Working on a situation with a sauna where we are referencing a voltage to ground with a certain component energized. Sauna is 240, and contains heating mats (240), near infrared boards (nir) (240), DVDs, led strip lights, mr16 lamps, and a iPad like device for control all of the latter devices are 12v. 240 comes into the sauna via a 3 wire chord, two hots and equipment ground, and terminate in a mother board. 240/12 switching power supply and the nir boards seem to be involved in the problem. Sauna company installer has changed the nir boards voltage still present, they have also taken a jumper from case equipment ground to the ground pin of the 12v supply to the DVDs, this has caused the gfi breaker to trip out. When the gfi breaker is removed for troubleshooting the two pole breaker will trip until it blows out what I believe is a component of the nir board. With the jumper attached and the nir board energized I reference no voltage to ground, remove the jumper and I see 111v ac to ground, when this first occurred voltage would only be read on my metere as a 144vdc voltage, after new boards and a new power supply it appears as a ac voltage.
Sauna
- Thread starter eds
- Start date
- Status
FionaZuppa
Senior Member
- Location
- AZ
- Occupation
- Part Time Electrician (semi retired, old) - EE retired.
sounds like a wiring issue. does the "ground" wire carry current (amp clamp it to see).
Ok, got some pictures of the sauna components, the readings have been taken from any metallic component in the sauna that receive power via 12v, i.e the metal trim of the 12v light (only when light is installed), metal case of dvd player, speaker jacks, to the nuetral buss of the main breaker panel this reading has been a constant 144v dc up until the last power supply and nir board swap out. After swap out I read 111v ac. Voltage reading is not present when nir boards are disconnected. Company sent installer out to perform the pictured fix, which promptly tripped by 240v gfi breaker (spa is 20 amp 240v 3 wire) GFI breaker was removed for trouble shooting and the power supply tripped breaker and burnt the card at the spot of nir board connection. I have included some pictures of components, and would like to determine what is causing this, and not just rely on the sauna company changing parts until it goes away
Attachments
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
160827-1439 EDT
eds:
I don't understand your description, and I know nothing about sauna wiring.
From what you have described I conclude the following:
1. Power source is via a two pole 240 V GFCI fed from 120-0-120 single phase from a 240 center tapped transformer with the center tap earthed and connected to EGC somewhere.
2. The neutral from the GFCI is connected to nothing, and therefore no current flows thru the GFCI neutral.
3. The GFCI is only looking at the current difference between the two hot conductors.
4. For the GFCI to trip there has to be a difference in current somewhat above 5 mA between the two hot conductors. Thus, an unbalanced leakage. Equal leakage from each hot would not cause a trip.
5. The EGC exists and connects to something in or on the sauna. Are all exposed metal parts on or in the sauna connected to EGC?
6. Presumably the sauna sits on a floor that may or may not be a conductor.
7. The sauna structure may or may not be a conductor.
8. I believe you were told to look at the ECG current.
If line the line to line voltage is V240, then a voltage reading between either hot line to EGC should be close to V240 / 2. Quite likely within less than 1 v if there is no load on the utility transformer.
Measure the EGC current.
If leakage current thru the EGC is considerably less than 5 mA when trip occurs (use scope for measurement), then look for some other place leakage current is going.
If leakage is thru the EGC, then search for the origin.
On my relatively new 50 kVA pole transformer with whatever loading and balance exists at the present the two line to neutral voltages are within 0.3 V at about 124 V.
Ask more questions as needed.
.
eds:
I don't understand your description, and I know nothing about sauna wiring.
From what you have described I conclude the following:
1. Power source is via a two pole 240 V GFCI fed from 120-0-120 single phase from a 240 center tapped transformer with the center tap earthed and connected to EGC somewhere.
2. The neutral from the GFCI is connected to nothing, and therefore no current flows thru the GFCI neutral.
3. The GFCI is only looking at the current difference between the two hot conductors.
4. For the GFCI to trip there has to be a difference in current somewhat above 5 mA between the two hot conductors. Thus, an unbalanced leakage. Equal leakage from each hot would not cause a trip.
