2 hp Franklin pump not drawing enough amps?

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Alan Waterman

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Hi. I have a MonoDriveXT with a 2hp motor with a 25fA2S4-PE that was installed back in 2014. It draws 11.4 amps (input from 240 volt supply side) or about 2750 watts (varies from 2700 to 2800 when running at full bore).

After comparing notes with some neighbors on their 2 hp pumps (most have upgraded to 2 hp by now from their 1.5 hp motors as the water level has dropped enough to warrant it), it seems like I'm not drawing anywhere near enough current for a 2 hp motor. It appears to be closer to that of a 1.5 hp motor.

The original installer admits that it's possible that it's a 1.5 hp motor rather than what was invoiced but I'd like to rule out anything I can. The installer asked me to measure the output frequency to the pump to make sure it's running a full 60 Hz, however the monodriveXT appears to run much higher frequencies due to it's VFD control. I'm seeing 36, 44, and 52 kHz depending on which 2 wires I measure of the 3 wires.

The first two dips on the left for SW1 are Up and Down (for 2 hp).

Any ideas? Defective motor? 1.5 hp motor after all? Can a 1.5 hp motor even be attached to a 25 gpm 2hp pump? Issue with the monodriveXT?

My next step will be to temporarily swap out a simple Franklin 2hp single phase control box to eliminate the electronics as a possibility but that won't arrive for another week. Figured I should have a swappable backup anyways in case the fancy constant pressure control goes out.

Note that I'm not having any issues other than not getting the expected flow from the 2 hp motor and pump end combo but that's been the case since it was installed. I never though to check that the 2800 watts that it draws is actually the right amount of power for a 2 hp motor.
 

Fitter30

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With a pump curve and depth can compare shut off pressure. Might have to talk manufacturer with technical or engineering to compare readings . Looking a install manual see your control has only lights not a display. Output of vrd is pulse- width modulation output need some high tech meter or scope to measure cycles.
 
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Valveman

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I am always surprised when any VFD or the pump it controls last 10 years. That is not what I normally hear. Anyway, volts times amps equals watts. 2800 watts at 240V is 11.6 amps, which is the same as the incoming amps. Incoming amps should be a little higher than the outgoing amps, as the VFD itself is what used the extra energy.

You are right to swap the Monodrive for a regular 2HP control box. Then if the amps are still 11.4-11.6 it is a 1.5HP pump and motor. A 2HP will draw 13.2 amps.

After switching to a regular 2HP control box you can add a Cycle Stop Valve like the CSV125-1 and have constant pressure without all the headaches and expense of varying the pump speed. Because yeah, the fancy variable speed controller will go bad. I can't believe it hasn't already.

 

Alan Waterman

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Forgot to add this bit. This is with sprinkler zones running 40 to 45 PSI with the controller setpoint at 60 PSI. Adding this because the Franklin support rep replied to my nearly identical email to them saying that I must not be using enough water to allow for full speed operation.
 

Alan Waterman

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I am always surprised when any VFD or the pump it controls last 10 years. That is not what I normally hear. Anyway, volts times amps equals watts. 2800 watts at 240V is 11.6 amps, which is the same as the incoming amps. Incoming amps should be a little higher than the outgoing amps, as the VFD itself is what used the extra energy.

You are right to swap the Monodrive for a regular 2HP control box. Then if the amps are still 11.4-11.6 it is a 1.5HP pump and motor. A 2HP will draw 13.2 amps.

After switching to a regular 2HP control box you can add a Cycle Stop Valve like the CSV125-1 and have constant pressure without all the headaches and expense of varying the pump speed. Because yeah, the fancy variable speed controller will go bad. I can't believe it hasn't already.


The MondriveXT was actually installed in 2013. I honestly don't think it will ever die and if it does, the 10 years and 5 months it's been since installing it I'll happily buy another.
 

Alan Waterman

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With a pump curve and depth can compare shut off pressure. Might have to talk manufacturer with technical or engineering to compare readings. Output of vrd is pulse- width modulation output need some high meter or scope to measure cycles. Standard vfd can read it on the drive and amps. Not familiar with your control.

My Fluke 77 can read the frequency just fine but it doesn't tell me what the higher frequency means in terms of the load. Again, we're talking full power since I'm running sprinklers at well below the target setpoint. It never exceeds 2800 watts.
 

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I have a pump that has been in the well since 1982 and running on a Cycle Stop Valve most of that time. That would be 10-12 year life of something that cost thousands to replace compared to something with a 40 year life than cost a couple hundred. :)
 

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Good chance that the reason my VFD has lasted so long is that I got the NEMA 4 version which has a very extreme operating temperature range with a massive and very loud cooling fan yet it's been mounted in doors it's entire life. I got the NEMA 4 version because it was only $995 vs something like $1400 for the indoor version(due to an awesome sale).

