Author Topic: wiring Transfer switch to 110v inverter  (Read 11704 times)

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freejuice

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wiring Transfer switch to 110v inverter
« on: October 16, 2010, 03:06:44 PM »
Hi Folks,
 I recently bought an AIMS 48V inverter which is rated for 7000 watts, The output on this huge beast is 110 volts.

However I have a transfer switch which is has 110v and 220v circuits/breakers...on the 220vots breakers the little tie bars can be removed to make them 110v....which I will eventually do...I do not plan on runnig 220 volts However  the plug in on the transfer switch has a 220volt male end, How can I make the transistion to 110 volts and this point?
 Here is a link to the transfer switch set up:
http://www.connecticut-electric.com/ConnecticutElectric/wwwroot/product/7d10a207-46b0-4145-8429-1b10381bf7be.aspx
 Would I simply not  hook up the other 110 volt  leg on the female plug in?

( From the inverter to the junction box, it will have a seperate ground ....I will not be hooking the common and ground together and letting out the magic smoke)
 Thanks for any advice,
 Gavin

joestue

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Re: wiring Transfer switch to 110v inverter
« Reply #1 on: October 16, 2010, 04:53:13 PM »
on the 220vots breakers the little tie bars can be removed to make them 110v....which I will eventually do...I do not plan on runnig 220 volts.

there is no difference between 120 and 240 volts, besides the scalar value... the reason 220 volt breakers are tied together is so that when one trips, the load is disconnected from any voltage relative to "ground", this is a function of the fact that the 220 volts is really  +/- 120 vac, relative to ground.

if you can ground either side of the inverter you only need one breaker, and when it opens the load poses no shock hazard.
if the inverter cannot be tied to ground, you shouldn't be using it.
My wife says I'm not just a different colored rubik's cube, i am a rubik's knot in a cage.

ChrisOlson

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Re: wiring Transfer switch to 110v inverter
« Reply #2 on: October 16, 2010, 05:58:52 PM »

if the inverter cannot be tied to ground, you shouldn't be using it.

Most of your post is correct except the above.  The AIMS inverter Gavin bought has an internal neutral/ground bond.  From the owner's manual:
Neutral and Ground are bonded inside the inverter to comply with the National Electrical Code (NEC) requirement that any AC source must have a Neutral to Ground connection

The inverter has an external ground lug that must be connected to a driven ground rod.  These inverters do not have a "hot" neutral so the service panel connected to the inverter must NOT have a neutral/ground bond per NEC.  The panel has to have a separate ground bus installed in it with the panel bonded to the ground bus and only the Live or "hot" has to have circuit protection via breaker or fuse - the neutral does not and connects to the neutral bus like any other common grid or genset installation.

I'm not familiar with that switchgear, but to comply with Code the switchgear has to switch BOTH the neutral and hot from grid to genset (or inverter) power.  There can be absolutely no connection to grid power via a shared ground rod with the grid service entrance, or sharing the neutral.
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joestue

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Re: wiring Transfer switch to 110v inverter
« Reply #3 on: October 16, 2010, 06:55:41 PM »

if the inverter cannot be tied to ground, you shouldn't be using it.

Most of your post is correct except the above.  The AIMS inverter Gavin bought has an internal neutral/ground bond.  From the owner's manual:
Neutral and Ground are bonded inside the inverter to comply with the National Electrical Code (NEC) requirement that any AC source must have a Neutral to Ground connection

The inverter has an external ground lug that must be connected to a driven ground rod.  These inverters do not have a "hot" neutral so the service panel connected to the inverter must NOT have a neutral/ground bond per NEC.  The panel has to have a separate ground bus installed in it with the panel bonded to the ground bus and only the Live or "hot" has to have circuit protection via breaker or fuse - the neutral does not and connects to the neutral bus like any other common grid or genset installation.

I'm not familiar with that switchgear, but to comply with Code the switchgear has to switch BOTH the neutral and hot from grid to genset (or inverter) power.  There can be absolutely no connection to grid power via a shared ground rod with the grid service entrance, or sharing the neutral.
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Chris

"These inverters do not have a "hot" neutral so the service panel connected to the inverter must NOT have a neutral/ground bond per NEC"


this is the dammed problem*... the inverter cannot be connected to ground (because the battery negative already is) (there's how many threads on this?)

in the case of an isolated inverter output, i should be able to float the 120vac 3000 volts above ground... (or whatever the optical isolator/transformer is tested to.. typically 4kv...). In which case, it doesn't care about what its connected to, and only one breaker is needed. Once the breaker trips, the leakage current is limited to micro amps.

