Carl can you provide a schematic to your setup?

John


--- Carl Denk <cdenk@alltel.net> wrote:

> Just to summarize symptom: Relay drops out,
> switching PLC from 120VAC > 
> 12 VDC switching supply to 2 lead acid batteries
> connected with diodes 
> to relay. Switches OK when 120 is from utility, PLC
> resets when 120 is 
> from generator. Switch over to 120 supply is OK with
> either utility or 
> generator source.
> 
> Did disconnect one battery at a time, no change. Did
> add house 
> electrical load, as opposed to just exercising
> generator with no 
> transfer, no change.
> 
> ??
> Replace relay - with what?
> Add capacitor to bridge during changeover - how big,
> where?
> While only with generator source?
> 
> ~)
> 
> Carl Denk wrote:
> > Yes, it's likely that the voltage is dropping
> causing the PLC to reset, 
> > but doesn't explain why, with the 3 voltages (2
> batteries and switching 
> > supplies, and the 120 volt are stable (though the
> 1 battery will be a 
> > volt or so higher due to the generator's engine's
> alternator (15 amp 
> > max.) being on line)(more on that below), the
> relay (have tried 3 
> > different manufacture's equivalents) is dropping
> out contacts pulled 
> > apart by spring, and while on utility power, no
> problem. The 2 batteries 
> > are connected to the PLC by diodes as you suggest.
> >
> > Currently the switching supply is 12.1 volts, the
> batteries are 
> > generally in the 13 - 14 volt range. It would be
> possible to provide a 
> > higher voltage switching supply, but there is
> other equipment on line 
> > including numerous automotive 1" cube relays rated
> at 12 VDC, 
> > electronics, and sensors that may have resistor
> voltage dividers, that 
> > makes that a poor choice at this time.
> >
> > After sleeping on it overnight :), the only thing
> different with the 
> > genrator running on the 12 VDC side is the
> generator's engine (27 Hp. 
> > Kohler) does have an alternator and regulator to
> service it's battery 
> > (beefy 12 volt deep cycle marine type lead acid)
> is on line. Both 
> > batteries have their own charger/maintainer also.
> Will do some 
> > experimenting with taking 1 or the other battery
> out of the circuit. The 
> > engine alternator to battery cable is heavy,
> probably "00", and then 
> > from the battery to the UPS area is 35' (10m) (one
> way) of #12 wire. 
> > Would expect the battery to absorb most spikes,
> noise, etc.
> >
> > The PLC does have LED's for pause, RTC Error, and
> Run Error. To the 
> > eyeball, the 3 LED's are indicating the same as if
> powering up the PLC, 
> > which tends to support the theory of dropped
> power.
> >
> > Please keep the ideas coming. :)
> >
> > Dwayne Reid wrote:
> >   
> >> At 07:06 PM 4/9/2007, Carl Denk wrote:
> >>
> >>   
> >>     
> >>> The DPDT relay (Square D 8501KP12P14V20) has a
> 120 volt coil going to
> >>> the house power with the PLC input going to the
> common contacts, the 120
> >>> power supply to the  N.O. contacts so if there
> is 120 volt power
> >>> available, the power comes from the 120 volt
> supply. Each battery goes
> >>> to one of the N.C. contacts so if the 120 isn't
> there, the batteries are
> >>> the supply.
> >>>     
> >>>       
> >> I take it that the PLC loses power during the
> time while the relay is 
> >> switching between its contacts?
> >>
> >> If so, I expect that to be the problem.
> >>
> >> Can I make a possibly simple suggestion?
> >>
> >> Ensure that your DC supply while operating from
> AC power is higher 
> >> than the float voltage on the batteries.  Then
> use diodes to OR all 3 
> >> sources of power: one diode anode from each of
> the batteries and from 
> >> the AC power supply.  The cathodes of all the
> diodes feed the PLC power input.
> >>
> >> By picking the output voltage of the AC-powered
> DC supply to be 
> >> higher than what is present on the batteries, you
> ensure that the 
> >> batteries are not loaded.  When the AC power
> disappears, the diodes 
> >> smoothly transition to whichever battery has the
> highest voltage.
> >>
> >> Easy to test to see if this fixes your problem. 
> I suspect that it will.
> >>
> >> dwayne
> >>
> >>   
> >>     
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