But you've definitely put me on my guard about the possibility of it failing. When I get the $180 Franklin control box I ordered to rule out the the Monodrive as the issue, I'm going to do a tear down and order replacement caps.

Now the purpose of my first post above is to try and rule out other possibilities. The installer believes it's likely that he just installed a 1.5 hp pump instead of 2 and has offered to make it right if that's what happened but I want do as much myself to rule out anything else and the biggest variable is a high tech VFD controller.
 

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Do you have a symptom, other than your finding the current is less than expected?

How are you measuring the current?

Does your system reduce the frequency below 60 hz? I would expect that would cause a clamp-around ammeter to read low. Or is your system one that keeps the 60 Hz, but turns the pump on and off more frequently?
 
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Alan Waterman

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Do you have a symptom, other than your finding the current is less than expected?

How are you measuring the current?

Does your system reduce the frequency below 60 hz? I would expect that would cause a clamp-around ammeter to read low. Or is your system one that keeps the 60 Hz, but turns the pump on and off more frequently?

Using a clamp meter on the circuit side so the 11.4 amps is certainly more than the pump itself is pulling since there's overhead for the VFD. The 11.4 amps is a ceiling so the pump can't be pulling more than the controller is being fed. Unfortunately, the VFD frequency measures in the kHz between the common and run wire on a Fluke 87(not actually the 77). So would probably need a scope if the output frequency can be interpreted. That's why I ordered a simple control box a single cap and no other electronics to provide and emergency backup and as a diagnostic.

Wattage is also constantly monitored with a CT. I have CTs on every single circuit in the main panel and two sub panels. I like to know how much electricity everything uses and I use system wide monitoring with alerts to both proactively look for waste and get alerts on unusual patterns.

I also have pressure sensor hooked up to CAI WebControl analog input to monitor pressure in real time. Using the pressure plus the current sprinkler zone pulled from the REST API on my sprinkler controller, I know what zone is running and what the pressure is. For instance, I got an alert last night when zone 4 was running that the pressure dropped below the minimum 43 PSI level for that zone so I knew something busted. Went out and checked with a flashlight and one of the sprinkler heads had popped off and a jet of water was shooting in the air.

I'm not having a new issue. It's been like this since since installing the the new pump and motor back in 2014. The old pump and motor are still fine. I just needed to lower my pump due to the water table dropping and figure I'd go new since the original was 16 years old.
 

Fitter30

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With the Franklin control that amperage , dead head pressure and depth with the proper pump info will tell what pump you have. With this info a discussion with your installer and the vfd manufacturer can go over all the settings. Every flow device has a pressure drop. Includes check valves, shut off valves, strainer or filters. Pump specs might published flow without discharge check valve. Pitless fitting some are built like a tee house water comes out from the side ( bull). How many feet and ells (90°) from well to gauge and pipe size.
 

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Using a clamp meter on the circuit side so the 11.4 amps is certainly more than the pump itself is pulling since there's overhead for the VFD. The 11.4 amps is a ceiling so the pump can't be pulling more than the controller is being fed.
That would not violate a law of physics, such as conservation of energy. Suppose the controller accepts 252 VAC from the breaker, and presents power factor 1. Then suppose the pump gets sent 240 volts and presents a 0.8 power factor.

I understand that this ignores inefficiencies (energy consumption) in the conversion. It might be interesting to read the current thru the yellow wire while the frequency is 60 hz.
 

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That would not violate a law of physics, such as conservation of energy. Suppose the controller accepts 252 VAC from the breaker, and presents power factor 1. Then suppose the pump gets sent 240 volts and presents a 0.8 power factor.

I understand that this ignores inefficiencies (energy consumption) in the conversion. It might be interesting to read the current thru the yellow wire while the frequency is 60 hz.

Right, so 2700 to 2800 watts in, assuming 100% efficiency, which it's not, and that is still not enough to produce 2 hp.
 

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With the Franklin control that amperage , dead head pressure and depth with the proper pump info will tell what pump you have. With this info a discussion with your installer and the vfd manufacturer can go over all the settings. Every flow device has a pressure drop. Includes check valves, shut off valves, strainer or filters. Pump specs might published flow without discharge check valve. Pitless fitting some are built like a tee house water comes out from the side ( bull). How many feet and ells (90°) from well to gauge and pipe size.

I've been through all the static and dynamic head calculations. This has nothing to do with my question.
 

