cpd/vrf presentation

1Optimising VRF Design for Energy Efficiency

An LG Electronics Presentationby

Graham Hendra

Duration 1 hour

1Great Company Great People LG Electronics

Designing VRF Systems

2Positioning of Outdoor Units

Airflow around the outdoor units is a primary concern. Reducing airflow greatly reduces efficiency, and therefore increases energy consumption.

Airflow around the outdoor units is a primary concern. Reducing airflow greatly reduces efficiency, and therefore increases energy consumption.

Positioning near other heat sources (such as other outdoor units) can also have a similar effect

Positioning near other heat sources (such as other outdoor units) can also have a similar effect

Positioning of Outdoor Units

3Graph showing effect of high outdoor temperature on cooling efficiency. Temperature increase = efficiency decrease!

Graph showing effect of high outdoor temperature on cooling efficiency. Temperature increase = efficiency decrease!

Cooling EER (Energy Efficiency Ratio)

w hat effect OD temperature has on efficency 130% connection cooling ARUN100LT2

3.50

4.00

4.50

5.00

5.50

6.00

6.50

20 22 24 26 28 30 32 34 36 38 40

w hat effect OD temperature has on efficency 130% connection cooling ARUN100LT2

3.50

4.00

4.50

5.00

5.50

6.00

6.50

20 22 24 26 28 30 32 34 36 38 40

Graph showing effect of low outdoor temperature on heating efficiency. Temperature decrease = efficiency decrease!

Graph showing effect of low outdoor temperature on heating efficiency. Temperature decrease = efficiency decrease!

Heating COP (Co-Efficient of Performance)

w hat effect OD temperature has on efficency 130% connection Heating ARUN100L2

2.50

3.00

3.50

4.00

4.50

5.00

5.50

6.00

-20 -15 -10 -5 0 5 10 15

w hat effect OD temperature has on efficency 130% connection Heating ARUN100L2

2.50

3.00

3.50

4.00

4.50

5.00

5.50

6.00

-20 -15 -10 -5 0 5 10 15

4Heating Mode High Load

Comp

30 bar, 50C

6 bar, -4C

Compression Ratio 5:1

Indoor temp 23 COutdoor temp 3 C

Heating Mode Low Load

Comp

30 bar, 50C

10 bar, 9C

Compression Ratio 3:1

Indoor temp 23 COutdoor temp 13 C

5Air Flow Restrictions

These examples show units working at low efficiency due to poor outdoor unit positioning. This type of installation can increase energy consumption by as much as 30%.

These examples show units working at low efficiency due to poor outdoor unit positioning. This type of installation can increase energy consumption by as much as 30%.

Three phase, heat pump and heat recovery.Three phase, heat pump and heat recovery.

Outdoor Units

730m

m

1607m

m

1280mm730m

m

809mm

1607m

m

Sizes 5 and 6 HpSizes 5 and 6 Hp Sizes 8 to 16 HpSizes 8 to 16 Hp

6Single phase, heat pump only.Single phase, heat pump only.

Outdoor Unit

Sizes 4, 5 and 6 HpSizes 4, 5 and 6 Hp

330mm950mm

1380m

m

What to do when Outdoor Unit Visibility is an Issue

Where planning permission and aesthetics are concerns innovative solutions must be used.

Where planning permission and aesthetics are concerns innovative solutions must be used.

Mounting outdoor units inside can be difficult unless they are designed for this application.

Mounting outdoor units inside can be difficult unless they are designed for this application.

And watch out for recirculation and inadequate airflow because it will cost you money.

And watch out for recirculation and inadequate airflow because it will cost you money.

7Size 8 HpSize 8 Hp Size 10 HpSize 10 Hp

Three phase, heat pump only.Three phase, heat pump only.

Internally Mounted VRF Outdoor Units:

495mm750mm

1790m

m

650mm 750mm

1790

mm

*Available 2009

Fan Design

Specially designed, powerful sirocco fan

Specially designed, powerful sirocco fan

8Mount them Inside?

With 120Pa E.S.P. this unit can be hidden inside a plant room, and exhaust air is not compromised.

With 120Pa E.S.P. this unit can be hidden inside a plant room, and exhaust air is not compromised.

Excellent acoustic properties mean that noise inside the building is minimised.

Excellent acoustic properties mean that noise inside the building is minimised.

