Clarification on Amps from Sunny Island to Critical Loads Panel?

midijeep

I'm a little confused about what the electrician told me about my (1) SunnyBoy,  (1) Sunny Island, (1) Midnite Solar E-Panel & (1) Midnite Solar AutoFormercsetup.  I have a grid-tied battery backup system.
The electrician told me that with my PV set up that instead of getting the 56 amps possible from the Sunny Island to critical loads panel , I would only get half that, 28amps.  He said I need two Sunny islands to get the full 56 amps.  That doesn't make any sense to me.
Can someone explain why I would be getting only 28 amps to the critical loads panel?

westbranch

a few questions first....  Are you referring to the ~1500W available from the SI?
What is your battery voltage?
What voltage are you talking about for the 56Amps?
How are you using the Auto-former.

midijeep

Are you referring to the ~1500W available from the SI?  Not referring to the 1500 Watt outlet on the SunnyBoy

What is your battery voltage? 48 volts

What voltage are you talking about for the 56Amps?  This would be AC going to the critical loads panel, so I am assuming 240 because the Autoformer is used to make the SI (120 V) and Autoformer to 240 V.

How are you using the Auto-former?  To bring the voltage up tp 240V.  The SI along is only 120V.

The Sunny Island is capable of handing 56 amps. 
I'm wondering if it is a limitation on the critical loads panel he installed?  He explained something about 2 sides to incoming power from the Sunny Island .  I can see the voltage being 120v on one leg and 120 volts on the other in the panel where the breakers are inserted.

westbranch

So you want 56A at the Critical Loads panel.

Is that when the grid is down?  To me that is when  those loads are CRITICAL... thus they would be limited to 1500W like a fridge and a few others.

He is correct as 28A x 48 V = 1344W,  and it looks like he threw in a fudge factor to account for system losses and the fact that the battery would be about 53.4V when discharging...

What loads have you declared Critical? Do you want to have to but another SI?

midijeep

westbranch said:

So you want 56A at the Critical Loads panel.

Is that when the grid is down?  To me that is when  those loads are CRITICAL... thus they would be limited to 1500W like a fridge and a few others.

He is correct as 28A x 48 V = 1344W,  and it looks like he threw in a fudge factor to account for system losses and the fact that the battery would be about 53.4V when discharging...

What loads have you declared Critical? Do you want to have to but another SI?

Well the problem is the microwave (on high at 1500watts) everything else on the critical loads panels works great i.e.  refrigerator , lights and furnace blower motor (natural gas).  The microwave when turned on high (100% power) will stop and start.  I'm thinking the only way to use the microwave will be finding the power that allows the microwave to stay on without stopping and starting which will take longer to heat what ever I'm heating up.

I thought about a small capacitor bank between the battery bank and Sunny Island but I don't know much about where to start.
Maybe another solution may be a Microwave Oven with Inverter Technology?

I don't have another SI but I thought the Autofromer was suppose to give me the voltage for 240 and amperage?

westbranch

the autoformer does give you 240V but at half the amperage on each leg of the feed.... still the same number of Watts...

midijeep

westbranch said:

the autoformer does give you 240V but at half the amperage on each leg of the feed.... still the same number of Watts...

Sounds like I will need to add another SI to get the amperage up?  But my initial plan was to have power to a few critical loads not the entire house,  Maybe I can experiment with a Microwave Oven with Inverter Technology and have an alternative source for cooking as another backup.

mike95490

Unless you are thawing blood at a hospital, a microwave is not a critical load (in my opinion)

midijeep

mike95490 said:

Unless you are thawing blood at a hospital, a microwave is not a critical load (in my opinion)

Opinion noted.

Raj174

Another option might be to get yourself a 700 watt microwave for when the grid power is down. They are probably less than 60 bucks.

midijeep

I wanted to come back and report what I did.  I bought a  microwave where the power level can be adjusted but the microwave works on full power with no problems.  It draws about 13 amps at ~ 1300watts at full power setting.