Can grounding *invite* surges?

2twisty

I have lived in my off grid home for 2 years now.  For the 1st 18 months, I did not have my inverter/house grounded via grounding rod.

Being of the mindset that grounding==good, I put in a ground rod and grounded the electrical panel.

Since then we have had 2 close lightning strikes that have done serious damage to computer equipment here in the house, despite being plugged into supressors and UPSes.

Prior to my grounding of the building, we had quite a few close strikes, and never once had any damage.

After today's strike that has cost me about $300 in damage, I went out and disconnected the grounding. 

How can I protect against these strikes while still having my system properly grounded?  There is too little data to say definitively that having my house ungrounded has protected me in the past, but I can't afford to have this damage every time lightning hits close.

I know -- unplug it.  That's not always an option since I am not always here to unplug it.

Please advise.

vtmaps

Grounding, if not done right, can definitely exacerbate the effects of lightning.  But if you do not have a grounded system it is necessary (for safety) to have fuses or breakers on your hot AND neutral conductors.

--vtMaps

Mountain Don

What is being damaged?  devices on the DC side or the AC side?

Do you use SPD's on the DC and AC; ones like Midnite's?  Or delta's, or both?  I believe John Wiles of SW Tech recommends both to be used together.

Do you have roof top air terminals (lightning rods) along with its own very well grounded rods and or plates?


We made it through 5 years of use before we were struck, probably multiple strikes during the same storm. We added the Midnite SPD's and the roof top air terminal system after that. That system is separate and uses multiple grounding rods and buried copper ground plates. The rods and plates are placed in areas that have rainfall water directed to them in an attempt to maintain the soil moisture to be high enough to promote the best "earthing". Since then we've had further strikes but only had to have the Midnite SPD's replaced under the warranty and repair a fault in the array to chage controller wiring. That was/is a mystery. but no other damage.  One further change we made was to set up the DC input wiring to the CC in a manner that makes it easy to disconnect and separate the wire from the CC by 10 feet. We do that when storms roll through during our lightning season of July - August.

The AC electrical system has been grounded from day one.

westbranch

Mtn Don, can you tell a bit more on the '' change we made was to set up the DC input wiring to the CC in a manner that makes it easy to disconnect and separate the wire from the CC by 10 feet.''
I'm curious as to how you managed that....
tks

ps this year we have had L & T  for the last 2 weeks steady, including overnight 2 nights ago  at 02;00 TO 04;00

Mountain Don

Sure.  

Warning:  My solution will most probably not pass an NEC inspection. Our cabin is remote and sort of hidden.  A word picture will have to do.

Our panels are in series for a rated Voc of 108.3 volts and Isc of 8.3 amps.  The conduit from the PV used to come up out of the erath at the SE corner of the cabin.   I installed a treated wood post twelve feet from that SE corner. I dug up the conduit and reconfigured it to rise on the downhill, facing PV array, side of the post. 

I installed a weather resistant Midnite box fitted with a DIN rail MNEPV breaker on the post. The wire coming from the PV is 2 AWG. I used a connector made to transition from 2 AWG the breaker connector. The positive DC line is connected to that breaker. There is also a terminal block for the negative and ground wires to downsize. This box is the location of one of our Midnite SPD's. Another MN-SPD is installed down at the PV array pole. Both of these locations also have delta lightning arrestors. Belt and suspenders approach. 

The wires then connect through fittings and conduit to an outlet box, weather proof type on the other side of the post. That box is fitted with a NEMA L6-50 twist lock outlet/receptacle. (female connector). Both sides of the post have warning labels I had made up on rain and sun proof sign stock. They warn against inserting or removing the NEMA plug without first pulling the breaker to off.  It is not foolproof, I know, but the warnings are very visible.  I know these are not DC rated, but the contact surfaces are robust and they are not to be plugged in or unplugged when powered. 

I then have an outdoor quality  10-3 cord with the matching L6-50 male plug on one end. The other end of this cord connects to The Kid  charge controller, via another MNEPV breaker installed just before the CC. The cord can be unplugged, coiled up and stored inside a box on the cabin wall.  There is a third MN-SPD installed at the CC position. Also an AC version of the MN-SPD is connected at the AC service panel. 

This works for us. We don't let others use the place when we are not there, except for one family member. 

The SPD green wires / electrical system grounds are connected to a series of 3 copper clad rods and 1 buried copper plate. All connected with a single continuous length of bare copper. Earthing points are separated by something like 12 to 15 feet. 

Our air terminal lightning protection system is also earthed to 4 copper rods and 2 buried copper plates, but separate and on the other side of the cabin. 

Mountain Don

To be clear: the disconnect sequence is (1) Pull the input to CC breaker. (2) Pull the breaker on the post (feed from array) (3) Unplug the cord and coil and store at cabin.

Connection is the reverse sequence: plug in cord, turn on breaker at post, turn on breaker by CC. 

jonr

If running ungrounded, I'd put a GFCI on each circuit.    These prevent most cases of electrocution.

Also consider installing a perimeter ground to divert differences in ground potential around your house.  

Do you have a grounded well pump?

Dave Angelini

Good old John Wiles!  His stories of his wife calling him at Sandia and telling him there was ball lightning floating around the room and was it safe for her there with their toddler. Those were the wild west days of solar.  

Good Luck Don! and prayer also....You too Westbranch! Stay low! It is the mean season!

westbranch

than ks Dave..  just 2 weeks ago , days before this onslaught,  our neighbourhood Helicopter base erected a new comm tower...  we watched it go up and left for grits etc, and came back 3 days later to....No Tower???  Bino's out , no tower, the next day it went back up and we overheard on the ICOM that  '' it looks like it was only the radio equipment that got nailed''   Yup 2days before it got blasted, now I watch the show at night  waiting to witness the ;fireworks, We are happy to have a higher sacrificial lamb up there on the ridge !!

westbranch

Well we must have missed some 'SParKS"  up on the hill very recently, a chopper just dropped off 3 people and they are checking the guy wires etc...

Dave Angelini

Those chopper lineman are amazing.  We look out into 2 river canyons out of Yosemite and the high voltage for the park is about 10 miles away.  When there is lightning I can see it dance off the guy wires. We don't get alot of lightning but we can get it at anytime of year. There is always someone here to shut it down if it gets close.  We still pray though.....