Scala2 thump on start, runs erratically.

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rsgard

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I bought and installed a Scala2 pump to help with my low pressure due to elevation. My incoming pressure is 30psi. When I set the pump any higher than 40psi it thumps when it kicks on and then runs erratically, changing rpms sometimes stopping for a split second, which results in another thump when it starts up.

I finally got around to trouble shooting it today. It appears that inlet check valve is allowing enough flow backward to pressurize the line between the pump and the check valve where it comes into the house (about 15' of 3/4 cpvc). When there is a call for water the pump starts and the check valve slams open causing the thump. The intake pressure jumps around quite a bit during this and I think it confuses the pumps controller and it runs erratically trying to maintain a constant output.

I'm waiting on the RMA to go through to refund/replace, the pump. My biggest question is this something that a functioning inlet check will fix or is it likely a design flaw and should I just get a refund and get a different pump.
 

rsgard

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I had removed the inlet check valve. Initially the pump stopped thumping and ran better but it did not last, it began thumping again within the hour.

I removed the outlet check valve and reinstalled the inlet check valve. This time I could hear the inlet check valve close with a very small click.

I dont think it was leaking back now. I realized the intake pressure going up to 40 from 30 when the pump stopped was the pressure of the moving water get trapped on the house side of the system check valve.

I no longer believe the thump is from a check valve. I attempted to run the pump with no internal check valves and it still thumped. When it thumps it hammers the intake line the hardest. I think instead of starting gently the motor starts hard and the intake pressure drops to zero for a split second causing hammer in the intake line. I'm not sure if its a problem with the sensors or the design. It seems most people think the thumping is normal.

I've reached out to Grundfos because I read about a recall but couldn't find the issue the recall was addressing.
 

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They have been recalling or "updating" all VFD type pumps for 30+ years now. It is all part of their planned obsolescence. The more electronic you have in a pump system, the less likely water is to come out of a faucet when opened, and the more it is going to cost you. A dumb pump will last 30 years and they don't like that. They will figure out a band-aid for the thumping on the next generation of VFD. It is always the next generation that is going to solve all the problems of the last generation. However some VFD pumps are in their 10th-12th generation. They solved some of the last problems but developed a "thump" in the process. Very typical.
jet pump PK1A.jpeg

"If I had only found this solution 10 years ago! I've suffered with mediocre water pressure for years from a "demand" pump system where you notice a pressure boost after a water demand is created. This system has given me all the pressure I could ask for and is CONSTANT - you notice no variation in pressure after the water demand begins and the pressure is excellent throughout your water demand. This system just plain works and will completely relieve your issues with your pump cycling on and off while the demand still exists, which creates pressure fluctuations. The quality of materials in this system is excellent with stainless fittings all the way." (from a customer review on the PK1A)
 

phil Tuttobene

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rsgard:
I was wondering how your new pump was working? Although it is true that most pump companies are reducing costs and building in obsolescence, not all companies follow this trend. There are engineering companies and there are "sales companies". Engineering companies have a passion for what they build, constantly improve and always striving towards perfection. They put quality and PR ahead of profit.

As a VFD consultant with over 40 years experience I get a bit disappointed when I hear about people that purchase a VFD controlled pump that is not built to last and more disappointed when I hear people say this is the norm. I can assure you it is NOT.

In a meeting last week with a long time Grundfos marketing manager, now working for a competitor, I shared my views with why the Grundfos Scalia2 is so problematic. Customers have given me their units to tear into and inspect. Of course they knew before hand that the pumps would never be usable again. Due to this inspection we came up with some clues to their problems and this helped me build better alternatives.

1) The Scalia uses a magnetic pin wheel to detect flow. Its embedded in the pump and it gets plugged up easily with Teflon tape, minerals or any contaminants in the water. When it fails, the pump fails and it's not serviceable.
2) The Scalia uses a bladder tank, its internal and if it fails, so will the pump and it's not serviceable.
3) The VFD is covered in plastic. Most VFDs are. This is a horrible design since plastic does NOT dissipate heat well.
4) The VFD board is not coated, if moisture builds up in the pump (easy due to plastic construction) the board will short.
5) The motor itself is very cheaply made, not a NEMA frame, not commercial quality, light bearings and light on iron.

Finally, a well designed VFD as described in my article soon to be published in Pump and Systems magazine should last 15-25 years. Some will say that is impossible. I can understand their apprehension. But then again, the VFDs they are accustomed to and I make a living repairing, are designed to fail. They have a 40 deg C operating temp. They are plastic, they have membrane keypads that will fail.

