Rigid Conduit

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AKB

Just wondering
Location
Hillsdale, NJ
Occupation
Contractor
I have a plan from engineer. It says Service for fire pump in PVC conduit encased in concrete OR rigid pipe through 2-hr rated room.
I know that room walls built by CMUs, floor and ceiling are concrete.
Is "OR" statement correct? 230.6 and 450, Part III stating different.
Your insight is appreciated.
 
Usually the fire pump room is on the exterior of a building. If the conduit enters straight into the 2-hour rated fire pump room from the outside it does not have to be encased in concrete.

If it runs through the building through a non-rated space before entering the fire pump room, it has to be encased in 2 in of concrete, or use 2-hour rated mineral insulated cable
 
Please check Art 695. Last fire pump service I was involved with required concrete encasement of service raceway inside pump room
John answered at same time
 
This room is ground level. Above has residential units. It is not outside. One entrance but different sections. So, engineer is wrong!
 
To find the code requirements, start in 695.A 1 services (you didn't say if service) - conductors must be outside of building or install per 230.6 1 or 2
230.6 1 under 2" of concrete beneath a building
230.2 encased in concrete of brick not less than 2" thick
450 does not apply as its not referenced in 695
I don't see a requirement for RGS or PVC, that may be job spec, or requirement by POCO.
Art 230 does restrict wiring methods for service conductors, and some areas may restrict further, for example in WA we can't use EMT for service conductors
 
I might be able to add some clarity here. Fire pump feeders (inside the building only) are required to hold a 2 hour fire resistive rating. There are several ways of doing this.....encased in 2 inches or more of concrete, fire resistive cable system or a listed protective system (an assembly of sorts). There is an exception in the NEC that states the fire rating is not required INSIDE the room they originate in (the fire pump room). So if you're inside the building, and not in the fire pump room, a 2 hour fire resistive rating is required on the feeders. Someone above mentioned MI cable, which is good but there are several others out there. MI is kind of the musket or rifles now. Works but it's hard, slow and not accurate. If you are going to use a fire resistive cable system, including MI, then Article 728 will apply and will trump the rest of the code if in conflict. 728 will direct you to follow the systems "listing" which is actually a UL document called an FHIT XXX. XXX is the system number. These can be found on UL's Product IQ website for free. Just register an email address and create a password, no cost. Then in the search menu, type FHIT and a whole lot of stuff pops up. All of those are "systems" that can be used. MI for example is FHIT 1850, but there are many others that are less expensive and easier to use. No active FHIT document....don't go near it as it's not 728 approved. Those documents will tell you what materials you must use, and some will be brand name specific (like conduits and couplers). And it will tell you how to install it. In essence, Article 728 which trumps the rest of the NEC will tell you to follow the FHIT to the letter or rather the FHIT is the golden rule. And trust me, deviating on any of the materials listed/required in the FHIT will violate the rating, so don't. I get asked all the time about approving this or that type of conduit that isn't listed on the FHIT, and I say nope, it has to come out and be replaced by the right stuff.

I can tell you that if installing a 2 hour fire resistive cable system......rigid conduit isn't going to work and not allowed (for feeders at least). Rigid has zinc on the ID which negatively affects the performance of those systems. Not to mention when testing at UL, rigid is heavy and will sag under the 1850 deg F test which can cause shorting of the wires inside as they come under tension. Rigid is a no no in that game. EMT's can be used, RTRC's can be used and there are some MC type cables as well.

So, in the fire pump room or outside the building, nothing outside of normal is required. But traversing through a building (not in the pump room) a 2 hour fire resistive rating IS required. How you go about achieving that rating is up to you. On new construction, I would go with concrete encasement whenever possible. Remodel or when concrete is not an option, I would go with a cable system (RHW-2 then MC followed by MI), in that order based on costs. Lastly I would go with assemblies, the most expensive option.
 
Did you compare cost of using type MI cable that can be ran on the outside of finished walls. At the large hospital/research center that I retired from they ran MI cable from 7th floor generator room down to basement to supply emergency power to a 200 HP Fire Pump. Neither burying conduit in 2" of concrete or MI cable is cheap,fast or easy. I'm from the old school and soon or later somebody too often drills a hole thru the concrete and rigid conduit.
 
garbo said:
Did you compare cost of using type MI cable that can be ran on the outside of finished walls. At the large hospital/research center that I retired from they ran MI cable from 7th floor generator room down to basement to supply emergency power to a 200 HP Fire Pump. Neither burying conduit in 2" of concrete or MI cable is cheap,fast or easy. I'm from the old school and soon or later somebody too often drills a hole thru the concrete and rigid conduit.
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Hi Garbo,
None of these are cheap, fast or easy that's for sure. But running MI as a cable system is only one of many cable systems that are out there. There are conduit/wire systems and MC systems as well. Generally when installing one of these "wire" systems, you really need to think about what you will need to do it properly. Like MI cable for example. It has solid conductors so you cannot terminate it to equipment and must splice stranded wires in (on each end). That take a special splice from MI and a box/brass plate to do. All that adds up. Other systems you can terminate directly which eliminates those extra costs of the MI cable. Some conduit/wire systems require boxes for vertical support every so often, whereas MI doesn't. So it is really important to look at an installed costs of one of these and not so much the foot price of the wire. Often there will be a ton of extra costs you weren't thinking about. It's always best to talk to the manufacturers of these type items before you purchase it. One may work great for your project without the need for "extra" stuff, and other may not. Below is some guidance on what to look for and ask:
MI: Lengths are limited so excess splicing may be necessary; cannot terminate to equipment (splicing always required); time consuming to install; hydroscopic filler often fails megger testing requiring drying procedure and new splices adding to the already long time it took.
Conduit/wire systems: Vertical runs are problematic (over 9 feet) and may require a different conduit type or support boxes; fill rates are not 40%; must use Polywater LZ pulling lube; components like conduit type and coupler type are brand specific.
MC cable: Fragile as the armor is copper; no limit on vertical runs, some components like boxes and connectors are brand specific, armor should be used as the ground (typically oversized anyway).

Sometimes a combo of two types is the best solution, say on a high-rise. Use the EMT/Wire system on the horizontal runs and splice in the MC to run it vertically 300 feet. Great idea but remember the wires must be made by the same company, meaning the same company must have 2 listed systems (FHIT documents) for the conduit/wire system and the MC system to be spliced on the same circuit. You cannot mix and match different systems from different manufactures together. Same manufacturer, no issues, but not other ones as there is no test data from UL to show how they react with one another.

Hope this helps and as always reach out with any questions.
 
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