Question about unexpected element on indication

[swander]

I am 99% done with my control panel (Kal clone). Nothing is missing relevant to this question.

When I engage the element select switch, with PID not firing the SSR control, my 240v indicator lights about 50%. When PID fires, it lights fully.

I don't yet have my elements attached yet as I am waiting on delivery of necessary bits. This is key to my question - there is no load on the output yet.

I think I can describe the wiring without providing a schematic. The main contactor is engaged, as is the element contactor. L2 of a/c is flowing through both energized relays and is present on one leg of the LED indicator. The L1 leg flows thru main contactor, the SSR, and the element contactor. LED is wired across the two controlled legs of element contactor, in parallel with the soon to be connected element.

Is it possible the SSR is allowing enough leakage current on the L1 leg to partially light the indicator?

If this is true, anyone with a Kal clone or most any other design, would probably know the answer as I would expect it to be a common observation, that with no element plugged in, the indicator would illuminate at a low level with element selected.

My hope is that with the element plugged in, the minor current lighting the LED will pass through the element and the light will behave as expected. I would rather not risk dry firing my element to test this theory though.

Has anyone seen this symptom?

Thanks!

 

[orangehero]

You've go it. It will (should) not be illuminated with the element plugged in.

 

[BrunDog]

Check the outputs (240VAC that will power elements) with a VOM. Should be 0VAC when off and 240VAC when on. That should put your mind at ease until you can connect the load of the elements.

-BD

 

[orangehero]

Check the outputs (240VAC that will power elements) with a VOM. Should be 0VAC when off and 240VAC when on. That should put your mind at ease until you can connect the load of the elements.

-BD

Doing this won't put his mind at ease because SSR's leak a small amount of current. With no load plugged in you will not see 0VAC. It's enough to light up an LED lamp.

 

[swander]

I think I have confirmed it is leakage current lighting the indicator. With no load my Fluke 77 says 101v.

Instead of risking my element, I decided to risk a 60w incandescent bulb and basically just took a lamp plug and held to the contactor lugs... lamp didn't light, indicator turned off, life makes sense again.

Thanks for the quick replies,

John

 

[bbohanon]

Yea Kal mentions this behavior with his panels and the SSR leakage..It does this on mine as well. No worries and no dry fires to date.

 

[-TH-]

I put a 7.5 kohm 8W resistor wired in parallel with my LED. Now the light no longer comes on when the element is unplugged.

 

[Dubchedford]

I put a 7.5 kohm 8W resistor wired in parallel with my LED. Now the light no longer comes on when the element is unplugged.

Interesting idea, I need to add this to my panel. Thanks for the tip.

 

[-TH-]

Interesting idea, I need to add this to my panel. Thanks for the tip.

Here's the full thread on it if you want more background info...
https://www.homebrewtalk.com/showthread.php?t=376020

 

[Riot]

I put a 7.5 kohm 8W resistor wired in parallel with my LED. Now the light no longer comes on when the element is unplugged.

I had this same issue with no load plugged in, went for the same solution. Pretty sure mine has 17k ohm across the outlet, indicator no longer lights unless the pid is actually trying to fire the element

 

[swander]

I think I'll live with the leakage current partially lighting the indicator and call it a feature. It will visually show me my contactors and element select switch are indeed working correctly and that my SSRs have not failed in the shorted position (as I read this is common when they fail). I think with mine I can tell the difference between leakage and full on, but can always switch between HLT and BK if I have any doubts. Anything other than a double failure would be obvious.

 

[ajdelange]

If you can't fix it, feature it! Supposedly the motto of IBM in the olden days.

 

[doug293cz]

If you can't fix it, feature it! Supposedly the motto of IBM in the olden days.

I always heard that phrase applied to Microsoft.

Back on topic. He can fix the LED lighting issue, but after thinking about it, he decided he liked the way it works now after all.

Brew on