- Occupation
- Licensed Electrician
Yep. I feel for the guy. Somebody says all you gotta do is hook it up. When it doesn't work your the only one involved with a local telephone number.
Motor Issues?
- Thread starter jahilliard
- Start date
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View attachment 14806
Like this but smaller scale
it sounds like a submersible mounted in a dry pit
suction line with isolation valve
agree
never restrict suction side
it's an isolation valve and not suitable for throttling
we installed like this often
if the pit flooded, ie, broken pipe, pump failure, etc, the pumps were salvagable
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- Occupation
- Licensed Electrician
That's a pump, but not a submersible one.
pretty sure it's submersible
std mntg arrangement
View attachment 14807
See if I can find a data sheet from flygt
article http://www.elongo.com/pdfs/drypitpumps.pdf
some can be mntd horizontal
http://www.xylemwatersolutions.com/...ible N-impeller Pumps in Manitoba, Canada.pdf
page 8 btm right
http://www.gsengr.com/uploaded_files/Large Submersible Pump Station Design Guide.pdf
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- Occupation
- Licensed Electrician
I think I see what you are saying now. Those pumps would be safe and operable if they were submerged, no? But they don't look like they live underwater which is what I would call a submersible pump.
Exactly
a submersible mntd in a dry pit adjacent to the wet well
i used them alot
the same pump can be mntd on slide rails in a wet well and hoisted out for service
I think the same way too here. When I did a fountain install once, it took us lots of pump changes because the designer wanted this high of spout, that wide a discharge and most of all, the only adjustment available for us was the nozzle size and type!
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
What this is sounding like now is that the fountain was designed without a good ME who understood the complexities of pump applications. They may have picked a pump by head height, likely to get some vertical effect in the fountain, without understanding the corresponding flow and that if the pump runs open channel, as it appears to be, it is overloading the motor. If it's not being overloaded, then as I said earlier, that pump motor is either incredibly inefficient, or has a very high service factor, which from my experience with submersibles is almost never the case.
I'd also take a wild guess that when they responded that they had tried turning down the valve and the amps went up, they were fibbing. They likely didn't even try it and are afraid to, so they are saying they did in order to avoid exposing their ignorance. Not that I think you should take on that responsibility as the EC either, in fact I suggest steering clear of that. Just stick to your guns and insist that a motor rated for 40A, running at 52-53A, is going to fail in short order. The nuisance tripping is not a "problem", it's a symptom and a warning. They need to get a hydraulics expert in there to straighten this out. Not your job...
And just to warn you, a pump vendor is not the right way to go with this. I've envountered some really idiotic pump vendors in my career who have zero clue, but possess the gift of gab and convince users that they know what they are talking about. I once had one tell an end user that he could replace a 400HP pump with a 100HP pump and get the same flow rate by using a VFD. I installed the VFD and got blamed for it not working, because the VFD couldn't keep up. I pointed out that the VFD was running at 100% speed, that's when I discovered that they had yanked out a 400HP pump. When I challenged the concept, the pump vendor told me to just run the pump at 240Hz!
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jahilliard
Senior Member
I'll try to send a picture of a 15hp fountain out of water in our shop right now.
jahilliard
Senior Member
[/ATTACH]
This fountain is obviously upside down, the head is sitting on the float to the left. The motor and pump are inside the large sleeve. There are bolts with angled steel suppporting the motor and pump. When it's in the water the sleeve is filled, the motor and pump are submerged in water forcing the water out the top through the head.
jahilliard
Senior Member
As you can see that one does not have a valve...the larger ones that we've been discussing have a valve in the smaller sleeve going to the head.
jahilliard
Senior Member
The ones in question are actually Shakti, 30hp, 460v, 3ph, rewindable submersible. You can access their manuals online with google I believe.
ptonsparky
Tom
- Occupation
- EC - retired
That is basically an open discharge. Throttle it back, change heads, put the proper pump on (not horizontal)
That motor will also require a minimum flow of water past it to cool. The casing around it will help, but throttling back the flow may end up increasing the heat.
No win situation for you.
That motor will also require a minimum flow of water past it to cool. The casing around it will help, but throttling back the flow may end up increasing the heat.
No win situation for you.
jahilliard
Senior Member
The Fountain company that built the ones we are discussing have decided to back off blaming the electrical once I talked to them about what's actually happened...the rewindable motors have thrown a variable in the system that could not have been accounted for without being given the proper information on those specific motors/pumps. I am more than familiar with this Fountain company, new owners as of March 1st have at least been open to feedback from our side....
Without a pn hard to pin the model down
but looking at their catalog it looks like a vert turb
they are pretty much linear with flow/power/head over a given range
in other words throttling flow does not reduce power much
sort of like a positive displacement
throttle it and it still pumps the same volume (for a given speed)
just requires more power to overcome the extra head
power hp = head x gpm x 8.34 /33000
if gpm stays the same but head goes up, so does power
a vert turb lies between the 2
but looking at their catalog it looks like a vert turb
they are pretty much linear with flow/power/head over a given range
in other words throttling flow does not reduce power much
sort of like a positive displacement
throttle it and it still pumps the same volume (for a given speed)
just requires more power to overcome the extra head
power hp = head x gpm x 8.34 /33000
if gpm stays the same but head goes up, so does power
a vert turb lies between the 2
Numerous issues
nec for 30 hp 40a
mfgs data for these motors 50 nml and 55 max per their catalog
ol's are set too low
cb is marginal
not essy to change since the conductor size is constraining
the pumps seem too large
Without seeing the piping drawing all speculation
but assuming per pump
20 t hd loss piping
20 across nozzle oriface
need 20 residual for spray height
60 total
assume 20 nozzles at 10 gpm each
hp = 60 x 20 x 10 x 8.34 / 33000 = 3 h
assume poor pump eff of 40% 7.5 hp
even if estimates are off by 2 still only 15 hp
does not compute
throttling the pump back may help a bit, but it lioks like a hot mess
pump application / mech design issues
elec sizing/coord issues
nec for 30 hp 40a
mfgs data for these motors 50 nml and 55 max per their catalog
ol's are set too low
cb is marginal
not essy to change since the conductor size is constraining
the pumps seem too large
Without seeing the piping drawing all speculation
but assuming per pump
20 t hd loss piping
20 across nozzle oriface
need 20 residual for spray height
60 total
assume 20 nozzles at 10 gpm each
hp = 60 x 20 x 10 x 8.34 / 33000 = 3 h
assume poor pump eff of 40% 7.5 hp
even if estimates are off by 2 still only 15 hp
does not compute
throttling the pump back may help a bit, but it lioks like a hot mess
pump application / mech design issues
elec sizing/coord issues
JFletcher
Senior Member
- Location
- Williamsburg, VA
Bingo. Throttling the suction side usually winds up with cavitation and eventually a blown up pump.
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