hillbilly1
Senior Member
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- North Georgia mountains
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- Owner/electrical contractor
From what I can find, one manufacture makes them 12-24 volt, so what you have may be dual volt or auto volt. The transformer may be dual voltage too.
24v GFCI’s?
- Thread starter morepower
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- Chapel Hill, NC
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- Retired Electrical Contractor
Read some of mike holt stuff. 50v will send you flying in water but so would 24V. I believe I heard mike holt say that he didn't know of any fatalities under 30v
winnie
Senior Member
- Location
- Springfield, MA, USA
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- Electric motor research
50A 24V? I presume some very fat conductors, or the transformers are very close to the loads.
-Jon
- Location
- Chapel Hill, NC
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- Retired Electrical Contractor
I believe gfci is needed on the primary only. I been so wrong all day I may as well go for it again
winnie
Senior Member
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- Springfield, MA, USA
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- Electric motor research
Huh.
If we apply Charlies Rule, I believe you are correct. This hinges on the question: does the wiring between the step down transformer and the actual light count as a 'branch circuit'? I don't think that it does.
In which case the code _as written_ is problematic. The required isolation transformer separates the branch circuit from the lighting local circuit, which means that a shock caused by the lighting local circuit would not be detected by the GFCI. Since this is the case, it should not matter what the voltage of the lighting local circuit is.
Going back to the original poster, one issue is how many lights are served by the secondary of the transformer. If the transformer supplies only a single light, then the shock risk is very low, no matter what the voltage. Current has to leave the secondary, pass through the person, and return to the secondary. Have one transformer feed many lights, and there is a larger risk because now faults can cause current to flow through the water.
However since this transformer is _not grounded_, it is not clear that a single GFCI could even detect a fault on the secondary. If you have a single fault on the secondary, you won't have much current flow, and if you have multiple faults, current could flow through the water (shocking someone) but it would return back to the transformer through the GFCI and thus not show up as detectable residual current.
-Jon
hillbilly1
Senior Member
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- North Georgia mountains
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- Owner/electrical contractor
As I believe it was Suemark posted?, the isolation transformer is required to have the windings shielded and double insulated, I believe, where the ground fault protection is for accidental higher voltage contact to the low voltage windings, not the output of the low voltage side.
synchro
Senior Member
- Location
- Chicago, IL
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- EE
680.23 is under Part II. Permanently Installed Pools.
At the start of Part V. Fountains, 680.50 says: "Part I and V of this article shall apply to all permanently installed fountains as defined in 680.2."
So I believe 680.51(A) quoted by suemarkp would apply to the OP's case with fountains but 680.23 would not.
Fred B
Senior Member
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- Upstate, NY
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- Electrician
True other than the fact 680.51 specifically references 680.23(A)(2) which means even though it's not contained of Part I it would still apply.
synchro
Senior Member
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- Chicago, IL
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- EE
Yes I agree that is true. But I think 680.23(A)(3) that calls for GFCI protection to be installed in the branch circuit would not apply.
Fred B
Senior Member
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- Upstate, NY
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- Electrician
But that is not the part of code being referenced by 680.51, only referencing 680.23(A)(2)
680.23(A)(2) Transformers and Power Supplies. Transformers and power supplies used for the supply of underwater luminaires, together with the transformer or power supply enclosure, shall be listed, labeled, and identified for swimming pool and spa use. The transformer or power supply shall incorporate either a transformer of the isolated winding type, with an ungrounded secondary that has a grounded metal barrier between the primary and secondary windings, or one that incorporates an approved system of double insulation between the primary and secondary windings.
So if it meets the criteria laid out as listed, labeled, and identified for pool and spa use, the mfg and listing agency has made implied warranty of intrinsically safe for use in specific way. So if installed in a manner consistant as specified by mfg installation should be safe in a given application.
As to OP ? 1. Does the lighting meet criteria list in 680.2 as definition of low voltage contact limit, if not does it meet the criteria listed in 680.4 "equipment and products shall be listed". If yes it is listed in accordance with 680.23(A)(2), if yes then do you trust listing agency or mfg, if yes wheres the problem, in no find a different product.
2. Are you sure if the product is listed as above, the product is 24V AC? Could it be 24V DC? Seems that it would have to be DC if the "24" value is correct and is listed as above.
synchro
Senior Member
- Location
- Chicago, IL
- Occupation
- EE
I said above that the 680.51(A) quoted by suemarkp would apply to the OP's case. When I said 680.23 would not apply I was not intending to be saying that the specific citation of 680.23(A)(2) within 680.51(A) would not be applicable, because of course 680.51(A) depends on it. What I was intending to say was that Dennis's post about 680.23(A)(3), which I listed right after suemarkp's in my post #27, would not apply in the OP's case. As far as I know there is no reference to 680.23(A)(3) within Part V. of 680 which would make it applicable to fountains, but I haven't searched for it. I should have been more explicit that I was agreeing to the entirety of suemarkp's post and that it was Dennis's citation of 680.23(A)(3) that I didn't think was applicable in the OP's case. I guess I didn't want to tee off a moderator, but maybe I'll need to start changing my ways.
- Location
- Chapel Hill, NC
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- Retired Electrical Contractor
You cannot offend me and please don't put anybody above yourselves just because we are mods. I was incorrect. I totally understand your post and I agree with you. I looked at 680.51 referencing 680.23(A)(2) and I didn't look closely at it. I assume all of 680.23.
That section makes no sense anyway as winnie pointed out.
Back to the OP--- how do you put gfci on 24v---
I am surprised that this is 24v ac. If it were DC which I suspect it is then there wouldn't be an issue.
That section makes no sense anyway as winnie pointed out.