I stand by my original statement, if you cannot connect the output to "ground", (which should be connected to "neutral" for a long list of reasons) then you shouldn't use it..

i don't care about theoretical ground loop problems... if code requires two breakers whatever... what's another 5$

*a grammar nazi would argue that you can in fact connect the neutral to ground, based on what you said.
« Last Edit: October 16, 2010, 07:01:14 PM by joestue »
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joestue

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Re: wiring Transfer switch to 110v inverter
« Reply #4 on: October 16, 2010, 07:30:59 PM »
I'm not familiar with that switchgear, but to comply with Code the switchgear has to switch BOTH the neutral and hot from grid to genset (or inverter) power.  There can be absolutely no connection to grid power via a shared ground rod with the grid service entrance, or sharing the neutral.
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Chris

where did you get this from? you are implying for any serious installation i have to install three circuit breakers, or *4* for a three phase installation.
My wife says I'm not just a different colored rubik's cube, i am a rubik's knot in a cage.

ChrisOlson

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Re: wiring Transfer switch to 110v inverter
« Reply #5 on: October 16, 2010, 07:45:00 PM »
I stand by my original statement, if you cannot connect the output to "ground", (which should be connected to "neutral" for a long list of reasons) then you shouldn't use it..

<sigh>

freejuice - just email me offline and I'll tell you how to wire your inverter so it meets code.
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ChrisOlson

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Re: wiring Transfer switch to 110v inverter
« Reply #6 on: October 16, 2010, 08:23:23 PM »
freejuice - just email me offline and I'll tell you how to wire your inverter so it meets code.

That being said, freejuice can't use that genset switch he sent the link to because it's UL rated at only 30 amps per pole.  A 7 kW inverter puts out close to 60 amps.  He needs a bigger switchgear.
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joestue

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Re: wiring Transfer switch to 110v inverter
« Reply #7 on: October 16, 2010, 08:39:54 PM »
I stand by my original statement, if you cannot connect the output to "ground", (which should be connected to "neutral" for a long list of reasons) then you shouldn't use it..

<sigh>

freejuice - just email me offline and I'll tell you how to wire your inverter so it meets code.
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Chris


why, because you can't post it here?

how are you going to convert your distribution panel from a bonded neutral to an unbonded neutral, without 6 breakers? (assuming a 120-0-120v inverter, for 0-120, you need two breakers for the inverter, and three for the grid)
my generator transfer panel has two, 100 amp breakers to disconnect the grid, and two 30 amp breakers to feed the distribution panel with power from the generator..
the neutral remains grounded, this according to the 2001 nec code.. if its any different.. i want to see the changes.
you can't have both on at the same time...an inverter is no different.
« Last Edit: October 16, 2010, 08:42:49 PM by joestue »
My wife says I'm not just a different colored rubik's cube, i am a rubik's knot in a cage.

freejuice

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Re: wiring Transfer switch to 110v inverter
« Reply #8 on: October 16, 2010, 09:03:05 PM »
Hi Folks,
I dont know if this helps...but the transfer switch allows me to switch out individual breakers.  The manul shows the switches as (I think the term is) "two Pole(?)  switiches.
 When the hot line is removed from the individual breaker within the service panel, it is wired through one of the individual  switchs on the transfer switch panel and then the other wire coming from the same switch goes back to the breaker...a loop so to speak.
 I see the issue with grounding or at least I think I do..on the inverter end I sure do...with magic smoke etc etc..
 
Here is the installation video...maybe you folks can understand this better then me trying to explain it than with my layman's terms.

http://www.connecticut-electric.com/ConnecticutElectric/wwwroot/Default.aspx

 Oh , I wont be pulling 7000 watts through it...more like 3000 watts, tops...some of the switches I simply wont hook up to protect against overloading

TomW

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Re: wiring Transfer switch to 110v inverter
« Reply #9 on: October 16, 2010, 09:18:51 PM »
I stand by my original statement, if you cannot connect the output to "ground", (which should be connected to "neutral" for a long list of reasons) then you shouldn't use it..

<sigh>

freejuice - just email me offline and I'll tell you how to wire your inverter so it meets code.
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Chris


why, because you can't post it here?




Joe;

I believe it is because you tend to obfuscate many discussions you join with out of context or overly complex data, and an attitude that you just cannot be wrong.

While you are not necessarily wrong, many times you just cloud the waters.  You give me the impression you are used to people just taking your word as fact.

As a matter of fact, I have gotten member complaints that you do this, but I try to stay out of these skirmishes as it is a lose lose situation.

Remember, most of our readers have never even seen an NEC code book. 

I know 30 year veteran electricians who cannot agree what the thing says about some things.

Because you asked.

I will leave it at that.

Tom

ChrisOlson

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Re: wiring Transfer switch to 110v inverter
« Reply #10 on: October 16, 2010, 09:28:39 PM »
Oh , I wont be pulling 7000 watts through it...more like 3000 watts, tops...some of the switches I simply wont hook up to protect against overloading

You need a double pole double throw switchgear because you have an inverter with built-in GFCI.  You MUST switch the neutral and have no connection to the grid neutral on inverter power or it won't work.  The inverter will sense a ground fault and shut down with an E01 error code.  So in this sense that switchgear will work.