5. The EGC exists and connects to something in or on the sauna. Are all exposed metal parts on or in the sauna connected to EGC?
6. Presumably the sauna sits on a floor that may or may not be a conductor.
7. The sauna structure may or may not be a conductor.
8. I believe you were told to look at the ECG current.
If line the line to line voltage is V240, then a voltage reading between either hot line to EGC should be close to V240 / 2. Quite likely within less than 1 v if there is no load on the utility transformer.
Measure the EGC current.
If leakage current thru the EGC is considerably less than 5 mA when trip occurs (use scope for measurement), then look for some other place leakage current is going.
If leakage is thru the EGC, then search for the origin.
On my relatively new 50 kVA pole transformer with whatever loading and balance exists at the present the two line to neutral voltages are within 0.3 V at about 124 V.
Ask more questions as needed.
.
Last edited:
What I am having trouble grasping is the voltage reading I am able to get from the neutral buss to the metal trim of a 12v sauna lamp, the trim is installed in a wood ceiling of the sauna. Voltage has been 144v dc until the last power supply was changed, and is now 112v ac. Voltage also goes away when the grounded conductor of the dvd player is jumper-ed to case ground of the sauna, thus tripping the 2 pole gfi breaker. Voltage is also not present when the nir boards are disconnected. My fluke clamp meter reads .02 when clamped around the egc at the panel
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
160827-2113 EDT
eds:
Does the neutral from the GFCI breaker connect to anything? I assume it does not from your earlier comments.
In your last post where are you connecting for the neutral connection to your Fluke meter? Are you using the EGC at the sauna to provide this connection?
For a good neutral/EGC reference point I would use an extension cord from the main panel neutral bus for this reference. From this known reference there should be essentially zero voltage to any exposed metal in or on the sauna.
0.02 A (20 mA) thru the EGC is going to trip the GFCI.
I would expect any low voltage DC for for electronics, etc., to be referenced to the EGC. In other words grounded. If this is referenced to a hot line, then there a problem. This would be a wiring error.
I do not know what an "nir board" is.
If the common (likely called ground) of electronic power supply outputs is connected to (referenced) to a hot AC line then this might explain some of your measurements. No idea of why DC and then AC with supply change.
Likely some kind of wiring error in the sauna, or defective components. With all power connections to the sauna disconnected you may be able to find a problem with a low voltage ohmmeter (a normal Fluke DVM). A Megger with a 100 V setting might also be useful.
.
eds:
Does the neutral from the GFCI breaker connect to anything? I assume it does not from your earlier comments.
In your last post where are you connecting for the neutral connection to your Fluke meter? Are you using the EGC at the sauna to provide this connection?
For a good neutral/EGC reference point I would use an extension cord from the main panel neutral bus for this reference. From this known reference there should be essentially zero voltage to any exposed metal in or on the sauna.
0.02 A (20 mA) thru the EGC is going to trip the GFCI.
I would expect any low voltage DC for for electronics, etc., to be referenced to the EGC. In other words grounded. If this is referenced to a hot line, then there a problem. This would be a wiring error.
I do not know what an "nir board" is.
If the common (likely called ground) of electronic power supply outputs is connected to (referenced) to a hot AC line then this might explain some of your measurements. No idea of why DC and then AC with supply change.
Likely some kind of wiring error in the sauna, or defective components. With all power connections to the sauna disconnected you may be able to find a problem with a low voltage ohmmeter (a normal Fluke DVM). A Megger with a 100 V setting might also be useful.
.
JFletcher
Senior Member
- Location
- Williamsburg, VA
Is this a brand new sauna, and the problem showed up immediately on initial install?
What is the exact make and model number of this sauna?
Can you post pictures of where the premise wiring attaches to the sauna?
What is the exact make and model number of this sauna?
Can you post pictures of where the premise wiring attaches to the sauna?
Breaker neutral pigtai connected to neutral buss, no neutral to sauna
No
Using a 20' piece of 12 thhn connected to neutral bus , then to one lead of meter, other lead to metal trim and this leads to a voltage when nir boards are on
When connected to egc voltage goes away but gfi breaker trips, standard breaker also trips until nir connections are burnt thru on power supply
Near infrared board , supposedly deep cleans skin tissue and muscle
JFletcher
Senior Member
- Location
- Williamsburg, VA
What was the original problem, someone getting shocked? Equipment failure? What prompted all the troubleshooting and replacement of parts?
