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Hello, question regarding voltage let through

APC UPS for Home and Office Forum

Schneider Electric support forum for our APC offers including Home Office UPS, Surge Protectors, UTS, software and services and associated products designed to share knowledge, installation, and configuration.

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jase_apc
Cadet
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202

Hello, question regarding voltage let through

This was originally posted on APC forums on 7/7/2011


Hi, I recently bought the P8VT3 surge protector.

I am using it to protect my tv, computer, game consoles etc.

I noticed this model has a less than 85 voltage let through. However, I saw other models where they have less than 40 voltage let through.

Is there a big difference between these two ratings? Will the less than 80 voltage let through be more than plenty? How does the P8VT3 compare to the P11GTV in terms of protection?

Thanks in advance.


Accepted Solutions
voidstar_apc
Janeway
Janeway
0 Likes
0
202

Re: Hello, question regarding voltage let through

This was originally posted on APC forums on 12/10/2012


>
Joules and guarantees mean nothing to my data.
>

Yes. To protect your data, you need geographically diverse backups. Protecting the electrical line can only do so much, and can't prevent damage from a lightning strike except by unplugging.

>
1)
If you put a 6000V, 500A surge (or any surge), it lets 330V go to my equipment?
>

I was confused why [P8VT3|http://www.apc.com/resource/include/techspec_index.cfm?base_sku=P8VT3] lists <85V for the let-through voltage rating, yet 330V for the UL rating (effective clamping voltage). Clearly that doesn't add up... 330V effective clamping - 169.7 peak = 160 V let-through which isn't <85V. Then I came across [this page|http://www.powerqualityanddrives.com/transient_surge_protection/]:

>
The unit bears an Underwriters Laboratory listing per UL 1449 specifying its rating to be 330 volts
peak Let-Through. UL 1449 allows no listing lower than 330 volts. A manufacturer may therefore
state in published literature test results that exceed UL 1449 specifications, but to bear the UL1449
label the manufacturer must label the device in accordance with UL specifications as per UL
test procedures.
>

So, the P8VT3 allows at most 85V let-through over the peak voltage, which means it allows 255V (effective clamping voltage) to reach your equipment. However it is labeled 330 V effective clamping voltage because that's the lowest listing UL provides.

>
So the average electrical gadget can handle an (approximate) maximum 330V? (That’s good to know.)
>

It's hard to say what products will do; UL's main concern is they don't catch fire. Most should be able to handle an small overvoltage over a short period of time and thus be protected by the surge protector.

>
And my Mother in Kansas has sequentially had 2 tvs, a printer, two answering machines wiped out (dunno if storms, wish she’d mentioned it sooner.) Does that mean her house wiring is bad?
>

Too many possibilities. It seems like you have your bases covered with distributed surge protectors and phone line arrestor.

See Answer In Context

5 Replies 5
BillP
Administrator Administrator
Administrator
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0
202

Re: Hello, question regarding voltage let through

This reply was originally posted by Angela on APC forums on 7/8/2011


this might help a little bit -> http://nam-en.apc.com/app/answers/detail/a_id/65 in relation to your first question

BillP
Administrator Administrator
Administrator
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0
202

Re: Hello, question regarding voltage let through

This reply was originally posted by ReRe on APC forums on 12/7/2012


In that article there is a confusing pair of statements.

1) Typically, MOV's with a higher joule rating also have a higher surge clamping voltage which will result in a higher let-through voltage to the protected equipment.

2) a surge protector should be selected based on the lowest let-through voltage capability and UL's best effective clamping voltage rating of 330V


So which is it?: higher, better? lower, better? how much better?
Is this voltage let through at the moment of a surge? If so, shouldn't it be 110 (or whatever the setting is)?

voidstar_apc
Janeway
Janeway
0 Likes
0
202

Re: Hello, question regarding voltage let through

This was originally posted on APC forums on 12/8/2012


>
In that article there is a confusing pair of statements.

1) Typically, MOV's with a higher joule rating also have a higher surge clamping voltage which will result in a higher let-through voltage to the protected equipment.

2) a surge protector should be selected based on the lowest let-through voltage capability and UL's best effective clamping voltage rating of 330V

So which is it?: higher, better? lower, better? how much better?
>

The two statements say:
2) lower let through is better and
1) joule ratings aren't as meaningful because higher joule rating may provide less protection.

You want let-through low enough to protect equipment by shunting as much of the surges as possible, but not too low that it burns up easily.

