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Sounds like you just lose your head when pump are off or valve closed. Imagine a vertical pipe pump push water to the to keeping pressure up. When pump of of valve closes allows water to settle under it's own pressure and drops abit.
Just a thought
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Might explain the pressure drop,
Because you don't lose all pressure do you just partial.
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Might explain the pressure drop,
Because you don't lose all pressure do you just partial.
 
I'd like to stress my correction to the wrong info I provided. I did made the correction already but it appears that Chuck haven't seen it. Actually when I open valve 1 pressure decrease. And since pump 1 is also running. pressure must increase but the opposite happened.
I haven't read the entire thread but that is what should happen if the pumps are in PP mode. When there is one pump running you have flow Vdot and head deltaP across the pump. Put a second pump in parallel then the flow per pump is halved so deltaP is also reduced. Depending on what's drawing the flow, that may also drop causing the pumps to reduce the pressure even further.

A smart pump doesn't need an external flow meter to operate, the flow is proportional to the pump RPM, which the motor controller knows. Also, don't forget that the 'pressure' referred to on pump curves is the pressure difference (hence deltaP) across the pump, not the outlet pressure.
 
Just thinking there again re these pumps, P1 and P2 refer to pump efficiency and pump+motor efficiency and grundfos give them on all sort of fixed speed pumps and even though pump pressures vs valve throttling can only logically be explained by some form of speed control I really wonder are these smart pumps like their much smaller domestic circulator cousins?.
 
Sounds like you just lose your head when pump are off or valve closed. Imagine a vertical pipe pump push water to the to keeping pressure up. When pump of of valve closes allows water to settle under it's own pressure and drops abit.
Just a thought
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Might explain the pressure drop,
Because you don't lose all pressure do you just partial.
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Might explain the pressure drop,
Because you don't lose all pressure do you just partial.
I'm pretty sure I still have my head in 1 piece. hahaha. Kidding aside I think the first step is to make sure this is a or not a variable speed intelligent pump system.
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I haven't read the entire thread but that is what should happen if the pumps are in PP mode. When there is one pump running you have flow Vdot and head deltaP across the pump. Put a second pump in parallel then the flow per pump is halved so deltaP is also reduced. Depending on what's drawing the flow, that may also drop causing the pumps to reduce the pressure even further.

A smart pump doesn't need an external flow meter to operate, the flow is proportional to the pump RPM, which the motor controller knows. Also, don't forget that the 'pressure' referred to on pump curves is the pressure difference (hence deltaP) across the pump, not the outlet pressure.
Thanks again, very nice tutorial on intelligent pumps but still does not explain the phenomena I have observed. Logically an intelligent pump system should minimize bill while giving the same pressures on the taps as the dumb pumps. That said an IPS must maintain same pressure on the taps at all times. I am imagining when all taps are close both pumps must be on standby. When one tap is opened primary pump kicks in at minimum speed and then increase speed as more taps is opened. When more taps are in service that primary pump cannot cope up, back up pump kicks in. If IPS lose pressure when closing discharge valve then its a dumb pump or in other words there is something wrong with it. The only thing I can think of is the control system starting from the transducer to the receiver/ interpreter. But I Will go and do as Snowhead suggested and perform same test as before to make sure. Now I am seriously considering that I indeed lose my head momentarily hahaha.
 
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Just thinking there again re these pumps, P1 and P2 refer to pump efficiency and pump+motor efficiency and grundfos give them on all sort of fixed speed pumps and even though pump pressures vs valve throttling can only logically be explained by some form of speed control I really wonder are these smart pumps like their much smaller domestic circulator cousins?.
Most probably yes because I still don't see any explanation to losing pressure when main discharged valve is closed other than the pump is trying to maintain a constant pressure.
 
