SPD Question

[plongson]

After Solar musher got me thinking about my SPD situation, Im going to order up some Midnite SPD's to replace the exsisting Delta's. Right now there are two Deltas on the Magnum for both legs of the 230vac that will be replaced with MNSPD.

I'm thinking one for the array too, would that one go on the combiner box, out on the pole or inside the garage, actually attached to the Classic?

Three 300's should do the trick?

Paul

[Halfcrazy]

Yes 300's are the choice. I prefer if doing a single SPD for the PV to have it closest to the Classic.

Ryan

[plongson]

Thanks Ryan, I'll order up 3...

Paul

[Westbranch]

Paul, what about the AC side.  There is a good discussion over on NAWS about lightning

[plongson]

Hmmm, is there more to protect than the two legs of the AC side of the inverter? Do you mean adding SPD to the house breaker/disconnect? Here is a picture of the Magnum now... 

I'll cruise over to NAWS and check out the discussion.

[TomW]

Paul;

Do not mistake me for an expert.

Since we happen to live in sky spark central here and have lost literally thousands of dollars in equipment to them....

I installed SPDs on every line coming in to my power room. AC in, AC out, Solar and turbine feeds. The house has one on each leg of the split phase AC in.

I  also buried about 400 feet of bare #8 copper in my recently installed trenches carrying conduit for all of this. All tied together and used as grounds at my breaker panels & solar array grounds.

Not cheap, but I will sleep better when it is lightning season.

We had those triangle deltas on the house AC in but they did not seem to help the last time we lost computers in there?

Just from here.

Tom

[plongson]

Ya, looking at my system I'm WAY under protected. I'm going to have to give this some serious consideration. The 3 SPD will certainly be just the beginning. Our lightning season is mostly during the summer months and a lesser threat the rest of the year. I need to get on it though. I cannot imagine anyone intentionally installing the Delta's given the results of the research.

[Westbranch]

I think it is Niel that favours putting SPDs on the AC side  first then then DC if you had to make a choice.  IIRC it is a long thread on NAWS.

[TomW]

The reality is, there is no real  protection from a direct strike.

But you can divert the induced voltage from near strikes and surges.

I often wondered what kind of spike a large solar array gets when a big bolt hits in front of them?

Its awful bright but short lived.

As usual more questions than answers,

Tom

[SolarMusher]

The reality is, there is no real protection from a direct strike.
But you can divert the induced voltage from near strikes and surges.

Agree with Tom here, to me the most important is to be protected from induced voltage and surge caused by strike.
Before SPD, I had Delta everywhere and my VFX had burned two times exactly as if I had nothing and this was just by surge from indirect strike. I never had problem with the Magnum mounted with SPD last summer.
Anyway, Paul, you have to know that a direct strike doesn't give you any chance to save your beloved electronic.
Erik

[niel]

westbranch is right that if you had to choose that the utility ac is the most prone due to the long lengths of wire the utility employs that kind of acts as a antenna for it and is the first choice to protect, but a surge can develop anywhere. windsun himself stated that of the failures he had seen that the majority came from the ac side of the equation and this makes sense due to the long wire lengths. as far as the service entrance breaker panel being protected, it just makes good sense to me that this is also a good idea to do and would afford a bit more protections for all house circuits.

now the wire on the dc side of things can also be long and prone to the lightning emp. if you suspect there will be a strong probability of a direct strike then you might want to find a way to divert the lightning by luring it through a better choice for its path to ground and hopefully it will not branch to the pvs or the utility wires in addition to going down the diversion path. you can be sure there would be a huge emp even though your diversion may have worked. an example of a diversion may be that of a flag pole and it could even be a wire run up the side of a tree, preferably up higher then the pvs and other wires sit, and attached to a ground rod.

know that in theory the diversion could work, but on the other hand it may also create the possibility of attracting lightning that may not otherwise have struck, so it may not be wise to put the diversion too close to the items you want protected. lightning does tend to do whatever it wants to so it can deviate from what one would think it would do. there are no guarantees, but any efforts are good efforts when properly planned and implemented.

[Vern Faulkner]

Looking ahead to the new build, I plan on erecting a tower next to the house, for the sole purpose of acting as a lightning rod.

The general rule of thumb is that whatever lies within a 45-degree angle of the top of the most lightning-prone structure (tree, metal-roofed house, or in the future case, a 30-foot tower with a big ol' grounded chunk of rebar/pipe at the top) ought to be safe from lightning strikes.

[dgd]

Looking ahead to the new build, I plan on erecting a tower next to the house, for the sole purpose of acting as a lightning rod.

Vern,
A courageous plan. Personally I cringe at the thought of 'inviting' a lightening strike. A very close hit would probably toast everything regardless of SPDs. It may even incinerate the house 
Just my humble opinion...

dgd

[Peter K]

Our Barn has a steel roof and Lightning rods to a pair of ground wires.  It is 50 yards from the house and solar panel array.  It may act as a target for lightning but I am planing a taller turbine tower.  Should an SPD be installed at the disconnect box at the base of the tower?  I am thinking I will put these in place in the AC and DC sides of the Outback system as well.
Pete   

[Vern Faulkner]

Vern,
A courageous plan. Personally I cringe at the thought of 'inviting' a lightening strike. A very close hit would probably toast everything regardless of SPDs. It may even incinerate the house 
Just my humble opinion...

dgd

Building a rock house - not an issue.



But seriously - the whole concept of a grounded object (AWAY FROM THE HOUSE) such as a tower with a big ol' grounded gizmo at the top - is ancient. Like Ben Franklin ancient.

http://www.physicsclassroom.com/class/estatics/u8l4e.cfm

There has been some thought that the lightning rod isn't as viable as once thought, however...