How to determine SPD configuation?

[rplarry]

I would like to install some spd's in my system to protect it from a possible lightning strike, but I am a little confused as to where and how many spd's to use in my system.
I am off grid, I have 2 pole mounted PV arrays, 2 CC- mx60 and fm80, 2 inverters- vfx 2812, Kubota 6500 gen set for AC in, and a 2000ah agm battery bank.
What would you suggest to protect my equipment?
Thanks
Larry

[boB]

Hi Larry.

Since you are using 150V charge controllers, I would say to just go for the SPD300 SPDs.  I think I would mount them onto the pole or you could mount them to the balance of systems box near the charge controllers themselves.

Ground of course goes to the system ground connection, and both plus and minus PV goes to a hot wire from the SPD.
There are two in each SPD.   2 hot wires and one ground.

Do you have separate array negatives coming to the inside system ( the charge controllers) ?   Or, are you using just
one common negative for both arrays ??

Ryan should also chime in here as he has used our SPDs more than I have.

You may also want to check out our videos about how we wire up the SPDs in our pre-wired E-panels.
Videos are linked from our front web page.

boB

[rplarry]

boB
Thanks for the reply. I have seperate negatives for each array. So you are suggesting only using the spd's on the arrays themselves and not on the AC in or out on the inverters themselves or the breaker boxes? That would be less expensive for me. The arrays are mounted on metal poles set 4' in the ground in concrete. Would that be good a enough ground to use for the spd's?
Larry

[boB]

boB
Thanks for the reply. I have seperate negatives for each array. So you are suggesting only using the spd's on the arrays themselves and not on the AC in or out on the inverters themselves or the breaker boxes? That would be less expensive for me. The arrays are mounted on metal poles set 4' in the ground in concrete. Would that be good a enough ground to use for the spd's?
Larry

I think I would run a separate ground rod as well since concrete is not the best conductor.  If the pole itself is in the ground as far as a ground rod would be and touching dirt, then you might not need to use the ground rod ?

Yes, an SPD300 on the AC side would also be good since lightning also likes to make its way into your system through the grid.

If I had to choose, I think I would first put the SPD on the AC grid side.  There is ~some~ protection in the Classic itself although an SPD has much more clamping power behind it and adding that near the pole should be even more good insurance.

The SPD115 is for basically for battery voltage and batteries don't usually need protection.  They're inside.

boB

[nigel]

Also bear in mind its good practice just to have one grounding point for the whole system multiple ground points around a property is not good.   

[rplarry]

boB
Thanks for the reply. I have seperate negatives for each array. So you are suggesting only using the spd's on the arrays themselves and not on the AC in or out on the inverters themselves or the breaker boxes? That would be less expensive for me. The arrays are mounted on metal poles set 4' in the ground in concrete. Would that be good a enough ground to use for the spd's?
Larry

I think I would run a separate ground rod as well since concrete is not the best conductor.  If the pole itself is in the ground as far as a ground rod would be and touching dirt, then you might not need to use the ground rod ?

Yes, an SPD300 on the AC side would also be good since lightning also likes to make its way into your system through the grid.

If I had to choose, I think I would first put the SPD on the AC grid side.  There is ~some~ protection in the Classic itself although an SPD has much more clamping power behind it and adding that near the pole should be even more good insurance.

The SPD115 is for basically for battery voltage and batteries don't usually need protection.  They're inside.

boB

I am off grid so I guess that I don't need any on the AC side, only on the arrays. Where would be the appropriate place to mount the spd 300's, on the poles outside or nearer to the CC's inside the garage?
Larry
PS Thanks for the reminder Nigel, long time no see, is this where you have been hiding out?

[Halfcrazy]

I would still protect the AC side of an off grid inverter as they can and do get zapped. I recommend that the SPD goes closer to the power electronics than the array but if it is a long way like 100ft away or more I would use one on each end. Any wire 100ft long or longer will act as an antenna and pick up induced voltages from near by strikes.

Ryan

[rplarry]

Ryan
I did as you suggested and installed spd's on both pv arrays and one on the ACin (from my gen set, no grid here) of each inverter. You said any wire over 100' long can/will act as an antenna and capture induced voltage from a near strike. Should I install a fourth spd on the AC out of both inverters?
Larry

[Halfcrazy]

Well I always protect my inverters In and Out as inverters are expensive. It is easy for me to say buy lots of SPD's but truly this is a time where there is no such thing as to much in my opinion

Ryan

[rplarry]

Thanks, and I agree there is no reason to only do it half way. A wise person once told me,"there is never enough time or money to do it right the first time and there is always enough time and more money to do it right the second time". So one more spd it is.
Larry

[TomW]

Thanks, and I agree there is no reason to only do it half way. A wise person once told me,"there is never enough time or money to do it right the first time and there is always enough time and more money to do it right the second time". So one more spd it is.
Larry

Larry;

+1

How true. Been there, done that myself.

Tom