I have a smart (circulating) pump which I can run in any one of three modes, Fixed Speed, Constant Pressure and Proportional Pressure mode and here is what the effect would be on the pressure indication if the pumps that we are discussing were run in these three modes bearing in mind where this pressure gauge is fitted. (manifold)
Both pumps running in all cases.
Fixed Speed: Open v/v1, pressure increase. Close main v/v, pressure increase.
Constant pressure: Open v/v1, no pressure change. Close main v/v, no pressure change.
Proportional Pressure: Open v/v1, pressure decrease. Close main v/v, pressure decrease.

If they are not "smart" pumps (which don't measure flow or pressure) it would seem that they are being controlled from somewhere in proportional pressure (PP) control using the pressure transducer on the manifold and pump power although one might think that constant pressure mode would be more appropriate.
As pointed out in post#27, one should hear the pumps speeding up/down if running in variable speed mode.
 
I have a smart (circulating) pump which I can run in any one of three modes, Fixed Speed, Constant Pressure and Proportional Pressure mode and here is what the effect would be on the pressure indication if the pumps that we are discussing were run in these three modes bearing in mind where this pressure gauge is fitted. (manifold)
Both pumps running in all cases.
Fixed Speed: Open v/v1, pressure increase. Close main v/v, pressure increase.
Constant pressure: Open v/v1, no pressure change. Close main v/v, no pressure change.
Proportional Pressure: Open v/v1, pressure decrease. Close main v/v, pressure decrease.

If they are not "smart" pumps (which don't measure flow or pressure) it would seem that they are being controlled from somewhere in proportional pressure (PP) control using the pressure transducer on the manifold and pump power although one might think that constant pressure mode would be more appropriate.
As pointed out in post#27, one should hear the pumps speeding up/down if running in variable speed mode.
What is the proportional pressure system? Does this mean that both pumps have proportional discharge pressure or that the pressure after and before main valve are the same?
 
Proportional pressure (PP) control is used mainly in heating systems with radiator thermostatic valves which throttle in the flow rates through the rads to give the desired room temperatures, in normal fixed speed pumps the pump head increases as the flow rate decreases but because the pipe friction losses decrease with decreasing flow then PP mode when selected is designed to reduce the pump head with reducing flow rates proportionally and because it is based on the theory that half the losses are in the pipework and the other half are in the rads then the PP minimum set point is 1/2 of the PP maximum setpoint. For example, I have my circ pump selected to a PP setting of 4M which is looking for a flow rate of 23 LPM and at zero flow rate will have a head of 2M So quite simply put if I connected my pump to a water supply and put a tap on the other end and shut it then the pump pressure would remain at 2M and if I started opening it then it would give a flowrate of 11.5 LPM at 3M and 23 LPM at 4M.
In your case IF and only IF there is some form of proportional control then simply shutting the main discharge valve will give the minimum set point pressure, whatever that is, and as you start re opening the main discharge valve the pump pressure should start increasing towards its maximum pp setting (assuming the neccessary flow demand.)

As was asked a number of times before can you hear the pump(s) speed changing? if not then back to the drawing board.
 
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Proportional pressure (PP) control is used mainly in heating systems with radiator thermostatic valves which throttle in the flow rates through the rads to give the desired room temperatures, in normal fixed speed pumps the pump head increases as the flow rate decreases but because the pipe friction losses decrease with decreasing flow then PP mode when selected is designed to reduce the pump head with reducing flow rates proportionally and because it is based on the theory that half the losses are in the pipework and the other half are in the rads then the PP minimum set point is 1/2 of the PP maximum setpoint. For example, I have my circ pump selected to a PP setting of 4M which is looking for a flow rate of 23 LPM and at zero flow rate will have a head of 2M So quite simply put if I connected my pump to a water supply and put a tap on the other end and shut it then the pump pressure would remain at 2M and if I started opening it then it would give a flowrate of 11.5 LPM at 3M and 23 LPM at 4M.
In your case IF and only IF there is some form of proportional control then simply shutting the main discharge valve will give the minimum set point pressure, whatever that is, and as you start re opening the main discharge valve the pump pressure should start increasing towards its maximum pp setting (assuming the neccessary flow demand.)