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Fitter was not doing dynamic head calculations. He was saying that if you know the deadhead pressure and depth to water, we can figure which size pump you have. But if nothing has changed and it has always been the same, the pump is most likely a 1.5HP because of the amperage. If you are having to set the pump deeper because of a lower water table, you will need a larger pump to make up for the extra head. Or, you will just get less flow with the same pump.

You will need a scope or something to see the output frequency. But as far as I know the monodrive never came with a pressure transducer, only a switch. The switch basically just turns the pump on and off about 45 times a minute, which is how it maintains pressure. At the set pressure the switch opens, which stops the pump. But within a second or so the pressure is below the set point and the switch makes again, starting the pump. When not using max flow the pump can produce the switch basically makes and breaks 45 times a minute, which brings the pump to 60Hz, then off, over and over. If the input amps are locked in at 11.4, then you must be using enough water to keep the pressure below the switch set point. With the switch staying in the closed position, the pump should be running full speed at 60Hz. VFD controllers usually either work or they don't. They do no usually just stop getting all the way to 60HZ. Especially the monodrive, as it basically works at 60Hz or is off.
 

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input power (252V* 11.4A)=2872.8W.
Aim Manual, page 13, or 2 HP at "full load". Amps in yellow wire: 10.0.

For maximum load, 2555 W and yellow 13.2A
 

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Fitter was not doing dynamic head calculations. He was saying that if you know the deadhead pressure and depth to water, we can figure which size pump you have. But if nothing has changed and it has always been the same, the pump is most likely a 1.5HP because of the amperage. If you are having to set the pump deeper because of a lower water table, you will need a larger pump to make up for the extra head. Or, you will just get less flow with the same pump.

You will need a scope or something to see the output frequency. But as far as I know the monodrive never came with a pressure transducer, only a switch. The switch basically just turns the pump on and off about 45 times a minute, which is how it maintains pressure. At the set pressure the switch opens, which stops the pump. But within a second or so the pressure is below the set point and the switch makes again, starting the pump. When not using max flow the pump can produce the switch basically makes and breaks 45 times a minute, which brings the pump to 60Hz, then off, over and over. If the input amps are locked in at 11.4, then you must be using enough water to keep the pressure below the switch set point. With the switch staying in the closed position, the pump should be running full speed at 60Hz. VFD controllers usually either work or they don't. They do no usually just stop getting all the way to 60HZ. Especially the monodrive, as it basically works at 60Hz or is off.
According to the specs in the manual model 58702044114 uses frequency to adjust speed. 2hp 16 amp max, 1.5 hp13 amps
Screenshot_20230718-102837.png
 

Alan Waterman

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Thanks folks. Just heard back from Franklin after providing them with more details and data. On thing I left out that I remembered after re-reading my emails to the installer:

Shortly after this pump was installed, I got nuisance underflow errors requiring resets. It would happen when in the shower while the pump was soft cycling on and off and holding at the 60 psi set point. The same Monodrive XT controller never through an underflow error on the previous 18gpm 1.5 hp pump/motor.

The installer couldn't figure it out and called in a local Franklin field rep to come out and look at the problem. His solution was to turn dip switch 3 to the on position and turn the pot all the way to the shallowest setting...despite the water level being 110 feet deep which is not a shallow well.

According to Franklin, if you run a 1.5 hp motor on the Monodrive XT with the 2 hp setting, it doesn't actually change the power drawn by the pump. It just tells the controller what it should expect. In this case, running a 1.5 hp in my scenario with the dip set to 2 hp, the controller is expecting a current appropriate for 2 hp but it doesn't see it so it throws underflow errors.

The Franklin rep says that I'm running a 1.5 hp motor.
 

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We knew it was a 1.5HP from the 11.4 amps you mentioned. Makes sense that a 2HP controller would trip on underload when running only a 1.5HP pump. I am glad you figured it out and understand you can only use 1.5HP worth of water. Most people would have given up on the Monodrive when it was nuisance tripping and they figured out it was "soft cycling" on and off rapidly instead of varying the pump speed the way a real VFD does. That is the first time I have heard it called "soft cycling", which I guess is better than "hard cycling" Lol. But cycling anyway you do it is not good for the pump system. And the Monodrive and Subdrive using the switch, "soft cycling" is just the way they work as they never just stay on at a reduced speed, they just go on and off about 45 times a minute.

Well over 30 years ago I too thought VFD's were the greatest thing invented. But then I started understanding how they really work and realized the multitude of problems and great expense that goes with a VFD. The idea of a VFD is a good thing, but the reality is they are expensive and more trouble than they are worth. The amps of a full speed pump will drop when the flow is restricted with a simple valve the same as when reducing the pump speed with a VFD. When you understand this natural way centrifugal pumps work it makes a simple, inexpensive, long lasting constant pressure valve a better pump control than a VFD.
 
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