Question for Anyone using Single Hose / VFD Self Serve System.
- Thread starter softsuds
- Start date
thoffmanjr
Member
Ours is at application strength. We use a GC Valve 6 port inlet manifold. Soap/Rinse, Bug, Degreaser, Presoak, Wax, and Spot Free. We are not seeing any ill effects doing it. The PLC controlled system does flush the pump with rinse water after the time expires running the pump at 50psi. We do the same thing while the customer is using the foam brush, wheel brush, or foam gun. When they return to use rinse they don't have to wait for the line to clear. We also have 1000psi or 1400psi available for the soap or rinse cycle selectable from an illuminated push button. Differentiation is what its about.
Does your system use 1 unloader with a VFD? If the VFD is running at a slower speed and the customer lets off the trigger in the selfserve bay doesn't the pressure go back up to the unloader pressure reguardless of the speed the VFD is running?
thoffmanjr
Member
The single unloader is set at 1600psi. When the customer lets go of the trigger the VFD maintains either 1000 or 1400 depending on the pressure selected by the customer. The motor runs at about 15hz or so when the trigger is released since the flow is restricted. The transducer detects the pressure and it is wired to the VFD. The pressure doesn't hit the unloader pressure.
mjwalsh
6 bay SS w/laundromat
Tom,
2 Questions:
I have heard that VFDs need a capacitor bank replacement after 5-10 years ... since you have been using VFDs for many years now ... have you any experience with that event?
We like the type of gun (Cat has a version) that unloads around the outside of the nozzle when trigger is released. That way we have zero concern about heat building up in our unloader-regulator bypass hose. Do you think there is any chance the VFD would work with well with that type of gun.
mike
Last edited:
MEP001
Well-known member
I can't believe you still think the dump gun is a good idea. Do you not realize that using a dump gun with a VFD pump system that if the customer is not pulling the trigger the tire cleaner will be dumping on the ground at around 4 gallons per minute?mjwalsh said:
Would you be able to provide the brand of transducer that you are using. I would like to build one of these systems.
thoffmanjr
Member
I've never had a capacitor fail and I'll bet it's because the vfds have a low duty cycle compared to the event you're talking about. VFD are popular in large buildings and run 24/7.
If you use a dump gun with a VFD and transducer the pressure drop would cause the motor and pump to run at full speed. I've never used a dump gun so I assuming that is the case.
The transducers we use are from www.transducersdirect.com and were a 0-2000psi 1/4" two wire 4-20 milli-amp.
If you use a dump gun with a VFD and transducer the pressure drop would cause the motor and pump to run at full speed. I've never used a dump gun so I assuming that is the case.
The transducers we use are from www.transducersdirect.com and were a 0-2000psi 1/4" two wire 4-20 milli-amp.
mjwalsh
6 bay SS w/laundromat
Thanks Tom for sharing your specific experience. There are a lot of vfds out there with different capabilities. I like to always have spare components on hand so I found this link potentially helpful:
http://catalogo.weg.com.br/files/wegnet/WEG-how-to-reform-weg-vfd-capacitors-brochure-english.pdfa
I could be missing something ... but it seems like with programming the conditions of both the selection & the lessened pressure ma signal to the PLC could make it so a lower rpm could occur fast enough to avoid the unwanted 4 gpm that Mep referred to. It must be changing HZ fast enough for you now with a customer switching to a low pressure while on high pressure??? Also, are you putting some air in the line for increased foaming of some of the low pressure items?
Whether it would be worth it just to use the CAT dump gun vs a regular gun with a vfd situation that is another question. Maybe with precise enough programming it could be accomplished without the wild chemical waste problem.
mike
thoffmanjr
Member
The way we do it is the Plc "tells" the VFD it wants, say, 1000psi and the VFD runs the motor at whatever speed to achieve it. I'm assuming the dump gun opens up flow which would cause a huge pressure drop which would cause the speed to hit 60hz.
We tried adding air years ago and I don't remember seeing much benefit but you could do it.
What we love about doing it: reduces energy since 1000psi runs the motor at 33hz. Reduces total pump wear and tear. Pressure boost feature: male customers love that.Fewer hose running out to te bay. We like applin spot free at 400psi compared to the 200psi we use to get with those multistage booster pumps.
We tried adding air years ago and I don't remember seeing much benefit but you could do it.
What we love about doing it: reduces energy since 1000psi runs the motor at 33hz. Reduces total pump wear and tear. Pressure boost feature: male customers love that.Fewer hose running out to te bay. We like applin spot free at 400psi compared to the 200psi we use to get with those multistage booster pumps.