As was asked a number of times before can you hear the pump(s) speed changing? if not then back to the drawing board.
Thanks for the tutorial.
I was there today and conducted the speed changing test. Put my ear right on the body of pump two and slowly open valve 1 ( currently about 20% open) until full open. Pressure drop from 70 to 60. Not a bit changed in speed. Close it again until I can hear the water straining to the almost close. pressure rise to around 83. not a bit changed in speed. Put my ear on pump 1 one and perform same test. Not a bit change in speed. As I perform the test I kept feeling both pumps discharge line. I can tell that pump two is straining or doing some work while pump one seems to be not doing any work. It is possible that pump one is not working. Motor is running but pump is not moving water. If I had my clamp ammeter with me I would have conducted an ampere test but I did not bring it with me. so will have to go back and test again.
Here is What comes to mind while doing the test. Pump one is broken and NRV one is also broken and that water is going back that route. Have inspected the cistern I can't see any foot valve although it wasn't very clear deep in the water. Maybe RPM "stab in the dark" hit its mark. Did not conduct the Main valve test as I was alone, and main valve is high up. I will need an assistant to do the test.. This is an unplanned test. I was there for emergency call regarding fire alarm. took some pictures.
 

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Hello everyone, I'm a Plumber/ pump man from the Philippines. I need advice regarding pump problem. I dont know if this the right forum, but here it is. Two pumps connected in parallel runs continuously. What puzzled me is that whenever I partially closed main discharge valve or any of the discharge valve of both pump the pressure drops. Now this my first encounter with such a pump. Please refer to attached files. Is it perhaps a variable speed/ discharge pump that reacts to the pressure transmitter installed at the discharge. Pump is servicing a four story building. pressure is 70 psi drops to 50 to 60 whenever I partially close any discharge valve. Looking forward to your advice.
Ive not read all the replies but this must be a chiller or cooling type Of
 
Been a long time but if my maths is correct that is around 200 ft head.
Plus earlier you said closing valves showed a reduction in pressure on the gauge now it raises.
 
There certainly seems to be the facility for VSD as the Grundfos controller has a SP and PV but both switches VSD 1 and VSD 2 appear to be in the off position so assume that pumps are running in fixed (full) speed mode then if pump 1 not doing anything and NRV not working then shutting valve 1 will certainly increase the system pressure but does not explain the puzzle as to the pressure decreasing when the main discharge valve is throttled in?, maybe worth repeating this test. Also that 83 psi, (57 M) would seem to point to a 60 HZ supply as the maximum no flow head running at 50 hz is 41 M. (see pump curve, post #34. and compare with pump name plate in post #1) and also is borne out in practice as head is proportional to speed squared, hence 41*(60/50)^2 = 59 M (no flow head)
 
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Not sure what you mean by the above but one other thing Julian could check is to shut valve 1 fully and see if the motor stops turning after a minute or so as it may not be switched on and is just turning in reverse because of a defective NRV.

Any ideas on why 50 hz motors are coupled to 3600 RPM pumps as 50 hz motors should not be fitted in countries that have a 60 hz electrical supply, if this is the case.?
 
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Been a long time but if my maths is correct that is around 200 ft head.
Plus earlier you said closing valves showed a reduction in pressure on the gauge now it raises.
Yeah my bad. I have corrected this twice already. I think I must correct also the original post.
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Not sure what you mean by the above but one other thing Julian could check is to shut valve 1 fully and see if the motor stops turning after a minute or so as it may not be switched on and is just turning in reverse because of a defective NRV.

Any ideas on why 50 hz motors are coupled to 3600 RPM pumps as 50 hz motors should not be fitted in countries that have a 60 hz electrical supply, if this is the case.?
Yes this also comes to mind, I will definitely check this. Even at first visit I have already doubts that pump 1 is not running I have check repeatedly if its turning.
I don't have the slightest idea why this is so. manager said that 1 pump is already replaced with new, by a contractor from grundfos. I ask her why she did not call them for this. She just make faces and tell me that they don't like the fact that grundfos refer them to the contractor.
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Is there a possibility to edit post one. So that new comers to this discussion won't be confused by my mistake.
 
