Neutral through a Transfer Switch? With an Off-Grid option

[Ellis Redding]

Ok,

I know that if you create a subpanel, you do NOT connect the ground to the neutral in the subpanel. The only place that is to be done is in the main panel.
But what if you put a transfer switch between the main and the sub?
I just got a transfer switch and the part that switches only includes the 2 hots. The neutral connection is constant between either input and the common out to the subpanel. Is this ok?

My current thought is that I would feed the second input with an offgrid system.
Is this going to cause an issue if I have an autotransformer associated with the off grid system trying to create it's own neutral?

 

[time2roll]

Need a transfer switch with three terminals for split phase.

What switch is connected?

 

[timselectric]

Ok,

I know that if you create a subpanel, you do NOT connect the ground to the neutral in the subpanel. The only place that is to be done is in the main panel.
But what if you put a transfer switch between the main and the sub?
I just got a transfer switch and the part that switches only includes the 2 hots. The neutral connection is constant between either input and the common out to the subpanel. Is this ok?

My current thought is that I would feed the second input with an offgrid system.
Is this going to cause an issue if I have an autotransformer associated with the off grid system trying to create it's own neutral?

It all depends on how you are using it and what you are using it for.

 

[Zwy]

Ok,

I know that if you create a subpanel, you do NOT connect the ground to the neutral in the subpanel. The only place that is to be done is in the main panel.
But what if you put a transfer switch between the main and the sub?
I just got a transfer switch and the part that switches only includes the 2 hots. The neutral connection is constant between either input and the common out to the subpanel. Is this ok?

My current thought is that I would feed the second input with an offgrid system.
Is this going to cause an issue if I have an autotransformer associated with the off grid system trying to create it's own neutral?

Much would depend on what inverter you use and how this will be wired.

For inverters that bond N-G under inverter power, you will want a 3 pole switch in order to switch neutral, some inverters have a built in transfer switch that will do this automatically. The reason for this is due to the N-G bond at the main service panel. As EGC is pass thru, there is potential for creating a parallel path on the EGC due to N-G bond in 2 locations.

 

[Ellis Redding]

Much would depend on what inverter you use and how this will be wired.

For inverters that bond N-G under inverter power, you will want a 3 pole switch in order to switch neutral, some inverters have a built in transfer switch that will do this automatically. The reason for this is due to the N-G bond at the main service panel. As EGC is pass thru, there is potential for creating a parallel path on the EGC due to N-G bond in 2 locations.

Interesting.

Ok, yes, this makes sense, if I was using something like the Enphase Smart Switch or the Sol-Ark, I wouldn't use a manual transfer switch.
However, I'm thinking of using something like the Growatt 5kW / 10kW off grid inverters with batteris to just take some portion of my house loads off the grid. I was assuming I'd add an autotransformer in a way that provided my neutrals and balanced things and shut off power if the transformer was lost. But the continuity of the utility neutral is a real problem. I need it when I'm on grid power, but dont' (I don't think) when I'm off grid. Somewhat surprised that it isn't switched as well.

 

[Zwy]

Go back thru the threads and read about using the 5000ES concerning grounding, neutrals and autotransformers. Educate yourself first before you decide on which inverter to purchase. There is plenty to read about, some threads are probably more than 30 pages.

My opinion is there are better choices out there for split phase. Adapting a Euro spec 240V inverter to use in North America split phase is probably not the best idea considering there are split phase capable units out there, either a pair of inverters or a single unit.

Just because you saw a video where someone was telling you how great this or that unit is/was, doesn't mean it is the Holy Grail. Educate yourself and make an informed decision for your application. There are also many threads about N-G bonding when using inverters and the problems with parallel paths created in system wiring.

 

[Ellis Redding]

Go back thru the threads and read about using the 5000ES concerning grounding, neutrals and autotransformers. Educate yourself first before you decide on which inverter to purchase. There is plenty to read about, some threads are probably more than 30 pages.

My opinion is there are better choices out there for split phase. Adapting a Euro spec 240V inverter to use in North America split phase is probably not the best idea considering there are split phase capable units out there, either a pair of inverters or a single unit.

Just because you saw a video where someone was telling you how great this or that unit is/was, doesn't mean it is the Holy Grail. Educate yourself and make an informed decision for your application. There are also many threads about N-G bonding when using inverters and the problems with parallel paths created in system wiring.

I totally agree with you on that. If I was choosing an inverter or system, I would probably go with either the SolarEdge or the Enphase systems and still may. I anticipate my system will really benefit from optimizers.

But the one thing that the Growatt offers is that it seems to work with affordable batteries.
Using this inverter would save me around $10 - 15k. The difference in the markup on the batteries on the Enphase battery is about 7 to 8 k each and I'd like to have 30kWh+.
I don't trust the LgChem battery.
I don't like SolArk after they put Chinese inverters in their machines and claim to be US made and represent veterans.
SolArk just made me give up on any sourcing, now I'm just trying to get a system.

 

[Zwy]

I'm currently in the process of installing 2 MPP LV6548's in my house with 3 DIY 48V batteries, Batrium BMS. I did look at the LV6048 also, PV capacity was the limiting factor.

 

[Ellis Redding]

I'm currently in the process of installing 2 MPP LV6548's in my house with 3 DIY 48V batteries, Batrium BMS. I did look at the LV6048 also, PV capacity was the limiting factor.

