As good at the Midnite SPDs are there is a serious gap in the product line when it comes to protecting items connected to a sub-panel where neutral and ground are not connected. This is particularly an issue when the sub-panel is in a remote building with its own grounding electrode. I'd really like to see a SPD for protecting L1, L2, and neutral; it could also be used in the main panel for a three-phase system. The attached sketch shows where the unprotected wire is located and how to correctly provide surge protection at a 120/240 split phase panel.
Kent
That is the 3 phase model and it is at ETL right now. Has 3 legs so we can protect L1, L2 and Neutral
Ryan
That's excellent news! I hope after it is approved the instructions for the existing SPD models will say that they should not be used in sub-panels where the neutral and ground are not connected together or will show how two (non-three-phase) SPDs can be used to protect L1, L2, and neutral.
OR, L1, L2 and L3
hi Kent !
being it is for surge suppression, would it matter what ground it gets diverted to? i see nothing wrong in grounding that spd to the ground rod at that building.
Quote from: niel on April 30, 2014, 11:35:30 PM
being it is for surge suppression, would it matter what ground it gets diverted to? i see nothing wrong in grounding that spd to the ground rod at that building.
It could matter (with lightning, anything can matter).
In the event that lightning strikes the ground near your system, the two ground rods could have 1000s of volts difference. The SPDs become conductors at relatively low voltages, and would allow current to flow from one ground rod to the other through any of the current carrying conductors.
If you want to 'crowbar' your ground rods, IMO it is better to do it with a non current carrying conductor.
--vtMaps
so what it'll present voltage differencials between grounds as it is a surge current being grounded out and it's not creating a ground loop on the main power wires. don't try to school one who made you aware of ground loops in the first place.
Quote from: vtmaps on May 01, 2014, 05:49:46 AM
Quote from: niel on April 30, 2014, 11:35:30 PM
being it is for surge suppression, would it matter what ground it gets diverted to? i see nothing wrong in grounding that spd to the ground rod at that building.
It could matter (with lightning, anything can matter).
In the event that lightning strikes the ground near your system, the two ground rods could have 1000s of volts difference. The SPDs become conductors at relatively low voltages, and would allow current to flow from one ground rod to the other through any of the current carrying conductors.
If you want to 'crowbar' your ground rods, IMO it is better to do it with a non current carrying conductor.
--vtMaps
VTMaps
I think I agree if there are multiple ground rods they really need to be bonded together. Induced voltage from lightning is a nasty thing and I have had several paid (By me) educations on this subject as I live on a rock at a high elevation.
it has nothing to do with the function of the spd as it could still send a surge to ground to that 1 rod.
i was always the advocate of the bonding of ground rods, if close enough in proximity and this is a separate issue from that of the spd functioning to that ground rod as it matters not if it's a bonded or unbonded group of rods or even a separate rod dedicated to the spd. it will function. more rods tied does lower the resistance to ground and may allow it to perform better, but this is not required for the spd.
Quote from: Halfcrazy on March 06, 2014, 06:24:20 AM
Kent
That is the 3 phase model and it is at ETL right now. Has 3 legs so we can protect L1, L2 and Neutral
Ryan
I don't see the specs for the new 3 phase SPD on your website, but previously you wrote:
Quote from: Halfcrazy on September 15, 2012, 12:24:50 PMWe are working on a 3 phase version. The downside is there will be less protection per phase as we can not fit any more MOV's in the case. I prefer on wind turbines to use 2 of the SPD's to get max protection.
--vtMaps
btw ryan, i should add that you may benefit from a faraday cage type of arrangement in addition to many rods in the circumstance of being more prone to lightning as an spd or even many spds will only do so much.
The SPD products have been at ETL for about 7 months now. We sent the three original SPD's as well as three new versions. 208 3PH, 480V 3ph and 1000VDC.
ETL has been messing around and costing us tons of money for a long time now. I finally stopped all testing on the three new versions due to costs. We are now up to about $80,000 in ETL testing and they are not done. They are not communicating very well either, so to limit our expenses, we are only finishing the three original SPD's at this time. When ETL gets more reasonable on costs we will finish the new three versions. If that never happens, we may send them to another agency such as UL, TUV or MET or CSA.
We are in the process of sending our Birdhouse to UL now. We have been using ETL exclusively since the beginning, but now feel we need to expand our agency testing to others.
