Lightning protection AND putting a receptacle on UPS

[Ignoramus32515]

I found an interesting chart.

According to APC, a similar SUA2200 can run a 400 watt load for 1 hr

28 minutes. No doubt on new batteries.

[w_tom]

The most common and destructive surge is common mode. In common mode surges, even wood, linoleum tile, and concrete become conductors. The fact that so many different circuits can exist is but another reason why we want the transient earthed outside the building AND why we prefer the earth to be equipotential - which is why Ufer grounds would be so useful.

The surge between hot and neutral is eliminated by a 'whole house' protector, typically does not exist, and is made irrelevant by protection already inside appliances. A typically destructive surge is common mode. Effective protectors for common mode transients also makes other transients irrelevant.

Don't let this idea grab you - that a protector will sit between the appliance and the transient source - blocking, stopping, or absorbing the transient. That just does not happen. Effective protection that even protects that telco switching computer works better when distant from electronics. Telcos prefer a 'whole house' protector on each incoming wire to be 50 meters from the electronics. Protection adjacent to the electronics - it's already inside the electronics.

Defined by effective protectors are protection from all types of transients. The APC unit only claimed to protect from normal mode transients. Now they even forget to mention which mode they protect from.

But lets see the spec for that APC protection that no longer even mentions normal mode: Surge energy rating 880 Joules Filtering Full time multi-pole noise filtering : 0.3% IEEE surge let-through : zero clamping response time : meets UL 1449

This is what they used to provide. At least they once provide more (but incomplete) information: Normal mode clamping response time 0 ns, instantaneous Normal mode surge voltage let through

[Ignoramus32515]

Would that common mode surge be a event where voltages of both hot, neutral as well as ground rise too much above true ground potential (potential of a copper rod buried in ground)?

Am I correctly describing what you have in mind?

If not, just what is it exactly?

I want to make sure that I understand exactly what you mean.

i

[w_tom]

The Soares book is an excellent source of translating code requirements into useful examples. That is grounding for human protection. Grounding for transient protection must enhance that system. Soares is about human safety. Here, we are discussing the same system enhanced for transistor safety.

Every incoming wire must connect to the same earth ground. That is now required for human safety - including a 20 foot or less wire connection. For example cable and dish wires should be earthed to same AC electric earth ground before entering building. Neither requires a surge protector. Surge protector is only a temporary connection to earth. But both wires are connected to earth by a dedicated wire. Therefore protector would do little more.

How each utility connects to earth include things not required by NEC nor in that Soares book. For example, earthing wire must remain separated from all other wires. Wires must have no sharp bends, no splices, meet only at a common point. Wires should be 'less than 10 feet' which is beyond what is required by code. Every foot shorter means increased protection.

Geology is an important part of protection analysis. Some locations can be sufficiently earthed with only a single ground rod. Others require extensive earthing to be equivalent. In your case, an AC controller should probably be mounted on equipotential earth - previous references to a halo ground.

If one needs better protection, then one starts by enhancing the earthing system. That is often a largest weakness in any protection system. That is where bucks can often return more value - which is why bucks spent on plug-in protectors would be better spent first on enhancing the earthing system.

If lightning is a major threat, then lightning rods are also part of the protection system. What determines lightning rod effectiveness? Earthing. How those lightning rods do and do not connect to the building earthing system is also important

- part of the art.

Ignoramus32515 wrote:

[w_tom]

5% THD should be sufficient for most electrical loads. That suggests this UPS was a more expensive type - is more than computer grade.

To define hot spots and protection, first define where the earthing spot is. Your primary protection is demonstrated in these pictures:

Also inspect your primary protection system - which you cannot repair.

That is your first layer of protection. Your 'whole house' protector and earthing system is a second layer. Protection inside electronics may be thought of as the third layer.

To be effective, point of use protectors must earth all the way back to the same earth ground provided to a 'whole house' protector. IOW point of use don't do much - no effective grounding. Even worse, point of use protector can induce transients onto other wires in that same wire bundle. The ground wire being too long and not separated from other wires.

In higher reliability facilities, whole rooms may become a building inside a building. Every wire entering the room is connected to a big ground that surrounds the room. Then a point of use protector is grounded to a third layer - a third single point earth ground system - that is that room. In this case, a point of use protector now has a function. A function, BTW, that can be compromised if any wire leaves the room without a connection (direct of via protector) first to that common entrance protection ground.

Layers of protection are defined by the single point ground. We keep it simpler in dwellings. Primary protector provided by the utility. Secondary protection is the household earthing system - with peripheral components such as 'whole house' protector (ie AC electric and telephone) or direct wire connection from each incoming utility wire (ie cable TV).

