Extending life of well pump relay...?? - Page 3

 

wmbjkREMOVE@citlink.net wrote:

I don't think that really helps. Do to slight differences in opening/closing
times, one relay ends up taking the switching load.

 

wrote:


Sure, but the object is to have one relay working. Consider it as
having the replacement waiting in the wings.  :-)

Wayne

 

The technique Wayne is tooting is quite a common technique used in
industrial controls.

The real cure is usually to put the two contacts in series.  This puts more
space in series with the contacts faster, on opening, to eliminate the
arcing and burning (counter EMF) that wears down the contacts.

If the current draw is too high for the contact rating then two in parallel
will be the cure. The opening counter EMF is usually the problem, though.

 Many contactors have more than one contact and this can be done quite
easily. Propagation speed differences are not a problem either
configuration.



Sure, but the object is to have one relay working. Consider it as
having the replacement waiting in the wings.  :-)

Wayne:


wrote
I don't think that really helps. Do to slight differences in opening/closing
times, one relay ends up taking the switching load.

 

On 2/11/2010 11:47 AM, wmbjkREMOVE@citlink.net wrote:

AHHHH....Great idea...!!!...thank you....have fun....sno
    

--
Correct Scientific Terminology:
Hypothesis - a guess as to why or how something occurs
Theory - a hypothesis that has been checked by enough experiments
  to be generally assumed to be true.
Law - a hypothesis that has been checked by enough experiments
  in enough different ways that it is assumed to be truer then a theory.
Note: nothing is proven in science, things are assumed to be true.

 


  All switches have a life expectancy - typically about 100,000 switch
cycles.  You must decide which is causing contact failure.  Do you
have a wiring problem?  Is your motor too large for the switch contact
ratings?  Is some defect in the motor causing switch arcing?  Or is it
just switching too many times.

  Well, your water pressure should drop by a certain amount before the
pump triggers.  To reduce the number of power cycles, that water
pressure variation should be greater.

  We once replaced switches with mercury wetted contacts so that
switch life expectancy was longer.  Today you can use a solid state
relay.

  If the pump motor is too deep, or is the wiring is too undersized
causing too must current on startup - both are examples of defective
wiring or pump that can cause contact failure.  Defective wiring means
the pump consumes too much current on startup - and will eventually
cause pump motor failure.  Low voltage would also cause this problem.
Then when you use heavier contacts, the symptom is cured but the
problem remains.

  Bottom line - nobody can provide a useful answer without critical
numbers that first define the problem.  Replacing something only on
wild speculation (ie SSR contacts) may only result in an expensive
pump motor failure later.  Only one with electrical knowledge (and the
necessary test equipment) can get numbers.  Until you have those
numbers, then nobody can recommend a solution.

  Of course, counting the number of power cycles per hour is a first
number you provide for a useful answer.