Sorry Man. Still confused. So there is a way to make it run continuously until demand is satisfied? He is saying it just thinks demand is satisfied when the hertz stabilize anywhere?
Pentek PID30 VFD Questions
- Thread starter Arlen Angell
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Boycedrilling
In the Trades
If the pump is running at MINIMUM hz with psi at set point psi and no drop in pressure for the duration of the boost delay, it then boosts pressure and then shuts off. the preset on the boost delay is 1 minute but can be adjusted to up to 5 minutes. the boost differential is preset at 3 psi. I normally adjust this to 5 psi, it can be up to 10 psi.
The pump then Shuts off until the wake up differential pressure is reached. The preset is 5 psi. I normally adjust this to the max of 15 psi. This gives me the full 20 psi drawdown of the pressure tank. And no, I don’t use a small pressure tank. I use an 80 gallon tank on all installs unless there is physically not room for a big tank.
Even though you recommend against it, I also use a full sized tank on CSV installs.
I give all my customers the option of a conventional pressure switch system, a pressure switch with a CSV, and a VFD system. We discuss the costs and benefits of all the systems and then make a decision as to what is best for their particular installation.
The pump then Shuts off until the wake up differential pressure is reached. The preset is 5 psi. I normally adjust this to the max of 15 psi. This gives me the full 20 psi drawdown of the pressure tank. And no, I don’t use a small pressure tank. I use an 80 gallon tank on all installs unless there is physically not room for a big tank.
Even though you recommend against it, I also use a full sized tank on CSV installs.
I give all my customers the option of a conventional pressure switch system, a pressure switch with a CSV, and a VFD system. We discuss the costs and benefits of all the systems and then make a decision as to what is best for their particular installation.
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Thanks man. That is the way I understood sleep mode to work. Then something must be wrong with his PID as it doesn't wait for minimum hertz. It apparently goes into sleep mode when running at any stable hertz for a certain amount of time.
Arlen Angell
New Member
You had it right. We are not confused. Minimum Freq has nothing to do with it. I wish I was confused.
I got this today straight from a Pentair Engineer...He confirmed what I already knew.
Hi Arlen
Below is a graph of the boost and sleep operation. The design engineers when this drive was being developed thought this was a better way for the sleep function to perform.
Other drives will allow setting a frequency slightly above min speed and when the drive goes below this frequency and adjustable time delay is programmed and then the drive goes to sleep.
I will also call you late afternoon today.
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Arlen Angell
New Member
Wow! So the Pentair PID variable speed drive doesn't hold a constant pressure or keep the pump from cycling on/off. That curve looks like a cycle from a regular pressure tank/pressure switch. I guess if it is going to cycle the pump on/off that many times the soft start and soft stop feature is pretty important.
Arlen Angell
New Member
Yes, Soft Start is a must! It definitely cycles more than a 60/40 pressure switch. I could set the wake deviation to 15 PSI and get more draw down, but the constant, even pressure is their selling point!
I could maybe make the PID control loop a little more unstable so it hunts around a little. Seems hoaky though.
Like the engineer said, their other drive listed in their electronics manual operates the way I want...just not the PID.
I played with it a little more last night...I increased the flow till the drive was operating at 50hz to maintain 60psi. I suppose 5 gpm maybe. It went right to sleep when the timer expired, then came right back on a about a minute later.
Kind of crazy when you think about it.
I could max out the sleep delay timer to 5 minutes, but it will still go to sleep after 5 minutes. But then it will run for 5 minutes EVERY TIME I SHUT OFF THE FAUCET.
At least it doesn't go to sleep when I'm watering cows at 55hz since I'm only building about 20 psi
Arlen Angell
New Member
I think I have a decent work around. I don't like the idea of increasing the boost delay, as that just kicks the can down the road.
1) I leave the boost delay at the default of 1 min (number 1 on the chart)
2)Leave the boost differential set to the default of 3 psi
3) Extend the wake delay to the max of 2 minutes (default is 30 sec) (#3 on the chart)
What this does for me... during the wake delay, it starts dropping the pump speed. If you are still using water, the pressure starts dropping. If it drops below setpoint, then the drive terminates the ramp down and resumes PID control.
If you aren't using water then the pressure holds near the Setpoint + Boost Differential as the Freq ramps down, and the drive will go to sleep when the wake delay expires.
So the drive goes from PID control, to pressure boost, to ramp down, to PID control over and over but does not shut down with a normal shower.
The pressure fluctuates between 58 and 63 which isn't bad.
If I could increase the wake delay to 3 minutes, I would, but 2 minutes is the max.
If I had it my way, I would put the wake delay at the begining...
1) Look for stable frequency
2) Begin ramping down to test for water flow
3) if no water flow, pressure boost and sleep
4) If water flow, go back to pid control
1) I leave the boost delay at the default of 1 min (number 1 on the chart)
2)Leave the boost differential set to the default of 3 psi
3) Extend the wake delay to the max of 2 minutes (default is 30 sec) (#3 on the chart)
What this does for me... during the wake delay, it starts dropping the pump speed. If you are still using water, the pressure starts dropping. If it drops below setpoint, then the drive terminates the ramp down and resumes PID control.
If you aren't using water then the pressure holds near the Setpoint + Boost Differential as the Freq ramps down, and the drive will go to sleep when the wake delay expires.
So the drive goes from PID control, to pressure boost, to ramp down, to PID control over and over but does not shut down with a normal shower.
The pressure fluctuates between 58 and 63 which isn't bad.
If I could increase the wake delay to 3 minutes, I would, but 2 minutes is the max.
If I had it my way, I would put the wake delay at the begining...