I looked it up. Yep, 3 wire cord and plug connection.
"Voltage also goes away when the grounded conductor of the dvd player is jumper-ed to case ground of the sauna, thus tripping the 2 pole gfi breaker."
If you remove the jumper, and run the sauna on a standard breaker, what happens? Did it burn up the internals with or without that jumper installed?
I looked at the mfg instructions for your model:
http://www.sunlighten.com/customerservice/images/mPulse-manual-011811.pdf
They do not require a GFCI breaker. afaik, nothing in the NEC requires one in this application either.
The voltage readings you are getting are likely phantom readings.
" they have also taken a jumper from case equipment ground to the ground pin of the 12v supply to the DVDs,"
Is that the 3 port orange WAGO in picture #5, with the green/yellow jumper to frame, and the two white wires inserted as well? Where are you grounding the power supply? If it's metal and attached to a metal board/frame, it's already grounded. Are you grounding the output (12V) side?
" Voltage also goes away when the grounded conductor of the dvd player is jumper-ed to case ground of the sauna"
If the DVD is 12V, and you wrote that it is, then there is positive and negative, not a grounded/ungrounded conductor. The positive or the negative, or neither, may be at the same voltage as the frame/ground. If the power supply is sending current to ground, it will trip the GFCI.
I'm not sure all what you have going on, however I would start by temporarily disconnecting the field installed jumper and take and record readings on everything. or if it's still under warranty, let the sauna co deal with it. I would ask them about the GFCI breaker; apparently, some saunas actually say 'do not use GFCI breaker' in the manual.
If you have verified that all the wiring to the receptacle is correct, breaker, wire size, voltage, ground path, it's on the sauna co and their techs to fix the guts.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
160828-0536 EDT
eds:
JFletcher is correct that it is a manufacturer's problem.
I would suggest that running a sauna without a GFCI could be a safety problem. This is somewhat akin to CNC suppliers telling people to disconnect the EGC from the machine and use a local ground rod.
There should be very low resistance from any exposed sauna metal parts to the sauna power cord EGC pin. And the EGC path must be good from any exposed metal parts back to the main panel.
Does the NIR board have have electrical isolation between its 240 V input terminals and its DC output? In other words does it contain a transformer? If the NIR diode arrays contain many series diodes, then the NIR board may produce a moderate DC output voltage. Like 100 or more volts. I would classify the NIR board as some sort of DC power supply. Possibly a DC constant current supply or an adjustable (meaning settable) constant current supply.
If the NIR board has internal leakage from its AC input to its DC output, then this could cause the problem. If by incorrect wiring the NIR board has its common connected to an AC hot and to EGC, then it would be a short from AC hot to EGC.
There should be no DC continuity between either hot input wire and the sauna EGC when the sauna power cord is unplugged. The AC impedance should be greater than probably 100,000 ohms at 60 Hz, and possibly to 2500 Hz or higher.
.
eds:
JFletcher is correct that it is a manufacturer's problem.
I would suggest that running a sauna without a GFCI could be a safety problem. This is somewhat akin to CNC suppliers telling people to disconnect the EGC from the machine and use a local ground rod.
There should be very low resistance from any exposed sauna metal parts to the sauna power cord EGC pin. And the EGC path must be good from any exposed metal parts back to the main panel.
Does the NIR board have have electrical isolation between its 240 V input terminals and its DC output? In other words does it contain a transformer? If the NIR diode arrays contain many series diodes, then the NIR board may produce a moderate DC output voltage. Like 100 or more volts. I would classify the NIR board as some sort of DC power supply. Possibly a DC constant current supply or an adjustable (meaning settable) constant current supply.
If the NIR board has internal leakage from its AC input to its DC output, then this could cause the problem. If by incorrect wiring the NIR board has its common connected to an AC hot and to EGC, then it would be a short from AC hot to EGC.
