Surge Unit

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Old 01-04-18, 08:52 PM
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Surge Unit

I have a whole house surge protection device. It has a threaded male stub and lock ring, which I understand going to a box 'knock out.' Can I also use this to do point of use protection? --Like for my furnace, or 220v dryer, or oven,(all of which have circuit boards) when mounted to a junction box?
 
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Old 01-05-18, 06:54 AM
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You COULD, but. There is a concept called coordinated surge protection, and it started upstream. The utility install surge (lightning) arrestors on your primary power feeds at recurring points. Then, at your service entrance, a secondary voltage rated (250V) is installed at your panel that has a fairly high momentary current rating. Further at the point of use (at the appliance) a lower breakdown voltage system is employed with a somewhat lower surge current rating.
The idea being, the most energy is being dissipated upstream, with progressivly lower current, and lower voltage devices installed closer to the user. If you place a service rated device at the appliance, that is suboptimum (technically and economically), and mostly redundant.
 
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Old 01-05-18, 07:24 AM
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The surge unit will be less effective the further it is electrically from your earth grounding system. The main panel is by far a better location. Surge "protectors" are really surge "redirectors" -- they are ineffective if the energy can't be easily dissipated into the earth.
 
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Old 01-05-18, 07:30 AM
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I have a whole house surge protection device...
,
But you don't tell us which one? In general, these are far more effective in the service entrance.
 
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Old 01-05-18, 07:35 AM
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It's this one: http://www.intermatic.com/en/surge-p...urge/ig1240rc3

Also, I already have a whole house breaker type surge protector at the panel.
 
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Old 01-05-18, 07:43 AM
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Is this some kind of power factor correctin' device? Shazam shazam, shazam. Golly good thing we don't get charged for that.
 
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Old 01-05-18, 11:02 AM
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THe Line to Line clamping of 1200V rated is not impressive.
Worse, even, is the Line to Ground of 1200V.
They don't give the test current, but I've tested plenty of MOV devices, rated at 300V rms and am getting on the order of 700 to 800V with a 2kV standard pulse waveform with 2 Ohm source R.


Not good enough for a point of use supressor. OK for a main panel.

edit: UL1449 rel 3 is showing a test voltage of 6kV in series with 2 Ohms. More in line with what a main panel will see. The point remains, however, is that you need to knock that down to much lower than 1200V at the appliance. So, you use MOV with a lower breakdown voltage, and not as much energy capability is needed.
 
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Old 01-05-18, 08:03 PM
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Today I went to the washer to put in the SPD,(hard wired KO type) but had to stop for understanding. Background:

It's not a 110v washer, It's a 220v unit (I guess because it heats the water also.) And just FYI the dryer is on a separate circuit.

Anyway it's on a 2 pole 15A breaker going to a 3 prong air cond. type plug. (The washer has always worked fine.) So here's what I don't understand:

The plug is supplied 12-3 from the panel. The ground is going ONLY to the metal box ground screw. The red and black are on their respective plug hot terminals. The kicker is the neutral is connected to the plug ground screw???

First of all why does this set-up need a third wire neutral, which is feeding into the washer?

Second how do I make sense of this and get a SPD, and the plug if needed, wired in properly?

Info if further help...at he panel, the 12-3 ground is going to the ground bus strip, the neutral is going to the neutral bus. However the ground bus strip is bonded to the case and it is not tied to the neutral bus strip

Thanks!.
 
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Old 01-05-18, 08:28 PM
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If it's a 240v only unit..... the ground should connect to the box and the receptacle. The white neutral should be capped off. The yoke of the receptacle is connected to the ground screw so when the receptacle is in place...... the ground and neutral are tied together. Wrong.

Here's the thing..... is that a 240v ONLY washer or is it 120/240v ?
The requirements should be on the ID plate.
If not.... post the model and we can check.
 
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Old 01-05-18, 08:57 PM
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Thanks. I'm thinking...what did they do on the dryer itself? Is the wht wire going to a ground terminal. I can't get the plate off easily.
Anyway, the receptacle looks like the attachment included
 
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Old 01-05-18, 09:01 PM
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And ironically maybe I could or should use the neutral for the SPD? I need a neutral for it any way, yes?
 
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Old 01-05-18, 09:02 PM
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Yes.... that's a 20A 240v receptacle and should not have a white wire on it.

How are you planning on installing a protection device there ?
 
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Old 01-05-18, 09:21 PM
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Install SPD via extension box on the handy sg box...actually it's gonna be tight, I may need to swap out for a big 4" SQ box.

But hence that's why I think that neutral will come in handy--the SPD needs it.
 
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