>
Is this voltage let through at the moment of a surge? If so, shouldn't it be 110 (or whatever the setting is)?
>

AC voltage is time varying, so it's never one particular voltage but rather goes up and down in a sinusoidal pattern. So what we call "110V AC" actually peaks at 155V. And of course the utilities could be running the line at a higher voltage. And of course surges may bring the line above 155 for longer than a MOV could safely shunt. While I'm not a safety engineer, I trust their judgement.

Your main concern seems to be determining which model is better based on let-through voltage. I don't think surge protection is a significant difference, because in the end if it does fail and your equipment is damaged, they both offer a $150,000 [equipment protection policy|http://www.apc.com/support/service/equipment_protection_policy.cfm]. Just make sure you register the strip and the data lines are protected by the strip.

BillP
Administrator Administrator
Administrator
0 Likes
0
202

Re: Hello, question regarding voltage let through

This reply was originally posted by ReRe on APC forums on 12/9/2012


Thanks for the info, but I guess I need some hand-holding:

Sorry, I’m still confused about some terms. I’m gaining two different conclusions from the same numbers.
1)
If you put a 6000V, 500A surge (or any surge), it lets 330V go to my equipment?
So the average electrical gadget can handle an (approximate) maximum 330V? (That’s good to know.)
And your products allow between 40 and 85 over this?
So why wouldn’t I want it to stop at 330V?
OR
2)
Effective Clamping – Peak AC = Let Through: in your example 330-169 =161
or X-169=40 and X-169=85?
Why wouldn’t I want to let through enough voltage for my equipment to operate? Wouldn’t I want it to leave me 169V instead of 161?

I’m in LA and a friend in Santa Monica had his new fax machine wiped out in a surge that wasn’t even a storm. So it’s easier than you’d think.
And my Mother in Kansas has sequentially had 2 tvs, a printer, two answering machines wiped out (dunno if storms, wish she’d mentioned it sooner.) Does that mean her house wiring is bad? I personally think she should complain to the electric company, it’s a newer housing area and perhaps they used cheap transformers? We have now distributed surge arrestors throughout the house, and a phone line arrestor on the answering machine.
So I don’t think of it as paranoia to want to protect something effectively rather than rely on a guarantee that will require more hassle and fine print-reading.
And for peace of mind I’d like to understand the process. Joules and guarantees mean nothing to my data.

voidstar_apc
Janeway
Janeway
0 Likes
0
203

Re: Hello, question regarding voltage let through

This was originally posted on APC forums on 12/10/2012


>
Joules and guarantees mean nothing to my data.
>

Yes. To protect your data, you need geographically diverse backups. Protecting the electrical line can only do so much, and can't prevent damage from a lightning strike except by unplugging.

>
1)
If you put a 6000V, 500A surge (or any surge), it lets 330V go to my equipment?
>

I was confused why [P8VT3|http://www.apc.com/resource/include/techspec_index.cfm?base_sku=P8VT3] lists <85V for the let-through voltage rating, yet 330V for the UL rating (effective clamping voltage). Clearly that doesn't add up... 330V effective clamping - 169.7 peak = 160 V let-through which isn't <85V. Then I came across [this page|http://www.powerqualityanddrives.com/transient_surge_protection/]:

>
The unit bears an Underwriters Laboratory listing per UL 1449 specifying its rating to be 330 volts
peak Let-Through. UL 1449 allows no listing lower than 330 volts. A manufacturer may therefore
state in published literature test results that exceed UL 1449 specifications, but to bear the UL1449
label the manufacturer must label the device in accordance with UL specifications as per UL
test procedures.
>

So, the P8VT3 allows at most 85V let-through over the peak voltage, which means it allows 255V (effective clamping voltage) to reach your equipment. However it is labeled 330 V effective clamping voltage because that's the lowest listing UL provides.

>
So the average electrical gadget can handle an (approximate) maximum 330V? (That’s good to know.)
>

It's hard to say what products will do; UL's main concern is they don't catch fire. Most should be able to handle an small overvoltage over a short period of time and thus be protected by the surge protector.

>
And my Mother in Kansas has sequentially had 2 tvs, a printer, two answering machines wiped out (dunno if storms, wish she’d mentioned it sooner.) Does that mean her house wiring is bad?
>

Too many possibilities. It seems like you have your bases covered with distributed surge protectors and phone line arrestor.