RIVETER

I am not a fire pump person, or a plumber or the like but why would you put a pump in place for anything other than it's potential? It seems to me that it's full load current would be with all valves open and water flowing.

Wirenuting

It's almost unheard of to pop all the sprinkler heads at one time. They are temp activated.
Remember the idea is to suppress the fire for only a short time and save the structure.

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RIVETER

So, you are saying that the pump must have the capacity to supply...possibly... 100 heads, but if only one zone...maybe 20 heads, is activated, the motor won't be overloaded...current wise?

Wirenuting

That's pretty much how it was explained to me.
The engineer decides how many may pop at once. It's based on location and space utilization. Size of a space is of second consideration as the heads can be directional or shaped to confine the fire.
ie: water curtain in a hotel hallway.

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RIVETER

OK, I get it. Thanks.

JRaef

Yes. Centrifugal only. It called the Affinity Law (or rather one of them). Power varies by the cube of the flow. And since flow and motor speed follow pretty closely, that's why VFDs save a lot of energy in centrifugal pumps and fans. At 1/2 speed the hp requirement drops to 1/8th (.5 x .5 x .5). But it's also something that people don't realize when they use a VFD to run a pump at more than base speed.

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jrannis

I have a meeting setup for tomorrow morning. I will investigate the series resister and measure the amperage values on the conductors feeding the pump and compare them to the conductors feeding the pump controller. If the theory established here proves to be true, I suspect that we will find the resister remains in the circuit while the pump is operating.

BTW, the same sprinkler guy has been testing this same pump for years by opening the test valve and has not had a high amperage/ low voltage incident.
Also, one of the other symptoms I mentioned is that the pump motor gets extremely hot.
I also understand, that the load, as far as how many sprinkler heads vs water column needs to be properly calculated. I was thinking that maybe the test pipe size was calculated for the load.

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JRaef

The resistors indicate you have a Primary Resistor type Reduced Voltage Starter, they used to be common on Fire Pump controllers. If the resistors were stuck in the circuit and the main Run contactor was closed, it would make no difference. The main contactor would be the path of least resistance and the resistors would be meaningless. But if it were stuck on and the main Run contactor didn't pull in, then you would have low voltage at the motor terminals, like 25% voltage (depends on the resistor value) and the pump would never finish accelerating. On addition those resistors ate only rated for a very short duty cycle, they would burn up if left on for even a few minutes I wouldn't put a lot of hope with that being the problem.

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frenchelectrican

I know someone mention 2.5 inch pipe however if you open that test valve on top of 12 th story and use the flow/ pressure meter you should able record it and throttle it a bit to the point where you get max current drawage on the motor nameplate and leave it there it will not get overloaded.

But if you ran the test valve wide open or unthrottled that where the issue will arise.

I am sure one of our member in the fourm will assist you with few hard numbers due he work in Fire Dept if my memory serve me right. ( Rsqcapt19 I think if that is correct if so I will ping him real quick so you can get more details asap)

Merci,
Marc

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jrannis

OK, the theory that the resister bank staying engaged may have just been crushed.
The pump could be designed for just one or two popped sprinkler heads plus what ever water column that exists.
If we are artificially creating an oversize water event by completely opening the test valve, we may unknowingly be overloading the pump.
It pains me to think that the sprinkler guy must have known something about these types of tests.

I also want to add that I noticed a burning paint smell in the fire pump room but it appeared to be from the freshly painted pump motor and not the resister bank.

I will measure the voltage and current at the motor this morning anyway, it could confirm Marc's post about overloading the pump.

Thanks again for the help guys!

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JRaef

It might also be that in the past, he didn't open the valve all the way and doesn't remember that. The usual acceptance test I've been involved in with Fire Pumps have been as French Electrician described: open the valve slowly until the pump produces maximum rated flow. The Sprinkler Guys probably never cared enough about that detail to pay attention. But the Fire Pump Guys did because that's what they get paid for, so they would watch a flow meter while the Sprinkler Guy opened the valve. The design specs for the Fire Pump would dictate the maximum flow at the necessary head, so they would simulate that with the flood valve and I would be called upon to check the motor current once they reached the design spec and if we were under FLA, the Engineer would sign off and everyone got paid.

In this case because you were dealing with a re-wound motor, there probably was no Pump Guy present. So the Sprinkler guy, who likely doesn't understand the flow issue, didn't realize he can't just crank it wide open. He's probably used to a Pump guy telling him what to do.

John Valdes

John, Close the valve and start the motor. Have someone slowly open the valve in increments and watch the current. As the valve opens the current rises. Once the current reaches max from nameplate, FLA, this is the amount of flow the pump and motor are designed to push.
Your issue is you are allowing to much flow which results in to much work. Reduce work, you reduce current.
I would bet if you had a flow meter installed in the discharge line on the roof, it would match max flow to max current. Simple principle of "Work" or "Load" Same thing.
Jraef is saying the same thing except he is being more technical.

In the same regard, with the valve completely closed, no current would exist. Water must be moving for work to be accomplished.
To much flow results in to much work which in turn draws to much current.

mcclary's electrical

I don't agree with that part of your post.

John Valdes

No water flow, no current. Simple as that. The motor current with no load would still exist, if that's what you mean. Then yes, you would have some current.

jrannis

I did the test today. All of the information gleaned here I used. Of course, that was it. The Sprinkler guy didn't have a clue as to what effect the 12 story head had on the flow he expected. He expected the pump to keep up with the 2-1/2" valve he open which was mounted on a six inch pipe.

The building next to the one we tested, had the same company testing the fire pump.
No data was recorded at that building that could help us. We have another test setup on the second building.
I am sure the equipment is rock solid and the testing procedure, which at best is non-existent, could destroy the 60hp pump.

Stay tuned..

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mcclary's electrical

Yeah, that's what I meant.

And I knew that you didn't actually mean the motor would use "0.0" current just because water was not flowing.

frenchelectrican

With the sprinkler guy he may not be well aware with water flowage can really affect the pump performace.

2.5 test port on 6 inch pipe that result a heckva large volume of water which it will be more than 400 GPM { gallons per min } depending on the PSI at the test port and that stated on unthrottled postion on the valve.


Eh I hope that you mention to the spinkler guy with the result of 60 HP pump if he ran that unthrottled that can destory the pump by serious overload.

Really I think someone should done recording the doucoment on the testing and I know NFPA have guideline on pump testing producures and the other source you can check is Fire Department they will be more than glad to assit you on this matter as well.

Let us know how it come out with test result.

Merci,
Marc

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Big John

Jrannis, you learn anything else about this or was this case-closed as too much flow?

-John

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wdestar

I didn't read all the posts that carefully, so pardon the ignorance. If the pump was designed to run at 50 hertz, you'd have big problems running it at 60 Hz.

JRaef

I think you replied to the wrong thread.