surge protector

[enireh]

can a whole house surge protector be mounted at a sub panel and still work properly?

 

[mike_kilroy]

Yes. That is how it is design.

Sent from my SM-G900V using Tapatalk

 

[gar]

190219-2111 EST

enireh:

My answer would be no. The whole house suppressor should located at the main panel, and connected as close to the output of the main breaker as possible, further and with the shortest possible leads. Even better would be outside the house just after the meter. Further it would be desirable to have an arc discharge lightning arrester at this point.

Note: an arc discharge takes some voltage higher than its conducting voltage to ionize, then drops to a lower voltage after conductions occurs. A much better characteristic than an MOV.

Additional suppressors would be a good idea at any sub-panels.

Further you want suppressors at any susceptible loads.

Lightning or transient protection is provided by some source impedance before a voltage clamping device. The sooner (closer) to the power entry point, relative to lightning, you can start to clamp voltage, and the lower you clamp voltage the greater protection you provide. For internal transients you would like to clamp transients at the source.

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[ATSman]

I can't speak for residential but in commercial and industrial applications the closer to the load the better. A general rule is 18 inches at the load and at the service entrance.
Could not download the files but just google SPD devices/ requirements.
Make sure the Joule ratings are applied to your application.

 

[ATSman]

I have seen a lot of damage to customer equipment on a utility/ industrial level and would like to point out that the SF bay area is not prone to lightning strikes. The causes are mainly due to utility events: PFCC (power factor correction capacitor banks, 12KV) switching, PFCC stricking ground faults, 12KV utility substation/ re-closure switching, animal intrusion, etc.

I have tried to send other files but they exceed the limit,
PM me if you require further info.

 

[junkhound]

can a whole house surge protector be mounted at a sub panel and still work properly?

The ;inductance of the wiring from the main to the sub will prevent the arrestor at the sub from doing much of anything to protect other main panel loads.

If you leave the leads too long or coiled of the arrestor, it will not do much even for loads downstream of the subpanel.

 

[tom baker]

Mike Holt once said regarding SPDs
1. You get what you pay for
2. More is better

And yes the best location for an SPD would be outside, a plug in device between the meter and the socket. If you double the lead length on an SPD you double the impedance.

There was a proposal to require SPDs for the 2020 NEC for dwelling units, not sure of the status, but with all the electronics we have, SPDs are inexpensive insurance

 

[mike_kilroy]

question was: "can a whole house surge protector be mounted at a sub panel and still work properly?"

Yes. That is how it is design.

Sent from my SM-G900V using Tapatalk

I was not wordy in my reply since it was on phone w/o keyboard. I should add more. Yes, a whole house surge protector will do its job mounted on a sub panel. What is that job? To clip off and direct to ground any energy in voltages that come along above its voltage clip rating.

So, yes, put it on a sub panel and it will do its job.

But one should ask, why is it being added to the system?

I assumed it was added to the sub panel because spike protection was wanted THERE. If the object is whole house spike protection, then no, that is not the best location as everyone else here has pointed out.

We mfgr and sell a 75,000amp peak 480V 3ph unit with internal fusing and LED indicators - to put at power entry to individual industrial aerospace machinery. One 8 million dollar 15 axis fiber tape laying machine was blowing $ 8,000.00 servo drives every other week for a year from incoming voltage spikes. The machine was well built, had isolation transformers on inputs. Although it was great business for us to replace those drives so often, I had to solve the issue so developed this little TVSS unit. There has not been a failure now in 5 years. So yes, putting these on 'sub panels' can work; one just has to identify what the object of the unit is to know if that is a good location.

 

[tersh]

can a whole house surge protector be mounted at a sub panel and still work properly?

The key is the leads should be as short as possible to avoid inductance of longer wires increasing "let-through" voltage at the loads (see technical explanations at bottom reference). For example in my house is the Siemens Whole House 140,000A SPD protecting the Whole House Siemens 2-pole GFCI breakers circuitry (the panel protects 100% of all loads in the house including the lights).

The Siemens panel and GFCI breakers are my main panel. And the Siemens whole house SPD is put beside it. See the short red leads (drawn in reds) to the loads. (note the neutral and ground are not connected because we don't have those, but as long as the two wires are connected together, the unit won't sound any alarm. My protection modes are just L-L, not L-N, or L-G)

Now imagine you put the SPD in the subpanel (imagine the following Siemens were the subpanel):

Then it would take longer distance (longer leads) to the other loads in the main panel. What will suffer are the loads in the main panel. Not the sub panel.

About reasons why longer leads can have larger let-through voltage at the loads. The following reference gives the technical explanations:

See: https://www.schneider-electric.com/...277471/en_US/Surge protection devices SPD.pdf