1) Look for stable frequency
2) Begin ramping down to test for water flow
3) if no water flow, pressure boost and sleep
4) If water flow, go back to pid control
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That is a pretty ingenious work around! It is just a shame you have to go to that trouble and have to put up with the pressure fluctuation and surging because that PID brand controller won't do what it should. I have one of the older Pentek drives on a trade show demonstrator and it doesn't work like the PID. But it has plenty of other problems, which is why they are trying other crazy stuff like what the PID is doing. You can see the old (10 years maybe) Pentex drive in this video.
HillsboroBob
New Member
This is brilliant information, the whole thread. A gold mine. I have the same concerns/problem with my new Pentek PID20, so I'll attempt the fix and extend the wake delay.
As of this date and software version 3.07 and 3.07, it is still a problem.
As of this date and software version 3.07 and 3.07, it is still a problem.
Let us know how it works. We also use Cycle Stop Valves to fix the problems with variable speed pumps a lot of the time. Setting the CSV slightly lower pressure than the set point of the PID will keep the pump running continuously as long as you are using more than the 1 GPM minimum built into the CSV. Then when not using any water the 1 GPM coming through the CSV will fill the pressure tank to the set point of the PID or VFD. The CSV will only let the PID go to sleep when there is no water being used, the way it should be.
HillsboroBob
New Member
This worked well, I initially extended the delay to 4 minutes, but it was unnecessary given the throughput of water with two sprinkler heads running. So I backed it down to 1 minute wake delay. My constant use levels out at 42 hz for a 16 gpm pump, 50 ft static water level, and 160 ft pump depth.
At least it is working well for now. When the VFD controller starts giving you problems, and it will, because that is what VFD controllers are designed to do, remember it can easily be replaced with a simple, mechanical, inexpensive, and long lasting Cycle Stop Valve.
Naked_Intruder
New Member
@Arlen
It would appear you ran into issues with the Wake Delay default setting because you are using a rather large (60gal) pressure tank with this Pentek VFD. Probably nothing wrong with that but it needs to be accounted for in the settings.
Here's the install/config pdf:
1) See the Wake Delay setting mentioned with larger tanks. You have a lot of psi reserve in that 60 gal tank so the system simply thought no draw was active and continued to sleep until the Wake Up Differential was met. Thus it kept cycling the pump even on a constant draw for low gpm activities like running a faucet.... Now that you have adjusted the Wake Delay to match your pressure tank size, the system can realize a draw and not stop the pump until the draw is stopped.
Probably would be better if their system had a sensor in the water line that could also detect water flowing and then they would not need to be doing all this psi boost business to test for draw. Not exactly an efficient process.
"PRESSURE TANK RECOMMENDATIONS Minimum tank size is two gallons. Use a pre-charged pressure tank with Intellidrive, as shown in Table 1. The tank size must equal at least 20 percent of the pump’s rated flow in gallons per minute (GPM), but cannot be less than two gallons capacity. For example, a pump rated at 7 GPM would require a tank of two gallons capacity or larger. A pump rated at 50 GPM would require a 10 gallon tank or larger. Tanks larger than 10 gallons can be used, but may require adjustment of Wake Delay parameter."
2) Recommended psi of the pressure tank should be 70% of psi setting. Assuming your PID is set to 60 psi as stated, that pressure tank should be 42 psi (60*.7) not 47 as stated. Perhaps that is also contributing to issues....
"Set pressure tank’s pre-charge to 70 percent of the system operating pressure. When using an external set point as well as an internal set point, pre-charge tank to 70 percent of the lower setpoint of the two. Some applications may require a different percentage when determining the setpoint."
The answer is always in the details. ; )
It would appear you ran into issues with the Wake Delay default setting because you are using a rather large (60gal) pressure tank with this Pentek VFD. Probably nothing wrong with that but it needs to be accounted for in the settings.
Here's the install/config pdf:
1) See the Wake Delay setting mentioned with larger tanks. You have a lot of psi reserve in that 60 gal tank so the system simply thought no draw was active and continued to sleep until the Wake Up Differential was met. Thus it kept cycling the pump even on a constant draw for low gpm activities like running a faucet.... Now that you have adjusted the Wake Delay to match your pressure tank size, the system can realize a draw and not stop the pump until the draw is stopped.
Probably would be better if their system had a sensor in the water line that could also detect water flowing and then they would not need to be doing all this psi boost business to test for draw. Not exactly an efficient process.
"PRESSURE TANK RECOMMENDATIONS Minimum tank size is two gallons. Use a pre-charged pressure tank with Intellidrive, as shown in Table 1. The tank size must equal at least 20 percent of the pump’s rated flow in gallons per minute (GPM), but cannot be less than two gallons capacity. For example, a pump rated at 7 GPM would require a tank of two gallons capacity or larger. A pump rated at 50 GPM would require a 10 gallon tank or larger. Tanks larger than 10 gallons can be used, but may require adjustment of Wake Delay parameter."
2) Recommended psi of the pressure tank should be 70% of psi setting. Assuming your PID is set to 60 psi as stated, that pressure tank should be 42 psi (60*.7) not 47 as stated. Perhaps that is also contributing to issues....
"Set pressure tank’s pre-charge to 70 percent of the system operating pressure. When using an external set point as well as an internal set point, pre-charge tank to 70 percent of the lower setpoint of the two. Some applications may require a different percentage when determining the setpoint."
The answer is always in the details. ; )
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I can see where a flow sensor would keep it from pulsing from 58 to 63 PSI over and over to see if water is being used. But flow sensors are not dependable and have been tried many times before, which is why they are now trying the boost/delay thing. There have been countless Band Aids tried on VFD's in the last 30-40 years for problems such as this. So many details and they still have not found the answer to all the problems with VFD's. All you need is water to come out of the faucet at a steady pressure when needed, and the simpler way of doing that with a CSV is much more dependable.
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