Transient Voltage Suppressors: Breaker line side or load side?

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LMAO

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We use TVSS (MOV) in our VFD cabinets; we have been connecting it to the line side of main breaker feeding the cabinet. I see 2 problems with this: (1)-there will be potentially energized cables in cabinet even if breaker is open and (2)-MOV may get damaged before a breaker upstream to VFD main breaker (which has higher trip rating) trips. There is nothing of our concern upstream to VFD main breaker that we'd want to protect against transient voltage. So I am thinking of moving the MOV to the load side of main breaker. Anyone sees anything wrong with this?
Your opinion is appreciated.
 
150203-0841 EST

My opinion is that the load side of the main breaker in your panel is the better position. This might cause the breaker to trip (good), and it adds a small amount of additional impedance in series with the MOV for line side transients (again good).

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I don't think it matters all that much.

I would read the instructions that came with the TVSS and abide by them.

Personally, I would probably have had the TVSS installed at the feeder breaker end anyway.
 
petersonra said:
I don't think it matters all that much.

I would read the instructions that came with the TVSS and abide by them.

Personally, I would probably have had the TVSS installed at the feeder breaker end anyway.
Click to expand...
When I sold TVSSs I ws as told by my division that it should be installed as close to the main breaker as possible. I have an Eaton in my home where I installed my TVSS by feeding it with a 2p breaker in the space just across from the main.
But what it seems being avoided as often happens is what does the instructions from the manufacture recommend.
 
templdl said:
When I sold TVSSs I ws as told by my division that it should be installed as close to the main breaker as possible. I have an Eaton in my home where I installed my TVSS by feeding it with a 2p breaker in the space just across from the main.
But what it seems being avoided as often happens is what does the instructions from the manufacture recommend.
Click to expand...

The code now refers to such things as SPD. There are different "types" that are installed at different places in the electrical system.

I am a fan of installing such devices as close to the service point as possible.
 
Since I posted did I did some more study. From UL 1449 point of view, there are 3 types of SPDs. Type 1 is connected to breaker line side (or transformer secondary) and type 2 connects to breaker load side. There is also a type 3 which has some definition but I don't quite understand it :? . I am still reading but I am pretty much sure I am going to connect this to breaker load side because I am not protecting anything upstream to breaker...
 
LMAO said:
We use TVSS (MOV) in our VFD cabinets; we have been connecting it to the line side of main breaker feeding the cabinet. I see 2 problems with this: (1)-there will be potentially energized cables in cabinet even if breaker is open and (2)-MOV may get damaged before a breaker upstream to VFD main breaker (which has higher trip rating) trips. There is nothing of our concern upstream to VFD main breaker that we'd want to protect against transient voltage. So I am thinking of moving the MOV to the load side of main breaker. Anyone sees anything wrong with this?
Your opinion is appreciated.
Click to expand...
To do their job and stop a surge, MOVs tend to sacrifice themselves in the process. If they are on the line side, how do you replace them? Shut down the feeder in the panelboard?

I would put them behind the main, or better yet, behind their own disconnect. That way if you have to replace them, you do your LO/TO right there.
 
Jraef said:
To do their job and stop a surge, MOVs tend to sacrifice themselves in the process. If they are on the line side, how do you replace them? Shut down the feeder in the panelboard?

I would put them behind the main, or better yet, behind their own disconnect. That way if you have to replace them, you do your LO/TO right there.
Click to expand...

Pretty much R56.
 
petersonra said:
The code now refers to such things as SPD. There are different "types" that are installed at different places in the electrical system.

I am a fan of installing such devices as close to the service point as possible.
Click to expand...
I agree as I am of the underdtanding that it was more affective in that location.
 
IIRC type 3 is located at a single piece of equipment (think the surge suppressor on a UPS at your desk).

We use 3 phase TVSS's at each of our two services. We have them on the load side of dedicated 3-pole breakers closest to the main in each MDP.

We get lots of lightning and have seen 3 poco 150kva trannys blow over a 2 year period. Never had damage on any of our equipment. When one phase goes down we get an alarm from the TVSS.
 
mgookin said:
IIRC type 3 is located at a single piece of equipment (think the surge suppressor on a UPS at your desk).

