Re: [Phys-l] Step down transformer trouble

[brian whatcott <betwys1@sbcglobal.net>]

On 7/6/2011 4:58 AM, Paul Lulai wrote:
> Hi.
> We can't keep our doorbell stepdown transformer working.  I thought i would check this group for thoughts.
> The transformer drops to 16v.  That matches the input for our doorbell. The transformer is connected to ground and both the black and white house wires (as directed on installation instructions).  It is installed onto a standard junction box with (which has a cfl attached).
> I've changed transformers multiple times.  I checked the doorbell.  I found no problem, but thought a $20 change of bells might so it, so I changed it anyway (after the 2nd transformer).
> Any thoughts?
>
> Paul Lulai
> Physics Teacher
> St Anthony Village Senior High
> 3303 33rd Ave
> St Anthony Village MN 55418
>
> (w) 612-706-1146
Door bells may be found which operate on 6 volts, 12 volts,
 even 24 volts.

Their transformers read higher off-load - around 8V 16V and
 28V respectively.   They should not DROP to 16 volts - as
a 24vac transformer might,when  connected to a 12 volt bell.

Applying a higher voltage rating transformer to a lower
voltage rated bell may overload the transformer.

Doorbells may be found to require different power input levels.
Operating a high-power bell on a low power transformer invites
the transformer to fail.

Some bells can produce vivid spikes of back EMF into the
 transformer - with similar consequences.

Some house wiring schemes whose ground to neutral connection
 is insecure, allow the nominal 120 volt half of the biphase
 output 120/0/120v from the pole pig (distribution transformer)
 to go unbalanced - whose immediate effect is on incandescents
 - sensitive as they are  to over volts.

Brian W