what discharge lighting factor to use for hf flurry luminaires?

[marconi]

I have been helping out a fellow with his lockdown assignments. One of the questions was about design. There were 60 or so high frequency electronic flurry luminaires each being 58W. The question was to work out the design current.

In the feedback on his first attempt his tutor said he had not taken into account the discharge lighting correction factor which indeed he had not. The question did not tell him what value to use so he came to me for why it was used and what value to assume.

Designing lighting is not in my bag of experience so I did a bit of searching and found an IET thread by some eminent folk which said use a factor of 1.2 for HF flurry luminaires because these have a higher power factor than conventional magnetic ballast flurries. As you know for the latter one uses a discharge lighting factor value of 1.8. I then found a Schneider technical paper which had a figure of 1.2 - 1.4 for HF flurries. So I told him to use 1.2.

The fellow was told by his tutor he should have used 1.8 not 1.2. So it seems I advised him wrongly. What figure would professional electricians have used for this question please?

PS: I don't mind being wrong and we will not be arguing with his tutor.

 

[telectrix]

i always was under the impression that the x 1.8 factor was to allow for inrush on start up. not the actual running factor accounting for PF etc.

 

[westward10]

1.8 is the general figure to apply but I would not say you are incorrect. If he/she have selected the type/manufacturer of the luminaires you could apply the manufacturers data however this may result in the circuit being "incorrectly" designed down the line if the original luminaires are replaced with alternatives.

 

[Lucien Nunes]

I don't do general lighting installation either, so it's a long time since I thought about this (HF was new and exciting). Surely the traditional correction factor depends on the gear class, taking in both the pf and efficiency to allow for a conversion from lamp watts to circuit amps? I looked up a couple of class A2 HF fittings and calculating the factor from the voltage and rated input current gave figures barely over unity, achievable because the lamps run at slightly below nominal rating, compensating for the (now very minimal) ballast losses. I would have thought a factor of 1.2 adequate and would like to know the reasoning behind 1.8. I take Westward's point about ensuring the circuit is adequate for generic fittings rather than relying on one particular type with good specs, but surely one would not allow for rolling back to wirewound gear as that would likely conflict with part L.

I remember my dad telling the story from when he was in radio and TV rental and retail in the 1960s. There was a large new store opening and he was there on opening day, during which the lighting fuses proceeded to blow one by one at intervals. After a couple had gone, he checked how many fluorescent battens were on each fuse and discovered that the contractor had loaded each up to the hilt based on the lamp wattage, not the circuit current, i.e. had not allowed any 'correction factor' for pf or efficiency. It had to be rewired with extra circuits over the following few evenings.

 

[westward10]

This 1.8 factor is something which stuck in my head from college days and is probably a bit out of date now with new lighting technology.

 

[ipf]

This 1.8 factor is something which stuck in my head from college days and is probably a bit out of date now with new lighting technology.

Same here, but I thought hf was a different matter, without the 'starter motors', as one bloke called them. Still an inductance though, I suppose. Usually replacing old fittings so never really gone into it.

 

[pc1966]

This 1.8 factor is something which stuck in my head from college days and is probably a bit out of date now with new lighting technology.

Indeed, a bit like the 3% volt drop limit for lighting circuits, even though LED lights are now the norm?