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2 x Brand new FGS221 Stuck Already?


M4T VW

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Okay. So let's double check. This relay switches 7 LED totalling 42 W of power? Or do you mean this relay switches other things? If so, what's the total power?

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  • It only switches 7 LED lights. All are 240V and total of 42W. They are large units sunk into a wall with built in transformers.

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    Sounds good. The NTC can handle the power (by a large margin) - so go ahead.

     

    Is it possible that you were thinking of a "snubber circuit"? These things are often mentioned when talking about extending the life of relays. These are put parallel to the contacts. They reduce sparking when the load is inductive, for example a pump. A snubber does not help with inrush current (LED with electronic transformer). But if you google "relay" you'll often find snubbers and NTCs mentioned in the same article.

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  • Ok Peter, I will give it a go thanks. Fingers crossed!

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  • All wired up and working. Just testing heat tonight as the thermistor gets warm. I want it to be on for an hour or so and see what it's like.

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    That's OK, just keep about 1 cm of free space around the NTC. That is part of its operation. Initially, the NTC has the resistance as specified. That causes the inrush current of the circuit to decrease. When current starts flowing, it heats up the NTC, causing its resistance to drop. This makes the voltage drop, which makes the power drop and further heating stops. This will happen fast, most part of it will happen in less than a second. For full equilibrium, you'll have to wait 1-2 minutes. After that, temperature doesn't change. If you switch of the load, heating stops and resistance increases again. After 30 - 60 sec it will have regained its room temperature resistance. If you don't wait that long, it will still decrease inrush current, but to a lesser degree. In theory, you should wait at least a few seconds before switching on again, but in practice I don't pay much attention to that rule. If you put the NTC in a closed box, the dissipation will be between 0,5 and 1 Watt, that's about the same as a Fibaro module. It will increase the temperature in the box (like adding a second module would do) a few degrees. Be careful with your fingers though, temperature of the device can (and should) reach up to +/- 100 °C. In fact, it should heat and one should not attempt to cool it (as that would increase power loss). The NTC can withstand even higher temperatures. I attached a document with some theory behind all this.

    So! Now all we have to wait a few months to test it

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    /emoticons/default_icon_smile.gif" alt=":-)" />

    The contacts shouldn't stick... And the whole circuit should work reliably!

    Please login or register to see this link.

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  • Great! I set the lights to come on at sunset last night and they did at 8:24. I left them on until about 11 so just over 2 and a half hours and the NTC was room temp.

    (I tried adding a picture from my phone on the last post but it didnt work. I will upload it when i get home tonight)

     

    Tonight i plan to solder some wires to the legs of the NTC and heatshrink them. This will make it easier to wire in and try and find it some space in the box.

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    • 2 years later...

    This discussion is very helpful, thank you!

     

    Having tested with the NTC, what would you say is the max load to use for led bulbs or spots? 42 W worked well, would it handle up to  a 100W?

     

    One more idea, since the Fibaro dimmer using a 2 wire setup does not cut the current completely when dimmed all the way down, do you think the inrush current can be disregarded in that case?

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