A well built VFD is IP66 (wash down duty, air tight so no outside air mixes with inside air) and is rated for 60 degrees C. The motor AND drive should be powder coated Aluminum as not to corrode and be TEFC with a minimum of an IP56 design. Even the color makes a difference, black dissipates the internal heat best.

Poorly designed VFDs & pumps pay my bills so I don't complain.

BTW, there is a reason pump companies do not build commercial pumps for the residential market. With quality, comes cost.
I could not survive on building pumps for residential. 9 out of 10 people that inquire about pricing simply are not willing to pay the money for a product that will last.

In the long run, they pay more, much more and that does not include the aggravation and time it takes to keep replacing cheaper pumps.

Lastly, there is a reason the Federal government has mandated the use of VFDs in commercial pumps over 10HP. All pressure reducing valves cause excessive energy loss. It is like driving your car and maintaining your speed with the brake as the gas pedal is kept to the floor. So if energy savings is not a big deal, go that route but over a period of 10-15 years, the energy you wasted would have paid for a commercial grade VFD controlled pump, depending on size.

All the best,
Phil Tuttobene
 
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LLigetfa

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All pressure reducing valves cause excessive energy loss. It is like driving your car and maintaining your speed with the brake as the gas pedal is kept to the floor.
I've read that poor analogy of the gas pedal/brake pedal but that does not apply to a pump that is not positive displacement. Energy use is roughly in line with gallons moved whereas a car would not get better gas mileage with you riding the brake pedal.
 

Valveman

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rsgard:
I was wondering how your new pump was working? Although it is true that most pump companies are reducing costs and building in obsolescence, not all companies follow this trend. There are engineering companies and there are "sales companies". Engineering companies have a passion for what they build, constantly improve and always striving towards perfection. They put quality and PR ahead of profit.

As a VFD consultant with over 40 years experience I get a bit disappointed when I hear about people that purchase a VFD controlled pump that is not built to last and more disappointed when I hear people say this is the norm. I can assure you it is NOT.

In a meeting last week with a long time Grundfos marketing manager, now working for a competitor, I shared my views with why the Grundfos Scalia2 is so problematic. Customers have given me their units to tear into and inspect. Of course they knew before hand that the pumps would never be usable again. Due to this inspection we came up with some clues to their problems and this helped me build better alternatives.

1) The Scalia uses a magnetic pin wheel to detect flow. Its embedded in the pump and it gets plugged up easily with Teflon tape, minerals or any contaminants in the water. When it fails, the pump fails and it's not serviceable.
2) The Scalia uses a bladder tank, its internal and if it fails, so will the pump and it's not serviceable.
3) The VFD is covered in plastic. Most VFDs are. This is a horrible design since plastic does NOT dissipate heat well.
4) The VFD board is not coated, if moisture builds up in the pump (easy due to plastic construction) the board will short.
5) The motor itself is very cheaply made, not a NEMA frame, not commercial quality, light bearings and light on iron.

Finally, a well designed VFD as described in my article soon to be published in Pump and Systems magazine should last 15-25 years. Some will say that is impossible. I can understand their apprehension. But then again, the VFDs they are accustomed to and I make a living repairing, are designed to fail. They have a 40 deg C operating temp. They are plastic, they have membrane keypads that will fail.

A well built VFD is IP66 (wash down duty, air tight so no outside air mixes with inside air) and is rated for 60 degrees C. The motor AND drive should be powder coated Aluminum as not to corrode and be TEFC with a minimum of an IP56 design. Even the color makes a difference, black dissipates the internal heat best.

Poorly designed VFDs & pumps pay my bills so I don't complain.

BTW, there is a reason pump companies do not build commercial pumps for the residential market. With quality, comes cost.
I could not survive on building pumps for residential. 9 out of 10 people that inquire about pricing simply are not willing to pay the money for a product that will last.

In the long run, they pay more, much more and that does not include the aggravation and time it takes to keep replacing cheaper pumps.

Lastly, there is a reason the Federal government has mandated the use of VFDs in commercial pumps over 10HP. All pressure reducing valves cause excessive energy loss. It is like driving your car and maintaining your speed with the brake as the gas pedal is kept to the floor. So if energy savings is not a big deal, go that route but over a period of 10-15 years, the energy you wasted would have paid for a commercial grade VFD controlled pump, depending on size.

