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Ratings for AC bypass caps




 
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WA2SQQ
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« on: December 24, 2017, 12:07:13 PM »

Merry Christmas to all!
I need to add a few .01 caps across the output side of the radiant heat thermostat in my bathroom. 75 / 40 RF trips the GFI circuit. How many volt rating would be recommended, connected across the 120V lines? I seem to recall, a minimum of 1KV.
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DMOD
AC0OB - A Place where Thermionic Emitters Rule!
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« Reply #1 on: December 24, 2017, 12:23:01 PM »

Quote
...The next important consideration is the location of your capacitor with respect to the mains net. Any capacitor that is directly connected across live (L) and neutral (N) on the mains lines is required to have self-healing properties in case of arc-over. Capacitors with this property are marked as X-class (X1, X2 denote different levels of this specification). For capacitors connected between either of the mains wires and earth, so between live (L) and earth (E), or between neutral (N) and earth (E) you are required to use a capacitor that will never fail short, as this can compromise protection earth safety. These capacitors are marked as Y class, with again Y1, Y2, etc. as different levels within this specification. Voltage ratings on these parts may not reflect what you would expect according to VDC = sqrt(2)*VAC. This is because DC and AC safety tests are conducted differently, and may cause different certified working voltages...

https://electronics.stackexchange.com/questions/85165/ac-voltage-ratings-for-capacitors

See also:

http://www.kemet.com/Lists/Filestore/EvoxRifaRFIandSMD.pdf

Since we are dealing with a 336 Volt peak to peak wave form, a 1kV rating would be suitable.

Phil - AC0OB
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"What kind of Koolaid do they make you drink in the Physics Department?" Charlie Epps to Dr. Larry Fleinhardt, NUMB3RS   Smiley
WD8KDG
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« Reply #2 on: December 24, 2017, 01:44:50 PM »

Merry Christmas to all!
I need to add a few .01 caps across the output side of the radiant heat thermostat in my bathroom. 75 / 40 RF trips the GFI circuit. How many volt rating would be recommended, connected across the 120V lines? I seem to recall, a minimum of 1KV.

1st: Consider the insurance implications of your modifications. Will it prevent the GFI from proper function in the "eye" of your home owner's policy.

Investigate how RF is getting into that circuit. Is it because of the position of antenna and or transmission line? After purchasing a new house last year, my first attempt of antenna building caused the smoke/carbon monoxide detectors to scream "Fire......Fire". 

Different antenna & transmission line went to the root cause. Home owner's insurance should be happy?

Regards,
Craig
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Ham radio is now like the surprise in a box of "Cracker-Jacks". There is a new source of RFI every day.
WD4DMZ
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« Reply #3 on: December 24, 2017, 08:04:17 PM »

Sometimes it is just the breaker. My home has a Crouse-Hinds panel and breakers. The CH GFI CB would trip on 75 meter rf. Just for a quick fix I swapped it for a GE that I had and that did the trick. Different circuitry I suppose.

Rich
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WA2SQQ
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« Reply #4 on: December 25, 2017, 11:56:10 AM »

So in my case, the GFI is an integral part of the thermostat for the radiant heating in the bathroom. The wire mesh is imbedded in the thinset cement beneath the tile floor. It is, as insulated as you can be. Moving the antenna is not an option, so it seems that the bypass caps are my only option. Donít have any of the required caps, so plan to look on line and order a hand full.

Thanks to all for their suggestions - looking forward, Happy New Year 2018
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