How to take out a GFCI from a "Transco" neon transformer

[charlie_mccartney]

I know that a huge problem for people here is finding a good, cheap, GFCI free, NST. Well I have asked around and my friend told me how to take one out, therefore turning it into a normal NST. He sent me these pictures which are self explanatory. I thought I would pass the info on. Here are his instructions -



The following process will only work with transformers that have the GFCI circuit exposed. In some transformers it is impossible to remove the GFCI because it is surrounded in tar and is inaccessible. As of this writing, I am aware of only two companies that leave the GFCI exposed, those being "Transco" and "France".


1. Unplug your transformer.

2. Remove the access panel from the top of your transformer. "Transco" transformers have one screw and one rivet holding the access panel on, remove the screw and cut off the rivet with some pliers.

3. With the access panel removed, you should see two partitions on the inside of the transformer. The first partition will be completely filled in with tar and is inaccessible, the second partition will contain the GFCI circuitry. The blue box shown in the pictures is the GFCI.

4. Pull the GFCI box out of the transformer so you can get a better look at it. Notice that all of the wires coming from the transformer go through a terminal block to connect to the GFCI box. Use a screw driver to disconnect all of the transformer wires from the terminal block and set the GFCI box to the side, we are done with it.

5. With the GFCI removed, we need to figure out which of the remaining wires are no longer needed and which of the remaining wires must be joined together. The remaining wires are green, brown, grey, blue, white and black. The green wire is ground for the components in the GFCI box. Since the GFCI box has been removed, we no longer need the green wire and it should be taped off to keep it insulated and out of the way. The brown wire is used to activate a relay in the GFCI box. Again, since the GFCI box has been removed, we no longer need the brown wire and it should be taped off to keep it insulated. The white wire and the black wire are the ends of the primary inductor within the tar-filled partition. In electrical terms, the white wire is neutral and the black wire is line voltage. The last two wires are blue and grey. The blue wire comes from the "line voltage" (L) terminal on the exterior of the transformer, where the power cord gets attached. The grey wire comes from the neutral (N) terminal on the exterior of the transformer. Connect the grey and white wires, since they both correspond to neutral. Solder them together and use tape to insulate everything. Connect the black and blue wires, since they both correspond to line voltage. Solder them together and use tape to insulate everything.

6. Put the access plate back onto the transformer and get ready to give it a test run. Attach one electrode of your spark gap to each of the two output terminals on the transformer. If your spark gap fires when you plug in the transformer, you have successfully re-wired your transformer and removed the GFCI box.

[Richard Hull]

Thanks for the info Charlie! I just bought a Transco 9KV 60ma transformer at a recent hamfest with GFCI for $5.00 and will remove it as per your instructions.
The Franceformers are all in tar but can be removed by careful hands and a bit of work.

Richard Hull

[Tom McCarthy]

Why not move this to the FAQs, Richard?

Tom

[Richard Hull]

A FAQ on GFCI removal should ideally explain how to remove all GFCI for most any neon transformer. I have removed one from a franceformer before. ( A tar riden mess!) Charlie told how to easily remove one from a specific make and model of neon xfmr. It can stand by itself I have added a qualifier to his title in this case.

As noted, I have never seen a "Franceformer" with an exposed GFCI. (though they may now be making them.)

Richard Hull

[Rich Feldman]

Especially if this is going into a FAQ, I'd like to add a few words about proper terminology.
Let's all practice saying SGFP (Secondary Ground Fault Protection), when that's what the NST label says.
And reserve the official acronym GFCI (Ground Fault Circuit Interrupter) for the gadgets on household circuits to interrupt electric shocks.

Short story: different flavors of "ground fault" protection circuits have different code requirements and different names.
I just found a reference on the Allanson NST company's website, which IMHO deserves a link in any FAQ: http://www.allanson.com/wp-content/uplo ... ection.pdf

Ground fault protection methods go way back (100+ years) as a way to protect industrial motors etc. from faults that do not trip the overcurrent protetion system.
Starting around the 1960's, inexpensive and extremely sensitive current transformers enabled the domestic GFCI. ( I think they use special core material with extremely low coercive force, and am looking forward to charting the BH curve of one specimen soon. )

The Allanson paper says:
"GFCI's are evaluated in USA to UL943. In Canada their evaluation is to C22.2 No. 144.
The evaluation of ground fault devices for equipment protection is to UL 1053."

NST's are governed by UL506 and C22.2 No. 13.
In the 1980's some vendors began to market a feature they called secondary ground fault and open circuit protection. The article discusses the subsequent history of efforts in the NST industry to address hazards of shock, fire, and equipment damage. It shows its age by saying
"With this product development activity as well as the activity in improving safety standards going on, it is expected that very soon SGFP for neon signs will reach the maturity now enjoyed by GFCI's."

[Ross Moffett]

Can add Franceformer instructions to this thread if you like.. mine does have the fault circuit in an open compartment.

[Richard Hull]

Add them and I will alter the title to mention both type transformers in the title.

Richard Hull

[Ross Moffett]

The Franceformer NST before modification

One of the two fasteners holding the lid on is a rivet, so I drilled it out and removed the other with a phillips head screwdriver.

The ground fault circuit is located in the small pocket that is not filled with tar. It will need to be pulled out. I had to drill out the rivets for the plate holding the fault reset button and also the rivet holding the ground lug in place in order to pull it out - it's a tight fit.

I poked my multimeter probe into each of the cables to trace them to their respective sources, setting the probe to resistance/ring mode. Since there is not a fault at this time, the AC inputs for hot and neutral ring out on both sides of the fault protection relays - that makes it easy to figure out which ones go where. In this case, Red-Orange and White-White are paired, while blue is clipped and tied off.

Here you can see that I've clipped the wires from the fault protection circuit and bypassed it by soldering them together, followed by heat shrinking them. You could also use wire nuts here, but it's not the best thing to do because most wire nuts you can find easily these days are junk and will fall apart inside the casing, shorting AC to the case. Bad news if that happens!

Buyers remorse - upon testing I knew there was no way that this arc is 9000 VAC @ 60 mA as advertised on the nameplate - that's because the primary voltage is rated for 277 VAC and I was running it on 120 VAC! Must re-configure the wiring on my variac.