Where can we find the Minimum Requirement System Efficiency of a VRV System?in ASHRAE 90.1?
Which of those systems mentioned in the ASHRAE 90.1 can we use to compare such equipment?
Well, there seems to be no ARI standard for testing VRV yet. So, you won't
find it in 90.1.
The closest you can get is packaged single zone (match cooling capacity) i
believe but you'll have to figure out a way of modelling the fresh air side-
as DOAS or others.
Thanks
Shubhra Kothari
Here's another opinion (non-authoritative): I believe the VRV efficiency requirements would match best with the "air cooled, cooling and heating modes" requirements in Table 6.8.1B (for heat pumps). In the ECB method, this would most likely be system 8, Packaged terminal heat pumps. I agree that the ventilation should be modeled separately as a DOAS.
I agree with Larry. There is no exact system specified in the ASHRAE 90.1 that
matches the VRV system. We used to model the VRV system using the efficiencies
in Table 6.8.1B, however note that these efficiencies are typically for full
load operations, hence it will not capture the advantage of the part load
capability of the VRV systems. I.e. to say, the savings calculated as such
will be typically conservative.
Also note that VRV systems are generally waived from the DOE test procedure
applicable to commercial package air-cooled central air conditioners and heat
pumps (2 systems that I know of are the Mitsubishi City-Multi and Sanyo
VRV-III systems) although they have to comply with the alternate testing
procedure. So just take note of the system efficiencies used for the modeling.
Gavin is correct that modeling VRV systems as heat pumps will not
demonstrate efficiencies related to part load operation. Additionally,
efficiencies related to heat reclaim during periods of the year when
applicable will not be captured in the model. Energy Pro, by
Energysoft, is the only software I am aware of that has the appropriate
algorithms programmed to provide accurate simulations. Energy Pro is a
front end software package for DOE-2 simulation. We have used it on
several occasions to demonstrate anticipated energy savings.
I understand that ventilation is modeled separately as DOAS, or dummy
outdoor air system for certain hybrid strategies, but would anyone have a
good idea of why dummy zones are modeled, from a building physics
perspective? Thank you.
Well, there seems to be no ARI standard for testing VRV yet. So, you won't
find it in 90.1.
The closest you can get is packaged single zone (match cooling capacity) i
believe but you'll have to figure out a way of modelling the fresh air side-
as DOAS or others.
Thanks
Shubhra Kothari
Here's another opinion (non-authoritative): I believe the VRV efficiency requirements would match best with the "air cooled, cooling and heating modes" requirements in Table 6.8.1B (for heat pumps). In the ECB method, this would most likely be system 8, Packaged terminal heat pumps. I agree that the ventilation should be modeled separately as a DOAS.
Larry O. Degelman, P.E.
I agree with Larry. There is no exact system specified in the ASHRAE 90.1 that
matches the VRV system. We used to model the VRV system using the efficiencies
in Table 6.8.1B, however note that these efficiencies are typically for full
load operations, hence it will not capture the advantage of the part load
capability of the VRV systems. I.e. to say, the savings calculated as such
will be typically conservative.
Also note that VRV systems are generally waived from the DOE test procedure
applicable to commercial package air-cooled central air conditioners and heat
pumps (2 systems that I know of are the Mitsubishi City-Multi and Sanyo
VRV-III systems) although they have to comply with the alternate testing
procedure. So just take note of the system efficiencies used for the modeling.
Gavin Gui
Gavin is correct that modeling VRV systems as heat pumps will not
demonstrate efficiencies related to part load operation. Additionally,
efficiencies related to heat reclaim during periods of the year when
applicable will not be captured in the model. Energy Pro, by
Energysoft, is the only software I am aware of that has the appropriate
algorithms programmed to provide accurate simulations. Energy Pro is a
front end software package for DOE-2 simulation. We have used it on
several occasions to demonstrate anticipated energy savings.
TIM REYNOLDS, P.E., LEED AP
I understand that ventilation is modeled separately as DOAS, or dummy
outdoor air system for certain hybrid strategies, but would anyone have a
good idea of why dummy zones are modeled, from a building physics
perspective? Thank you.