Diesel fire pump in basement... am I going to step in it? 3

[SprinklerDesigner2]

I am looking at a seven story residential building (it is not a high rise by definition) and at this location local authorities will only accept diesel engine driven fire pumps or electric fire pumps with generator backup and transfer switch.

On this job the pump has to be in the basement. I've always hated pumps in basements but there isn't a choice on this one.

I will need 120 psi boost @ 750 gpm so without looking it I would would guess 60 to 75 hp. Not horribly big.

To those who have done it would you say it is cheaper to upsize an emergency generator to handle the pump and use a power transfer switch for an electric pump (only 208 v available) or would I be better off installing a diesel pump in the basement and be done with it?

I've heard horror stories around diesel fuel storage over the years and I'm skittish especially when it comes to what local AHJ's might think is best. Fueling would be a problem as would venting not to mention combustion air that would be needed plus the noise in a very upscale motel.

Writing this I convinced myself to tell the GC to upsize the generator and go with the transfer switch but what code issues would one be facing with a stand alone diesel pump?

Thanks.

 

[stookeyfpe]

Electric fire pumps are more reliable when compared to diesel fire pumps. An article in the SFPE journal a couple of years ago looked at this issue, the costs, and when it was best to use diesel versus electric drivers.

Your driver is probably going to be one of the largest loads so the generator cost will increase. However, in this scenario its going to provide a more reliable power supply.

If you install a diesel driver, here are just a few issues I've had to deal with:

-- All aboveground storage tanks have a normal and emergency vent. NFPA 30 requires they be terminated outdoors. The problem with terminating the emergency vent outdoors is the backpressure on the tank if its not properly done. The problem compounds itself when dealing with small (<1000 gallon) tanks. It can be solved but it's a pain and it offers no benefit. If the backpressure issue under fire conditions is not addressed, the tank can be subject to a pressure explosion.

-- Diesel fuel is a Class II combustible liquid. Depending on which edition of the IFC the jurisdiction has adopted, your pump room could turn into a Group H-3 occupancy if the quantity of fuel exceeds either 240 or 660 gallons. H-3 occupancies are allowed in a basement - but the IBC would require the room to be treated as a Storage Tank Room which adds lots of expensive components.

-- All petroleum storage tanks inside of buildings require overfill protection. The problem is no off-the-shelf overfill prevention devices (OPD) are available for tanks with < 2 inch diameter fill openings. Most of the fuel tanks I've seen for fire pumps have 1 1/2 inch fill openings. This is quite a problem, because your solution generally involves installing a load cell and a magnetic solenoid valve in the tank fill line, which is not cheap.

-- Under NFPA 20, your pump room requires a 1-hour separation. Because the vents have to be terminated outside the building, your GC will now need to build you a one hour shaft without dampers to comply with the IBC requirements for continuity of fire-resistive construction. I have yet to not note this as a IBC plan review violation, which means the plans are denied and your GC waits another 3 weeks before he gets the building permit.

Need any more justification?

 

[SprinklerDesigner2]

Stookey,

Nope.

And thanks. A bunch.

 

[PEDARRIN2]

A few years back I had a school remodel p0roject where they needed a fire pump and storage tank for the sprinkler load.

The water storage tank was located under a new classroom because we didn't have anywhere else to put it.

The fire pump was diesel powered - though I wanted electric, but didn't win that battle. It had a small enough storage tank to allow the pump to run for the required minimum 30 minutes. If I remember, it was 600 gallons of storage. The tank was located in the same room as the pump and was just off an existing mechanical room which did have a 2 hour separation

The tank was filled via a remote fill station located on an exterior wall. It had overfill protection as part of its components.

The normal vent was 2" and the emergency vent was 4" if I remember correctly so I didn't see any problem with back pressure.

The design complied with all the requirements - or at least nothing was brought up during AHJ review and/or construction.

I am not saying diesel is the route to go for you, but we did it with only a little headache.

 

[EEJaime]

In addition to what Stookey quoted, the new electrical fire rated conductors that can be installed in standard EMT conduit from the generator to the pump ATS and to the pump eliminate the expense of fire rated shafts, soffits or Mineral Insulated Fire pump conductors. Just be careful with all the Electrical code requirements and you can have a very successful installation.

Regards,
EEJaime