Re: [EnergyPlus_Support] VRF Min/Max Operating Temperatures

["Jim Dirkes jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx>]

Steve,

VRF systems have more curves than Heinz has varieties of ketchup :) Are you referring to the indoor units or outdoor?

The outdoor units have curves dependent on the INDOOR wet bulb and OUTDOOR dry bulb. The outdoor unit min / max temps are almost certainly based on dry bulb, especially for the heating season when wet bulb and dry bulb are similar.

You might want to post this on the UnmetHours forum; Richard Raustad is the expert on these systems for EnergyPlus and I'm pretty sure he participates frequently there.

p.s., The wild card here would be if you had an evaporatively cooled outdoor unit ... but you probably would have mentioned that.

On Wed, Jun 1, 2016 at 8:43 AM, ssnyder3415@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

 

Hi All,

I'm modeling an air-cooled VRF system with custom performance curves developed from manufacturer's data. For the cooling mode, the outdoor air temperature data is dry-bulb. For the heating mode, the outdoor air temperature data is wet-bulb. I'm assuming that the minimum/maximum outdoor temperature fields should agree with the range of temperatures used to build the performance curves to prevent extrapolation. 

For the min/max temperatures in cooling mode, I've entered in the min/max dry-bulb temperatures from the performance data. (The Input/Output Reference specifically says "dry-bulb temperature").

For the min/max temperatures in heating mode, should I put in the min/max wet-bulb temperatures from the performance data? The Input/Output Reference just says "temperature". 

For heat recovery mode, the Input/Output Reference says the min/max temperatures should be dry-bulb temperatures that do not exceed the smaller range from the heating and cooling min/max values. This leads me to believe that the heating mode values should also be dry-bulb. Correct?

Thanks for any clarifications!

Best,
Steve Snyder

--

James V Dirkes II, PE, BEMP, LEED AP
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The Building Performance Team Inc.
1631 Acacia Dr, GR, Mi 49504

Direct: 616.450.8653
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Posted by: Jim Dirkes <jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx>

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