HUB whitepaper Daikin-VRV-2P
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Daikin VRV Two Pipe White Paper June 2019 of 1 10 automation White Paper Daikin VRV Two Pipe
Transcript of HUB whitepaper Daikin-VRV-2P
Daikin VRV Two Pipe White Paper June 2019 of 1 10
automationWhite Paper Daikin VRV Two Pipe
How to Improve Thermal Comfort in Buildings using Daikin VRV Two Pipe Systems
Daikin VRV Two Pipe White Paper June 2019 of 2 10
Introduction
Heat Recovery VRV system designs using design tools such as computational fluid dynamics modelling is the gold standard for providing thermal comfort in buildings where a design requires more than a single thermal zone. Unfortunately budget restrictions often result in a pragmatic approach where a level of thermal comfort across a larger number of rooms is more desirable than a high level of thermal comfort in a lower number of rooms. Often Daikin VRV two pipe systems are implemented in designs that have budget restrictions.
This White Paper evaluates how changes to the control strategy of a Daikin VRV two pipe system can improve comfort outcomes and shift the performance closer to a three pipe system with minimal impact on the project budget.
Assessing Thermal Comfort
Thermal comfort is vital at home, at school, as well as at the office. Designing an air conditioning system that provides the best possible thermal comfort outcome for the nominated budget has always been a challenge for HVAC professionals. To evaluate how a change in control strategy can improve the comfort outcome for a Daikin VRV two pipe system, first we have to understand the parameters that impact on thermal comfort.
1. Ambient temperature (room temperature)2. Relative humidity (RH)3. Air movement4. Air quality5. Mean radiant temperature
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The Science of Compromise
This White Paper examines how a HUB Automation proprietary control strategy can impact on the performance gap between designs utilising Daikin VRV two pipe systems in place of heat recovery VRV. At the time of publication of this white paper, data was not available on the performance of heat recovery VRV within the buildings that make up the case study.
The case study was completed on an existing school with many years of operation using Daikin VRV two pipe systems. Daikin VRV two pipe was selected to allow the school to provide some comfort to more blocks, more students and more teachers within the budget restrictions compared with Daikin VRV heat recovery.
Additional features such as fault harvesting and notification, real time cloud and local system diagnostics, after hours run timer, whole of site graphical user interface, and improved energy performance were included in the control system upgrade but do not form part of the evaluation process for thermal comfort enhancement.
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Daikin VRV Mode Master - Strategy
Daikin VRV two pipe systems utilise the same series of room controllers as one-plus-one split units and VRV heat recovery. This creates a problem for the Daikin control strategy in that all indoor units connected to a two pipe outdoor unit must share the same operating mode. Part of the initialisation and commissioning procedure is for an indoor unit to be designated as a “Mode Master”. The designated mode master indoor unit then dictates the operating mode of the outdoor unit and all other indoor units.
Inadequacies - Daikin VRV Mode Master Control Strategy
A significant shortfall of the “Mode Master” approach to selecting the most appropriate operating mode of the outdoor unit is that a single thermal zone determines the operation of all thermal zones. The ratio of perimeter walls to floor area, the aspect and size of windows, the changing number of people or their activity level within non-master thermal zones are excluded from the mode selection algorithm.
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Solution - Daikin VRV Mode Master
By removing system wide mode selection from the Daikin internal control strategy a more sophisticated approach can be adopted. Each individual thermal zone can generate a cooling and a heating demand. Individual indoor unit capacities are included in the set up process of the controller allowing the control system to correctly identify the demand in kW for each thermal zone. The demand can then be aggregated and a mode selected based on a contribution from all thermal zones.
Daikin VRV - Hunting and Overshooting
Daikin VRV two pipe systems continue to provide corrective action for an additional 0.5℃ after the temperature error is corrected. By shifting the setpoint for each thermal zone to the end of the proportional band the need for a wide deadband is removed for all thermal zones. This adjustment is required to achieve proportional system wide mode selection. Failing to implement this component of the control strategy results in hunting and overshoot.
Case Study: Sheldon College, Brisbane, Queensland, Australia 4157
Block ID Thermal Zones
System kW
Main System Type Other System Types Notes
AS 4 50 Daikin VRV 2P None
JA 6 79 Daikin VRV 2P None
JB 6 79 Daikin VRV 2P None
JC 7 101 Daikin VRV 2P None
JD 7 79 Daikin VRV 2P None
JE 6 79 Daikin VRV 2P None
MA 3 72 Daikin VRV 2P 1 x Actron
MB 12 79 Daikin VRV 2P None
MC 8 56 Daikin VRV 2P None
MD 10 45 Daikin VRV 2P None
PA 3 39 Daikin VRV 2P 2 x Daikin Multi
SA & SB 12 125 Daikin VRV 2P None Daikin iTouch with ClimateHub
SC 8 73 Daikin VRV 2P None Daikin iTouch with ClimateHub
SLC 9 190 Daikin VRV 2P 3 x Actron
SI 2 40 Daikin VRV 2P None
Stadium 1 240 Dunn Air None Event and sports mode included
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Scope of Study
Sheldon College has a series of existing blocks that are mostly serviced by Daikin VRV two pipe systems. A small percentage of blocks had other systems from multiple manufacturers. After a consultation period the following objectives were confirmed:1. Improve thermal comfort in thermal zones not designated as Mode
Master.2. Automate the system mode change over so that the maintenance team
does not have to attend the block to make changes manually.3. Provide an after hours run function so that systems are not inadvertently
left running for long periods.4. Provide a graphical user interface at network level so that the college
administration and maintenance teams could observe and evaluate system performance.
Equipment Schedule
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Site Plan
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Typical Block Control System Parts List (SB)
Item Description Item Code Manufacturer Qty Approximate Cost
ClimateHUB CH-VRT-D3NET HUB AUTOMATION 1 AU$600.00
D3NET Gateway DTA116A51 DAIKIN 1 AU$350.00
After Hours Switch Daikin BRC used to activate after-hours timer N/A
Installation Cost Not provided by HVAC Contractor N/A
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Typical Block (SB)
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Control System Network Architecture
Each ClimateHub includes field level expansion to the VRV communication gateways, smart sensors, touchpads, touchscreens, after hours switches and other digital or analogue expansion as required.
ClimateHub’s include a unique system for automatically configuring a network level human machine interface that links all HUB Automation products together as a central control and/or performance diagnostic point.
Unlike many BMS or BAS systems connecting between blocks does not require an independent BMS LAN line, on this case study the school IT department provided a switch port ID and a fixed IP address at each block.
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Case Study Conclusion
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Overview of Findings
• Trend point data clearly shows a dramatic decrease in temperature error in all non-mode master thermal zones.
• Trend point data shows no significant difference in mode master thermal zones if the system mode is set to cooling or heating. When compared with the Daikin automatic mode changeover setting the trend data clearly showed a decrease in temperature error.
• Reported thermal comfort dissatisfaction reduces considerably for all blocks.
• Labour hours were saved by the maintenance team each week due to the mode selection being automated, the after hours timer switching systems off automatically and the fault notification being sent to the HVAC contractor often before thermal comfort was disrupted.
More Detailed Analysis
A complete report detailing the actual data is available on request. It is required by the school that permission is granted to access real data and or live viewing of the school network level interface. A NDA and a Use Agreement needs to be signed and approved by Sheldon College prior to distribution.
Applications for higher level data should be made to: [email protected]