I think I crossed MPP off my list because max in voltage was 250V.
DIY is tempting, but in this, I think Will et al. have a point. The EG4 or BigBattery options are pretty close to DIY prices.
That said, How did you get the MPP to talk to / monitor the battery?

 

[newbostonconst]

Just use a Hybrid inverter....so much easier....

 

[Ellis Redding]

Just use a Hybrid inverter....so much easier....

That's what the Growatt is. However a number of them have 'Approved battery manufacturer lists' instead of a blanket, 'Any battery with rs485'.
As such, I assume they don't work unless I have a video or other proof that they'll work.

 

[newbostonconst]

I don't know of any that you have to use a certain battery with.....you can make your own.

How much money are you looking to spend....a transfer switch is going to add a $1000 to your install and a hybrid inverter pretty much has one built in. How much power do you want to supply?

Size the battery to how long you want to be able to run without sun.

Back to the transfer switch I have never seen a residential install with a 3 pole transfer switch. Wiring a 2 pole one the grounds are left connected and separate from the neutral that are all connected and as you stated the ground and neutral are only connected in one place, and that one place can be the transfer swtich if that makes things easier.

 

[time2roll]

I don't know of any that you have to use a certain battery with.....you can make your own.

I assume an approved battery would possibly enable communication between the two. Otherwise I agree a battery is a battery.

 

[Ellis Redding]

I assume an approved battery would possibly enable communication between the two. Otherwise I agree a battery is a battery.

Yea, pretty sure you can't just hook a EG4 up to the enphase or solaredge inverters.
Even if you got it to the right voltage, you'd probably end up with a flaming mess.

 

[Zwy]

I think I crossed MPP off my list because max in voltage was 250V.

I don't see that as a problem. First, each LV6548 has two PV SCC's, the SPF5000ES only has one. The LV6548 can have 8000W total PV input, the SPF5000ES only has 6000W.

You will also find when it comes to components (switches, breakers, etc) to handle 450V DC, the components will be more expensive than 250V DC which many components rated for AC are also rated for 250V DC.

DIY is tempting, but in this, I think Will et al. have a point. The EG4 or BigBattery options are pretty close to DIY prices.
That said, How did you get the MPP to talk to / monitor the battery?

Use one of their approved batteries if you really want comms. Is it needed? No, and you will find there will be conflicts even if one manufacturer states their product will work another manufacturers product.

I don't see the need for it for my system. If you really feel that it is important, then my advice would to keep looking as those 2 choices may not work out so well. Read this thread, I think the BMS is shutting everything down. https://diysolarforum.com/threads/growatt-3000-24-volt-shutting-down.34024/

 

[Zwy]

I don't know of any that you have to use a certain battery with.....you can make your own.

How much money are you looking to spend....a transfer switch is going to add a $1000 to your install and a hybrid inverter pretty much has one built in. How much power do you want to supply?

Size the battery to how long you want to be able to run without sun.

Back to the transfer switch I have never seen a residential install with a 3 pole transfer switch. Wiring a 2 pole one the grounds are left connected and separate from the neutral that are all connected and as you stated the ground and neutral are only connected in one place, and that one place can be the transfer swtich if that makes things easier.

You are most likely are looking at wiring for standby power using a generator without N-G bonding.

Any inverter with N-G bonding at the inverter should have a 3 pole transfer switch in order to switch neutral. The issue is the N-G bond at the service panel creates a ground loop and current on G.

 

[newbostonconst]

Yea, pretty sure you can't just hook a EG4 up to the enphase or solaredge inverters.
Even if you got it to the right voltage, you'd probably end up with a flaming mess.

I don't think you can buy Enphase's "battery system" without being an approved installer....Generac for that matter either.

You flaming mess comment is unfounded.....if you don't know what you are doing then maybe, but it isn't that hard.

 

[RV10flyer]

I totally agree with you on that. If I was choosing an inverter or system, I would probably go with either the SolarEdge or the Enphase systems and still may. I anticipate my system will really benefit from optimizers.

But the one thing that the Growatt offers is that it seems to work with affordable batteries.
Using this inverter would save me around $10 - 15k. The difference in the markup on the batteries on the Enphase battery is about 7 to 8 k each and I'd like to have 30kWh+.
I don't trust the LgChem battery.
I don't like SolArk after they put Chinese inverters in their machines and claim to be US made and represent veterans.
SolArk just made me give up on any sourcing, now I'm just trying to get a system.

90% of our goods come from China. I've been totally off-grid for 2 1/2 weeks on my China manufactured solar system. My two Sol-Ark 12K's, 20.6 pv, 132kWh battery bank, 10 ea/6 brands of BMSs's, 100A dp dc breakers all have been working great. My Fujitsu 9k 33 SEER mini-split hp from Thailand works great keeping the power shed comfy. My US-sourced 200 amp main transfer switch, 100 amp transfer switch for my generator, 10 ea Midnite Solar SPD's, most wiring and Spats all working wonderfully. Both transfer switches L1/L2 only.

"Sol-Ark prides itself at American Engineering, making its products the best in the industry."

 

[timselectric]

"Sol-Ark prides itself at American Engineering, making its products the best in the industry."

LMAO