Found standard dimmer on low voltage transformer - Electrician Talk - Professional Electrical Contractors Forum

duckdodgers · 12-24-2007, 11:57 AM

Hello All,
Just real quick, I bumped into an existing installation where a low voltage transformer has a standard incandescent dimmer ahead of it (wired to the line side). All seems to be working well and the owner claims its been there for a couple of years. Is this dangerous at all? If not dangerous, will the transformer give out early?
thanks

**Speedy Petey** · 12-24-2007, 12:31 PM

Some low voltage systems do use a standard dimmer. Not many, but some.

sbrn33 · 12-24-2007, 02:23 PM

I believe that all the low voltage dimmers do differently than a standard is to eliminate lamp hum that is so common with dimming low volt lamps.

goose134 · 12-25-2007, 11:33 AM

A lot of whether or not the transformer gives out depends on what kind it is. As stated above, some LV fixtures can be dimmed with a standard dimmer. I've seen situations go both ways, where the dimmer smoked the transformer, and vice versa. Often, if the incorrect dimmer is installed at capacity, you'll know soon enough. But sometimes the wrong dimmer using a fraction of its capacity will run for years, just a lot hotter. Merry Christmas!

kbsparky · 12-28-2007, 03:09 PM

Keep in mind that most standard dimmers will reduce the average Voltage, while not reducing the peak Voltage.

This results in a standard incandescent bulb dimming, but can wreck havoc on the windings of a transformer with the constant switching on and off that is characteristic of such a waveform.

Some of the heavier winding units may be able to withstand this scenario, while cheaper units can burn out more easily.

The use of a "low voltage" dimmer can minimize this effect.