Re: Advices in Ynet how to prevent fire caused by an old electrical system « Reply #16 on: January 31, 2013, 04:39:33 PM » Author: Medved
I would need better, more detailed photo of it look like and how that is arranged, I really can not see that on the picture. If the two fat ones are 3 pin, there could be indeed something included, most likely some sort of PTC. But the PTC's could not be used alone on mains, as their voltage and current breaking capability is rather limited. It tend to end up in the very hot short circuit mode (when increaseing the temperature beyond the "switch off point", the resistance tend to go back down, until it end up as a low impedance short), mainly when exposed to really high current, what heat up the device very unevenly. So it need the fuse as well... I just do not trust the PTC "resettable fuses" when used alone. They are good to prevent the real fuse blowing up, but they are simply not that reliable in breaking the faulty circuit. Mainly when there is abnormally elevated voltage present, as the prime cause of all that heating. The MOV to PE: The MOV's go into a kind of low impedance breakdown when overheated, so in case it become overheated, it enter a kind of thermal runaway, what "make sure" the overcurrent fusing (or the RCD) trip in time.
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	Re: Advices in Ynet how to prevent fire caused by an old electrical system « Reply #17 on: January 31, 2013, 04:55:44 PM » Author: dor123
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I lives in Israel, which is a 220-240V, 50hz country.

	Re: Advices in Ynet how to prevent fire caused by an old electrical system « Reply #18 on: February 01, 2013, 01:59:39 AM » Author: Medved
Hard to say, what it is, the 3'rd lead seems to be connected only to the LED's... It could be the PTC, but it could be as well two sections, so allow to serve as a trigger for relay cut out,... In any case, from safety perspective, knowing how PTC's behave on higher voltages, it does not look to be able to replace the real fuse...
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	Re: Advices in Ynet how to prevent fire caused by an old electrical system « Reply #19 on: February 01, 2013, 02:53:24 AM » Author: dor123
Quote from: Medved on February 01, 2013, 01:59:39 AM Hard to say, what it is, the 3'rd lead seems to be connected only to the LED's... It could be the PTC, but it could be as well two sections, so allow to serve as a trigger for relay cut out,... In any case, from safety perspective, knowing how PTC's behave on higher voltages, it does not look to be able to replace the real fuse... Medved: If you need, I can put only the two closeup pictures from the three pictures collage i put earlier, so they will look larger and clearer to you: Upper part of the PCB: Lower part of the PCB:
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I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.

I only working with the international date format (dd.mm.yyyy).

I lives in Israel, which is a 220-240V, 50hz country.

	Re: Advices in Ynet how to prevent fire caused by an old electrical system « Reply #20 on: February 01, 2013, 03:28:52 AM » Author: Medved
I see there the 3-pin MOV's being connected by their side contact between the protected potentials and the middle pin used only for some indication purposes. Still, I don't know what the 3 pin MOV's are about, for that I would need at least their detailed datasheet. And still, even when they contain a PTC, I'm suspicious about their ability to remain safe without any fuses - the PTC's just proved to me to be not reliable above ~40V, regardless of the thickness, as they tend to heat up unevenly...
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	Re: Advices in Ynet how to prevent fire caused by an old electrical system « Reply #22 on: February 01, 2013, 02:19:17 PM » Author: Medved
The shape look more like there would be the PTC style ressetable fuses. The non-ressetable fuse won't fit there into quite thin disc shape...
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	Re: Advices in Ynet how to prevent fire caused by an old electrical system « Reply #24 on: February 02, 2013, 02:10:23 AM » Author: Medved
Well, when the VDR's remain functional, the LED would be always ON even when the VDR's are effectively disconnected by the PTC, as the PTC holding current would be enough to feed the LED's. And from this state the circuit would auto-recover, so there is no need to panic the user.   The LED's would turn OFF only after the VDR fail short circuit (what is their normal failure mode at their end of life or after very heavy overload, in the normal application even the desired one). But as the VDR's tend to fail short circuit, the PTC's tend to end in that mode too...
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	Re: Advices in Ynet how to prevent fire caused by an old electrical system « Reply #26 on: February 02, 2013, 07:56:28 AM » Author: Medved
The MOV's normally carry current only when the voltage become above the threshold. Once the voltage drop, they are not conductive anymore. So normally they carry only the current necessary to keep the voltage on their clamping level during the overvoltage spike. When the spike disappear, they stop conducting and so remain passive. With a longer overvoltage the PTC lower the current, but the VDR continue to clamp the voltage. After thevoltage lower back, the VDR stops conducting, so the whole thing cool down and again, the PTC get closed. With the eventual thermal breakdown the temperature is limited by the PTC below the limit, where the VDR clamping voltage get down, so if it is not damaged, it just recover by itself. Only when the MOV get damaged by the overvoltage (into a short circuit), the PTC keep the current at it's holding current and the LED stop illuminating, as it is shorted by the failed MOV.
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	Re: Advices in Ynet how to prevent fire caused by an old electrical system « Reply #27 on: February 03, 2013, 01:53:01 PM » Author: dor123
This is the maximum that I can do, to show you the numbers of the MOVs of the surge protector:
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I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.

I only working with the international date format (dd.mm.yyyy).

I lives in Israel, which is a 220-240V, 50hz country.

	Re: Advices in Ynet how to prevent fire caused by an old electrical system « Reply #29 on: February 03, 2013, 02:52:03 PM » Author: dor123
As the pictures I put, are on the max size allowed in Picasa, I can post the numbers and letters by myself: Left and right thick MOVs reads: "TVT 14431" Center thin MOV reads: "TVR 14???" and the rest is unknown as that MOV have been distorted.
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I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.

I only working with the international date format (dd.mm.yyyy).

I lives in Israel, which is a 220-240V, 50hz country.