Intuitively, a fluorescent starter ought to draw a little
Extra to heat up a tube of gas, then level off and the
Tube itself draws a lot less than a similar incandescent.

I am about to change a 20A breaker to a 20A GFCI breaker
In order to install a jacuzzi. The only other thing on
The whole circuit is a pair of tube flourescents. The
Jacuzzi states it must be ON ITS OWN breaker, but my
Box is maxed out.

Will a fluorescent trip this with the tub on? The
Tub has a pump and a 1kw heater and doesn't
Get near 2.4kw usage. The lights are only 100W but
I wonder just how much of a ballast boost they draw?

Why not do it right? Swap out your existing breaker for a 2-in1, piggy back or slimline (or what ever it is called for your brand of panel) breaker.

It is a Square D standard box. Are you saying I can put in a half-size 20A GFCI and leave space for a half-size regular 20A breaker? Wouldn't I have to fish new wires to the jacuzzi? The jacuzzi only draws 15A.

Yes, one full size breaker can be replaced with two thin (half size if you want to use that terminology) breakers. Since you probably will have problems finding a slim line GFI breaker, replace two other circuits with slim line breakers and use the freed up space for the GFI. Yes, you should pull new cable. That's what manufacturer recommended isn't it?

I could swap boxes before pulling cable under 1500 ft of concrete. Doesn't anyone know if a fluorescent starter has a bigger load than the rated lamp?

I could just remove the lamps, but that seems paranoid.

The jacuzzi circuit will work fine with this one fixture on it.

If you want to know more about the load the fixture draws, provide the lamp and ballast make and model numbers.

TK
Note the 1500 ft run. I was assuming 12 gauge wire because 20 amp circuit was stated. All the voltage drop calculators say 3/0 cable.

1500 feet is ridiculous distance to run even the jacuzzi. Adding another #3/0 wire just for a fixture is silly. He has more problems to deal with than having one fixture on the same circuit as the jacuzzi.

Well, he just told us that. Maybe it's 150 ft.

Thanks for all the responses. The fixture is built into an overhead so I can't remove it to inspect. The starters are a pair of GE-FS4's.

The present 20A breaker is part of a secondary circuit: a 125A-rated Square D box that is on an 100A breaker from a master box. It has WAY more than 100A worth of breakers in it, but has never tripped. That is why I mentioned upgrading the box. Someone decided to put almost everything on its own 20A circuit: a dryer, a microwave, a fridge, a dishwasher, a fireplace blower, another bathroom jacuzzi (on GFCI), various indivdual rooms, the circuit with these fluorescents and one remote outdoor plug (I do not know the gauge of the wire--it looks fat, the distance to my barn is approximate and A LOT is under concrete; I run power tools including a welder off the plug and nothing trips so I am GUESSING the spa will run on it), the list goes on.

If I swap it for a GFCI the tub will surely draw almost a steady 15A all by itself... thus going over some unknown theoretical threshold. I was thinking of putting a space heater on that remote outlet and turning everything on in the house to test it, then swapping.

Perhaps this is foolish(?)

An alternative is to run off my poolhouse box (second meter) that has similar maxed issues: a 100A heater, a 100A pump, 50A spa blower, 20A cleaner, 20A lights, etc. I could do only a 200ft. Run from it. This 3rd spa is for the winter only so I don't have to use that 4kw heater attached to a 100A breaker (it is incredibly expensive... so much so buying another spa made sense). I would simply never use it because I can heat my inground spa with solar Apr-Oct. and use this new spa Nov-Mar.

I have two remote slabs I want to put things on that are only 100 feet beyond my new spa site. I was thinking of trenching a line and just burying some outdoor-rated romex on a 50A breaker, setting up a slave box next to the jacuzzi with just one GFCI, then tapping off that box to the other slabs. Is that more sensible?

Does that seem more sensible?

When you say FS4 starter is this what yo are speaking of.

Yep,
That pretty much looks like those guys. A couple of fancy shoplights with outlets and those in them, basically.

A starter does not use power, it can be considered more as a switch:

HowStuffWorks "How does a fluorescent starter work?"


You mentioned 1500 foot run, but do not clarify if it was a typo.


You have no access to the ballast to be able to give the make and model number, so we can determine the actual amp draw? What will happen when the ballast fails and needs to be replaced?

This statement:
It has WAY more than 100A worth of breakers in it,

Means nothing, or better I should say, adding up the amp ratings of breakers in a panel means nothing.