Where s> According to the specs at

[Ignoramus32515]

Thanks Tom. I asked you in another post to describe just what is the exact scenario for a common mode surge that an ordinary UPS cannot properly take care of. I am very interested to find out.

i

[Ignoramus32515]

It was indeed quite expensive. I got a pallet of four for $60, but they cost a lot more new.

The ground is near electrical panel. I will check tonight to be sure.

Not sure what you mean, sorry.

I am confused, there is a ground at the receptacle and the UPS is grounded to that ground.

i

[w_tom]

That is the problem with common mode transients. For example, the transient can go down a battery powered wire, be same voltage on both sides of the battery, never be seen by battery, and proceed to destroy electronics. Replace battery with MOV protector to have same problem. The voltage is never seen by a protector connected across both wires. Common mode transients are created by lightning and by other events such as AC electric power line switching. The latter should be irrelevant since any protection for the former also makes all other transients (except NEMP) irrelevant.

In another event, the computer were powered off when lightning struck. Two computers were connected to point of use protectors. Transient was traced by replacing ICs - making computers work again. Transient only entered on AC hot wire. Adjacent protector shunted transient to safety ground wire at computer. Transient entered both computer motherboards. Exited via network cards (ground plane to network wire). Down to third computer. Out via third computer's modem to earth ground via the telco 'whole house' protector.

Point of use protector contributed to damage of adjacent and powered off computers by providing a common mode transient path from AC hot, around computer power supply, into computer motherboard via safety ground wire. BTW, it does not matter much whether computer is on or off as demonstrated by this example. To damage computer, the transient must bypass protection already inside a power supply.

What do typically destructive transient seek? Earth ground. Electr> >> The most common and destructive surge is common mode. In

[w_tom]

[w_tom]

Don't remember if I made previous references to impedance. Yes, wall receptacle safety ground has low resistance. But it has higher impedance. Impedance created by things such as sharp wire bends, inside metallic conduit, splices, wire length, etc. Previous references to ground being 'less than

10 feet' were about wire impedance. Wall receptacle is just too far to be considered earth ground. It provides low resistance ground to conduct (60 Hz) AC electric. But it has too many junctions, too many bends, too bundled with other wires, and too long to be an effective earthing ground.

View those pictures of

to appreciate your primary protecti> It was indeed quite expensive. I got a pallet of four for $60, but

[w_tom]

[Chris Lewis]

According to Ignoramus32515 :

No. But I'm worried about a UPS surviving a 15-20A or more several cycle startup transient. If it can't "keep it up" (voltage), the startup takes longer, and the current draw is longer -> yet more agony for the UPS.

I'd be very hesitant about running 1/4+ HP motors on UPSes, unless they're _seriously_ beefy.

With motor-generators you have rotational inertia, and there aren't any semiconductors in the direct current paths. UPSes have no inertia. Lots of semiconductors right in line with the current.

[trader4]

"Ignoramus32515 So... I do not need protection against direct lightning strike that blows up all wiring, I rather want to be protected against lower power, but more frequent events such as the one that already happened near my house 3 years ago.

I will use cheap used APC 2200 UPSes for the expensive stuff.

I may use a whole house protector also. "

Since that is still your belief, I think we should all just give up on you, as you still obviously haven't understood anything that's been said. Go put those UPS's on your furnace and TV and make yourself happy!

[Ignoramus16420]

w_tom, can you explain to me what is the exact scenario where such a common mode transient would occur. Does it apply to a lightning strike, if so, where would it strike. I would like to hear something a little bit more precise.

I find it a little bit difficult to visualize how exactly a common mode transient would actually happen. And I think that I do understand what is common mode, from my electronics experiences. What I do not see is just how it would realistically happen.

That would make following your suggestion a little bit easier.

thanks

i

[Ignoramus16420]

Good point, I will try. In fact, I will try powering up my 1/2 HP Baldor bench grinder. It is a good approximation of a furnace blower.

i

[Ignoramus16420]

Well, the only way to find it out is by trying, which I will do. I will start with my 1/2 HP Baldor grinder, which is a good approximation of a furnace blower (a lot of inertia).

i

[Ignoramus16420]

Tom, can you describe the scenario for a common mode transient.

Just what would happen and where to cause it.

i

[Chris Lewis]

Actually it isn't. The bench grinder doesn't startup/operate under full load.

[Chris Lewis]

According to Ignoramus16420 :

Actually, it isn't. blowers start under light load which rapidly builds to full load once it hits full speed. Grinders have virtually no load on them until you really lean into it with what you're grinding.

[Ignoramus16420]

I think that its startup conditions are actually comparable.

i