We use 3 phase TVSS's at each of our two services. We have them on the load side of dedicated 3-pole breakers closest to the main in each MDP.

We get lots of lightning and have seen 3 poco 150kva trannys blow over a 2 year period. Never had damage on any of our equipment. When one phase goes down we get an alarm from the TVSS.
Click to expand...

OK then so type 3 is just one more level down stream from type 2...

Do you happen to know how type 1/2/3 are different physically? I guess it is just their peak current rating; the higher it is the closer they can be to the transformer?
 
LMAO said:
OK then so type 3 is just one more level down stream from type 2...

Do you happen to know how type 1/2/3 are different physically? I guess it is just their peak current rating; the higher it is the closer they can be to the transformer?
Click to expand...

It's just a matter of where it is located and what it does.

Between main & poco tranny, at your MDP load side, or somewhere down a branch circuit.
 
mgookin said:
It's just a matter of where it is located and what it does.

Between main & poco tranny, at your MDP load side, or somewhere down a branch circuit.
Click to expand...

I understand that but if you look at a SPD datasheet it specifies it as type 1/2/3. Type 1 can be used anywhere, type 2 can be used where type 2 and 3 are used, and so on...

So physically, what is the difference between these SPDs? How are they manufactured differently? I was just curious....
 
LMAO said:
I understand that but if you look at a SPD datasheet it specifies it as type 1/2/3. Type 1 can be used anywhere, type 2 can be used where type 2 and 3 are used, and so on...

So physically, what is the difference between these SPDs? How are they manufactured differently? I was just curious....
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Just looking at it from outside of being a listing agency, I would have to say the Type 1 needs to have a certain amount of ability to contain a catastrophic fault since it can be installed without overcurrent protection ahead of it. Type 2 (maybe) is a unit that is "hardwired" but still designed to need overcurent protection ahead of it, where type 3 is (maybe) about the same thing as type 2 but is a little more "plug and play" or "user configurable/installed". Just my guess and may only be partly true, or may even be way off base.
 
This was a discussion between myself and 2 other engineers regarding
the effectivness of installing SPD's to minimize the damage to ATS's that
I have seen blown up due to HV transients. It may shed more light on this
subject.
The file is a modified email string so read from the bottom up.
 

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ATSman said:
This was a discussion between myself and 2 other engineers regarding
the effectivness of installing SPD's to minimize the damage to ATS's that
I have seen blown up due to HV transients. It may shed more light on this
subject.
The file is a modified email string so read from the bottom up.
Click to expand...


Very good stuff there ATSman. Thanks. :thumbsup:
 
I am not in with transient overvoltage field. However it seems the new UL 1449 third edition
presents 4 destination types:
?Creation of Four Type Designations:
Previous editions of UL 1449 classified surge protective devices into two types: permanently connected or cord-connected. The 3rd edition scraps that system and sorts SPDs into four types, depending on where they are located within an electrical distribution system:

Type 1 - Permanently connected SPDs intended for installation between the secondary of the service transformer and the line side of the service equipment overcurrent device, as well as the load side, including watt-hour meter socket enclosures and intended to be installed without an external overcurrent protective device.

Type 2 - Permanently connected SPDs intended for installation on the load side of the service equipment overcurrent device; including SPDs located at the branch panel.

Type 3 - Point of utilization SPDs, installed at a minimum conductor length of 10 meters (30 feet) from the electrical service panel to the point of utilization, for example cord connected, direct plug-in, receptacle type and SPDs installed at the utilization equipment being protected. The distance (10 meters) is exclusive of conductors provided with or used to attach SPDs.

Type 4 - Component SPDs, including discrete components as well as component assemblies.?
It seems to me that type 2 would be still located on the supply side of the line-overcurrent device is here located. Does not it? :weeping:
 
mgookin said:
Could you clarify/ restate your question?
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I have to admit: it is a little bit confusing. If "overcurrent device" is a circuit breaker [low voltage system] then "the load side of overcurrent device" will be downstream of breaker [Pos.1].
However on medium voltage systems the current transformer could be located at line side of the breaker [Pos.2] I think.Transient Voltage Suppressors Breaker line side or load side.jpg:?
 
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