There should be no DC continuity between either hot input wire and the sauna EGC when the sauna power cord is unplugged. The AC impedance should be greater than probably 100,000 ohms at 60 Hz, and possibly to 2500 Hz or higher.
.
I agree that it is a manufacture issue, I am only putting in the time and research to better understand what is happening, and to rule out any issue on the premise wiring side of the sauna.
The fact that the sauna company doesn't what it on a gfi protected circuit leads me to the conclusion that the egc is being utilized in some form as an current carrying conductor.
How can I read voltage from the metal trim of the lamp, when the lamp is supplied via a 2 conductor feed with no direct connection from lamp to trim. I have ohmed the pins of the lamp to the outer case of the lamp
, it presents it self as isolated.
This is not a ghost voltage, as I have ruled that out, 1 as a slight shock during testing, 2 the jumper wire touched to the trim will produce an arc.
Initial trouble call, was because of a shock
The fact that the sauna company doesn't what it on a gfi protected circuit leads me to the conclusion that the egc is being utilized in some form as an current carrying conductor.
How can I read voltage from the metal trim of the lamp, when the lamp is supplied via a 2 conductor feed with no direct connection from lamp to trim. I have ohmed the pins of the lamp to the outer case of the lamp
, it presents it self as isolated.
This is not a ghost voltage, as I have ruled that out, 1 as a slight shock during testing, 2 the jumper wire touched to the trim will produce an arc.
Initial trouble call, was because of a shock
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
I think Gar is likely on the right path in post 12, there likely is not any isolation between AC input DC output. Could be a design issue, could be a malfunction of something, you need to figure out which it is. No isolation will mean any ground faults on the DC side are going to cause tripping of the GFCI on the AC supply.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
160828-1301 EDT
eds:
So this particular manufacturer does not want a GFCI used to supply the sauna. Almost certainly this means they are using filters in the system to reduce exported RFI (radio frequency interference), and that these filters have capacitors from the hot lines to the EGC. This does not explain the problem of tripping a standard breaker when the NIR board is installed.
A 1000 ohm resistor has a voltage drop of 1 V with 1 mA of current flow. At 50 mA the power dissipation in 1 k is 0.05^2/1000 = 2.5 W. At least a 2 W resistor would be needed for short time measurements. The reason to use a resistor and auto-ranging DVM for current measurements is to prevent damaging an ammeter or its fuse. Carbon composition resistors are cheap. For 50 mA use a 1/4 W 100 ohm resistor.
You mentioned reading 20 mA on the EGC. I believe this was with the NIR board removed. This is 120/.02 = 12,000/2 = 6000 ohms. An 0.5 mfd capacitor has a reactance of about 5300 ohms at 60 Hz. At higher frequencies, there are lots of high frequency components with switching supplies, this same reactance value will occur with a much smaller capacitance value.
With the NIR board installed you apparently have a much lower impedance from a --- hot line to the EGC ---, or --- hot to hot --- to cause a standard breaker to trip.
If the manufacturer had brought the GFCI neutral to the equipment and connected the filters to the GFCI neutral instead of the EGC, then the filter current would not flow around the current transformer in the GFCI, and you might tolerate a large filtering current without tripping the GFCI.
.
eds:
So this particular manufacturer does not want a GFCI used to supply the sauna. Almost certainly this means they are using filters in the system to reduce exported RFI (radio frequency interference), and that these filters have capacitors from the hot lines to the EGC. This does not explain the problem of tripping a standard breaker when the NIR board is installed.
A 1000 ohm resistor has a voltage drop of 1 V with 1 mA of current flow. At 50 mA the power dissipation in 1 k is 0.05^2/1000 = 2.5 W. At least a 2 W resistor would be needed for short time measurements. The reason to use a resistor and auto-ranging DVM for current measurements is to prevent damaging an ammeter or its fuse. Carbon composition resistors are cheap. For 50 mA use a 1/4 W 100 ohm resistor.
You mentioned reading 20 mA on the EGC. I believe this was with the NIR board removed. This is 120/.02 = 12,000/2 = 6000 ohms. An 0.5 mfd capacitor has a reactance of about 5300 ohms at 60 Hz. At higher frequencies, there are lots of high frequency components with switching supplies, this same reactance value will occur with a much smaller capacitance value.
