I'm a bit late to the party, but I can answer this. There are 5 ways to achieve a 2 hour fire resistive rating. Article 700.10(D) lists them. The sprinkler rule isn't allowed for 695 (fire pumps) or 708 (COPS). As for fire resistive cable systems, there are 3 types as mentioned above. MI, MC and Conduit/Wire systems. It was stated above the EMT systems were "rotting out". Not true at all. In 2012 UL found some conduits had zinc as part of the galvanization process on the ID of the conduits. That zinc vaporized during testing and caused a chemical reaction witht the copper conductor. Turning that copper to brass which melted during testing. Since 2012 UL now mandates certain brand EMT's that do not have any zinc in them. Allied, Western and Wheatland EMT's don't have zinc in them (so nothing fancy). An EMT install is by far the most economical, followed by an RTRC install. MC is next but risky followed by MI. Everyone thinks MC is the way to go since you don't need conduits, but it's not normal MC. It has a very soft copper armor which is easily damaged, and if so the fix is in the thousands at least. Not to mention you need to rent equipement to install MC or MI (sheaves and rollers). MC and MI will also take 3 to 5 times more labor and components required are stainless (expensive). Top Tip....if you are using these cable systems, read Article 728! It's a one page article with lots of helpful rules. If a conflic between 728 and all of the NEC happen, 728 wins. You also don't need these cables inside the "fire rated" rooms they serve, and it doesn't give a fire rating, so technically a 1 minute rating meets code. There is a 12 inch rule where it needs to be inside a protected space at least 12 inches, but beyond that you don't need these wires. 728 will require you to follow the "listing" which is a UL document called an FHIT XXX. XXX is the individual system number. Essentially that FHIT document is what you follow. As for the system types, EMT systems are always the way to go. Faster, cheaper and easier to do. The exception is when you need sets due to ampacity or voltage drop. Once 2 or more sets are needed, single conductor MC is usually the best option. Single conductor MC has a free air rating so it has a much higher ampacity and generally will reduce the number of sets needed. But outside of that, EMT systems are always better. When looking at what these systems cost when estimating, don't look at the price per foot. Look at the installed cost including labor. MI needs all kinds of special tools you have to buy from MI, need lots of pulling equipment and are expensive. MC systems take stainless boxes and connectors, need that same rental equipemnt as well. EMT systems don't use any of that and are the fastes to install. I do project reviews all over the USA so if you have one, let me know and I'll tell you which would be the best. About 20% of my reviews determine they don't even need these systems anyway, which saves a ton of money.