All the best,
Phil Tuttobene

Hi Phil
Boy did you hit the nail on the head with most of that stuff. I can think of a few more, but you listed most of the problems associated with Variable Frequency Drives, or VFD controlled pumps. Whether there are no well built VFD's for domestic use because no one will pay the price required, or just because the manufacturers are taking out quality to build in planned obsolescence is a matter of opinion. Kind of like which came first the chicken or the egg. The fact is there are no well built VFD's made for the residential market.

The few well built VFD's made for the commercial market are priced accordingly. Which would be fine if they actually did save energy. Most of the VFD's I have seen that lasted any length of time used an air conditioner to keep them from overheating. And in many southern installations the air conditioner for the VFD uses more energy than the pump and VFD combined. Not a good way to save energy.

Then if you look at systems like the ones in the pump and well and fresh water supply business, there is always a static pressure to maintain. When maintaining a static or constant pressure, a VFD will always increase the energy used as the pump is slowed down. The drop in horsepower and flow rate is not linear. Reducing the RPM of a pump will cause the horse power to drop by 50% alright, but the resulting flow rate will decrease by 90%. This means a VFD can increase the cost per gallon of water pumped by 300% to 500%.

When the water in the well is always 100' deep and the house always needs 50 PSI (115' of head), the pump must always produce 215' of head, regardless of the flow rate being used. Look at your pump curve. According to the Affinity Law when maintaining a constant head or pressure the pump can only be slowed by 10%-20% at most. With the drop in horsepower being many times less than the drop in flow rate, the cost per gallon pumped goes up, not down. Only with positive displacement pumps and pumps for friction dominated systems like large chillers could there possibly be any energy savings from a VFD. And nearly all pumps in the well pump and fresh water supply business use centrifugal impellers and are not positive displacement.

Then like LLigetfa says your analogy of one foot on the brake and one on the gas does not work with centrifugal type pumps. When the output of a pump with a regular centrifugal impeller is restricted, the horse power is reduced almost exactly as much as if you reduced the RPM. If you are going to say a VFD reduces energy consumption, then you have to say restricting with a valve also saves energy, because the cost per gallon will be almost exactly the same between a VFD and a valve.

It is a fact that restricting the flow rate of a pump with a valve will reduce the horsepower almost exactly the same as slowing the RPM with a VFD. This is a completely counter intuitive property of the centrifugal impeller. I would venture to say that only 2%-5% of the engineers in this world understand this counter intuitive property. Engineers don't do well with counter intuitive things. Everyone, even most engineers have it in their heads that restricting a pump with a valve makes the pump work harder, which is the opposite of the truth. Some of them get very angry with me for saying "restricting a pump with a valve makes the pump work easier", but that is a fact.

Lastly, the engineers who work for the Federal Government are obviously not in that top 2% to 5% of engineers who really understand how pumps work. Mandating the use of a VFD on pumps of any size is ludicrous, as it will actually increase the energy consumption in any system maintaining a static head or constant pressure. When a review of the actual work needed to be accomplished is done, (ie; pump x amount of gallons at y pressure), a VFD will always increase the amount of energy used. The fact that a VFD reduces the energy needed to spin the pump and motor confuses people into thinking a VFD saves energy pumping water, and that is far from the truth.
 

phil Tuttobene

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"
The fact is there are no well built VFD's made for the residential market.
"
UNTRUE. Sorry but I design and repair VFDs for a living. Our VFD is all aluminum, IP66 with a 60 degree C operating temperature. NO PLASTIC, conservatively designed power components with PRV voltages doubled from any competitor. If a replacement is ordered, it costs $300.00 for a 2HP unit that provides up to 9 amps at 230v 3 phase out, 1 phase in. So it does not really cost a lot but it's all relative to whats out there.

When I have time I will show you in real time on our test stand the KW of choking a centrifugal pump at full speed vs. reducing the speed to maintain pressure. Our test stand will chart this in real time. You are INCORRECT, we have proven reducing the speed of a VFD saves over choking the discharge on a centrifugal single stage booster pump.

BTW, I personally know the people that helped author this law. They know what they are doing.

I am discussing a booster pump here, NOT a well pump. One of the largest pump companies in the world are presently evaluating our VFDs to be used on their pumps. The resultant product, if accepted will be a well pump but more importantly they are considering using our VFDs on larger commercial buildings up to 600HP. I have designed many high rise systems including the Freedom tower in NYC. 106 stories, we use pressure reducing valves in the lower zone BRANCHES but VFDs on the main headers.
 

rsgard

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It seems like all the individual components of a "constant pressure pump" are sound technologies but they aren't engineered to work well/reliably at the price marketed for residential use.

