[RE-wrenches] GTWB outage monitor question

[JRQ]

Allan,

I was thinking more of a CT relay. Although you're right, if it's going to be on the battery cables, there would need to be some kind of programmable option to relay mechanism that would trigger only under a range of current values, not merely the presence of DC current. I'm sure there is something like that out there for industrial applications, but it would seem to be some exotic fauna. 

On second thought, it would make more sense to use a CT relay on the AC input from the grid to the inverter. As long as the customer is pulling power from the grid, or supplying it, there will be current on that circuit, and no current when the grid goes out. You would have to supply power, then, to the relay and then run another circuit to the alert load through the relay. I'm not sure exactly how the wiring for this system is set up, but that's an easier bar to clear. Near the BOS, you could mount a 125A sub-panel from the inverter AC protected loads output with 3 breakers: one feeding the load center in the house, one for the relay power supply and one for the alert load. Then you could run two #12 wires from the relay through the raceway that contains the main load center feeders to the alert load.

I found a company supplying AC and DC CT relays and switches on a cursory search on google:

http://www.automationdirect.com/adc/Overview/Catalog/Sensors_-z-_Encoders/Current_Sensors_(AC_-a-_DC)


Jeffrey Quackenbush


________________________________
 From: Allan Sindelar <allan at positiveenergysolar.com>
To: JRQ <quackkcauq at yahoo.com> 
Sent: Sunday, August 12, 2012 4:00 PM
Subject: Re: [RE-wrenches] GTWB outage monitor question
 

Jeff,
Great in theory...but I'm missing a few details as to how to put
      it into practice.

Can you tell me where I might find a relay with a 175A contactor
      capacity, with a rating of at least 65V DC and an AC coil? If I
      understand you correctly, that's what you are describing. I would
      be surprised if such a product exists. Then how would you set up a
      circuit to close the relay when current exceeds a few amps DC?

And yes, the batteries are with the rest of the BOS, away from the
      home.

Thanks, Allan


 Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com 

 
On 8/12/2012 11:17 AM, JRQ wrote:

Allen,
>
>
>If it's a backup system, the batteries aren't going to draw a significant amount of current until the grid goes down. If you can find a DC relay that triggers after, say, 2A or 3A, install it on the battery conductors. The relay should come on, then, when the grid goes down, but not when the battery bank is in float charge-mode. It will stay on for sometime after the grid comes back up, but that won't compromise its alerting function, and it could even be useful to the customer to have a sense of the whole discharge-charge cycle for his system. This is assuming that your batteries aren't also remote from the home.
>
>
>Jeffrey Quackenbush
>
>
>
>________________________________
> From: Allan Sindelar <allan at positiveenergysolar.com>
>To: RE-wrenches <re-wrenches at lists.re-wrenches.org> 
>Sent: Thursday, August 9, 2012 11:18 AM
>Subject: [RE-wrenches] GTWB outage monitor question
> 
>
>Wrenches,
>For a grid-tied-with-backup system that is still in the
                design stage, we have a customer request for a signal to
                let them know when an outage occurs and they are running
                on backup power, so that they may turn off unnecessary
                loads and "go into backup consciousness". The problem is
                that the entire home would be on backup, with the GTWB
                system tied into a meter and main disconnect location
                away from the home, rather than the more typical main
                panel/subpanel approach at the home. Any relay-based
                alarm based on loss of grid AC would not likely trigger,
                as the switchover is too quick. Any ideas for simple
                solutions, please?
>Allan
>
>-- 
> Allan Sindelar
>Allan at positiveenergysolar.com
>NABCEP Certified Photovoltaic Installer
>NABCEP Certified Technical Sales Professional
>New Mexico EE98J Journeyman Electrician
>Founder and Chief Technology Officer
>Positive Energy, Inc.
>3209 Richards Lane (note new address)
>Santa Fe, New Mexico 87507
>505 424-1112
>www.positiveenergysolar.com 
>
>
> 
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