Onsite Issues Regarding Product Ta Rating

March 6, 2017

 

This weeks blog looks at onsite issues regarding product Ta rating and onsite reliability.

 

It may seem straightforward to select a product with a suitable Ta rating for a particular site – however the following problems can occur:

 

A . the manufacturer/supplier competitively overstates the Ta rating of a product [ as they are using  the drivers spec, sheet instead of the products thermal test results- possibly for 110V use!]- or they take the Ta rating of the driver ,but forget the driver is mounted in an additional  sealed compartment [and not in free air]- the result can be a 10C to 20C reduction in the products expected Ta rating.

 

B. light plan designers ,rely on information given regarding the highest expected onsite temperatures on the hottest day of the year – however ,if this information does not come from a measured source,

 but is guessed/estimated - it can cause errors/onsite failures.

 

C . Maintenance/cleaning schedules for the fittings are not sufficient [ as dust/dirt/moisture levels and type of dust/oil /grease vary with each type of manufacturing process ] – it is very hard to say how much dust will build up [ the factory may even change the materials/processes  used ]

While recommendations are given – they cannot cover all circumstances.

 

D. if onsite voltage supply is low – the lowered voltage will result in an increase of current consumptions [ to achieve the same wattage ]- the increase current running through the wires/copper PCB tracks can increase the internally generated heat generated by the driver ,which then lowers the products Ta .

 

E . The onsite service personnel are not used to new technologies  - Please note : all electronic power supplies require a heat sink!  if the heatsink is dirty the fitting will overheat/fail [ unlike old technologies- such as magnetic ballasts] .

If the user thinks the new LED based goods should have the same thermal handling as magnetic ballast HID lamps – they may neglect required cleaning regimes. It is However a matter of common sense – it’s just the same as never maintaining  a car engine while expecting to work for its intended warranty- and then being suppressed when the engine overheats!

 

F . A misunderstanding when requesting max, onsite temperatures – if the site owner uses ground level readings ,the temperature at ceiling height [or in a ceiling cavity] will be higher –  or ,if heat generating equipment [ such as ovens/furnaces]is used onsite ,the hot columns of air below fittings- will push the air temperature around the fitting  well above the expected average for the site!

 

G .A possible combination of errors from points A/B/C/E/ and F! [ this can make fault cause investigation very difficult/complex- with the potential for it turning into a blame game ]

 

It is for this reason that design engineers incorporate a degree of headroom [ however some don’t]- though ,we would never advise assuming a product has built in Ta headroom .

At MGLites ,we are aware that  products from a range of differing wattages ,may not have the same Ta rating [ despite being advertised as being so]  - each differing wattage model may have a differing amount of head room , so you might find that there is one wattage model that may not have any headroom [ which when combined with the points above – could cause onsite problems ]    

 

Sometimes a product may have its life span reduced ,after being subjected to one day of high ambient summer temperatures – as this can reduce the capacitors lifespan greatly. The product could then go onto fail in winter, and with no record of onsite temperatures  - the installer is left to believe ,the fault was not caused by a Ta problem [ the danger being that the real problem has not been identified/addressed and could occur again]

 

Our advice to installers ,is to allow for a degree of onsite error ,and to take into account excessive onsite dust build up levels [ and recommended a reasonable cleaning schedule]

It is good practise to make sure all the  data comes from a reliable/accurate source - to minimise assumptions and compounded errors.

 

Best regards

Keith   

      

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