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Topic # 157669 9-Dec-2014 10:12
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Hey guys,

I am using a load of the Fibaro 2x1.5kW relays for controlling all the lighting circuits in my house. Most of my lighting is LED aside from a set of flouros in the garage.

However on two of my Fibaro relays I get an occasional 'jam' where the relays lock in the ON position. It only happens on the garage flouro circuit and the main hallway lighting circuit, which has 6x13W LEDs. After discussing with the Fibaro guys they indicated it is most likely due to in-rush current causing the relay contacts to arc and lock on. The only way to resolve the issue is to gain access to the relay itself and give it a few 'taps' and this releases/jiggles the relay and then everything is fine.

This has only happened a handful of times over the last 18 months but I would like to get it resolved. 

The Fibaro guys suggested I install a contactor between the relay and load/transformer, so I was wondering if anyone had any suggestions for something suitable? Low cost, low rating (only needs to handle 10A), and the most important thing is it needs to be small - so it can fit in behind my switch plates alongside the Fibaro relay modules.

Any tips or suggestions?

Cheers,
Ben



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  Reply # 1192492 9-Dec-2014 23:55
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If the relays you already have are those little circuit board mounted relays. They are unlikely to be rated to switch loads that are inductive or with big inrush currents. Meaning not suitable for either fluro lights or mains fed LEDs. Imagine that the mains is at it's peak (360V) when the relay contacts close. You will get some serious inrush current to charge those filter capacitors in the power supplies of all those LED drivers. You will very easily exceed 10A. What is the coil voltage of those relays? If it is 12V then remove the failed relays and install some of these http://www.jaycar.co.nz/productResults.asp?keywords=sy4040&keyform=KEYWORD&SUBMIT=Search







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  Reply # 1192596 10-Dec-2014 08:08
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The coil voltage is 240VAC - the existing light switch is used to manually operate the relay using mains 240VAC. So what about something like this?

http://www.surplustronics.co.nz/products/4013-240-ac-relay-240-ac-coil-16a-230v-ac-contact


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  Reply # 1192636 10-Dec-2014 09:19
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Do fibro have anything uprated to suit your situation?
Do you know how high your inrush is?



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  Reply # 1192638 10-Dec-2014 09:21
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They do have a 3kW rated relay - but I am not sure what the in-rush is sorry. 

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  Reply # 1195267 10-Dec-2014 21:54
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BTW Omron makes good relays (and other stuff).  You can check the data sheet for the contact power rating.

Solid state relays are available with zero crossing switching, it turns on only when the mains goes through a 0V point.  (Sorry, too tired to look for one now.)




You can never have enough Volvos!




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  Reply # 1195273 10-Dec-2014 22:01
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Thanks for that tip Niel - I will check out that brand.

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  Reply # 1195310 10-Dec-2014 22:31
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Just be a bit careful with SSRs. When they fail they fail closed rather than open. They have caused a number of fires on air conditioning systems with electric duct heater banks that don't have adequate saftey circuits. Probably not an issue on lighting circuits.



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  Reply # 1195312 10-Dec-2014 22:39
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That is pretty much what is happening with the existing ones - the relays fail closed due to the inrush current - not a huge deal just means you can't switch off the lights, but definitely not a safety concern.

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  Reply # 1195357 11-Dec-2014 00:23
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Solid state relays are not the best for running LEDs. As when off their internal capacitance allows a small current to bleed through so the LEDs will very dimly glow. And when on They have approx 1.2V volt drop. Meaning they get hot. And they don't conduct any current near the 0V point of the mains cycle. Which means they can affect some dimmers or electronic power supplies that need to sense the 0V point.

Short answer - Stick with a mechanical relay / contactor. You need to find one that is rated for use with electric motors.

Now if you were wanting to control some filament lamps. A solid state relay would be ideal. Because a solid state relay only switches on at the 0V pint. This means less inrush current to the lamps. Less filament stress. Longer lamp life.





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  Reply # 1195373 11-Dec-2014 06:41
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You want a good quality SSR, not the ones that leak a bit of current.

True, there is a 1.2V drop which wastes power.  But it is only 1/4W for a 50W load (i.e. nothing).

Mechanical relays are simpler.  Their failure mode (for an incorrectly spec'ed relay) is the contacts weld together.  An SSR on the other hand fails only because the silicone fused, and the likelihood is less than the likelihood of your computer failing.

With mechanical relays you get a range of different contact materials and platings.  Some don't work for signals but works for inductive loads.  The data sheet will tell you, but sometimes not clearly so read carefully.




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  Reply # 1195380 11-Dec-2014 08:04
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Yep - to be honest I am struggling a bit with the data sheets. I have emailed Omron with some questions so will wait and see what they suggest for my use-case. Appreciate the comments guys.

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  Reply # 1195381 11-Dec-2014 08:16
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you need the omron Ly1n or similar. they are a din mounted plug in relay that will do what you need. youll have to mount it in the switchboard or box in the roof space etc. take note that they come in different coil voltages so make sure your gettin the 240v coil one.

of course they come in 12 and 24v ac/dc too so you could get a relay that could be directly switched from the fibaro (may need a reverse blocking diode for back EMF)



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  Reply # 1195383 11-Dec-2014 08:18
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Yeah - that is my big problem - space. I don't have any attic/roof space so this relay is going to have to live behind the flush box along with the Fibaro relay. Pretty tight in there already so that is why I am trying to find a very small form factor relay. Proving difficult which is not surprising since we are dealing with higher voltages etc.

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  Reply # 1195386 11-Dec-2014 08:31
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Can you install another box next to what you have for larger items?
Even if its a tight fit behind your current one there are requirements for heat dissipation that I would recommend following.  Could one be installed below maybe?



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  Reply # 1195387 11-Dec-2014 08:33
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For one of the switches it won't be a problem - it is in the garage and I have custom wood lining so easy to get in behind and make some space. The other one however is in an internal aerated concrete (Celcrete/Hebel) wall - 50mm panels...not so easy...

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