[RE-wrenches] common ground on fm80 aux output?

[Ray Walters]

I don't believe the aux is PWM.  It should be a straight 12 v 200 mA 
output as I recall.  Its just enough to run a battery fan, or a 12 v 
relay.  You shouldn't need anything else.  Being current limited, it 
doesn't even need a fuse.
Also you need to run both leads (pos and neg) from the aux output to the 
control side of the relay.  It is its own output and you will probably 
cause unfortunate things to happen if wired in common with anything 
else.  I usually use signal wire with multiple conductors, so trying to 
get away from one control conductor is fool hardy anyway.

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 12/5/2014 3:09 PM, Hugh Piggott wrote:
> Hi Hugh again
> Just to clarify the set up:
> The SSR controls the AC power from the inverter to the heating load. 
>  It switches partway through each half cycle and thus controls the 
> power to the load.
> The input to the SSR requires a power supply 8-32 V present all the 
> time it is working.  I suppose it might be feasible to take this from 
>  the AUX but as this will be pulsing PWM I don't want to rely on that. 
>  Its a supply voltage to the input and not a control signal and for 
> that reason I want to take it from the main battery which happens to 
> be a 24 volt one which is ideal.
> The control signal is 0-10 volts DC and this controls the amount of 
> power the unit delivers smoothly.  I want to get this from a capacitor 
> that charges off the aux output so that is turns the PWM into an 
> analog voltage signal that controls the SSR and controls the load.  I 
> do this all the time with tristar outputs so it does work.  I have 
> just never done it with the AUX of a FM80 controller.
>
> So my question again is simply this.  Can I connect the ground of the 
> AUX to the inverter batter ground negative?  Most likely it is already 
> connected, but I'd like to know if connecting it will damage the FM80. 
>  I am also trying the outback forum.
>
> thanks for any help
> Hugh
>
> On 5 Dec 2014, at 18:44, Hugh Piggott wrote:
>
>>
>>       hi wrenches,
>>
>> I am installing some load controls for a client who has a FM80 
>> controller. I don't have experience with this product. It has a 12V 
>> aux output that I wish to drive an SSR but the wiring is complicated 
>> by the fact that this SSR also needs a power supply as well as a 
>> control signal. I want to use 24V nominal system battery for the SSR 
>> power and AUX for the signal. Can I connect the grounds together?
>>
>> Additional info. I am using a phase control SSR driven by a 0-10 volt 
>> signal to control an AC load with phase angle shift control. I plan 
>> to put an RC filter that converts the PWM output of the AUX from the 
>> CC to give an analog voltage output that determines the loading of 
>> the inverter. Crydom MCPC2450
>>
>> thanks for any help before I go on site next week
>> Hugh
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