No thermal carry over from one system to the next.No thermal carry over from one system to the next.

All access is from inside the building, so no health and safety issues during service and maintenance.

All access is from inside the building, so no health and safety issues during service and maintenance.

Short pipe runs possible so outdoor units can be close to the indoor units.Short pipe runs possible so outdoor units can be close to the indoor units.

This building is one of four which have a total of 1750 LG Multi V Space VRF systems, serving a total of 7000 indoor units. Can you spot the outdoor units?LG Multi V Space II: The ONLY VRF outdoor unit designed specifically for indoor location

9Optimising VRF Design for Energy Efficiency

Diversity

Capacity Reduction Explained

It is generally believed that VRF systems with more than 100% connection ratios, will not be able to adequately serve all of the indoor units if they are all running flat out

It is generally believed that VRF systems with more than 100% connection ratios, will not be able to adequately serve all of the indoor units if they are all running flat out

This is not true in cooling operation, but is true in heating operation.This is not true in cooling operation, but is true in heating operation.

10

Diversity

Capacity vs Connection Index

10

15

20

25

30

35

40

50 60 70 80 90 100 110 120 130Connection Ratio

Capa

cit k

W

Cooling Heating

Capacity vs Connection Index

10

15

20

25

30

35

40

50 60 70 80 90 100 110 120 130Connection Ratio

Capa

cit k

W

Cooling Heating

You can see here that this 10hp Multi V II system can easily cope with 130% connection with no capacity drop. This means if only 100%

connection is used the system will never run flat out.

You can see here that this 10hp Multi V II system can easily cope with 130% connection with no capacity drop. This means if only 100%

connection is used the system will never run flat out.

A relatively Small effect in HeatingA relatively Small effect in Heating

How does Diversity Affect Efficiency: Heating

the ef fect on COP of loading on the unit at 0C OD and 21C indoor ARUN100LT2

3.95

4.00

4.05

4.10

50 60 70 80 90 100 110 120 130

the ef fect on COP of loading on the unit at 0C OD and 21C indoor ARUN100LT2

3.95

4.00

4.05

4.10

50 60 70 80 90 100 110 120 130

11

How does Diversity Affect Efficiency: Cooling

the ef fect on EER of loading on the unitat 30db OD and 23w b 16 db indoor cooling ARUN100LT2

4.00

4.30

4.60

4.90

5.20

5.50

5.80

50 60 70 80 90 100 110 120 130

the ef fect on EER of loading on the unitat 30db OD and 23w b 16 db indoor cooling ARUN100LT2

4.00

4.30

4.60

4.90

5.20

5.50

5.80

50 60 70 80 90 100 110 120 130

More pronounced in cooling this is because as the load rises the relative size of the heat exchanger falls pushing the heat exchanger temperature

higher making it less efficient.

More pronounced in cooling this is because as the load rises the relative size of the heat exchanger falls pushing the heat exchanger temperature

higher making it less efficient.

So what can you do..?

If you want pure energy efficiency keep the connection ratio low, BUT you also have to ask How often will all of the capacity be required?.

If you want pure energy efficiency keep the connection ratio low, BUT you also have to ask How often will all of the capacity be required?.

Installing larger outdoor units is efficient, but initially more costly.Installing larger outdoor units is efficient, but initially more costly.

12

Optimising VRF Design for Energy Efficiency

Can we re-use the heat inside the building?

Problems with DX Systems.

In summer all the unwanted heat from the building is discarded outside, and in winter we have to bring that heat back in again. There is little that we can do about this, however in Spring and Autumn we may be able to recycle some of this waste heat..

In summer all the unwanted heat from the building is discarded outside, and in winter we have to bring that heat back in again. There is little that we can do about this, however in Spring and Autumn we may be able to recycle some of this waste heat..

13

Heat Pump at Midday in Spring

All Cooling

All HeatingNorth

Heat rejected

here

Heat rejected

here

Heat re-claimed

here

Heat re-claimed

here

Is this sensible..? No, but it would mean cheaper installed costs. Is this sensible..? No, but it would mean cheaper installed costs.

What are HR Boxes?

Using a 3 pipe system with Heat Recovery boxes, heat from 1 room requiring cooling can be re-used in another room which requires heating.

