling capacity are condensing unit?s inputs. Based on this, number
systems (multiplier) will exceed 1 when we are modelling a condensing unit
which is serving multiple VRF units (PVVT and/or DOAS).

So in your case, inputs will be:

1.

Number outdoor units: 2
2.

Cooling capacity: 24 Tons (12*2)

Not sure how you have modeled the VRF units, so no comments on the other
two inputs. I hope it helps.

Let us wait and see how fellow eQuesters interpret this.

Warm Regards,

*Bhartendu Awasthi*

-------------------------------------------------

LEED AP BD+C, WELL AP, IGBC AP, GRIHA CP

GEM CP, ECBC Design Consultant ? PEDA

Energy & Sustainability Consultant

Pithoragarh, Uttarakhand, India

*M*: +91 97846 53604 | *S*: bhartendu_awasthi

*L*: bhartenduawasthi | *T*:
iam_bhartendu

On Wed, Sep 8, 2021 at 7:57 PM Chris Hadlock via Equest-users <

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Thank you to Ethan and everyone else who responded to my VRF questions.

To close the loop on this, Brian Fountain has pointed me towards Doug
Maddox?s video that provides in-depth overview of the VRF capabilities of
2.3 and answered all of my questions.

For all those who may benefit from this video as I did, here it is:

Thank you,

Chris

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thank you for your response Bhartendu, much appreciated.

Chris

On Wed, Sep 8, 2021 at 12:35 PM Bhartendu Awasthi <

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