[Equest-users] URGENT: VRV modeling - input variables

[Pasha Korber-Gonzalez]

Hi Omar,

At least your life is normal with having to do some sim runs last minute for
your engineers, and they think it is easy for you...

This is not an easy thing to do with one day notice....based on my one time
experience with modeling a VRV system.

What I learned from modeling my VRV model was this:

   1. One it is critical to know the Mfg (or use a sample Mfg as a place
   holder until they specify which Mfg will be used).  I learned from speaking
   with a Mitsubishi rep that the Mfg will be able to give you the specific
   performance data that you need for thier equipment.  When I used the Mfg
   data provided to me for the project units that were specified the energy
   efficiency of the VRV systems could be demonstrated in eQuest better than
   just using the 90.1 baseline performance #'s.
   (The advantage to using VRV systems is that they are SUPER
   HIGH efficiency compared to other HVAC systems types including hydronic
   systems.  These are the new premium efficiency systems that are being chosen
   for more and more designs lately.)
   2. There were two numbers that I received from the Mfg for each of the
   equipment models that were being installed.  He gave me a new EIR number to
   input for the dx cooling input, and he gave me a new fan power number.
   After inputting these manufacturer-provided data, this is when I really saw
   the drop in energy use in my proposed model---YAY!
   3. I attempted to input custom curves for the equipment, but I was under
   a time crunch and I couldn't get them to work, so I had to go with only the
   partial estimate of energy savings (without the effect of the
   part-load curves.)   If I could have taken more time to work on the specific
   curve data then I know I could have shown even more savings than what I was
   seeing with the two previous inputs.
   4. It is best to use the system type of "PVVT" (pkg vari vol & temp)
   system.  This system has a check box in eQuest to select *variable speed
   compressor.*  This option is not available in other system types which
   makes this system choice the best representation for a real-life VRV heat
   pump system.

I will also forward you a file of a presentation done a few years ago that
has some guidance info on how to perform VRV system inputs into eQuest.
This will help get you going on your analysis.

In my case I was happy that I could show a good chunck of energy savings
with only the first 2 inputs...at least I could show my client that "yes,
your choice for VRV systems will offer higher energy savings."   It was
better for me to be able to show some energy savings with my inputs as
opposed to not being able to demonstrate any savings because eQuest (and
other sim programs) cannot accurately perform simulations for VRV systems.
In this case, my client was happy (& content) with seeing 'some rather than
none.'   I just explained to them that there are limitations in simulation
software to do this, but a good educated "guesstimate" from eQuest was
better than nothing.

I don't think that you will be able to complete this analysis before your
meeting, but you can let your client know that you are working on the
analysis and this type of system is difficult to represent in our current
software packages available.

I know other simulators on this list have more experience with VRV systems
than I do, so maybe do a search in the eQuest archives for more discussions
on VRVs.


Hope this helps, good luck.

Pasha


On Wed, Oct 6, 2010 at 2:33 PM, Omar Katanani <omar at ecoconsulting.net>wrote:

>  Dear all,
>
>
>
> I have a meeting with the Mechanical engineers tomorrow, and one of the
> topics to be discussed is VRVs.
>
>
>
> The HVAC strategy was VAV for all the school, with FCU’s for 15 specified
> zones.
>
>
>
> An update to the design changed 4 of these 15 zones into a VRV system (I do
> not know why they decided on this!)
>
>
>
> So I must now model these zones with VRV systems.
>
>
>
> My urgent questions that may require further discussion with the Mechanical
> design engineers are:
>
>
>
>    1. I think I must know the performance curves of the VRV system.
>    However, the final choice of the VRV brand is not finalized, and I may need
>    to assume a typical performance curve. Any idea on which curve to use?
>    2. I have the EER of the VRV system to be 10. Where should I enter
>    this? Is it that I need to create a separate chiller for the VRVs with an
>    EER of 10?
>    3. What additional important input variables do I need from the design
>    team? (zone supply air flow rate, outdoor air flow rate)
>
>
>
> Many thanks for your kind help!
>
>
>
> Best regards,
>
> Omar
>
> ___________________________
>
> Omar Katanani
> Sustainable Design Engineer
>
> Email: omar at ecoconsulting.net
>
>
>
> EcoConsulting (Lebanon)
>
> Nahas Building, 4th floor
>
> 4 St-Maron Street / Georges Haddad Avenue
>
> Postal Code: 2028 5806 SAIFI
>
> Beirut, Lebanon
>
> Tel:          +961 (0) 1 971 266
> Mobile:    +961 (0) 3 045 045
>
>
>
> EcoConsulting (UK) Ltd
> 28 Marshalsea Road
> London, SE1 1HF
> Tel:  +44 (0) 207 939 0989
> Fax:  +44 (0) 207 939 0981
>
> Website: www.ecoconsulting.net
>
>
>
>
>
>
>
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