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Yeah my bad. I have corrected this twice already. I think I must correct also the original post.
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Yes this also comes to mind, I will definitely check this. Even at first visit I have already doubts that pump 1 is not running I have check repeatedly if its turning.
I don't have the slightest idea why this is so. manager said that 1 pump is already replaced with new, by a contractor from grundfos. I ask her why she did not call them for this. She just make faces and tell me that they don't like the fact that grundfos refer them to the contractor.
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Is there a possibility to edit post one. So that new comers to this discussion won't be confused by my mistake.
Re your corrected statement..... just to be quite clear again, you are stating that opening valve 1 results in reduced pressure and shutting the main discharge results in reduced pressure??

Check with your clamp ampmeter if the No1 pump is drawing power, if so, check direction of rotation which, if reversed will still pump but at much reduced head (~50%) and flow rate. It then only requires two phase change to get correct rotation.
If you havn't got your ampmeter carry out the (pump 1) closed valve test and see if pump stops.
 
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That control box has 2 Variable Speed Drives in it.
1 is the Schneider at the top, showing 60 which could mean it's being driven at full speed, 60hz (the frequency in the Phillipines) or may just be showing the incoming frequency, it depends which parameter the display is set to show.
The other is the Grundfos.
Whether they were the same and 1 has been replaced I don't know.
They control speed from pressure and can do Duty / Standby changeover, depending how they are set up.

The Grundfos at the bottom is in fault, O. P,, Over pressure.
This may need resetting, depending whether the parameters are set to turn of the pump in fault or leave it running.
As there is only 1 pressure sensor, only 1 VSD can have a Pressure input.
However they will most likely be linked so when 1 fails the other takes over

I've found links to the manuals to both VSD

To check if either or both pumps are running you should be able to see the Fan on the top end of the motor running.
If one pump is not being powered but is being driven by the flow from the other pump passing through the NRV, then it will be running slower.

The 2 switches at the top will be to bypass the VSDs if they fail.
 
Re your corrected statement... just to be quite clear again, you are stating that opening valve 1 results in reduced pressure and shutting the main discharge results in reduced pressure??

Yes, this is correct

Check with your clamp ampmeter if the No1 pump is drawing power, if so, check direction of rotation which, if reversed will still pump but at much reduced head (~50%) and flow rate. It then only requires two phase change to get correct rotation.
If you havn't got your ampmeter carry out the (pump 1) closed valve test and see if pump stops.

I will go back with my ampmeter and check power draw. direction of rotation and fully close valve 1 test and also the main valve partially close test.
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That control box has 2 Variable Speed Drives in it.
1 is the Schneider at the top, showing 60 which could mean it's being driven at full speed, 60hz (the frequency in the Phillipines) or may just be showing the incoming frequency, it depends which parameter the display is set to show.
The other is the Grundfos.
Whether they were the same and 1 has been replaced I don't know.
They control speed from pressure and can do Duty / Standby changeover, depending how they are set up.

The Grundfos at the bottom is in fault, O. P,, Over pressure.
This may need resetting, depending whether the parameters are set to turn of the pump in fault or leave it running.
As there is only 1 pressure sensor, only 1 VSD can have a Pressure input.
However they will most likely be linked so when 1 fails the other takes over

I've found links to the manuals to both VSD

To check if either or both pumps are running you should be able to see the Fan on the top end of the motor running.
If one pump is not being powered but is being driven by the flow from the other pump passing through the NRV, then it will be running slower.

