Welcome to the Solar Collector
Brainstorming and Development Page!


 

Home

Hot Air Collector

Hot Water Project 1

Hot Water & Space Heating

Solar Electric

Solar Construction 101

FAQs

Best Collectors

Simply Solar
Sign up Calendar Latest Topics
 
 
 


Reply
  Author   Comment   Page 1 of 2      1   2   Next
woodwaterwheel

Registered:
Posts: 6
Reply with quote  #1 
I've got a local solar installer who says he can grid tie a Magnum 4048 inverter using a shunt and programing the inverter to not backfeed the grid and will island itself when the grid is down.       He said he has done this for several customers.       

I wouldn't gain the benefit of net metering but instead the inverter would run the circuits which would run through a separate breaker box and tied to allow both the grid and the battery bank to feed them.

As I understand it if the batteries are full the circuit would run off battery power and when the batteries were low the circuit would automatically switch to run off the grid.

I run a smaller (1kw) in panels home built system.       Does this sound like it is feasible and safe as far as not backfeeding the grid if it went down?      

I've just never heard of doing this before and want to make sure the method makes sense.

stmbtwle

Avatar / Picture

Registered:
Posts: 2,802
Reply with quote  #2 
I'd contact the utility so they can verify its safe.

The way I understand it, that type of inverter is NOT "grid tie" but rather backup.  The "grid" feeds through the inverter through a relay or whatever to supply a secondary breaker panel with "essential" circuits.  During this time the inverter acts as a battery charger and charges your batteries.  When the grid fails, the relay drops out and the inverter switches to inverter mode, taking power from the batteries to supply the essential loads.  Solar panels are not really required for this operation but of course could help maintain the batteries.  

It's an either/or setup, you have the grid OR the inverter, not both.  If a conventional inverter were paralleled with the grid, the microsecond they got out of phase there would be hell to pay. 

Properly connected it should work fine, but once the batteries are charged the PV panels will have nothing to do, as they can't feed the grid.

At least that's the way I understand it works. 

I think there ARE grid-tie inverters with battery backup circuitry built in, which will give you the best of both.



__________________
Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
woodwaterwheel

Registered:
Posts: 6
Reply with quote  #3 
From what I understood before talking with this guy I fully agree with your response.        Using a non- grid tie inverter that isn't actively trying to stay in sync with the grid to back feed the grid is a major no-no.        This installer says that the inverter would supply the energy until the solar charged battery bank gets low before switching to grid power.      Somehow an amp shunt is involved in the switching process.

I'm willing to get a grid tie with battery backup inverter but the price is too high for my wallet so I've been using a stand alone system with batteries  to power a few minor items on a dedicated circuit the last few years from my home built setup.    

Your thoughts on this "automatic" switching between grid powering the circuits and battery power???

I just don't want to risk hurting a line repairman someday or starting a fire. 
stmbtwle

Avatar / Picture

Registered:
Posts: 2,802
Reply with quote  #4 
As I'm not sure just what this guy is proposing I can't advise other than say to contact the manufacturer of your inverter and see what they say about it.

That said I see no reason you can't use your inverter/battery/solar setup to power part of your home, AS LONG AS THOSE CIRCUITS ARE SEPARATE FROM THE GRID. As far as automatic switching is concerned, I think the inverter may be designed to do that already (contact the manufacturer). Whether it is wise to do so depends on the application. Say for instance you lose the grid while away, an automatic setup could switch to batteries and deplete them unnecessarily. On the other hand if the inverter powered something vital, I'd go for the automatic switching. I'd at least want the option.

Batteries are expensive and have a finite life. Emergency backup is one thing, but I don't think a battery-based system is all that cost effective compared to commercial power if available. You might be barking up the wrong tree. Do the math.

__________________
Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
NYNick

Registered:
Posts: 95
Reply with quote  #5 
I have a manual inverter to battery to grid system in my cottage in Canada. A large switch is manually thrown to activate EITHER the batteries as my power source to the inverter to the breaker box, OR the GRID as my power source. I used to utilize a generator to charge my batteries when they got low as a result of no sun for a few days, but now the grid just powers the house while the collectors charge them up.

If I had to do it over again I'd spring for the Grid Tie inverter. While I don't use enough power there to justify the payback today, I think it's the way to go. I agree with Willie.
stmbtwle

Avatar / Picture

Registered:
Posts: 2,802
Reply with quote  #6 
That's about the same setup I have on my houseboat. A big switch to select between shore (grid) and inverter. PV panels keep the inverter batteries up. It's only a 12v system, but it works.
__________________
Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
woodwaterwheel

Registered:
Posts: 6
Reply with quote  #7 
With the power outages in my area I'm willing to live with the additional cost of a small battery bank.     My concern is the "automatic switching" between inverter supplied power and grid supplied power.

With my smaller setup the additional expense of paying for a full grid tie setup is too much for my wallet.       The "automatic switching" between battery and grid poswe would allow me to make good use of the energy but not if it isn't reliable and safe.
stmbtwle

Avatar / Picture

Registered:
Posts: 2,802
Reply with quote  #8 
I think that inverter will do the switching automatically, and as designed I'm sure it's safe. Meddle with it, who knows?

Check the manual.

__________________
Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
Bruce

Registered:
Posts: 111
Reply with quote  #9 
This is similar to something I have been wondering....pardon me if I am hijacking...
If I have an Enphase mini converter system that "Islands" itself whenever the Grid goes down and if I hook up a whole house transfer switch to a generator, will the Enphase system come back online once the generator kicks on and trips the automatic transer switch (or a manual tranfer if I go that route) when the generator is providing power?  That would mean the generator and the solar would be working at the same time and hopefully reduce the amount needed from the generator?  Has anyone seen something like this?
stmbtwle

Avatar / Picture

Registered:
Posts: 2,802
Reply with quote  #10 
I wish I knew.  I should think the grid tie system would come on as it "sees" an outside power source.  My question is could anything be damaged? 

Before I did anything I'd talk to the folks at Enphase.  They should know.



__________________
Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.

 

web statistics