Seems that your last plan is reasonable. However someone that is qualified and knowledgeable really needs to look this all over and come up with reasonable solutions. In addition to powering a spa, comes the knowledge of grounding a spa properly, along with proper wiring methods, circuit sizing, etc.

Report me if necessary, or cuss me out, whatever, but I have to say this. If one can afford to own three jacuzzi tubs, poolhoues, etc. one can afford to hire a qualified electrician to review the entire installation and system and get it done correctly.

There really seems to be some convoluted or otherwise complicated installation and sizing issues to deal with. Guessing is not allowed nor helpful in trying to get this al done right.

To begin with, I am absolutely grateful to every response I get here, flaming or not.
I am not proud and you guys have no idea who I am so I will rectify that below.

I didn't clarify the "typo" because it wasn't one; I should have been more clear in my post:
"the circuit with these fluorescents and one remote outdoor plug (I do not know the gauge of the wire--it looks fat, the distance to my barn is approximate and A LOT is under concrete; I run power tools including a welder off the plug and nothing trips so I am GUESSING the spa will run on it)".
This was meant stipulate 1500 feet was an estimate, and that the outlet at the end of it runs a welder so it probably will run a spa.

When I said:
"It has WAY more than 100A worth of breakers in it,"
What immediately followed was list of 8 sample breakers. I didn't want to install it and have the panel fail. I sought an opinion like: "don't bother, 100A service is inadequate for such a box even without adding another spa".

About me: I live on a ranch in far south coastal Texas. I hired the TWO most pre-eminent area "experts" to inspect this place, and have been correcting oversights ever since. Things like ungrounded buildings, mis-wired receptacles, holes in the roof, and HVAC vented into the open attic. I have had locals quote $600 to replace a $200 spa blower before I replaced $10 motor brushes. I have seen them charge $1400 for running 10 feet of conduit and installing a $20 GFCI breaker after telling a lady "you don't want to make a mistake mixing water and electricity to your spa." They tried to replace my whole A/C unit before I put in an $8 capacitor. I see them installing things that are meant to fail because they don't warrant labor. I had parts stolen out of my new car at a chain franchise the single time I didn't change my own oil. A dealer insisted I pay $800 for a whole wiring harness and tried to physically prevent me from driving my truck home to repair 4 rodent-chewed injector wires with $1.50 worth of wire from Autozone. Two years ago I got four quotes to paint my house. Three were $15000+. One was $2500... quite a story.

I have lots of degrees and am qualified as a number of kinds of engineer, yet admit I know nothing and humbly ask advice. I have had thousands of engineers work for me all over the world and billed them at $800/day to put their official stamp of approval on something someone could have looked up at the library. I have personally re-wired and plumbed whole houses, installed two jacuzzies at former homes (with GFCI's, grounding, 220V, etc. used them for decades). I discovered early even though I was successful I LOST money by taking off work to let some "expert" in and pay them $90/hr. with my after-tax dollars for something that I could do in my spare time.

Result: I can afford what I have. All I really wanted to know was about the amperage in fluorescents. In physics when we studied neons the electrons had to get excited somehow. I always thought of a starter as a switching capacitor: its upper limit being the draw I am looking for as the limit of the ballast current. I cannot get at the ballast without a complete removal from a recessed setting, and when it fails I would replace the whole unit, as always, because ballasts tend to be more expensive (and noisy) than whole swaps. Perhaps that is flawed. I knew the tub will work on that circuit without fluorescents because my welder on its highest setting does. I've been shying away from adding up the load of everything in the house to see if it's on the wrong panel. And yes, both panels I am considering are grounded.

P.S. I have almost finished painting my own house after 2 years, and my 22-yr. old truck's still going strong.

Just for everyone's edification: I contacted my old physics professor
Who cussed me out then sent me to this link:

The key quote is: "In any case, the relatively higher "inrush" current required lasts for half a cycle, or 1/120th of a second. The amount of electricity consumed to supply the inrush current is equal to a few seconds or less of normal light operation."

Energy Savers: When to Turn Off Your Lights

After testing a space heater in place of the spa, sure enough: we turned on the
Fluorescents and the circuit blew. He knew we had some physical problems so we didn't need to move a spa twice (lots of Jacuzzis and concrete don't necessarily mean wealthy... might just mean disabled.)

Anyway, thanks to everyone who helped us! Problem solved.