I have a decent understanding of moving water, mostly with Hale QMax pumps, and it was very frustrating that I could not get this pump to behave. I read several account of a click on startup with the Scala but I didn't believe I had the same issue because in my case the intake line was getting hammered on start.

I'll be going with a CSV and jet pump once the Scala is returned. I know I've got the volume because I can open every faucet/shower in the house and the residual pressure is only 4-5 psi less than static.

As far as the CSV is concerned I know I'd only need the 4-5 gallon tank, but my understanding is that a 10 gallon would decrease the cycles? Trying to decrease the noise. The jet pump is going in the basement.
 

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"
The fact is there are no well built VFD's made for the residential market.
"
UNTRUE. Sorry but I design and repair VFDs for a living. Our VFD is all aluminum, IP66 with a 60 degree C operating temperature. NO PLASTIC, conservatively designed power components with PRV voltages doubled from any competitor. If a replacement is ordered, it costs $300.00 for a 2HP unit that provides up to 9 amps at 230v 3 phase out, 1 phase in. So it does not really cost a lot but it's all relative to whats out there.

When I have time I will show you in real time on our test stand the KW of choking a centrifugal pump at full speed vs. reducing the speed to maintain pressure. Our test stand will chart this in real time. You are INCORRECT, we have proven reducing the speed of a VFD saves over choking the discharge on a centrifugal single stage booster pump.

BTW, I personally know the people that helped author this law. They know what they are doing.

I am discussing a booster pump here, NOT a well pump. One of the largest pump companies in the world are presently evaluating our VFDs to be used on their pumps. The resultant product, if accepted will be a well pump but more importantly they are considering using our VFDs on larger commercial buildings up to 600HP. I have designed many high rise systems including the Freedom tower in NYC. 106 stories, we use pressure reducing valves in the lower zone BRANCHES but VFDs on the main headers.

Booster pump, well pump, any pump with a centrifugal impeller will work the same. If you have figured out how to make a VFD last for any length of time, you have accomplished something nobody else has been able to do in 30+ years. I am glad you are having good luck selling your VFD's, but they are an easy sell because of the myth-understanding about energy savings. There is a sucker born every minute.

If in your test stand you are maintaining a low pressure with a booster pump that can build high pressure, then you will be able to slow it down quite a bit. But if you are maintaining a high pressure, closer to the BEP of the booster pump, you won't be able to slow it down much or reduce the energy consumption. Even then anytime you reduce the RPM of a pump, it takes more energy to pump a gallon of water than when the pump is running at full speed and BEP. There is nothing more efficient than a pump running at full speed at its Best Efficiency Point (BEP). Anything else is WASTING energy in comparison. It is all about what you are comparing it too. If you compare to a greatly over-sized pump, the VFD can show some savings. If you compare to a correctly sized pump, a VFD will always increase the energy consumption.

In your test stand measure how many gallons you can pump per KW with the pump running at full speed and BEP. Then you will see that any reduction in speed using the VFD will decrease the gallons per KW.

And I am sorry to talk badly about people you personally know, but they do not know how to read a pump curve or they would never claim a VFD can save energy.

Here is a video of my test stand.
 
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Valveman

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Here is a technical paper from Grundfos. The top is my response, the bottom is the original memo from Grundfos. If I said anything incorrect in this article, which is now 8-10 years old, I would have at least got a reply if not a summons. They didn't do anything because everything I said is true. You just have to be able to read a pump curve to see that VFD's do not save energy.

https://cdn.shopify.com/s/files/1/0147/4392/files/pumpman_3.pdf?6329703011502475871

BTW this is a booster pump and Grundfos produced these curves that show little to no difference in energy consumption between a VFD and a CSV. Reputable pump companies no longer claim energy savings as a sales tool for VFD's. But the myth survives!
 
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LLigetfa

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You are INCORRECT, we have proven reducing the speed of a VFD saves over choking the discharge on a centrifugal single stage booster pump.
. . .
I am discussing a booster pump here, NOT a well pump...
Then we are talking apples versus oranges. IMHO most installations will be with multi-stage submersibles and the current drop on those will vary based on their design, with floating impellers drawing more.

I am sure anyone can design a test to get a particular result to support their theories.
 

Valveman

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This is usually where I get told that I am entitled to my own opinion, but that is just not possible. Well here is a pump curve for you with a booster pump system requiring 145' of lift, which is the same as 62 PSI boost. The flow rate needed can vary from 50 GPM to 250 GPM, but the height of the building being serviced requires 145' of lift all the time.

