The popularity of LED and other innovative technologies for outdoor luminaires is driven by today’s focus on cost savings, energy savings and environmental sustainability. But if the outdoor luminaire fails prematurely, the costs of repair or replacement quickly offset any savings or other benefits that might have been realised. Multiple studies have shown that the root cause of premature failure in outdoor luminaires can often be traced to a failure to equalize pressures within the luminaire’s housing. Susan presented findings from a comparative study of vented and non-vented LED Roadway Streetlight housings. She discussed how luminaire longevity can be affected by the formation of condensation, the diffusion process, and the impact of factors such as temperature. As this study demonstrates, pressure differentials can compromise housing seals and joints, as well as other connection points within the LED lamp itself – which can reduce the longevity of the power-supply drivers and other electronics. Additional data, from a lifetime study of Protective Vents in outdoor enclosures, will further substantiate the benefits of venting enclosures to prevent premature failure of the sensitive electronics within. Talk by Susan Chambers, W.L. Gore & Associates (UK) Ltd

1. Vent to Prevent
How pressure equalization
prevents premature failure of
outdoor luminaires
Presented by: Susan Chambers
W L Gore & Associates UK Limited

2. Content:
• Basics of pressure equalization
• Preventing pressure differentials
• How condensation forms
• Diffusion process
• Comparative Study – LED Streetlight
- vented v’s non-vented
• Life time study results
• Conclusions

3. Causes of pressure differentials
Causes of pressure
fluctuations
Temperature changes
Heat generating internal
electronics / external weather
patterns – rain/sun/wind
Altitude changes
In transit or during use
Pressure fluctuation
Pressure build-up
Stress on seals
Compromised seals
Product failure

4. Protecting the electronics
Desiccants
+ Bind the relative humidity within the enclosure
- Cannot equalize pressure
Potting
+ Encapsulates electronics against contaminants
- Stresses electronics
- Prevents long-term maintenance or recycling
- Requires labour-intensive chemical processes
Tortuous paths or leak hole
+ Equalize pressure
- Typically cannot achieve required IP levels
Venting
+ Rapidly & continuously equalize pressure
+ Effectively reduce condensation
+ Block ingress of dust, dirt and water

5. ePTFE Membrane Properties
• Engineered with expanded PTFE
• Microporous structure
- Blocks liquid and particulates
- Allows air and vapor to flow freely
• Diffusion of corrosive gases

6. Pressure equalization

7. How does condensation form?
(thermodynamics)
In the case of sealed housings, it is important to note that humidity from the air can enter the
inside of the housing ;
- either by air inclusion during the production process
- and/or via the housing seal
- or during operation due to penetration through the housing plastic
What is condensation?
Condensation refers to the change of state of a substance from the gaseous to the liquid state
of matter caused by temperature differences. This process results in the formation of
condensation.

8. Plastic absorption rates
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Water Absorption (%wt)
Water Absorption for Various Plastics
(24 hrs ASTM D570)
Maximum
Minimum
2.8 Maximum

9. Effects of condensation
Without ventilation, the trapped condensation is not able to escape
and there is a risk of corrosion on the sensitive electronic components.
W. L. Gore & Associates
GORE Corrosion Test - exposure to temperature cycles
in combination with submersion under water.

10. How can this condensation be removed?

11. Diffusion: direction of water vapour
• Diffusion is a physical process which leads to an
even distribution of particles, and therefore the
complete mixing between two or more substances.
• Diffusion is based on the thermal proper motion of
water vapour particles.
• The diffusion direction of water vapour exclusively
depends on the absolute air humidity, and is always in
the direction from a high to a low concentration.
W. L. Gore & Associates

12. Moisture Diffusion – Small Opening
High Concentration Low Concentration
Rate

13. Moisture Diffusion – Large Opening
High Concentration Low Concentration
Rate

14. Comparative Study

15. IP66 Rated

16. Light Construction
One piece aluminum shell
Lens and LED
Latch door for pole installation
and wire connection
Water proof housing for LED
driver

17. Vented vs. Non Vented
• Temperature
• Pressure
• Relative Humidity

18. Thermal Shock Wash Down Cycle

19. Temperature
60
50
40
30
20
10
0
6/20 00:00 6/20 12:00 6/21 00:00 6/21 12:00 6/22 00:00 6/22 12:00 6/23 00:00
Date and Time
Temperature (°C)
Sealed Temp (°C)
Vented Temp (°C)
Ambient temp (°C)
Test # 1,
midday
Test # 2,
early morning
Test # 3 and 4,
midday

20. Pressure

21. Relative Humidity

22. Additional example:

23. Life Time Study
Gore® Protective Vents
1 2 3 4 5
European Alps

24. Differential Pressure
-150 -125 -100 -75 -50 -25 0 25 50 75 100 125 150
-150 -125 -100 -75 -50 -25 0 25 50 75 100 125 150
-150mbar< Box1 <131mbar
No Vent
-149mbar< Box2 <147mbar
No Vent
High differential pressure for the non-vented boxes
-150 -125 -100 -75 -50 -25 0 25 50 75 100 125 150 -150 -125 -100 -75 -50 -25 0 25 50 75 100 125 150 -150 -125 -100 -75 -50 -25 0 25 50 75 100 125 150
-30mbar< Box3 <30mbar
One Vent (side)
-4mbar< Box5 <4mbar
Two Vents (side)
-40mbar< Box4 <41mbar
One Vent (top)
Almost atmospheric conditions for the Gore® vented boxes

25. Visible results

26. Gore® Protective Vents reliability
Vent of Box 5 Vent of Box 5 New Vent
Airflow @ 70mbar
[ml/min] 320 340 400
WEP
@ [0,6 bar/60s] OK OK OK
Membrane after 5 years
in outdoor use
Product after 5 years
in outdoor use
(No UV degradation) (No UV degradation)
Gore® Protective Vents are still functioning after many years
in outdoor use!

27. Conclusion
• Pressure differentials, caused by temperature changes,
compromise the housing seals.
• Vacuum occurs reducing long-term performance.
• Condensation build up decreases light efficiency.
• Integration of an ePTFE vent equalizes pressure,
allowing continuous airflow, reducing condensation.

28. Thank you
FOR INDUSTRIAL USE ONLY.
Not for use in food, drug, cosmetic or
medical device manufacturing,
processing, or packaging operations
For further information:
Web: www.gore.com/protectivevents
Email: protectivevents_uk@wlgore.com