Grundfos MC4000 2Hp Controller question....

[Towforce]

Working on cleaning up and reconfiguring the layout and electrical in my pump house. Last year we did an emergency pump replacement, upgraded the pump to Grundfos MC4000 2hp pump (from a 1.5 Aeromotor).

Wire down the well was replaced/upgraded, we retained the original controller (Pentek SMC CR2021-02 rated 12.2 amp and identical cap configuration to the Grundfos spec). Note: we also replaced the start and run caps and the relay with new components, Relay is a nice heavy duty 40 amp Furnas brand/new.

My question relates to the original controller (Pentek) rated @ 2hp 230v 12.2amps. The Grundfos controller SA-SPM6 98315254 that is specified for use on the Grundfos 2hp MC4000 motor specs are base on 230v / 13.2 (max SF) . My electrical test are coming up with (@ 240v and a line loss of 1%) 14.4 amps run and 28amps start. Tho my Pentek is essentially new internally, should I just order the Grundfos?....

At first glance, yah, just ordering the specified controller seems to be the answer but if the the Grundfos is essentially the same thing? I will say the Pentek does not appear to be that robust, wire sizes are bit marginal by my way of thinking, have no idea what the Grundfos will be....

Related to my slightly higher than spec load on my amp load test, could my controller be the culprit or could it be contributed to my discharge/delivery setup?

The pump sits at 250', lift to the house is roughly 25 ft, distance 150', via 1.25" poly at the well head, dropping to 1" for the run to the house (currently working on reducing line loss on this setup). I'm running the pressure tank at the house (set 30-50). The pump will see roughly 95psi at the well head to achieve pressure at the tank. As I said, working on cleaning up the line loss and hopefully reduce the amp load.

Thanks

Martin

 

[Valveman]

If it has the same run cap the amps should also be the same. 13.2 amps shows to be max for the Grundfos motor. I would be worried that it is drawing 14.4 amps. Grundfos pumps are really good at reducing amps as the pressure increases. I would try turning the pressure switch up to 40/60 or even 50/70 and see if the amps stay below 13.2. Higher pressures or back pressure is good for a pump/motor as it makes it draw lower amps and run cooler. Running high flow at low pressure is the hardest thing for a pump to do. I know you will like the higher pressure in the house.

If you really want to reduce the amps, add a Cycle Stop Valve. With the back pressure from a CSV I doubt that pump will draw more than about 8-9 amps.

 

[Sponsor]

 

[Fitter30]

Just because the caps are the same size doesn't mean thst the specific back EMF voltage generated by the motor speed changes over to the run cap as the correct speed 75%. Pickup voltage needs to match the pump characteristics.
425' run 15 amps 3% max voltage drop 6 gauge
www.inchcalculator.com/voltage-drop-calculator

 

[Towforce]

If it has the same run cap the amps should also be the same. 13.2 amps shows to be max for the Grundfos motor. I would be worried that it is drawing 14.4 amps. Grundfos pumps are really good at reducing amps as the pressure increases. I would try turning the pressure switch up to 40/60 or even 50/70 and see if the amps stay below 13.2. Higher pressures or back pressure is good for a pump/motor as it makes it draw lower amps and run cooler. Running high flow at low pressure is the hardest thing for a pump to do. I know you will like the higher pressure in the house.

If you really want to reduce the amps, add a Cycle Stop Valve. With the back pressure from a CSV I doubt that pump will draw more than about 8-9 amps.

Seems counter intuitive to my way of thinking, can't really see how increasing the work load will reduce the amperage (having monitored the amp load during the entire cycle), by your suggestion I should see amp draw go down during the end of the cycle. Measured at the head, I peak out at 90- 100 psi getting my storage tank charged to 50 psi. (I'm working on reducing this line loss/restriction)

I admit, I don't really get how a Cycle Stop Valve could possibly reduce amp draw on the fixed specifications of a pump. I've worked with motors and pumps for early 50 years... admittedly not well pumps so maybe there is some sort of magic that I have missed? Anyway thanks for the suggestion.

