Trouble shoot quandry

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electricmanscott

electricmanscott

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Location
Boston, MA
Reworked some wiring for a chandelier as part of a large remodel. Removed a three way and made other end a single pole. Installed a dimmer. "Worked fine before you did anything" The problem is this. When dimmed there is intermittent brightening of the fixture. Maybe every 20-30 seconds or so the light brightens and then goes back to the level it was at. The brightening lasts for just a second. This is the only fixture I have seen that is affected.

I have isolated it to when the heating system is running. It is a new energy hog geo thermal system. So it only happens when the house is under the heavy load of the geo thermal. No other time. Apparently no other circuits.

Thoughts?
 
As you probably know, brightening of a light while under load is a key sign of a loose grounded conductor somewhere from the service all the way to the xfmr. However, you would probably see that on other lights on the same phase.
 
Replace the dimmer, first with a switch to see what happens, then a new dimmer if the old one does it again.
 
electricmanscott said:
Installed a dimmer. "Worked fine before you did anything" The problem is this. When dimmed there is intermittent brightening of the fixture. Maybe every 20-30 seconds or so the light brightens and then goes back to the level it was at. The brightening lasts for just a second. This is the only fixture I have seen that is affected.
Thoughts?
Click to expand...

Was the light not previously on a dimmer? If so how can the comparison be made in order to say it worked fine previous to your work?
The condition you stated is normal for the light in my dining room when dimmed when other loads go on and off.

Is it true that this does not happen when the dimmer is on at 100%? My dining room light is fine when set full on at 100%.
Seems like it is just easier to observe line voltage fluctuations on some dimmers when set to a low setting.
 
I've heard that lights on dimmers are much more sensitive to voltage fluctuation. It may be that you have simply rendered the normal voltage fluctuation in that home visible.

-Jon
 
There was a dimmer on the light before I worked on it. It was a cheapo rotary dimmer. The new dimmer is a Lutron Ariadni. I replaced it again.

I didn't see the light in operation before I worked on it.

I'll be back there today to look deeper.
 
Problem solved. Kind of. I ran the heat with the fixture dimmed. I measured voltage at the fixture. It would jump about 5 volts every 10 20 30 or so seconds and last for a couple of seconds max.


I moved the circuit feeding the light to the opposite phase and the problem ceased. I could only detect the jump on the circuit after the dimmer.

Still not sure of the cause.
 
It's weird, but it's such a sexy trick when it works.

Similar oddity in my own house, cured it the same way. Whenever I dimmed the kitchen lights, the furnace would register a trouble code and kick the fan on. They were on the same phase, I moved one and the problem stopped. Very weird.
 
George Stolz said:
It's weird, but it's such a sexy trick when it works.

Similar oddity in my own house, cured it the same way. Whenever I dimmed the kitchen lights, the furnace would register a trouble code and kick the fan on. They were on the same phase, I moved one and the problem stopped. Very weird.
Click to expand...

I'm not surprised as the control boards in these new-fangled furnaces have little or no EMI/RF filtering on their power inputs. Typical of the lack of quality in a lot of today's products.

Putting a high-quality EMI/surge strip (Tripp-Lite makes them but they are pricey) would probably also have cured the problem and would help protect the furnace control board (which is also very pricey) as well.
 
sameguy said:
Is there a speed drive in the new furnace?
Click to expand...

Not sure. It's a pretty "high tech" unit. At least it looks like it is. It's stainless steel. :grin:


I didn't have any involvement in it's installation but know that I think about it when listening to it it does vary in speed. Starts of blowing slowly, ramps up, goes back down etc.


Tell me more. :confused:
 
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