With the NIR board installed you apparently have a much lower impedance from a --- hot line to the EGC ---, or --- hot to hot --- to cause a standard breaker to trip.
If the manufacturer had brought the GFCI neutral to the equipment and connected the filters to the GFCI neutral instead of the EGC, then the filter current would not flow around the current transformer in the GFCI, and you might tolerate a large filtering current without tripping the GFCI.
.
FionaZuppa
Senior Member
- Location
- AZ
- Occupation
- Part Time Electrician (semi retired, old) - EE retired.
me just being picky here, but a 240ct is not 120-0-120 :thumbsup:
its really +240/+120/0 or 0/-120/-240 (pole / neutral / pole, pole-to-neutral 120, pole-to-pole 240)
120-0-120 indicates +120 & +120, their diff is zero. and technically, 1ph so you cant really have +120 and -120 at the same time.
ok, i be quiet now
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
me just being picky here, but a 240ct is not 120-0-120 :thumbsup:
its really +240/+120/0 or 0/-120/-240 (pole / neutral / pole, pole-to-neutral 120, pole-to-pole 240)
120-0-120 indicates +120 & +120, their diff is zero. and technically, 1ph so you cant really have +120 and -120 at the same time.
ok, i be quiet now
But it still has a 120-0-120 ground reference if supplied from such a system.
JFletcher
Senior Member
- Location
- Williamsburg, VA
me just being picky here, but a 240ct is not 120-0-120 :thumbsup:
its really +240/+120/0 or 0/-120/-240 (pole / neutral / pole, pole-to-neutral 120, pole-to-pole 240)
120-0-120 indicates +120 & +120, their diff is zero. and technically, 1ph so you cant really have +120 and -120 at the same time.
ok, i be quiet now
Writing aside, I think everyone understood the OP with what he wrote. and if on a resi service, two hots equals 0 (same leg) or 240 (different legs).
Btw, I didnt say THIS mfg doesnt require a GFCI breaker, just that SOME sauna mfgs recommend against using one.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
160829-1500 EDT
In the post numbered 13 "eds" said that the sauna manufacturer does not want the sauna on a GFCI. I did not go back to see if "eds" indicated this earlier.
Since no neutral is brought to the sauna it implies that the sauna could be run from a totally isolated 240 V source. If that isolated source had no leakage path to earth, and nothing providing a voltage to it from earth, thus the EGC wire, then one would not get a shock or read a voltage to earth.
eds's goal has been stated that he or she wants an understanding of the cause of the observations.
Clearly the sauna has internal conductive paths to the EGC connected to the sauna. There is no conductive path to the GFCI neutral output wire. Thus, any stray or not so stray path to the EGC bypasses the current transformer in the GFCI and causes it to trip. Sometimes this has been measured at about 20 mA, and under other conditions (the NIR board installed) it is sufficient to trip a standard 240 V two pole breaker. Quite likely thru the EGC path.
.
In the post numbered 13 "eds" said that the sauna manufacturer does not want the sauna on a GFCI. I did not go back to see if "eds" indicated this earlier.
Since no neutral is brought to the sauna it implies that the sauna could be run from a totally isolated 240 V source. If that isolated source had no leakage path to earth, and nothing providing a voltage to it from earth, thus the EGC wire, then one would not get a shock or read a voltage to earth.
eds's goal has been stated that he or she wants an understanding of the cause of the observations.
Clearly the sauna has internal conductive paths to the EGC connected to the sauna. There is no conductive path to the GFCI neutral output wire. Thus, any stray or not so stray path to the EGC bypasses the current transformer in the GFCI and causes it to trip. Sometimes this has been measured at about 20 mA, and under other conditions (the NIR board installed) it is sufficient to trip a standard 240 V two pole breaker. Quite likely thru the EGC path.
.
FionaZuppa
Senior Member
- Location
- AZ
- Occupation
- Part Time Electrician (semi retired, old) - EE retired.
there is only one hot if on same leg.
- Status