Simplest electromechanical relay circuit

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NFPA certainly cares about fires, and we continue to have electrical

fires.

Geez, really? The installed wiring base spans at least 90 years so, unless there is a requirement for retrofit, don't expect an abrupt decrease in frequency.

 

[RosemontCrest]

That is not really the best. There are special cases (Classified
locations and some specific safety equipment relating to classified
locations) where switching neutral is correct, but generally it is not the
best idea. See NEC article 500 et seq.

Thank you. Your example suggests that instead of "not *really* the
best," it is "not *always* the best."

 

[josephkk]

I should qualify that statement. Always switch at least the hot leg. If
you have a double-pole relay, switch both hot and neutral.

That is not really the best. There are special cases (Classified
locations and some specific safety equipment relating to classified
locations) where switching neutral is correct, but generally it is not the
best idea. See NEC article 500 et seq.

?-)

 

[Maynard A. Philbrook Jr.]

That is not really the best. There are special cases (Classified
locations and some specific safety equipment relating to classified
locations) where switching neutral is correct, but generally it is not the
best idea. See NEC article 500 et seq.

?-)

Low side switching is very common but it usually does not leave the
safety zone. For example, inside an industrial control cabinet and
integrated reversing relays that passes the neutral of a pair of coils
through an overload contact.

Other examples where you may need various voltages to be switched from
a single triac output module array. Those would have it's common leg
tied to neutral and all the devices coming to each triac output would be
alive at all times with their required voltages, 24, 48, 115, 230, 480
AC. Etc.

Jamie

 

[Greegor]

Chances are, you have a 12V coil.

The relay case clearly says 24V. It
surprises me that a mere 11 VDC
energizes it.

Wasn't there a "rule of thumb" for
voltage rating relays yourself?

I seem to recall 1.5 times the voltage
that barely actuates it, but it could
have been double just for reliability.

How did they figure the top end of
the voltage range?

I seem to recall some relays marked
with resistance and a current but
no voltage specified.

 

[Jasen Betts]

Wasn't there a "rule of thumb" for
voltage rating relays yourself?

I seem to recall 1.5 times the voltage
that barely actuates it, but it could
have been double just for reliability.

How did they figure the top end of
the voltage range?

A bit less than what melts it? *


(*)
or degrades plastic parts too quickly etc
at max rated ambient temperature