The 2 switches at the top will be to bypass the VSDs if they fail.
Can you please post links of the manuals. for both VSD's.
My guts tells me that pump 1 is running slower.
what does SP and PV stands for?
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How do I switch off pump 1 or pump 2. In case I need to?
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Thanks for staying with me guys. I've confidence now I can solve this, I mean we can :)
 
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I will go back with my ampmeter and check power draw. direction of rotation and fully close valve 1 test and also the main valve partially close test.
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Can you please post links of the manuals. for both VSD's.
My guts tells me that pump 1 is running slower.
what does SP and PV stands for?
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How do I switch off pump 1 or pump 2. In case I need to?
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Thanks for staying with me guys. I've confidence now I can solve this, I mean we can :)
Its certainly very interesting , SP probably stands for Set point and PV for Process value, I would be doubtful if the controllers were designed to maintain a given variable speed, generally the SP would be a desired manifold pressure ( or in the case of a very tall building may have the pressure transducer located near the top) and the variable speed controller would then modulate the variable speed output to maintain this constant pressure which would possibly be ~ 50 psi.
I had a lot of experience with a mixture of fixed speed combined with VSD on cooling tower circulating pumps and I can definitely say that if the VSD, for whatever reason, ramped down so much that its head was much lower than the fixed speed pump then the NRV would shut to stop reverse flow through the pump, so obviously if the NRV on your pump 1 is defective and the pump is running at a much lower speed then its quite possible to get reverse flow through that pump. Its also possible, however unlikely, that this pump is running at full speed in the wrong direction which will give a much reduced head to give this reverse flow. Your tests on this pump will solve that mystery easily enough.
The big mystery for me is as to why the manifold pressure reduces when the main discharge valve is throttled in but again you are going to carry out a confirmation test on this.
 
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Not sure what you mean by the above but one other thing Julian could check is to shut valve 1 fully and see if the motor stops turning after a minute or so as it may not be switched on and is just turning in reverse because of a defective NRV.

Any ideas on why 50 hz motors are coupled to 3600 RPM pumps as 50 hz motors should not be fitted in countries that have a 60 hz electrical supply, if this is the case.?
1440 ish at nominal voltage
 
Its certainly very interesting , SP probably stands for Set point and PV for Process value, I would be doubtful if the controllers were designed to maintain a given variable speed, generally the SP would be a desired manifold pressure ( or in the case of a very tall building may have the pressure transducer located near the top) and the variable speed controller would then modulate the variable speed output to maintain this constant pressure which would possibly be ~ 50 psi.
I had a lot of experience with a mixture of fixed speed combined with VSD on cooling tower circulating pumps and I can definitely say that if the VSD, for whatever reason, ramped down so much that its head was much lower than the fixed speed pump then the NRV would shut to stop reverse flow through the pump, so obviously if the NRV on your pump 1 is defective and the pump is running at a much lower speed then its quite possible to get reverse flow through that pump. Its also possible, however unlikely, that this pump is running at full speed in the wrong direction which will give a much reduced head to give this reverse flow. Your tests on this pump will solve that mystery easily enough.
The big mystery for me is as to why the manifold pressure reduces when the main discharge valve is throttled in but again you are going to carry out a confirmation test on this.
"The big mystery for me is as to why the manifold pressure reduces when the main discharge valve is throttled in but again you are going to carry out a confirmation test on this."

this is the thing that make me doubt if I lose my head momentarily:)
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Manual for the drive Labelled Grundfos, I suspect Grundfos had these rebadged with their name;

Manual for Schneider drive;
Thanks snow, I downloaded it for learning.
 
