Breaker Size

[siva]

Hi
Here there is a ckt having 110 light fixtures.As per original drawing each fixture had one 26 watts lamps,all controlling through a 3-way switch.Later we asked the contractor to provide one more lamps in each fixture.Now the issue is,
Originally the total load was 2860 and ampere was 13 A which was OK with 20 amps breaker.Now the load doubled and ampere becomes 25 amps which is above the 20 A breaker rating.My question is that,is NEC will allow to replace the lighting breaker with 30 amps and is this 3-way switch will be enough for control the new circuit?Otherwise we have to split it into two circuits which will cost us more since there are more than 20 similar circuits.
Thanks in advance
Siva

 

[iwire]

Re: Breaker Size

Siva.

Short answer, probably not.

It would be unusual that a circuit was run with a conductor large enough to be able to double the load and still be within the conductor rating.

That said we need more info.

1) What voltage are you running at?

Your figures of 2860 watts and 13 amps suggests that your calculations are based on 220 volts.

2860 / 13 = 220

220 volt lighting circuits are non existing in the US.

120, 208, 240, 277, 480 would all be possible. I would expect 277 volt being the likely voltage for that many fixtures.

2)26 Watt lamps?

The only 26 watt lamps I know of are compact fluorescent which in that case we need the line current from the ballast to calculate the circuit load.

3) We need to know the conductor size used to run the circuit.

Can you provide the voltage, the type of fixture and the wire size?

 

[kiloamp7]

Re: Breaker Size

No. - If these are fluorescents, they are not allowed on branch ckts. larger than 20A, doesn't matter if wiring is larger than #12.

 

[iwire]

Re: Breaker Size

Originally posted by kiloamp7:
No. - If these are fluorescents, they are not allowed on branch ckts. larger than 20A, doesn't matter if wiring is larger than #12.

You got a code reference for that?

 

[siva]

Re: Breaker Size

Hi
To Bob...
You rae right.This site is not in US.Its in Bahrain,US Naval Base.Here supply is 230 V and we are following NEC standards inside the Base.Your second assumption is also right,fixtures are compact fluorescent.We are using 6 mm2 wire, approximately 10 awg.
Can we controll all these load by single switch or we have to provide a contactor? Or can we controll the half of the fixtures by one switch and other half by another switch..??

Thanks to all
Siva

 

[iwire]

Re: Breaker Size

Siva, From what info you have provided I see no way to run all these fixtures from one 30 amp circuit.

I suggest splitting the circuit and use two 20 amp circuits.

You have 110 fixtures each with two 26 watt fluorescent lamps. We can not figure the load as 2 x 26 = 56 watts, that is to low, the ballast consumes power also.

Looking in a ballast catalog it shows a ballast running two 26 watt lamps will draw about 63 watts.

So 110 fixtures x 63 watts each = 6930 watts.

6930 watts / 230 volts = 30 amps.

A lighting circuit for non dwelling units is usually considered a continuous load.

Based on that a 20 amp circuit should be 16 amps or less and a 30 amp circuit should be 24 amps or less.

If you split the circuits in half you will have a 15 amp circuits.

 

[kiloamp7]

Re: Breaker Size

iwire - 210.21(A) branch ckts. over 20A - any lampholders must be heavy-duty type - - -

210.23 for (2) or more outlets; 30A branch ckts. require heavy-duty lampholders.

If I remember, Joe McPartland's books from 15 years or so ago talked about admedium lamp bases.

This is similiar to the restriction of regular 15A & 20A recepts. being held to 20A maximum branch ckts., even if #10 wire was used.

 

[pierre]

Re: Breaker Size

If the original conductor size is 12 AWG, this is a moot question and additional wiring will most likely be necessary.

 

[iwire]

Re: Breaker Size

Originally posted by kiloamp7:
iwire - 210.21(A) branch ckts. over 20A - any lampholders must be heavy-duty type - - -

210.23 for (2) or more outlets; 30A branch ckts. require heavy-duty lampholders.

Kilo, I see, you are correct, I had always thought of that as applying to screw shell type sockets.

I am at a loss to understand why it applies to fluorescents.

The branch circuit supplies the ballast, the current that the ballast is capable of suppling the lamp sockets will not change much regardless of the branch circuit size.

 

[George Stolz]

Re: Breaker Size

Another head-scratcher: The fluorescent could be "utilization equipment", see the definition in 100. So, then 30A would be okay again...?

[ February 22, 2005, 09:23 PM: Message edited by: georgestolz ]

 

[arkiesparky]

Re: Breaker Size

I actually ran into this same issue of whether a fluorescent fixture was considered a "heavy-duty" socket.

The inspector decided it was since the connection was actually to the ballast.

I typically run 277V fluorescent lighting on 30A circuits.

 

[kiloamp7]

Re: Breaker Size

arkie - I do not know, but I would hope you are one of the few who puts fluor. on 30A ckts.

If you typically put fluor. on 30A ckts. & that's your take on 210.21,210.23, & 210.24 - then why not put them on 40A or 50A branch ckts.?

Do ballast mfgr's. usually have a maximum OCP
that they call for upstream of their ballasts?