Fire Pump Load Calculation

[Fitzdrew516]

I have recently designed an industrial building with a service size of 2000A with a 100% rated MCB (480V). My total calculated loads are about 1200 amps and all of the equipment is subject to change (one of the reasons I decently oversized the service). Soon after this phase is completed an office will be added on so I was banking on 100-200 amps of power for the future office build out.

Well we have recently been told that we will need a fire pump for the building now and since electric is the cheapest option, I assume it will be an electric fire pump. My question is this - Do I have to account for the load of the fire pump in my calculations for the main service? The fire pump will be tapped ahead of the main and utilize it's own section of switchgear. I would think the load would have to be accounted for, but since the fire pump never runs (unless a fire obviously) it seems like there may be some sort of exception out there somewhere.

As you may be able to guess my concerns are with the client possibly significantly adding/changing the equipment that is scheduled + future office load + fire pump load could get close to that 2,000 number. And yes my calculations are based on "calculated load" and my main is 100% rated so technically my calculated load could be over 2,000A, but sometimes it's hard to get that concept through a plans reviewer's head. For example - They often would just see 2,200A at the bottom of the panel schedule on a 2,000A service and freak out without understanding the demand factors, etc. I'm just trying to make this process as smooth as possible.

Thanks,

-Drew

 

[iwire]

Who owns and controls the transformer supplying the building?

 

[Fitzdrew516]

Who owns and controls the transformer supplying the building?

The utility. Underground service. Responsibility of the client is from the secondary of the transformer to the building.

 

[iwire]

The utility. Underground service. Responsibility of the client is from the secondary of the transformer to the building.

In my opinion based on the fact the service conductors are under the NEC you would have to include the fire pump in the load calculations.

Is it to late to run a second set to the pad exclusively for the fire pump?

 

[Fitzdrew516]

In my opinion based on the fact the service conductors are under the NEC you would have to include the fire pump in the load calculations.

Is it to late to run a second set to the pad exclusively for the fire pump?

I agree with your instincts because the wires are sized only for the 2000A. I was just hoping there was some exception somewhere that I was missing. It's not "too late" in a sense that it hasn't been installed yet, but since bids are done the owner would likely freak out if we tried to add another run of conductors and blame it on us even though we were never told about a fire pump. Likely my service is big enough for everything, but like I said - I have no idea what the fire pump load will be, not to mention the unknowns of the office addition and the up in the air equipment selection. Having an engineering mind I want to be certain about everything (especially something as important as the service), but it's hard to do so with so many unknowns.

Thanks,

-Drew

 

[Tony S]

The wires are only sized for 2000A? Unless the pumps are gargantuan I can’t see that being a problem.

BMS will shutdown air handling units and non essential services to stop fire and fume propagation within the building. That will free up power for the pumps.

Look at the full picture, do diversity calculations.

Of more concern to me would be the reliability of the supply to the fire pumps. In which case I concur with iwire’s post “is it too late to pull in a separate pump supply?”

This isn’t a subject to be taken as a purely load based exercise, safety overrides just about everything.

 

[iwire]

The wires are only sized for 2000A? Unless the pumps are gargantuan I can’t see that being a problem.

In reality it won't be a problem, code wise it likely will be.

BMS will shutdown air handling units and non essential services to stop fire and fume propagation within the building. That will free up power for the pumps.

That is a huge assumption, in many cases the activation of the fire pump will not shut down anything.

Of more concern to me would be the reliability of the supply to the fire pumps. In which case I concur with iwire’s post “is it too late to pull in a separate pump supply?”

My suggest will not change the reliability, the source would still be the same utility transformer. I made my suggestion as a way to avoid adding load on the existing service conductors.

 

[topgone]

. . . . .. . . . . . . . . . . .
Of more concern to me would be the reliability of the supply to the fire pumps. In which case I concur with iwire’s post “is it too late to pull in a separate pump supply?”

This isn’t a subject to be taken as a purely load based exercise, safety overrides just about everything.

I agree re above points. Methinks, the fire pump requirement can be best complied using an engine-driven unit. If the chosen system will be a wet system, only the power requirement for a jockey pump, which is a small pump, should be his problem. Maybe, just maybe, the OP sees it differently.