Martin

 

[Reach4]

Seems counter intuitive to my way of thinking, can't really see how increasing the work load will reduce the amperage (having monitored the amp load during the entire cycle), by your suggestion I should see amp draw go down during the end of the cycle.

Yes, that is correct. Counterintuitive, and you will see the amps go down as you continue to fill the pressure tank. I would also expect to see the power factor to drop as the pressure tank fills, but that is harder to measure.

The gallons per Watt-hr will drop also, however.

 

[Towforce]

Just because the caps are the same size doesn't mean thst the specific back EMF voltage generated by the motor speed changes over to the run cap as the correct speed 75%. Pickup voltage needs to match the pump characteristics.
425' run 15 amps 3% max voltage drop 6 gauge
www.inchcalculator.com/voltage-drop-calculator

I've measured a running line voltage drop of around 1% (240v down to 237-238) and true I have a Fluke meter its not the high end meter so perhaps not fast enough to catch the true initial line drop (and your correct the calculator does suggest close to a 3% drop which calculates out to 232v). Of course, I'm measuring the at the breaker panel in the pump house and not taking into consideration the additional loss going down the 250' of well..... Either way, if the line loss is true and is 232v, pretty sure its well within the 230v Grundfos specifications of 230v and best as I can tell from the manual, wires meet the book specs.

I was kind of focusing electrically on the controller (its internal wire) and breaker to controller wiring (breaker to controller has some short lengths of what I believe to be #12 and or #10.... internally the controller appears to have a bunch of #14.... kind of a weak link?)....

Thanks

Martin

(edit: just out of Curiosity....I ran the calculator for a 30amp start load on 400ft of #8, source to pump and then you start to see some serious drop! 224v/6% ..... still within spec for a 230v motor and book spec... but interesting)

 

[Valveman]

Seems counter intuitive to my way of thinking, can't really see how increasing the work load will reduce the amperage (having monitored the amp load during the entire cycle), by your suggestion I should see amp draw go down during the end of the cycle. Measured at the head, I peak out at 90- 100 psi getting my storage tank charged to 50 psi. (I'm working on reducing this line loss/restriction)

I admit, I don't really get how a Cycle Stop Valve could possibly reduce amp draw on the fixed specifications of a pump. I've worked with motors and pumps for early 50 years... admittedly not well pumps so maybe there is some sort of magic that I have missed? Anyway thanks for the suggestion.

Martin

Lol! I know right? I would venture to say 99% of all engineers and 90% of all pump engineers do not understand this basic principal of how a centrifugal pump works. It is truly counter intuitive, and engineers don't take well to counter intuitive things.

But that is how pumps work. The "work load" is not how much pressure the pump can build but rather how many gallons per minute it is lifting. Water weighs like 8.3 pounds per gallon and lifting 20 GPM is 166 pounds per minute, while at 2 GPM the pump is only lifting 16.6 pounds per minute.

You can see from this pump curve that at 25 GPM the 2HP Grundfos is drawing 2.4HP. But when restricted to 2 GPM draws only 0.7HP. All centrifugal pump work like this, some just drop more than others because of impeller design.

PS... If the amps increase when the flow is restricted the thrust bearing in the motor is bad. A worn thrust bearing can also cause a little higher amperage at normal flow and pressure. Test the thrust bearing by closing a valve and see if the amps decrease.

 

[Valveman]

I've measured a running line voltage drop of around 1% (240v down to 237-238) and true I have a Fluke meter its not the high end meter so perhaps not fast enough to catch the true initial line drop (and your correct the calculator does suggest close to a 3% drop which calculates out to 232v). Of course, I'm measuring the at the breaker panel in the pump house and not taking into consideration the additional loss going down the 250' of well..... Either way, if the line loss is true and is 232v, pretty sure its well within the 230v Grundfos specifications of 230v and best as I can tell from the manual, wires meet the book specs.