Without a VFD a full speed regular pump uses 13 HP to produce 250 GPM, which is 19.23 Gallons Per Horsepower.

Slowing the pump with a VFD when only 50 GPM is being used requires 6HP to pump 50 GPM, which is 8.33 Gallons Per Horsepower.

The energy needed to spin the pump reduced from 13HP to 6HP by slowing the RPM with a VFD. That is easy math. The VFD just saved 54% in energy right? WRONG!!!! That is the hook that feeds the myth and makes people THINK a VFD saves energy.

Even though the energy needed to spin the pump dropped from 13HP to 6HP, the energy needed to pump the water increased by 230%.

Only 8.33 Gallons Per Horsepower using a VFD compared to 19.23 Gallons Per Horsepower with a normal speed pump means the VFD is increasing the energy consumption by 2.3 times or 230%. It is as plain as the curve on this page.
B2.5 Variable speed calculations.jpg
 

Valveman

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Now lets use that same pump curve to look at your "one foot on the brake and one on the gas" analogy for using a valve to control the pump. Notice the energy required drops from 13HP to 7HP, WITHOUT EVER REDUCING THE RPM BELOW FULL SPEED OF 3450 .

Slowing the pump down to 3278 RPM with a VFD only makes 1HP difference, reducing the energy used to 6HP in the 50 GPM flow scenario.

Actual energy saved by the VFD would only be 7% compared to controlling the pump with a valve like a CSV. I can assure you 7% energy savings is never going to pay off the added expense of a regular VFD, much less one that is designed to last and priced accordingly, if that is even possible.

Even when a VFD controlled pump is running at full speed and should be at its most efficient, the power needed to operate the VFD itself adds more to the cost of pumping water. High flow or low flow, when a constant pressure must be maintained a VFD always increases the energy cost.

When you realize energy consumption is almost exactly the same with a CSV as with a VFD, you will understand how silly that "one foot on the brake and one on the gas" analogy looks.

Again, everything you need is in the pump curve. You just have to know how to read it. I hope my marking up these curves helps you understand.

PS; It gets even worse with larger pumps as they tend to be 1750 RPM. Since VFD's cause head to be lost by the square of the speed, there is even less room for a VFD to be useful with 1750 RPM pumps compared to 3450 RPM pumps.

B2.5 CSV verses VFD.jpg
 

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This thread started with the same problem I have, but seems to have gone off the rails to a very interesting technical discussion.

Anyway, I just had a SCALA2 pump installed and it also thumps while it’s hunting for the right pump speed. Is there anyone out there that has this pump and it doesn’t thump? If it’s some sort of operating characteristic, I’d appreciate options.

City water, 64 psi at meter, no pressure regulator, want to be able to get 50 psi to my second floor at 6 gpm. I have another thread going about problems with my softener, but based on my measurements I’m going to need a booster to get there.
 

Valveman

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The Scala2 is a booster pump, just not a very good one. They are made to be easy to install, so you can easily install a new one every year or two at best. A regular jet pump like a Goulds J5s and a PK1A constant pressure control kit will be much more reliable and longer lasting. And there will be no thumping.

PK1A with Jet Pump vertical sized.jpg
 

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Thanks for the advice, I've seen these around this site a bunch. Can you comment on how much noise that pump might make? How exactly does a Cycle Stop Valve work?
 

Valveman

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The CSV doesn't make any noise. But a good pump made with good metal and enough meat to give you strong pressure and last a long time is going to make some noise. You can put these in an insulated and vented box to quieten them down. Not any louder than a washing machine or a dishwasher though.

 

Timothy Stuart

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I bought and installed a Scala2 pump to help with my low pressure due to elevation. My incoming pressure is 30psi. When I set the pump any higher than 40psi it thumps when it kicks on and then runs erratically, changing rpms sometimes stopping for a split second, which results in another thump when it starts up.

I finally got around to trouble shooting it today. It appears that inlet check valve is allowing enough flow backward to pressurize the line between the pump and the check valve where it comes into the house (about 15' of 3/4 cpvc). When there is a call for water the pump starts and the check valve slams open causing the thump. The intake pressure jumps around quite a bit during this and I think it confuses the pumps controller and it runs erratically trying to maintain a constant output.

I'm waiting on the RMA to go through to refund/replace, the pump. My biggest question is this something that a functioning inlet check will fix or is it likely a design flaw and should I just get a refund and get a different pump.
Hello I have the same issue. Did you ever discover a fix for this issue?

Thank you
 
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