MEP001
Well-known member
That's exactly what it does. It's just like taking the tip out of the gun and pulling the trigger.thoffmanjr said:
I think you're missing something too. It solves a problem of wanting lower pressure available to the customer by letting them vary it in a wasteful manner that can even be done with a standard trigger gun. The whole discussion started when someone wanted to REDUCE the use of their product and you suggested the dump gun which would only INCREASE the use. That complete lack of understanding of the particular issue shows a lack of logic in choosing to use dump guns in the bay at all.mjalsh said:
mjwalsh
6 bay SS w/laundromat
Only a small percentage of the time do the customers let up on the trigger during the high pressure. When they do it is less pressure but not the "all or nothing" like you describe. The increased volume during those times it is not that drastic. The Flojets for the tire motor & presoak with air actually makes for more of a foaming experience which helps the customer with the "dwell factor". As far as more waste ... it is not even close to how you describe with our specific Flojet low pressure-air combination from our two 6 solenoid manifolds. Softsuds as shown below was was seeking to understand similar to myself ... how the VFD driven pump can function with the proper controls ... specifically with the low pressure chemical... being drawn in the pump or premixed. If the VFD-controls makes the motor-pump go to an almost idle state when that type of low pressure selection is made ... then it seems like it could perform similar to the way our Flojets do. At no time did I state that I knew the VFD has that capability like the Flojet. Like Softsuds ... that is why I was asking hoping that someone had tinkered a bit VFD wise & saw first hand & documented exactly how the volume varies with the pressure & the slightly increased nozzle area opening ... based on the Flojet less than 100 psi similar level.
Softsuds,
Was you original question answered thoroughly enough?
Is it clear to you whether the VFD driven single pump can draw the more concentrated chemical into the pump or is it required to have it premixed??? Application Level??? What is your visualization of the chemical mix point & potential tanks needed?
For the sake of greater understanding ... it does appear that Tom gets the VFD-motor driven pump down to 50 psi for his unique flush approach. It would be interesting to see how much the volume increased at the lower psi with a bit more flow allowed than just the nozzle as with the style of dump gun that I am referring to & am very familiar with.
mike
MEP001
Well-known member
The pressure is controlled by the VFD based on FLOW. It ramps the pump speed up (increasing flow) until the desired pressure is met. Your dump gun doesn't allow "a bit more flow," it allows the full capacity of the pump to be dumped around the tip. That means the flow to achieve 50 PSI can never be met even with the pump running at full RPM. It's not an issue with your FloJet system because there's presumably a needle-valve adjustment in the room preventing more flow when the dump gun is opened. It is once again not relevant to this situation.mjwalsh said:
mjwalsh
6 bay SS w/laundromat
Mep & other VFD-Pump experts,
For the sake of understanding better. As a reaction to your above statement we went from my office to our pump room & the closest bay. Gradually squeezing the trigger the pressure climbed from 250 psi on the accurate gauge to 1500 psi with the non VFD 3 phase 3 HP motor driving the Cat 310 pump at the full (no choice) 60 hz. When we suddenly release the trigger the pressure again went to 250 psi. Of course, the volume of 2-3 gpm was slightly affected but like I said before ... most of the time the customer wants his or her's "moneys worth" & squeezes the trigger all the way. Except when he or she is shown on a low pressure selection that more foam occurs when not pulling the trigger on their whitewalls etc.
I assume that it does not hurt the Cat 310 pump to meter the flow going into it & I assume that is what Tom & others are doing when they use the VFD single hose from single pump to bay approach. Technically ... there is probably a flow control available that would respond in the proper context with a flow tranducer current or voltage. To be fair & not misleading ... the practicality of cost & maintenance ... could be a different story.
I believe Tom's approach is using a transducer for pressure monitoring mainly to allow for a slightly lower pressure as a choice. Again, our observation on our specific gun does allow for gradual lower pressure. When we were testing dump guns many moons ago we chose to not use the "all or nothing" specific style of dump gun that you are referring to! That reminds me ... maybe I should take those specific "tested only" guns out of storage & put them on Ebay ... just in case a non carwash person prefers them. To free up space ... I might try to give them away.
mike
MEP001
Well-known member
You're mistaken. The transducer, along with the VFD, is also the pressure regulator. In order to make pressure, you need flow and a restriction. With a dump gun, rather than increasing the restriction when the trigger is released the restriction is reduced. The pump will speed up to try and achieve the pressure programmed into the controls.mjwalsh said:
You're kidding yourself if you think the customer wants to try and control the pressure by varying the trigger.