I was kind of focusing electrically on the controller (its internal wire) and breaker to controller wiring (breaker to controller has some short lengths of what I believe to be #12 and or #10.... internally the controller appears to have a bunch of #14.... kind of a weak link?)....

Thanks

Martin

(edit: just out of Curiosity....I ran the calculator for a 30amp start load on 400ft of #8, source to pump and then you start to see some serious drop! 224v/6% ..... still within spec for a 230v motor and book spec... but interesting)

It would be hard to measure the voltage drop at the motor. But if there is enough voltage drop it will cause the amps to increase. A little voltage drop on start up keeps the start amps lower, kind of like a reduced voltage soft start.

Also, it is very common with large centrifugal pumps for a need to restrict the flow enough to keep the amps below the service factor. You might be able to increase the pressure enough to keep the amps below the service factor.

 

[Reach4]

(edit: just out of Curiosity....I ran the calculator for a 30amp start load on 400ft of #8, source to pump and then you start to see some serious drop! 224v/6% ..... still within spec for a 230v motor and book spec... but interesting)

Wire sizing for motors is special. You would best use the Franklin AIM manual. For single phase motors see table 11 in the 2015 version, and table 32 in the 2023 version. Distances are each wire.

Lengths in BOLD only meet the US National Electrical Code ampacity requirements for
individual conductors 60 °C or 75 °C in free air or water, not in magnetic enclosures,
conduit or direct buried.
Lengths NOT in bold meet the NEC ampacity requirements for either individual
conductors or jacketed 60 °C or 75 °C cable and can be in conduit or direct buried. Flat
molded and web/ribbon cable are considered jacketed cable.

 

[Fitter30]

It would be hard to measure the voltage drop at the motor. But if there is enough voltage drop it will cause the amps to increase. A little voltage drop on start up keeps the start amps lower, kind of like a reduced voltage soft start.

Also, it is very common with large centrifugal pumps for a need to restrict the flow enough to keep the amps below the service factor. You might be able to increase the pressure enough to keep the amps below the service factor.

Factory panel wiring doesn't follow the same nec code as residential wiring. Centrifugal pumps for cooling tower, chilled or hot water have the impeller trimmed to get into spec or adjust the hertz with a vfd. Start to throttle the discharge raises head and lowers flow. Only time dead head a pump is to check shut off pressure to see what size ( diameter) the impeller is and performance.

 

[Towforce]

Wire sizing for motors is special. You would best use the Franklin AIM manual. For single phase motors see table 11 in the 2015 version, and table 32 in the 2023 version. Distances are each wire.
View attachment 107116
Lengths in BOLD only meet the US National Electrical Code ampacity requirements for
individual conductors 60 °C or 75 °C in free air or water, not in magnetic enclosures,
conduit or direct buried.
Lengths NOT in bold meet the NEC ampacity requirements for either individual
conductors or jacketed 60 °C or 75 °C cable and can be in conduit or direct buried. Flat
molded and web/ribbon cable are considered jacketed cable.

Grundfos specs are pretty much the same, at the head we upgraded from 12/4 to 10/4.

Cheers

 

[Towforce]

It would be hard to measure the voltage drop at the motor. But if there is enough voltage drop it will cause the amps to increase. A little voltage drop on start up keeps the start amps lower, kind of like a reduced voltage soft start.

Also, it is very common with large centrifugal pumps for a need to restrict the flow enough to keep the amps below the service factor. You might be able to increase the pressure enough to keep the amps below the service factor.

My background is Commercial Dish Washers.... Closed and open impellers, Cavitation was the enemy.... that and soils... Have repaired/replaced 1000's through the years. Trimming and design vs housings and discharge was a science, it would strike fear every time a manufacture would play with plastic impellers (common in well pumps?).... our Customers would work hard at trying destroy motors. One infamous design (Older company call Stero) had a wonderful 2 hp open impeller capable of grinding up spoons, forks, but struggled to chop up a steak knife ;-)...

