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I am modeling a multifamily residential building where one of the energy savings measures will be low flow plumbing, which reduces hot water usage. How can I model the energy impact of these fixtures in Sketchbox?

The easiest way to model destratification fans in Sketchbox is to simulate the energy savings impact they have on the he

How can I model low flow plumbing fixtures in Sketchbox? I am modeling a multifamily residential building where one of t

Thanks Scott, I checked the unmet hours for both cases and they are more or less the same:

22 hours in heating, 150 hours in cooling for PTHP; 25 hours in heating, 167 hours in cooling for VRF.

Thanks David, I looked in the error file and one warning I'm getting for the VRF is:

Warning ** AirConditioner:VariableRefrigerantFlow "VRF SYSTEM" -- Exceeded VRF Heat Recovery min/max outdoor temperature limit error. VRF Heat Pump Min/Max Outdoor Temperature in Heat Recovery Mode Limits have been exceeded and VRF heat recovery is disabled.

I've tried expanding the range of the min/max outdoor temperature for the heat recovery mode but I'm still getting this error.

I'm having an increase of energy mainly in heating, a little bit in cooling and some in fan energy.

Hello,

I'm trying to compare the energy use between a VRF system and a PTHP system in EnergyPlus. Both systems have a DOAS to supply outdoor air (efficiencies of the DOAS are the same, OA rates are the same), and all other parameters are the same. The VRF and PTHP system have the same rated efficiencies: cooling COP 3.3, heating COP 3.5. Capacities and supply air flow are being autosized. Both systems' fan mode is cycling. Other parameters are using the default values in OpenStudio.

I'm getting higher energy use in the VRF model, and I'm not sure what the reason is to that... any insight would be greatly appreciated.

Thanks Tina

Thanks Michael and Kyle, that definitely cleared things up for me. I appreciate both of you taking the time to answer my questions!

Hmm I don't have an economizer in my model and the HVAC operation is set to "Always On"... One thing that was interesting though - I tried putting in zeros in the design OA specs for each space type and now the "minimum OA schedule" method works - during night time OA can be lowered to 0 cfm, and during occupied hours it is what I specified in the OA controller under the systems tab. Not sure why this is since the design OA specs are only used for system sizing and not actual operations...

I just did a quick test run and saw that even with the min OA sch set to 0 during unoccupied hours the zone mech ventilation standard density flow rate does not entirely drop to 0 (screenshot link below). link text

Any thought on this?

Thanks!

Will setting the "Minimum Outdoor Air Schedule" to 0 during unoccupied hours and using a hard sized OA flow rate be the same effect as setting the "Maximum fraction of outdoor air schedule" to 0 during unoccupied hours?

Thanks Kyle, the link was very helpful. So even if I put in a hard sized number in the OA controller fields, it will get overridden by the design OA specs in each space type, correct? If I would like to have OA turned off during unoccupied hours, do I assign the OA schedule to the OS:Controller:OutdoorAir object, or put it under the design OA specs object?

Many thanks!

Hello,

I am relatively new to Openstudio/Energyplus and have run into some problems recently:

I am trying to specify the OA flow rate under the systems tab in OpenStudio, but when I run the model the results show that the zone mechanical ventilation current density flow rate does not match what I specify. I have put in cfm numbers for minimum outdoor air flow rate and maximum outdoor air flow rate under the OS:Controller:OutdoorAir object. Is there another control switch that I have to turn on to hard size the OA flow rate?

Thank you in advance.