Back to the OP--- how do you put gfci on 24v---
I am surprised that this is 24v ac. If it were DC which I suspect it is then there wouldn't be an issue.
synchro
Senior Member
- Location
- Chicago, IL
- Occupation
- EE
Here's what I see in the code for determining what is (and is not) required for the OP's situation, although I could be missing or misinterpreting something:
"250.22 Circuits not to be grounded:
250.22(4) Secondary circuits of lighting systems as provided in 411.6(A)
250.22(5) Secondary circuits of lighting systems as provided in 680.23(A)(2)
ARTICLE 411 Low-Voltage Lighting
411.1 Scope. This article covers lighting systems and their associated components operating at no more that 30 volts ac or 60 volts dc. Where wet contact is likely to occur, the limits are 15 volts ac or 30 volts dc.
Informational Note: Refer to Article 680 for applications involving immersion.
411.6 Secondary Circuits.
(A) Grounding. Secondary circuits shall not be grounded.
(B) Isolation. The secondary circuit shall be insulated from the branch circuit by an isolating transformer."
In the OP's case wet contact is likely to occur and so the 15VAC upper limit applies for defining the scope of Article 411. Therefore because the OP is using 24VAC I don't believe Article 411 is applicable to his case, including its requirements for circuits not to be grounded and for isolation.
Now referring to Article 680 as the informational note above indicates, we go back to what suemarkp posted:
Because the OP is operating above the low voltage contact limit, the option in 680.51(A) to use a transformer or power supply complying with 680.23(A)(2) and its requirements for isolation with an ungrounded secondary is not applicable.
I don't see anywhere else in Article 680, Part V. Fountains requiring the secondary of a transformer to be ungrounded. If true, then by grounding the secondary of a 24VAC transformer, a GFCI on the output of this transformer could trip if there's a ground fault on the secondary. Otherwise, as we have discussed, a GFCI on an ungrounded and isolated secondary appears to be useless but still required for the OP's situation.
"250.22 Circuits not to be grounded:
250.22(4) Secondary circuits of lighting systems as provided in 411.6(A)
250.22(5) Secondary circuits of lighting systems as provided in 680.23(A)(2)
ARTICLE 411 Low-Voltage Lighting
411.1 Scope. This article covers lighting systems and their associated components operating at no more that 30 volts ac or 60 volts dc. Where wet contact is likely to occur, the limits are 15 volts ac or 30 volts dc.
Informational Note: Refer to Article 680 for applications involving immersion.
411.6 Secondary Circuits.
(A) Grounding. Secondary circuits shall not be grounded.
(B) Isolation. The secondary circuit shall be insulated from the branch circuit by an isolating transformer."
In the OP's case wet contact is likely to occur and so the 15VAC upper limit applies for defining the scope of Article 411. Therefore because the OP is using 24VAC I don't believe Article 411 is applicable to his case, including its requirements for circuits not to be grounded and for isolation.
Now referring to Article 680 as the informational note above indicates, we go back to what suemarkp posted:
Because the OP is operating above the low voltage contact limit, the option in 680.51(A) to use a transformer or power supply complying with 680.23(A)(2) and its requirements for isolation with an ungrounded secondary is not applicable.
I don't see anywhere else in Article 680, Part V. Fountains requiring the secondary of a transformer to be ungrounded. If true, then by grounding the secondary of a 24VAC transformer, a GFCI on the output of this transformer could trip if there's a ground fault on the secondary. Otherwise, as we have discussed, a GFCI on an ungrounded and isolated secondary appears to be useless but still required for the OP's situation.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
GFCI can work on ungrounded systems.
I just haven't seen any rated for 24VAC.
My issue was with a GFCI on the primary sensing a ground fault on the secondary of an isolation transformer. The example of a primary to secondary fault, effectively turning the isolation transformer into an autotransformer, appears to be valid although it requires two failures.
LarryFine
Master Electrician Electric Contractor Richmond VA
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- Henrico County, VA
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"Lucy, you got some 'splainin' to do!"
How would the GFCI know that a contact has been made between an energized conductor and earth or other grounded-surface?
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- Placerville, CA, USA
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- Retired PV System Designer
All it could do is detect an imbalance between the currents on the two nominally ungrounded conductors. As with any ungrounded system, except for possible capacitive coupling, it takes two faults to provide an external return path.
The big problem remains of how to provide power to the electronics of the GFCI.
Sent from my Pixel 4a using Tapatalk
winnie
Senior Member
- Location
- Springfield, MA, USA
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- Electric motor research
Agreed on a fault requiring two paths, and this means that (for example) if you have a single transformer providing the low voltage and a single GFCI on the output of that transformer it would be unlikely to actually 'see' the faults. Say you have a single 50A 24V secondary feeding a 100 separate lights. A fault causing current to flow through the water from light #20 to light #53 would flow from the transformer back to the transformer. A single GFCI on the output of the transformer would simply see this as balanced load.
With regard to powering the electronics of the GFCI, it is trivial for a GFCI circuit to be powered by one circuit but sense a totally different circuit. The common GFCIs that we use are powered by the same circuit they are protecting, but there is nothing essential about this.
-Jon
Touch it to your tongue
So wouldn’t the 24VAC need to be grounded to have a gfci work? Looks like one wire shorting wouldn’t do anything until the other wire shorts to same as first wire.
There are some out there that are relays that work with a contactor.
There are some out there that are relays that work with a contactor.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
If there is a pathe for current to flow (i.e. a complete circuit), the GFCI will see current leaving the device, but not returning. This is true of any zero sequence CT sensor.
However as winnie pointed out, is is also possible that the ground fault returns on an intended path, but this is true for all GF common circuits.
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