BTW.... if I read my Grundfos pump spec, looks like an 18stage pump..

Martin

 

[Valveman]

My background is Commercial Dish Washers.... Closed and open impellers, Cavitation was the enemy.... that and soils... Have repaired/replaced 1000's through the years. Trimming and design vs housings and discharge was a science, it would strike fear every time a manufacture would play with plastic impellers (common in well pumps?).... our Customers would work hard at trying destroy motors. One infamous design (Older company call Stero) had a wonderful 2 hp open impeller capable of grinding up spoons, forks, but struggled to chop up a steak knife ;-)...

BTW.... if I read my Grundfos pump spec, looks like an 18stage pump..

Martin

If you are lifting from close to 250' and need 95 PSI at the well head, the 18 stage 16S20-18 would be the right pump. Still drops from 2.5HP to 1.2HP at low flow when restricted.

 

[Valveman]

Factory panel wiring doesn't follow the same nec code as residential wiring. Centrifugal pumps for cooling tower, chilled or hot water have the impeller trimmed to get into spec or adjust the hertz with a vfd. Start to throttle the discharge raises head and lowers flow. Only time dead head a pump is to check shut off pressure to see what size ( diameter) the impeller is and performance.

What most people do not understand is that throttling a pump to decrease flow does raise the head, but the amps still drop similar to trimming the impeller or slowing with a VFD. I have dead headed lots of pumps to check shut off head and the thrust bearing. That is how I know how much the amps drop and that you can't "deadhead" for very long or the pump gets hot. Which is why a Cycle Stop Valve can never deadhead a pump because it can never close completely.

 

[Towforce]

What most people do not understand is that throttling a pump to decrease flow does raise the head, but the amps still drop similar to trimming the impeller or slowing with a VFD. I have dead headed lots of pumps to check shut off head and the thrust bearing. That is how I know how much the amps drop and that you can't "deadhead" for very long or the pump gets hot. Which is why a Cycle Stop Valve can never deadhead a pump because it can never close completely.

I assume when you say "dead" head a pump your mean shutting off the pump discharge prior to any control device (pressure switch)? As I clean up my pump house, I was looking at a potential scenario of having a supply valve (in the house) being shut off to deal with a failed plumbing in the home. First rule of any flood is to "turn off the damn water" ! ;-)

I added a pump control on off switch in the house utility room, but back at the pump house I was looking to add port to the distribution manifold that I could install something like a high pressure cut off and a event timer to shut down the control leg. Was hoping to keep it simple and not rely on any sort of amp monitor system. I figure cut off criteria would be a max pump pressure setting (like a 110-120 psi) and perhaps a timeout of no more than 15 minutes... Does such a beast exist? Alternatively an adjustable pressure relief valve and timer could also be configured.

Thanks!

PS.... new shinny Grundfos control has arrived... now I just need the time....

Martin

 

[Bannerman]

looking at a potential scenario of having a supply valve (in the house) being shut off to deal with a failed plumbing in the home. First rule of any flood is to "turn off the damn water"

Deadhead in this context means all flow from the pump is fully blocked. While deadheaded, the pump will build to its maximum pressure capacity, but, there will be no flow passing through the pump, and therefore, no flow past the pump's electric motor to provide cooling. When there is 0 flow, a submersible pump is likely to rapidly overheat, which will negatively impact the pump's lifespan.

To prevent a deadhead situation, all valves including the main shutoff valve to the house, are to be located after the pressure tank & pressure switch, not before. In this manner, an incoming valve cannot be unintentionally closed which would prevent the pressure tank from absorbing flow from the pump while also preventing the pressure switch from shutting off the pump.

I figure cut off criteria would be a max pump pressure setting (like a 110-120 psi) and perhaps a timeout of no more than 15 minutes.

The pump running for 15-minutes with 0 flow is far too long.

