My SS system has tanks with hydrominders for all low pressure functions. All high and low pressure functions use one hose from the pump stand to the bay. When you switch between low pressure functions there is a high pressure purge for a few seconds to clear the line and get the next product to the gun fast. On the circuit board in the pump stand there are dip switches that have to be set for it to purge correctly, either (gravity hot water) or (city cold water). If I leave these switches off with neither selected all the low pressure functions work great until you switch products and the pump tries to purge. Without either hot or cold selected the pump starves because there is not enough liquid with the pump running wide open, when it slows back down(15 hz) it works fine and the pump runs fine. If I turn either hot or cold on it dilutes my low pressure products so much you can't even tell they are coming out of the gun. I need a way to engergize the city solenoid only when it purges or energize it for say 5 seconds when a low pressure function is selected that way it can purge, shut the city feed off and then the low pressure gravity tank would be enough to feed the pump as it runs in low pressure. Anyone have an idea? I have attached a wiring diagram.
Help with VFD SS system
- Thread starter APW
- Start date
JGinther
Zip-tie engineer
Where does it get its water if you have both selections off?
JGinther
Zip-tie engineer
You mentioned the pump starving when it runs a full speed with no switch on during purge... That means that there is a solenoid on the hot water gravity tank also? If so, where does the water come from when you use low pressure products?
Each individual low pressure tank has a solenoid that feeds the pump. As long as the pump is running slow it is enough flow for the pump. Yes there are hot water solenoids on the gravity tanks as well.
JGinther
Zip-tie engineer
It sounds like the system is designed to pull water from the tank also, not just the hydrominder tanks - even on low pressure options. Have you thought of richening up the products and allowing the hot water solenoid on all the time for low pressure? How slow can you spin the pump on low pressure options?
Your correct. I believe that is the way it's designed but it will waste so much chemical. It works fine with the hot water valves off other than the purge. I guess I'm trying to re-engineer it to work in a more efficient manner. As far as the pumps I believe I can make them do whatever I want to by changing the htz.
JGinther
Zip-tie engineer
Why would it use too much chemical if you have water from the pump diluting it to a desired final concentration? If you can turn the pump slow enough, the result concentration should be around the same? I.E. If the pump was rotating at 10% and gave the desired result coming from the mix tank only, running it at 10% - from both the mix tank and the hot water tank should give you the same amount of product output in the end (after adjusting chemicals to make up for the additional source of water).
If you want to do your plan though, I think it would be possible to upsize the plumbing coming from the chem tanks to the pump so that it didn't starve... Would be expensive probably - especially if the chem solenoids are small. You probably wouldn't hurt the pumps cavitating them for 5 seconds during a purge as much as you do by running the chems through the pump all the time. I'm not much of a fan of that design.
If you want to do your plan though, I think it would be possible to upsize the plumbing coming from the chem tanks to the pump so that it didn't starve... Would be expensive probably - especially if the chem solenoids are small. You probably wouldn't hurt the pumps cavitating them for 5 seconds during a purge as much as you do by running the chems through the pump all the time. I'm not much of a fan of that design.
JGinther
Zip-tie engineer
JGinther
Zip-tie engineer
Where does the air inject?
JGinther
Zip-tie engineer
So the air isn't causing the cavitation.. I don't understand why the pump would be starving. There is no metering valves in the plumbing between the pump and chemical tanks? It still shouldn't hurt your pump to cavitate for a couple seconds compared to the damage of having the chemicals run through the pump. You will end up chemically damaging the pump before the seals go out from that little bit of cavitation for a couple seconds.
From the solenoid on the low pressure it goes through a check valve and then directly into the pump. I have found the 3/4-in hose flat sometimes almost like it can't suck enough liquid. I even replaced the hoses that were flat just to make sure there wasn't something wrong with them on the inside.
MEP001
Well-known member
Check the pulleys on the pump and motor. Some of the GinSan stands I've seen have Cat 5CP5160 pumps and the motor and pump pulleys are the same size, so the pump is running way above its maximum RPM and flow with the motor running 1725 RPM. The plumbing manifolds are only 1/2" and it just can't flow enough water to keep the pump from cavitating. Even a 5CP2120 will cavitate in this setup.
JGinther
Zip-tie engineer
If you removed the check valve temporarily, would it cavitate? Maybe a larger flow one might be all that is needed.
