Re: Surge protectors in series
- From: bud-- <remove.budnews@xxxxxxx>
- Date: Tue, 05 May 2009 12:01:40 -0500
On May 4, 9:48 am, bud-- <remove.budn...@xxxxxxx> wrote:ransley wrote:On May 4, 12:49 am, bud-- <remove.budn...@xxxxxxx> wrote:You aren't specific about which of the many things I said I should tellCaesar Romano wrote:Tell that to Tripp Lite, they sell one of the best units made. In factIf two surge protectors are connected in series, is the amount ofOutlet strips are not intended by anyone, including UL, to be connected
surge protection available at the down-stream protector approximately
equal to the sum of the two individual protections??
Which protector does the protecting depends on which MOV clamps at a
lower voltage. Voltage ratings, like 330V, are UL categories and cover a
wide range. Even MOVs with the same part number that are not from the
same batch would not likely have identical clamp characteristics. The
upstream or downstream protector may initially do the clamping or it may
be partially or evenly shared.
You would probably get a combined Joule rating equal to the sum of the
individual ratings. If the clamping was actually evenly shared the
combined cumulative rating would be higher than the sum of the
IMHO loads should only be connected to the downstream protector.
I recommend not connecting in series. Suppressors with very high ratings
are readily available at relatively low cost.
And all interconnected equipment needs to be connected to the same
plug-in suppressor, or interconnecting wires need to go through the
suppressor. External connections, like phone, also need to go through
the suppressor. Connecting all wiring through the suppressor prevents
damaging voltages between power and signal wires.
im fairly certain they were the first to offer a warranty against
to Tripp Lite.
I presume it is that suppressors shouldn't be connected in series. From
the UL White Book:
"Relocatable power taps [power strips, which plug-in suppressors are a
variation of] are not intended to be series connected (daisy chained) to
other relocatable power taps or to extension cords."
Again tell that to Tripp Lite. Some of Trips units with multiple
outlets have increased protection for each outlet as you move away
from the power cord, daisy chaining is only like a strip with
additional outlets. Stick your UL book and learn, call Tripp, mr UL
It is refreshing to know that a phone tech at Tripp Lite is smarter that UL.
(Incidently I like Tripp Lite as a brand.)
Results may not be predictable when using 2 suppressors in series. Take the example in the IEEE guide
starting pdf page 40. There is as surge coming in on the cable service. Because the “ground” wire from the cable entry block to the system ground at the power service is far too long (30 feet) there is 10,000V between the power ground and the cable ground. That appears at TVs connected to both power and cable. The example shows how a plug-in suppressor protects connected equipment.
Now use 2 suppressors connected in series with the 2nd connected to the TV and the cable going through the 2nd. There will be a current through cable sheath and power ground wire which lifts the ground at the suppressors away from the ground at the power service (as is clearly indicated in the IEEE example). That lifts the ground at the suppressors from the hot and neutral so the MOVs will limit the voltage H-G, N-G. If the only MOVs that conduct are in the 1st suppressor you will have the ground wire in the line cord to the 2nd suppressor (maybe 6 feet) separating the power ground reference and the cable ground reference. The voltage drop over 6 feet of the ground wire from the cable entry ground block to the power service is 2,000V. It will be far lower in the line cord but will add to the difference in voltage between the power and cable wires going to the TV. Is that a problem? Who knows - but I would rather not run the science project.
Multiple MOVs in a single suppressor do not have 6 feet between them.
Since suppressors with high ratings are readily and cheaply available I don’t see a good reason to connect suppressors is series (except maybe to connect a UPS with relatively low ratings downstream from a high rated plug-in suppressor).
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