Using a 3 pipe system with Heat Recovery boxes, heat from 1 room requiring cooling can be re-used in another room which requires heating.

HR boxes are installed between the indoor units and the outdoor unit.HR boxes are installed between the indoor units and the outdoor unit.

An HR Box is used to control the modes (Cooling or Heating) of all the indoor units connected to it.

An HR Box is used to control the modes (Cooling or Heating) of all the indoor units connected to it.

14

Heat Recovery at Midday in Spring

North

All Cooling

All Heating

Heat re-claimed

here

Heat re-claimed

here

Heat rejected

here

Heat rejected

here

Is this sensible..? Yes, but it is more expensive to install and purchase.

Is this sensible..? Yes, but it is more expensive to install and purchase.

Less or no heat rejection

Less or no heat rejection

Payback Time for Heat Recovery System

If we assume a 3 pipe system runs 33% in cooling and 33% in heating, it has no advantage over a heat pump system, as it has to pay for itself in the last 33% of its operation.

If we assume a 3 pipe system runs 33% in cooling and 33% in heating, it has no advantage over a heat pump system, as it has to pay for itself in the last 33% of its operation.

A 30kW VRF system in an office with an area of 250m costs 1500 per year to run. 500 for cooling, 500 for heating, and 500 for heat recovery.

A 30kW VRF system in an office with an area of 250m costs 1500 per year to run. 500 for cooling, 500 for heating, and 500 for heat recovery.

If we assume that heat recovery is being used 100% of the time, then the run cost will be reduced by just 250 per year.

If we assume that heat recovery is being used 100% of the time, then the run cost will be reduced by just 250 per year.

The installed cost of a VRF system is 125 per m for 2 pipe system and 155 per m for 3 pipe system So a 3 pipe system costs 7000 more to install.

The installed cost of a VRF system is 125 per m for 2 pipe system and 155 per m for 3 pipe system So a 3 pipe system costs 7000 more to install.

It will take the system 7000 250 = 28 years to pay back.It will take the system 7000 250 = 28 years to pay back.

15


The effect of field piping lengths on indoor unit capacity

Longer Field Piping

50m

15m

16

Pumping Losses

Although huge pipe lengths are possible, to realise the efficiency of the indoor units falls with pipe length and with level difference between indoor and outdoor units a 150m pipe length will reduce the indoor unit capacity by up to 77% of rated.

Although huge pipe lengths are possible, to realise the efficiency of the indoor units falls with pipe length and with level difference between indoor and outdoor units a 150m pipe length will reduce the indoor unit capacity by up to 77% of rated.

Rates of change in cooling capacity:Rates of change in cooling capacity:

Why Such Losses?

8.5 bar here = 5C8.5 bar

here = 5C

9 bar here = 7C

9 bar here = 7C

10 bar here = 10C

10 bar here = 10C

Air temp = 23C t = 16 CAir temp = 23C t = 16 C Air temp = 23C t = 13 CAir temp = 23C t = 13 C

All VRF indoor units are sized and rated with 7.5m pipe runs (check this in any catalogue). This is due to no pressure losses at 7.5m.

All VRF indoor units are sized and rated with 7.5m pipe runs (check this in any catalogue). This is due to no pressure losses at 7.5m.

17

Pipe Size Increase to Increase Indoor Unit Efficiencies

Main Pipe Sizes

1 3/87/826-34

1 3/83/424

1 5/87/836-40

1 3/83/418-22

1 3/85/816

1 1/85/812-14

1 1/81/210

7/81/28

7/83/86

3/43/85

GasLiquidHpIf the pipe run from the outdoor unit to the furthest indoor unit exceeds 90m, you can reduce pressure losses by increasing the main pipe sizes as per this table.

If the pipe run from the outdoor unit to the furthest indoor unit exceeds 90m, you can reduce pressure losses by increasing the main pipe sizes as per this table.

The effect will be to halve the pressure losses therefore giving up to 10% better performance.

The effect will be to halve the pressure losses therefore giving up to 10% better performance.

Interestingly this is almost never done on site.

Interestingly this is almost never done on site.


Controls

18

Advantages of Using Controls to Save Energy

Controls is the area where enormous savings can be madeControls is the area where enormous savings can be made

It is possible to operate the system to limit the minimum and maximum building temperatures, protecting the fabric of the building at minimum cost.