But you need a switch rated at 60 amps or better.  That one you sent the link to is a 30 amp switch.  The only way you can use that switch is if you put in a single pole 30 amp breaker between the inverter and the transfer switch so the inverter can never deliver more than 30 amps to that switch.  In other words, power say a 70 amp panel with the inverter and put a 30 amp breaker in that panel that feeds the sub-panel you want to switch back and forth from grid to inverter power.  The 70 amp panel will always be on inverter power - but you need to provide 30 amp circuit protection to that switchgear.  Neither NEC nor the UL requirements on that switch allow you to parallel the poles in it to push 60 amps of 120 volt single phase power thru it.  Can you do it?  Yes.  But if you burn your house down because you exceeded the rating of the panel you're going to be in hot water with your insurance company when they find out about it.  And there's no way it will ever pass any sort of inspection if you parallel the poles in that switch.
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freejuice

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Re: wiring Transfer switch to 110v inverter
« Reply #11 on: October 16, 2010, 09:55:20 PM »
Hi Chris,
 That is what I was looking to do a safe way, but was unsure about things...At first I thought I could just follow Ohms law and say 7000 watts divided by 110 volts"= 64 amps, and I could gage my amp loading accordingly...something in the neighborhopod of 4 gage wire as the supply cables  from the inverter to the transfer switch...since I'll never be using the double pole 220volt switches anyway.

However I got to looking at things in realistic terms...since I dont have a garage full of batteries and that 220 volt loads pull tremendous amounts of power, I thought I would simply designate a few 110 switches for my 3000 watt max load. The 30 amp breaker box between the inverter and transfer switch will be the ticket!
 I dont want to do anything that gets me in voodoo with the insurance company. But I also like not ever having to call in the marker on the insurance company either!  :D
 Sure its "underkill" for my inverter but the deal on the inverter was the make or break decision...that was one time when fee-bay actually paid off.... about 1/3 of the normal price.

Those AIMS inverters are beasts!

ChrisOlson

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Re: wiring Transfer switch to 110v inverter
« Reply #12 on: October 16, 2010, 11:22:25 PM »
That is what I was looking to do a safe way, but was unsure about things...At first I thought I could just follow Ohms law and say 7000 watts divided by 110 volts"= 64 amps, and I could gage my amp loading accordingly...something in the neighborhopod of 4 gage wire as the supply cables  from the inverter to the transfer switch...since I'll never be using the double pole 220volt switches anyway.

Well, unfortunately switches aren't rated that way   :(

Quote
However I got to looking at things in realistic terms...since I dont have a garage full of batteries and that 220 volt loads pull tremendous amounts of power, I thought I would simply designate a few 110 switches for my 3000 watt max load. The 30 amp breaker box between the inverter and transfer switch will be the ticket!

I think what I'd do is put in a 100 amp panel for the inverter.  You can get like a SquareD homeline 100 amp 6 place panel for usually under 30 bucks.  That way you could use the full output of the inverter by wiring whatever you want to power with it to the panel.  For the circuits you'd like to be able to switch back and forth from grid to inverter, put in a 30 amp breaker in that 100 amp panel and feed the transfer switch with the 30 amp circuit.

Quote
Those AIMS inverters are beasts!

They are.  I got three of them - two 3 kW units with built-in transfer switches and a 8 kW unit in my shop.  You really can't tell that they're modified sine inverters without hooking up the scope.  The two 3 kW units I got powering my house will each deliver 1.5 kW and the fans don't even come on in them, nor does the cases warm up on them.  If I push them to 2 kW or so then the fans come on after awhile but they run very quiet - about as much noise as what you hear from a heat register in the house when the furnace blower is running.  The auto transfer switches in the 3 kW units switch from genset to battery power very fast - the lights barely flicker.  But they're quite slow (2-3 seconds) switching from battery to genset power when I fire up the genset.  I guess they "test" the AC input power to make sure they got 60 Hz and the proper voltage before switching.  But I wish they'd leave stuff on battery power while they "test" the AC input instead of having the power go off for 2-3 seconds while they do it.  Otherwise I'm very happy with mine.
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freejuice

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Re: wiring Transfer switch to 110v inverter
« Reply #13 on: October 28, 2010, 06:03:29 PM »
Success! The AIMS inverter,  and the transfer switch work perfectly! Those AIMS invertes can handle the Neutral/common and ground being tied together.

It wired right into my panel and works flawlessly...now I can select between grid power and inverter power at the flip of a switch...or I can flip a few switches and run grid power along with inverter power, with no backfeeding the lines or letting the magic smoke out of the inverter!
 Chris, thanks for your help!
 All the best folks!
 Gavin