Joules rating for surge suppression

A client sent me down a rabbit hole recently. I did a little reading about surge suppressors for PCs and found information advising that a surge suppressor for a computer should be rated at least 2000 joules. I checked APC products and discovered that several of their surge suppressors are well above that, in the 3000 - 4000 range. Surge suppressors provide protection from transient voltage spikes but don’t help with a sag or temporary power outage. Only a UPS can do that. I discovered that all of the APC UPS units I checked did have surge suppression capability, but were only rated around 300 - 400 joules. So, I’m puzzled, If APC believes that a Surge suppressor should have 3000 - 4000 joules rating but a similar capacity isn’t available even for a UPS designed for a server then I am baffled. Any experts out there that care to offer an explanation? If you have a free hour ++ this is worthwhile. Grounding - Safety Fundamentals (1hr:13min:19sec) - YouTube


A good discussion of surge suppression can be found here Surge Suppression - Zero Surge.
It is assumed the the circuit the ups is attached to is protected. I lost an UPS when its internal MOVs blew all the other surge protectors did their job but had just fancy power strips. Also with surge should shunt to the Neutral not the safety ground that is used but the network as a reference.

I’ve been familiar with zero-surge for several years. I shared the link in the OP because the distinction between the neutral source and ground is often not well understood. APC does not recommend putting surge suppression and UPS in series. I think because they are concerned about amperage overload. I have found under desk electric space heaters plugged into a UPS. My thought is that they are unlikely to put zero surge suppression in their UPS, the UPS should at least be designed with a suitably sized internal MOV circuit. An introduction to sizing of MOVs can be found here; We tend to give little more than cursory thought to proper grounding and transient voltage conditions in supplied power at workstations and server racks, we should do a better job.

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The problem with MOVs is they deteriorate over time and yes sizing matters. I do not like the idea of MOVs being integral to an UPS since once sacrificed the UPS is a loss. Been there done that.

Grounding and power conditioning is a complex subject that should be addressed when considering locating your business just as you would with available communication lines. Many IT issues are caused by inadequate power or dirty power so do your due diligence before signing that lease.

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additional information of interest; Current Technology Surge Protection (TVSS/SPD) Part 1 of 2 - YouTube