Lets get back on track. This model skimmer is a IN SUMP skimmer. Just like any other IN SUMP skimmer, except the part where this thing works amazing(most other skimmers can't say that!). It wasn't intended to run external. So when run in sump, it runs efficient and as COOL as most water pumps.
It does offer a recirculation feature that is nice, because if attached to the overflow, it will theoritically clean all the water in your tank, with no water missing the skimmer. It will also theoritically skim out hard to skim proteins through the recirculation and longer contact time. This is a nice added bonus, that most other skimmers do not offer. Because of this nice bonus, there is some confusion. This model is a IN SUMP skimmer.
*Note. As with all most all IN SUMP model skimmers of all brands, asking if it can run externally, would cause pump heat questions. And would point towards irresponsible usage of the skimmer by the user. But that of course won't stop a few curious Georges, and I know of only one person that has run the older model(grey volute) externally, and he has found that he needed to cool the pump. He has done so by using a fan. He claims for it to work successfully. I wouldn't feel comfortable doing so, I'd be worried about long term pump problems. The manufacturer suggest, that this pump be used IN SUMP. I am sure they are working on a external model, but at this time I have not seen it available on their web site. Probably any further questions on how to make it run externally would belong on the DIY forum, because there are ways to make it run cooler externally, with a little DIY work. Another place to find out more info would be direct from SWC or MSX by email. This is after all a skimmer review of a IN SUMP skimmer.