 

[ducks1333]

You've got a 1200A calculated load on a 2000A service, unless you are planning on a 600HP fire pump I don't see a problem. As for future loads the actual loads will likely be much less than your calculated load, put a demand meter on the service and use the optional calculation per 220.87 for future loads.

 

[Julius Right]

Let’s say the actual load is 1200 A [installed] and in the future an office [200 A installed] and a fire pump [of 2200-1200-200=[ 800 A. By-the-way 800 A and 480 V= 1600 HP-could it be?:roll:
If you’ll compare the facility you have to supply with a farm as per NEC Table 220.103 Method for Calculating Total Farm Load:
First load-the fire pump-800*1.25= 1000 A
Let’s say a motor half of 1200=600*0.75=490 A
The third load of second half=600*0.65=390 A
And the remaining 200 *0.5=100 A
Total load =1940 A :bye:

 

[Tony S]

That is a huge assumption, in many cases the activation of the fire pump will not shut down anything.

It’s an assumption based on “if the system works to start the pumps the system will work to shut down ancillary loads”

See my comment about AH units and fire propagation.

 

[iwire]

It’s an assumption based on “if the system works to start the pumps the system will work to shut down ancillary loads”

See my comment about AH units and fire propagation.

It is not how it is done here. We can not use BMS for fire protection.

Here fire pumps have their own stand alone controller which stops and starts the pump based on water pressure of the lines.

The fact the fire pump runs will not shut down any building systems.

The air handlers will be shut down by smoke detector activation and the fire alarm control panel.

 

[Fitzdrew516]

You've got a 1200A calculated load on a 2000A service, unless you are planning on a 600HP fire pump I don't see a problem. As for future loads the actual loads will likely be much less than your calculated load, put a demand meter on the service and use the optional calculation per 220.87 for future loads.

I'll likely have to do an existing calc based on actual loads per 220.87 if I run into an issue. I just know we're going to get yelled at about it from the owner because he's going to think we should have sized a larger service when in reality we had no knowledge of a fire pump prior. The problem now is that apparently the existing building that we are building on to may need to be fed off of this fire pump as well so it will probably be a monster fire pump. Couple this with the fact the owner can't make a decision on any equipment so all our loads are "educated guesses" on what equipment they're actually using. To sum it up - Yes I think we'll be OK, but the fact that there is any doubt in my mind freaks me out a little.

 

[Tony S]

It is not how it is done here. We can not use BMS for fire protection.

Here fire pumps have their own stand alone controller which stops and starts the pump based on water pressure of the lines.

The fact the fire pump runs will not shut down any building systems.

The air handlers will be shut down by smoke detector activation and the fire alarm control panel.

The classic oxymoron response (look up the definition before responding. It’s not an insult).

Fire control and BMS can and should be seamlessly linked.

Fire pumps maintain pressure but a sustained pressure drop equals a fire or fault which in turn equals an emergency. Smoke detectors also equal an emergency therefore a signal to the central control for the fire pumps.

Simple logical system control.

 

[iwire]

The classic oxymoron response (look up the definition before responding. It’s not an insult).

Oxymoron is not an insult, on the other hand telling me to look it up...

Fire control and BMS can and should be seamlessly linked.

They often still are for things that are not legally required and 15 years ago we were using BMS to provide HVAC shut down, smoke evacuation, or pressurization etc. In my are that is no longer allowed and I think with good reason.

• BMS circuits are not supervised circuits
• BMS equipment is not listed as life safety equipment
• Any HVAC tech can muddle around with BMS programs and goof things up
• There are no requirements to maintain BMS equipment or keep it on line.
• And lastly, and this is a huge one to the local firemen, BMS is not painted red.

Fire pumps maintain pressure but a sustained pressure drop equals a fire or fault which in turn equals an emergency. Smoke detectors also equal an emergency therefore a signal to the central control for the fire pumps.

Here a pump run is not an alarm, it is a 'supervisory' signal.

If there is water flow for about 45 seconds that will ring a general alarm

The general alarm will may or may not shutdown HVAC, this seems to be at the whim of the local fire department.

What will shut down the HVAC is activation of the in duct smoke detector at that particular unit.

It may not be what you are used to but it does not make it an oxymoron.