As an additional precaution in case of a pressure switch malfunction or it's inlet becoming blocked, a pressure relief valve is normally utilized, located at the inlet to the pressure tank such as threaded into the tank Tee. The PRV will then permit flow from the pump to be discharged once the pressure exceeds an excess specific pressure such as 75 psi. This ensures continuous cooling flow for the pump until the discharge from the PRV is noticed, permitting the pump's breaker or power switch to be turned off manually until the cause of the issue is investigated and appropriate repairs are performed.

Any repairs or maintenance needed between the pump and pressure tank, will be addressed by shutting off the pump manually, then draining the pressure tank contents to a suitable drain or to the home's exterior.

 

[Reach4]

As I clean up my pump house, I was looking at a potential scenario of having a supply valve (in the house) being shut off to deal with a failed plumbing in the home. First rule of any flood is to "turn off the damn water" ! ;-)

If you turn off the switch/breaker (one should be handy), the pump will stop pumping. Putting a valve before the pressure switch runs the danger of somebody shutting that valve. For experimentation with throttling it could be useful, but then at least remove the handle when you are not actively experimenting.

 

[Towforce]

Fully understand the issues with the shutoff being prior to the pressure switch, Emergency only. Which is why I would like to put a "high pressure switch" at the pump house to automatically shut down the pump should there ever be an occasion where someone shuts down the emergency valve at the house. Same goes for some sort of timer feature that will shut down the pump if there is an unusual long cycle caused by a failed delivery line, failed irrigation valve.... worst case, nobody around to notice.

I know... should worry less and drink more?.... ;-)

Martin

 

[Valveman]

Fully understand the issues with the shutoff being prior to the pressure switch, Emergency only. Which is why I would like to put a "high pressure switch" at the pump house to automatically shut down the pump should there ever be an occasion where someone shuts down the emergency valve at the house. Same goes for some sort of timer feature that will shut down the pump if there is an unusual long cycle caused by a failed delivery line, failed irrigation valve.... worst case, nobody around to notice.

I know... should worry less and drink more?.... ;-)

Martin

I have tried all those things. Most are more trouble than they are worth. I tried the Drop pressure switch which has some of the features you ask about. They make a high pressure kill switch for pivot sprinklers. But they are a pain and you have to manually reset them if they trip on high pressure.

A simple pressure relief valve is the best way to prevent damage to the pump or high pressure in the house. You can add something to the discharge of the PRV that would shut the pump down when it gets wet if you wanted. But as long as the PRV is plumbed to where the water can keep flowing, it can just keep flowing forever without hurting anything. Low pressure cut off switches only work if the leak is big enough to cause low pressure from the pump. They also make leak detectors that can be placed around the house where needed, and they can shut the pump off when a leak is detected.

If no one notices they left a facet on, the pump can run forever without damage as long as it is not cycling on and off. A Cycle Stop Valve will keep the pump from cycling even if it is just a 1 GPM leak. Running 24/7/365 won't hurt the pump. I have one pumping to a stock tank that hasn't shut off since 1996. But if the long run dries up the well, a Cycle Sensor can detect a dry run and shut the pump off before there is any damage.

Shutting the pump off is better than closing a valve. Even an 80 gallon pressure tank only holds 20 gallons of water. Then if using a CSV a much smaller tank, like 5 gallon actual size can be used. Using a leak detector to shut the pump off when there is a leak will let the tank drain into the house. That would be 20 gallons leaked from a large tank, but only 1.2 gallons from a 5 gallon size tank.

Cycle Sensor Pump Monitor – Cycle Stop Valves, Inc

Buy It! Interactive Animation General Information Specifications Wiring Diagram Installation Instructions Installation Video Troubleshooting

cyclestopvalves.com

 

[Towforce]

Anybody use one of these? ..... (a little on the expensive side, couple features look interesting like rapid cycle and amp load monitor).

5800060100 — PUMPTEC-PLUS SMT,.5-5HP,60HZ

Years of experience in designing and manufacturing our own motors mean that we also know how to protect them. Franklin’s single-phase pump protection devices have been exclusively designed to help

www.franklinwater.com

Martin