Surge protection recommendations

Got a new CNC press brake on the way. Salesman and install tech have both highly suggested some form of surge protection. I've seen all types of surge protectors - some device specific, some that supposedly protect the whole panel (but only need to install in an empty breaker slot), etc.

New machine is a Turkish made brake with 7 hp 230v 3 phase main motor, plus backgauge servos and whatnot. I'm in a single phase shop, so I'll be running off a brand new American Rotary ADX-20 RPC.

Should I be looking at protecting the single phase line going to the RPC, or should I protect the 3 phase line past the RPC? The rest of my shop is all standard motor loads and inverter welders - no CNC anythings.

In a city with seemingly clean power - we don't seem to have the crazy fluctuations that some of you in rural areas seem to have. City discontinued offering whole panel surge protection about a decade ago.

What should I be looking for in a surge protection unit? Any specific brand/model recommendations?

The first question to ask is where are the surges coming from, then what are you trying to protect? Presumably we are worried about transient overvoltages from your utility source. For a small service with a fair bit of inductance upstream (weak source) we're probably not worried about fast rise time transients as much as the elevated voltage itself. The simplest approach is to install a metal oxide varistor (MOV) type surge protector. Operates like a zenar diode that passes a few milliamps leakage current near nominal voltage, then turns into a low impedance path during an overvoltage and shunts a lot of current to ground to trim down the overvoltage. They are rated for maximum continuous operating voltage, the amount of voltage across them while passing various levels of surge current, and a power dissipation rating. Their typical failure mode is thermal from dissipating too much power. This aging adds up over time, then eventually they fail open and stop protecting the power system. Sometimes they fail closed and trip the upstream breaker - so don't wire it directly to the line side of your main breaker. Many of the small ones have a window on the front and if you can see any dark coloration in the window the active material is damaged and the unit should be replaced.

I don't have any specific product recommendations - I buy these at work but I do all of my surge protection at higher voltages, and the low voltage product lines are different.

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jdsmith said:

The first question to ask is where are the surges coming from, then what are you trying to protect? Presumably we are worried about transient overvoltages from your utility source.

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I'm guessing that's my highest concern. Maybe lightning as well (my best understanding is that would be an equivalent type of transient overvoltage - is that right?), though I do make an effort to disconnect my inverter welders during lightning storms, and always overnight. I plan to flip the breaker on the RPC panel whenever the RPC is off - effectively disconnecting this machine when not using it or overnight.

I found a very attractive price on this whole panel unit. Do the specs here look suitable? I've got a commercial building, but just a 200 amp single phase service, so equivalent to residential panel.

http://download.schneider-electric....&p_Doc_Ref=6671CT9701#page=4&zoom=100,-93,777

Square D™ Whole House Surge Protective Devices (SPDs) provide
suppression of electrical surges to AC power as well as telephone and
television cables (optional with SDSB117
5CB). Installed next to the circuit
breaker panel, the device is hard-wired to the electrical panel. The
telephone module (SDSA4P) accommodates four telephone lines (eight
with two telephone modules). The coaxial module (SDSA2V)
accommodates one coaxial television
line (two lines with two modules).
Features
•
Design allows for field replacement of components.
•
Multi-path surge suppression capabilit
y covers all electrical entrance
points to the home.
•
80,000 A surge current capacity for a longer service life and suppression
of high-energy surges.
•
LED status indicator allows for visual indication of the SPD status.
•
Hardwire connection method provides direct connection means to the
electrical panel.
•
Coordinated fuse technology allows disconnection methods for thermal
and high-current events.
System Performance
Electrical
•
Surge suppression capability up to 80,000 A per phase
•
Discrete thermal disconnect surge suppression
•
cULus Listed to UL 1449 3rd Edition, Type 2 SPD
•
Modes of surge suppression: Line
1-to-Neutral, Line 2-to-Neutral,
Line 1-to-Ground, Line 2-to-Ground,
Line 1-to-Line 2, Neutral-to-Ground.

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Performance—AC Protection
Surge Current Rating per Phase
80 kA
Short Circuit Current Rating
25 kA
Modes of Protection
6
Fusing
Individually fused MOVs
Thermal Fusing
Yes
Overcurrent Fusing
Yes
Operating Frequency
50/60 Hz
Mechanical Description
Enclosure
Carbon Steel
NEMA Rating
NEMA 1
Connection Method
#12 AWG, Stranded
Weight
10.5 lbs
Mounting Method
Four screws, #10
Circuit Type
Parallel
Operating Altitude
Sea Level to 12,000 ft. (3,658 m)
Storage Temperature
-40°F to +149°F (-40°C to +65°C)
Operating Temperature
-40°F to +149°F (-40°C to +65°C)
Diagnostics
Green status LEDs
Listings and Performance
•
cULus Listed to UL 1449 3rd Edition Type 2 SPD
•
CSA C22.2 No. 8-M1986, C233.1-87
•
UL Recognized to UL 497A 3rd Edition
•
UL 497B 4th Edition
•
CSA C22.2 No. 226-92

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That will work, keep in mind you want to keep the wires from the surge protector to the main panel as short as possible. A layered surge suppression system is used if you have sensitive electronics. So main service entrance, I may repeat at a sub-panel and then at the machine. The voltage is attenuated with each surge suppressor device. I previous was in Tucson with a lot of lightening and power outages, a voltage spike counter on the system indicated that surges were occurring. The need is dependent on the area you are located, and the stability of the electrical system, but I always have at least two surge suppressor levels, one the service entrance and at the machine.

mksj said:

That will work, keep in mind you want to keep the wires from the surge protector to the main panel as short as possible. A layered surge suppression system is used if you have sensitive electronics. So main service entrance, I may repeat at a sub-panel and then at the machine. The voltage is attenuated with each surge suppressor device. I previous was in Tucson with a lot of lightening and power outages, a voltage spike counter on the system indicated that surges were occurring. The need is dependent on the area you are located, and the stability of the electrical system, but I always have at least two surge suppressor levels, one the service entrance and at the machine.

Click to expand...

I just purchased the unit I had linked to above. I'll mount it right next to the incoming panel to keep the leads short.

I'll keep researching other options to put at the power entry to the machine.

To get the most effective performance of any surge suppressor, it would be prudent to check for good connections to the grounding electrodes, to your shop panel.

Without them surge protection can be pretty ineffective, especially for disturbances occurring on the utility system.

SAF