It is possible to operate the system to limit the minimum and maximum building temperatures, protecting the fabric of the building at minimum cost.

Temperature limit functions can be set on a unit by unit basis (i.e. 20-23C), to prevent units being run at unreasonable set points.

Temperature limit functions can be set on a unit by unit basis (i.e. 20-23C), to prevent units being run at unreasonable set points.

Time clocks can be set with a final unit off time, to prevent indoor units from running all night (if able to be operated locally).

Time clocks can be set with a final unit off time, to prevent indoor units from running all night (if able to be operated locally).

Every indoor unit can be monitored to see how much energy it uses.Every indoor unit can be monitored to see how much energy it uses.

New Central Controller

A suite of controls is available from simple wall controllers through to touch screen central controllers, PC based controllers, and BMS interface options.When set-up well, these controllers can ensure that the systems operate efficiently and effectively.

A suite of controls is available from simple wall controllers through to touch screen central controllers, PC based controllers, and BMS interface options.When set-up well, these controllers can ensure that the systems operate efficiently and effectively.

19

Wet Systems and Ventilation

It is quite common for wet systems to be installed to heat buildings and VRF systems installed to cool them.

It is quite common for wet systems to be installed to heat buildings and VRF systems installed to cool them.

It is essential that if this is done the controls are inter-linked to make sure the systems don't fight each other.

It is essential that if this is done the controls are inter-linked to make sure the systems don't fight each other.

Ventilation systems are similar. They should only run when the area is occupied, and again they should be inter-linked to the VRF controls.

Ventilation systems are similar. They should only run when the area is occupied, and again they should be inter-linked to the VRF controls.

Both are easily achieved but rarely done, as designers and installers are not always aware of these functions.

Both are easily achieved but rarely done, as designers and installers are not always aware of these functions.

Heat Reclaim using Water Cooled VRF

25C

30C

25C

20C

25C

Heat rejectionHeat

rejection

Heat input

Heat input

Using a common water loop, heat from one part of the building can be pumped to another

part where it is needed.

Using a common water loop, heat from one part of the building can be pumped to another

part where it is needed.

Using water instead of Air as the heat transfer medium it is possible to easily recapture any waste heat available and to move it around the building easily.

Using water instead of Air as the heat transfer medium it is possible to easily recapture any waste heat available and to move it around the building easily.

20

Using Waste Heat Sources

Waste Heat:If the Water cooled system is being installed into an area with any waste heat this can be harnessed using heat exchangers, for example waste heat from industrial processes.

Waste Heat:If the Water cooled system is being installed into an area with any waste heat this can be harnessed using heat exchangers, for example waste heat from industrial processes.

Ground Source:Heat can be extracted from the ground, if bore holes are sunk into the ground heat can be removed using water as the heat transfer medium. Permission from the appropriate authorities will be required to do this.

Ground Source:Heat can be extracted from the ground, if bore holes are sunk into the ground heat can be removed using water as the heat transfer medium. Permission from the appropriate authorities will be required to do this.


Designing VRF systems easily and efficiently.

21

software

Designing VRF using free software is easy in either a graphical or CAD format but

Designing VRF using free software is easy in either a graphical or CAD format but

The software will only tell you the capacity of the indoor units once the system has been designed. It will not tell you how to increase efficiency or capacity. You have to bear this in mind at design stage.

The software will only tell you the capacity of the indoor units once the system has been designed. It will not tell you how to increase efficiency or capacity. You have to bear this in mind at design stage.

Software CAD Screen Shot

CAD drawing showing icons of room load, indoor units, outdoor unit, and Y-branches/headers

22

Software CAD Screen Shot

Designing VRF Systems Conclusion

Keep the field piping as short as possible.Keep the field piping as short as possible.

Keep diversity % down.Keep diversity % down.

Let the outdoor units breath.Let the outdoor units breath.

Make full use of the sophisticated controls on offer, and advise how best to set-up and use these up on site.

Make full use of the sophisticated controls on offer, and advise how best to set-up and use these up on site.

Do all of this, and the customer could reduce energy consumptionconsiderably, thus reducing their energy bills.

Do all of this, and the customer could reduce energy consumptionconsiderably, thus reducing their energy bills.

23

The End

Thanks for your attention.

Questions

45Great Company Great People LG Electronics

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