X10 Community Forum
💬General Category => General Discussion => Topic started by: bkenobi on December 13, 2018, 03:07:28 PM
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I inherited a GFCI extension cord module that I've been using in my garage to charge my camper. For some reason plugging in the camper sometimes trips the breaker in the basement, so I had hoped this would trip first and avoid the walk. It didn't really help but I was already in the habit of using it, so...
Anyway, the module stopped working and I was curious why. It is nicely constructed so I am vonsidering fixing it. But, I'm confused about the construction. It's basically a standard 2 outlet GFCI module in a plastic weather resistant box. But, for some reason, there's also a relay inside between the mains and the outlet. What would that be for?
I haven't tested it yet so I'm not sure if the relay or the outlet failed. Should be easily fixable either way. I just don't understand the reason a relay is in there.
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Are there more spade lugs in the back, because I only see two, which wouldn't be a relay. If the are more in back could it be for increased current capacity? Like 20 amp? Do or did you hear the relay close when you plugged in the cord?
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It's definitely a relay. The unit was made by Leviton adsays "Pro-Grade Electrocord" as the name. It has a Potter Brumfield K10P-4311 inside between the mains and the gfci outlet.
The attatched pictures show the label and the connections.
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I am thinking the same as Dave W.
The relay could be used to carry a higher current. Though the outlet on the GFCI has a 20 amp style outlet on it.
It looks like it breaks the Neutral output also. So both the Line and Neutral are both disconnected when the GFCI trips off.
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I contacted the relay mfg for a datasheet and it confirms that is a standard 15A 120VAC relay in a standard form factor. I think I even have one sitting in my project supplies somewhere if this one tests bad. I don't understand how it works since it appears that the hot and neutral are switched but don't connect to the mains (unless that's internal to the relay).
https://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Data+Sheet%7F1308242_K10%7F0413%7Fpdf%7FEnglish%7FENG_DS_1308242_K10_0413.pdf%7F4-1393144-0 (https://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Data+Sheet%7F1308242_K10%7F0413%7Fpdf%7FEnglish%7FENG_DS_1308242_K10_0413.pdf%7F4-1393144-0)
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I don't understand how it works since it appears that the hot and neutral are switched but don't connect to the mains (unless that's internal to the relay).
Based on the diagram in your photo, it appears to be internal to the relay. I didn't see it at first, either, but there is a line between A and 5 and between B and 6. So terminals A and B connect to the coil, but they also are connected to 5 and 6, respectively. When there is a sufficient current between A and B, the relay actuates, effectively connecting A (and 5) to 3 and connecting B (and 6) to 4. Your other (output?) wires are connected to 3 and 4.
Another side effect is that there will be no connection to the GFCI until the relay's pull-in voltage threshold is met and a disconnect happens as soon as the voltage sags below the relay's dropout voltage threshold. Connected equipment may respond slightly more favorably to power sags as a result, possibly resetting more fully than otherwise.
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It does look like they are using the relay. To act like a 15 amp switch. So the GFCI is not powered at all until the 120 volts AC input is there.
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I pulled was testing another couple relays last night anyway, so I tried that one as well. You are correct. When AC is applied, I do see 120V across the connected pins. I thought relays were always isolated from the control and switched side. This is the first relay I've seen that bridges the two sides internally.
On the up side, the relay seems to work fine. So, I should just need a new GFCI outlet to put it back in service.
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I have no idea why or if it will continue to work, but simply reassembling the cord got it working again. My only guess is that for some reason the relay was not quite latching on power up so it didn't send power to the outlet. Perhaps some rough handling knocked it back into working order.
Results of this investigation: I learned that there is a new-to-me type of relay out there! >!
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I have no idea why or if it will continue to work, but simply reassembling the cord got it working again. My only guess is that for some reason the relay was not quite latching on power up so it didn't send power to the outlet. Perhaps some rough handling knocked it back into working order.
Results of this investigation: I learned that there is a new-to-me type of relay out there! >!
Sounds like the problem I had with my dehumidifier last summer. One of the relays was sticking closed (which kept the compressor (only) running as long as the power cord was plugged in). My initial fix was to open it up, bang on the relay, and put it back together. Eventually, though, I ended up having to replace the relay.
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I would replace it, but the mfg (Potter Brumfield) CSR said the relay is deprecated with no direct replacement. If I could source one, I'd buy it and stash it away for when it acts up down the road.
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You could probably find an equivalent on Allied, Newark or even Amazon but buying just one would probably be more than the cost of a new outlet ($11 @ Walmart).
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This isn't a standard extension cord or else I'd have just tossed it from the start. It's a pretty nice Leviton Pro unit that's pretty nicely weatherized (though not water proof) and armored. But yes, it wouldn't take much to get past the cost of a new one (probably ~$50). On the up side, the only 2 components that can fail are the outlet (standard GFCI ~$15) and the relay (~$20).
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This isn't a standard extension cord or else I'd have just tossed it from the start. It's a pretty nice Leviton Pro unit that's pretty nicely weatherized (though not water proof) and armored. But yes, it wouldn't take much to get past the cost of a new one (probably ~$50). On the up side, the only 2 components that can fail are the outlet (standard GFCI ~$15) and the relay (~$20).
I still don't understand what the relay is there for.
The only thing that might make sense is the relay is there to cut power in the case of a brownout or a voltage drop due to a very long cable run. In that case, the relay would open due to insufficient voltage, and the outlet would be dead.
I can't think of any other reason to need a relay there.
The one thing I found when trying to look it up is that the part number is K10P-A311 (not 4311). :-)
Once I looked for the correct part number, I found more references to it - but none that involved GFCI's at all.
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Might this cord be a Coleman/Southwire 28228802 or similar? If so, the cord features an "automatic power-on reset" that would likely explain the purpose for the relay. Here's the spec sheet: https://goo.gl/4h8H8E
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I wasn't able to find any listings for the module with pictures until just now.
https://www.ebay.com/i/301748032907 (https://www.ebay.com/i/301748032907)
The link will die, so these are the pictures from their listing.
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I think I found something that might explain it, here: https://www.ericson.com/wp-content/uploads/2015/08/How-a-GFCI-works.pdf
It looks like it might be designed to kill power in the event of an open Neutral - with an intact Ground. Since a portable cord has a much higher chance of being damaged (as opposed to a GFCI mounted in a wall box in a home), and since the GFCI can't protect from a short to ground without the Neutral in place to measure against, the relay kills the power if either the Hot or the Neutral are damaged between the breaker and the outlet (like by nicking the cord with a saw).
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That explanation sounds reasonable. I'm not sure how it works in practice, but damaging a cord is obviously more plausible when they aren't armored by a wall.
Btw, the link is dead for me.
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That explanation sounds reasonable. I'm not sure how it works in practice, but damaging a cord is obviously more plausible when they aren't armored by a wall.
Btw, the link is dead for me.
Sorry, I fixed the link. It should work now.
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Thanks for that! It doesn't explicitly say they are using a relay inside their portable GFCI devices, but knowing that mine is wired that way it does make sense how that could solve the problem of an "open neutral".
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Thanks for that! It doesn't explicitly say they are using a relay inside their portable GFCI devices, but knowing that mine is wired that way it does make sense how that could solve the problem of an "open neutral".
I found a patent document describing using a relay to protect against an open neutral condition, which is what I based my search on to find this one.
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I especially liked the "shocked" user on that pdf. rofl