Re a few of the responses, supposedly from knowledgeable engineers . . . .

1. Daisy chaining surge suppressors (running them in series) would not increase or decrease their current interrupting capability. The current is the same every where in a series circuit, so the first fuse or breaker would be exposed to the total demand of chained surge protectors, and it should interrupt at its rated capacity. No matter it was something plugged into that unit or one down stream.

2. Now if you place multiple protectors in parallel into the same outlet, the house breaker would be exposed to the total demand. Either way the smallest rated fuse device would pop first, as they should. No problem here either.

3. I believe the liability factor has a lot to do with posting the "Do not daisy chain" warnings.

4. Also, the internal nesting of the MOVs in parallel should be more of an issue than anthing. Even tho, the ratings of the MOV devices are the same, they all do not react at the same time, the first to fire, takes the biggest energy burst and would be the first to fail, and the next to activate would get the 2nd highest burst, and so on. Even tho, this happens in micro or milli-seconds, it still happens. However this is what is needed to build up large, electrical shock absorbers. Because MOVs are not made in large capacity, they must be bundled in parallel to get high ratings.

5. Also, important to realize, is that the joule ratings on the box or device are the total capacity between all three leg-pairs. Therefore, the actual ability is one third between any two legs, at one time.

6. As for aging, metal-oxide-varistors (MOVs) age like other electronic components. One way to check them, tho it's a bit tricky, is to unplug the arrestor from the mains first. Then setup a multi-meter set for about four to five MegaOhm range of resistance. Place the probes into the socket holes and look for any resistance between the three pairs, neutral to hot, neutral to ground, hot to ground. You should see OL (over-load) readings, which means the resistance is too high to register on this range. However, you may also see initial readings that then climb until they go OL. This is the effect of capacitance charging. If the readings just stay fixed at some Mega-ohm (or lower) reading then this is probably a leaky MOV.

7. I worked electronic-technical-support for major fortune 500 companies for 25 years. As the ability of surge suppressors increased, We always recommended a minimum of 2,000 joules. Now days, I would recommend at least 3 thousand joules and a clipping voltage of no more than 330 volts, preferably lower. I recommend surge suppressors on all electronic devices and also on devices that have motors or compressors because they are the sources of most local spikes. The power grid in the U.S. has consistently become more and more dirty. It is now awash with all kinds of R.F. and other switching hash which travels collectively up and down the power lines between sub-stations.

8. Like belly-buttons, we all have our opinions. But, hopefully they are based on sound electronic theory. Later.

Re a few of the responses, supposedly from knowledgeable engineers . . . .

1. Daisy chaining surge suppressors (running them in series) would not increase or decrease their current interrupting capability. The current is the same every where in a series circuit, so the first fuse or breaker would be exposed to the total demand of chained surge protectors, and it should interrupt at its rated capacity. No matter it was something plugged into that unit or one down stream.

2. Now if you place multiple protectors in parallel into the same outlet, the house breaker would be exposed to the total demand. Either way the smallest rated fuse device would pop first, as they should. No problem here either.

3. I believe the liability factor has a lot to do with posting the "Do not daisy chain" warnings.

4. Also, the internal nesting of the MOVs in parallel should be more of an issue than anthing. Even tho, the ratings of the MOV devices are the same, they all do not react at the same time, the first to fire, takes the biggest energy burst and would be the first to fail, and the next to activate would get the 2nd highest burst, and so on. Even tho, this happens in micro or milli-seconds, it still happens. However this is what is needed to build up large, electrical shock absorbers. Because MOVs are not made in large capacity, they must be bundled in parallel to get high ratings.

5. Also, important to realize, is that the joule ratings on the box or device are the total capacity between all three leg-pairs. Therefore, the actual ability is one third between any two legs, at one time.

6. As for aging, metal-oxide-varistors (MOVs) age like other electronic components. One way to check them, tho it's a bit tricky, is to unplug the arrestor from the mains first. Then setup a multi-meter set for about four to five MegaOhm range of resistance. Place the probes into the socket holes and look for any resistance between the three pairs, neutral to hot, neutral to ground, hot to ground. You should see OL (over-load) readings, which means the resistance is too high to register on this range. However, you may also see initial readings that then climb until they go OL. This is the effect of capacitance charging. If the readings just stay fixed at some Mega-ohm (or lower) reading then this is probably a leaky MOV.

7. I worked electronic-technical-support for major fortune 500 companies for 25 years. As the ability of surge suppressors increased, We always recommended a minimum of 2,000 joules. Now days, I would recommend at least 3 thousand joules and a clipping voltage of no more than 330 volts, preferably lower. Also the line cord should be at least 14 gauge, 12 gauge if really long. I recommend surge suppressors on all electronic devices and also on devices that have motors or compressors because they are the sources of most local spikes. This includes dish washers, washing machines, dryers, refrigerators, freezers, air conditioners, etc.The power grid in the U.S. has consistently become more and more dirty. It is now awash with all kinds of R.F. and other switching hash which travels collectively up and down the power lines between sub-stations.

8. Like belly-buttons, we all have our opinions. But, hopefully they are based on sound electronic theory. Later.