I agree that the three phase will be nice to protect the neutral also. The present devices are stronger though. We do a great job of protecting equipment according to reports from the field. We have had only a few SPD's destroyed in the last few years. We tried to make them indestructible and it appears that has been working quite well.
The UL standards have some test requirements that will require series breakers to protect the SPD's from burning up. These tests are anything but reality, but we have to pass the tests regardless in order to put the ETL label on them. We will have more on this subject when and if ETL ever finishes their testing. In the mean time they do continue to send invoices on a regular basis.
Quote from: vtmaps on May 01, 2014, 05:49:46 AM
Quote from: niel on April 30, 2014, 11:35:30 PM
being it is for surge suppression, would it matter what ground it gets diverted to? i see nothing wrong in grounding that spd to the ground rod at that building.
It could matter (with lightning, anything can matter).
In the event that lightning strikes the ground near your system, the two ground rods could have 1000s of volts difference. The SPDs become conductors at relatively low voltages, and would allow current to flow from one ground rod to the other through any of the current carrying conductors.
If you want to 'crowbar' your ground rods, IMO it is better to do it with a non current carrying conductor.
--vtMaps
The reason you should connect the SPD ground close to the E-panel and electronics is because the SPD's basic clamping protection function is to keep the system component's insulation from arcing-over.
If the SPD's ground is connected thousands of volts away form the E-panel and component chassis grounds, then the electronic components run the risk of breaking-over and hurting the units. i.e. the system electronics ground can be momentarily MUCH higher than the ground rod while the lightning stroke and their high induced electric fields are active.
Each listed component should be tested at the factory (Hipot) to make sure it can withstand a certain breakdown voltage between its chassis ground terminal and all of the other wires and connections in the unit.
Adding an SPD between the chassis ground and the hot wires, tries to keep the common mode lightning induced voltages below that hipot test voltage. The Classic, for instance, is hipot tested up to around 2,270 volts DC.
bob,
that's a good argument for putting another leg of another spd from neutral to ground, but all spd legs must be able to go to ground. it doesn't change what i said as he can put it to that ground rod and putting it to neutral instead of ground will leave all at the potential to be far above ground in volts. spds work against ground as that's where the surge is supposed to go to.
One problem/question is "what is ground" ? Ground isn't always where it should be or the voltage you think it might be compared with other points in the circuit. And AC neutral is grounded too but I'm not sure if the NEC will allow SPDs to connect to neutral ?
But yes, the lightning current is trying to get to ground and it will get back there through the
ground line. The situation that the SPD tries to prevent is to keep that current from going through
the sensitive non-ground circuitry on its way back to real ground.
yes, one can go spd crazy between all wires for added protection. the point you brought up is 100% accurate.
"The situation that the SPD tries to prevent is to keep that current from going through
the sensitive non-ground circuitry on its way back to real ground. "
this is better done to ground rather than through neutral as the surge through the neutral could induce voltage into the other wires as it often is running parallel to them. unfortunately, if the ground lead also parallels the other wires (as mr wiles insists) the same scenario can be made. sometimes you can't win no matter what you try to do, but now you can see my logic in sending it off to that ground rod.
in rereading this it occurs to me that many may be misunderstanding what i said. i do for the record fully agree with kento's assessment. my argument was that with the present 2 legged spd only that it should not ground out to the neutral, but rather to the ground rod at that remote location as the neutral could be above ground potential and present a longer path to the actual ground while it could also induce that surge into the other wires. going to the ground rod there at the building will at least put the 2 hots to ground surge wise, but i acknowledge there is still the problem of the neutral being above ground and picking up the same energy the hots picked up and the reason 3 spd legs to ground are needed. yes, neutral does eventually go to ground, but long distance grounds are really a no no when it comes to surges from lightning emp. i recommend kento's 3rd pick to that ground rod at the remote building. that's the proper scenario.
now referring to the separate issue of ground rods if the buildings are close together then go ahead and tie the ground rods together via heavy gauge bare copper wire buried underground, but if spaced apart like typical telephone poles are then it isn't necessary to tie tied then as the ground resistance is then high enough to quell a surge potential or loop between the rods. ideally they should be tied though, but if it's good enough for utilities then it's good enough for us at those distances.
Any news on the four-wire SPD for three-phase or 120/240 subpanels where the neutral should be protected?
I am looking to quote a 10Kw Enphase 3 phase 120/208 system and want to use your MNSPD
what model and when ready?