Sodium Lamps

Match the circuit breaker to the wiring, just as British Standard 7671 requires. After all, it is the wiring that the breaker is selected to protect....

its look like learning swimming by postal.....

Fly by internet wire.

There will be some current surge on start, but right off hand I don't know how much or how long. Running current is ~5.22A, so I wouldn't be surprised if it takea a 10A or 15A circuit breaker to handle the starting current. Determine that first, and then size the wire accordingly. (In the U.S., it would probably be 15A breaker and 14AWG wire, but your local requirements may differ.)

Switching of discharge lamps is called Utilisation Category AC5a and calls for switching on and switching off 3X the rated current for 50 opeations, as per IEC 60947-4. You should really use a contactor for this duty, since it is meant for millions of operations. The MCB should be used for protection, preferably, not switching.

yes i think u can u the 6amps MCB for your work. The total amp of the lamps is I = P/V = 1.2kv/230 = 5.217amp. In future u can add more load to it.

Er...i read somewhere that gas discharge lamps operate at ≈ 0.5 PF (i could be wrong). If this is correct, the 6A MCB itself is a wrong choice. It will certainly nuisance trip. And, as i said, an MCB is not the best device anyway.

These should be on thhn #10 with 30A breaker, then individually fused with cartridge dual element 10A fuses...

discharge lamps take a massive current on start up - in the order of 30 times for a few milliseconds

Check manufacturers recommendations but a 10A or maybe 16A type C would do a single 400W lamp.

Suggest you go from 3 phase - use a contactor and a 10A type C MCB for protection.

The type B or C is important.

Remember you have to protect the wiring not the device so if your cables are not protected by a 10 or 16A MCB you will need to upsize.

The Merlin Gerin cat, as do others, will give you some good hints on breaker sizing.

If you are asking these questions though maybe its time to get a qualified guy.

You must also take into account the voltage drop in the supply cables. If this is too high the lamps may not start up at all. This has happened to me! If I had the units I would rig up a test circuit and check the startup current myself. Better safe than sorry.

We run 400w sodiums in our factory using 2.5 mm cable, 20 amp breaker and a 15 amp switch to run the 3 lights as a bank, if switching individually standard 10 amp switch should be ok. Naturally you will need to take length of cable run and how it is run when sizing suitable cabling for your installation. The above is a guide only.

You do not say whether you are running these lamps on a single phase or on a 3 phase supply - 1 lamp per phase.

At 3 phase a suitably rated switch could switch 3 x 400W SONs and a 20amp breaker would suffice.

You are running into fixed equipment so you have a known electrical load. The 2.5mm cable is within the load limits of the cable and the breaker only really needs to clear a short circuit fault.

Volt drop is still a consideration and the I.E.E. regs require no more than 3% under normal load conditions.

Please refer Schneider Electric - Electrical Installation Guide 2010 . Topic is Reactive energy and power factor . It says a pf of 0.4 to 0.6 is to be considered.

Also, ZUMTOBEL STAFF - The Lighting Handbook -Chapter 9 Page 18

if you running lamps with a PF of 0.4 its time to put them in the skip. Most discharge lamps are around pF 0.8 with a further improvement if are running the ones equipped with an electronic ballast.

Its not my recommendation , its by Schneider Electric who suggested . I was just referring it.

It is not important whether the PF is 0.1 or 0.9 or in between....the OP is dividing Watts by Volts and arriving at Amps. And one more poster is supporting it !!! Can prove to be a dangerous mistake....

It is important, i think, that they appreciate that the current will be considerably higher (a) due to power factor being below 1 and (b) there is always a current surge when switching on the lamps.

"if you running lamps with a PF of 0.4 its time to put them in the skip. Most discharge lamps are around pF 0.8 with a further improvement if are running the ones equipped with an electronic ballast"

In smaller installations, one would usually use control gear with an integral power-factor correction capacitor which would give a PF of better then 0.8.

In larger installations, it is common to install the lighting without the integral PFC, and use a large, central PFC-correction system. Without the integral correction, the PFC of the lights may well be as low as 0.4. Nothing wrong with them, mind, that's just the way they are.

To accommodate these two scenarios, the switchgear manufacturer's data usually publish sets of figures for both configurations.

I have a 1000W SV lamp connected with three capacitor of 25µF.

4 lamps are from 32A MCB.

I know this has already been stated by other members but Appart from the selecting the correct type of MCB to handle the current surge at start up The only answer I see here is You size the cable to be able to take the load & select the correct MCB to protect the cable supplying the lights because the MCB is not there to protect the load on the circuit it is only to protect the cable. & often many sodium vapor lamps I have seen have had an individule fuse built into the fitting

This is taught to apprentises in first year college & I fear if you do not have this knollege/ training you may not be qualified to carry out the work & I sugest you employ a tradesman to do the work

I haven't posted for a while so this is like cracking my knuckles.

Good answer to Paulusgnome who is also from NZ so double points!

Several things have not been mentioned.

First circuit watts. 400W is the wattage of the lamp. The lamp has a ballast which also requires power. Lamp manufacturers like Sylvania will give you plenty of information but a rule of thumb is 10% for conventional wire-wound ballast (CB) and 5% for electronic ballast (EB). So the circuit takes roughly 1320w (CB) & 1260W (EB).

Power factor is ~1 for EB but ~0.4 for CB. This is typically corrected with a capacitor to ~0.95. However the cap dries out in use and we do calcs at PF ~0.8.

So for conventional wire-wound ballast VA is up to 1650 which equals ~7.2amps @ 230V.

However you have to allow for power supply voltage fluctuation which is typically +/- 6%. So running current could rise to ~7.6amps.

This is the figure you need to calculate voltage drop. Your 6A MCB is history.

Hot re-strike next. This is when the lamp is turned on again after just being shut off. This could be due to a power drop-out say, or simple switching. The lamp could take 4-7 mins to re-strike. Typically at 2-3 times running current. This should trip a 10A MCB unless its a Type D. I'm not a fan of Type D and would prefer a 16A Type C in this situation.

For the real anoraks, during hot re-strike the lamp can behave as a rectifier and the resulting DC will saturate a wire-wound ballast. The PFC cap then acts like a virtual short-circuit. My secret squirrel files tell me the cap in a 400W ballast is 40 uF; I leave you to do the maths.

So EBs are best for these lamps.

However, who wants sodium these days? I would heavily recommend HID for better colour rendering.

Finally a decent answer. All points go to New Zealand. You would need to weigh the shorter life of HID against the poor colour rendering of the SON. Depends on the application.

No points for the Guru who thinks PF plays no part in Watts, Volts and amps.