It`s certainly more interesting than the average plumbing post Julian.
I'm glad that you find this interesting. And when we get to solve this... I sincerely wish I can buy you all some beer/whisky... for a lil celebration :):).
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I have little knowledge with motors, so I'd like to throw this question out there. If a 50hz motor run on 60 hz, is it going to run at 20% more speed than its designed to run at.
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Ok, so we, me and my son, did the test. Pressure at 70 psi to start with. first test was the direction of rotation test. I did a simple poke test with a twist tie at the back of the motor. The twist tie bent to the direction of rotation when it hits the fan blade. we did the test at least 3 times for each pump and found out that pumps are running in opposite directions. Second test. Valve 1 full close test. Pump 1 stop spinning as soon as valve is full close. pressure is around 85psi. Did the test 2 more times. each time the pump stop turning as soon as the valve is fully closed. But it takes time for pressure to go down to 70 even when valve 1 is already full open. I Cancelled the ampere test as motor 1 is clearly not operating. So we have already the "broken NRV 1" confirmed. Proceeded to main valve fully closed test. pressure at 70 psi. pressure does not change but motor 1 appeared to be running faster. closed valve 1 slowly pressure increase to around 80. repeat the same test and got same result. All throughout did not hear the motor changing speed.
Motor 1 nameplate says 60hz and is connected to dunfoss VSD. Motor 2 nameplate says 50hz and is connected to schnieder VSD. Pump 1 appear to have previous leaking as there is dry mud all over. see photo.
So yeah I've lost my mind for a moment on the main valve test. Maybe because I was alone and have to go up and down the ladder to close the valve little by little and look at the pressure gauge. by chance the pressure drops courtesy of valve one, at the precise moment when main valve is almost closed. Yes it took time for pressure to drop after opening the valve 1. Its because the pump has to gain momentum going to the opposite direction.
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MY course of action plan. First is to study the manuals of VSD's. Get a new NRV and replace NRV1. Test pump one if ok. If ok put it as the lead drive and reprogram the whole thing to operate at constant pressure. If pump one is broken but motor is ok, interchanged pumps and motors and put 60hz motor and good pump in service. Overhaul broken pump and attached to 50 hz motor as backup.
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Re pump 1 leakage, that will be the mechanical seal in the top housing, the top of it can be seen if you remove the coupling guard but the bad news is it is a complete strip down of the pump to replace it. Could this be the reason pump 1 has been taken out of operation? Unless you have experiance and the tool I wouldn`t recommend you attempt the rebuild tbh.
 
Re your query of 50hz vs 60hz, yes a 50 hz motor will run at 60 hz but not as efficiently and there are greater electrical losses as well apart from mechanical stresses on the windings due to the greater centrifugal force and if the pump is running at end of curve conditions (flat out) then the motor can trip out on o/load as the power required will be 1.7 times higher, ((60/50)^3)). Motors can be designed for 50/60 hz operation, don't know if the Grundfos one installed is of this type but it certainly has the power, 3KW. I can,t find the pump curve for the (60 hz) installed pumps but the above curve (post #34) shows that the maximum required power at 50 hz is ~ 1.56 kw so it would still be ok at 60 hz as it would be drawing 2.7 kw ((1.56*(60/50)^3) so maybe these motors are designed for dual frequencies. I wouldn't bother changing it withourt at least contacting Grundfos for advice. I reckon that based on that 8.8 m3/hr and assuming running the VSD to maintain a constant pressure of 50 psi (3.5 bar) that the savings would be ~ 0.6 kwh/hr, 14.4 kwh/day or 5256 kwh/annum.
I estimate that at 80 psi the 60 hz pump is supplying 8.8 m3/hr with a motor load of 2 kw.
No comment needed on your tests as everything is adding up now.
You could do a quick test on the gland to confirm the leak by shutting the suction valve and cracking open the discharge valve which will put full system pressure on it.

I would be grateful if someone can post a link to the 60 hz pump as shown in the label photo as I can't locate it on the Grundfos site.
 
I would be grateful if someone can post a link to the 60 hz pump as shown in the label photo as I can't locate it on the Grundfos site.

If logged in on Grundfos you need to change the Location to the Phillipines to get 60hz info;

60hz, shaft speed, output etc matches, but the product number doesn't;

 
Thanks for that, for some reason or other it doesn't seem to be accepting my editing but I have the above now anyhow.

OK, able to edit/change now.
 
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Re pump 1 leakage, that will be the mechanical seal in the top housing, the top of it can be seen if you remove the coupling guard but the bad news is it is a complete strip down of the pump to replace it. Could this be the reason pump 1 has been taken out of operation? Unless you have experiance and the tool I wouldn`t recommend you attempt the rebuild tbh.
I do have countless experience overhauling pumps, but not of this kind, almost all of them different from each. Thanks for the suggestion. I will think about it. Basically it all depends on the price, if the owners will agree. New vs rebuild cost.
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I have read the manuals for the VSD's you provided. Is Rhymebus same as grundfos? also I cant find the programming manual. Its only for installation.
 
Re your query of 50hz vs 60hz, yes a 50 hz motor will run at 60 hz but not as efficiently and there are greater electrical losses as well apart from mechanical stresses on the windings due to the greater centrifugal force and if the pump is running at end of curve conditions (flat out) then the motor can trip out on o/load as the power required will be 1.7 times higher, ((60/50)^3)). Motors can be designed for 50/60 hz operation, don't know if the Grundfos one installed is of this type but it certainly has the power, 3KW. I can,t find the pump curve for the (60 hz) installed pumps but the above curve (post #34) shows that the maximum required power at 50 hz is ~ 1.56 kw so it would still be ok at 60 hz as it would be drawing 2.7 kw ((1.56*(60/50)^3) so maybe these motors are designed for dual frequencies. I wouldn't bother changing it withourt at least contacting Grundfos for advice. I reckon that based on that 8.8 m3/hr and assuming running the VSD to maintain a constant pressure of 50 psi (3.5 bar) that the savings would be ~ 0.6 kwh/hr, 14.4 kwh/day or 5256 kwh/annum.
I estimate that at 80 psi the 60 hz pump is supplying 8.8 m3/hr with a motor load of 2 kw.
No comment needed on your tests as everything is adding up now.
You could do a quick test on the gland to confirm the leak by shutting the suction valve and cracking open the discharge valve which will put full system pressure on it.

I would be grateful if someone can post a link to the 60 hz pump as shown in the label photo as I can't locate it on the Grundfos site.
If the motor is designed to run at 50/60 hz, would not it be indicated on the label. I see only 50hz there and not 60/50hz. and the other one 60hz.
Thanks for the computations. I am wondering though, this is a water supply system for tap, for hotel guest use, How is it suppose to enable power savings if it keeps on running even if no one is using the tap. Is not the on/ off system with a big pressure tank and pressure regulators on each floor, more suitable for the purpose.
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"You could do a quick test on the gland to confirm the leak by shutting the suction valve and cracking open the discharge valve which will put full system pressure on it".

Good suggestion this I will do. I am also planning to do a quick test on the motor via emergency switch, what do you think?
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But before I take out pump one I want to reduce the speed of pump 2, as I can sense an increase in vibration and hear what seems water hammering, every time I close fully valve 1. So I leave it crack open to ease pressure a bit. I am thinking I can do speed modulation by adjusting VSD2 frequency. that is why its important that I learn first to program this thing.
 
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If the motor is designed to run at 50/60 hz, would not it be indicated on the label. I see only 50hz there and not 60/50hz. and the other one 60hz.

Yes it should be so most likely isn't suitable for 60hz.

Thanks for the computations. I am wondering though, this is a water supply system for tap, for hotel guest use, How is it suppose to enable power savings if it keeps on running even if no one is using the tap.

The pressure sensor / transducer in the pipework should detect the pressure and signal the VSD to reduce speed or shut down.
Either the sensor isn't working, the VSD isn't working or the settings have been changed so it only runs at full speed.

But before I take out pump one I want to reduce the speed of pump 2, as I can sense an increase in vibration and hear what seems water hammering, every time I close fully valve 1. So I leave it crack open to ease pressure a bit. I am thinking I can do speed modulation by adjusting VSD2 frequency. that is why its important that I learn first to program this thing.

See above, it may be the sensor has failed and the VSD is manually set to full speed or it's set to full speed anyway.

If so you should be able to reduce the speed setting on the VSD.

I suspect this boost system has had several faults which have accumulated over the years with various people attempting to fix and have failed, most likely through lack of knowledge.

You need to be prepared to cap the open ends of the pipes from the pump you are removing , it's quite likely the valves will pass some water when closed.
Or if you can't reduce the other pump speed you may be able to pipe some of the flow to a drain to reduce the pressure temporarilly through the removed pump valves.
 

Reply to Two pumps connected in parallel runs continuously in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

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