JG plumbing
Well-Known Member
Does the motor on your ceiling fan, in your living room, get bogged down when you close the doors to your house?
Does the motor on your ceiling fan, in your living room, get bogged down when you close the doors to your house?
There's nothing preventing it from turning. That's the point. It's grabbing air from behind it and throwing it in front of it. So you can open the door and let some go into your bedroom or keep the door closed and leave it in the living room.It would bog down If I grabbed a hold of it to try preventing it from turning.
It doesn't control it electronically that's a vfd.
It does it by choking the flow.
The motor and the pump are the two distinctions. The motor doesn't get choked the pump does. It's not working harder against ever increasing back pressure.
Obviously not.And it's not a piston pump.
So in your example, the bedroom door is the CSV valve, and the water pump is just circulating water around in the living room.There's nothing preventing it from turning. That's the point. It's grabbing air from behind it and throwing it in front of it. So you can open the door and let some go into your bedroom or keep the door closed and leave it in the living room.
Air can do that, but not water. If the pump is thrashing paddles through the water without moving any of it, doesn't that create destructive cavitation?It creates differential pressure. Negative behind and positive in front. So when it just spins it just spins.
Right. That one I do understand. That type of controller electrically varies the current to the pump motor to actively control its speed.
I get that too. The CSV is an automatic mechanical valve inserted into the pipe in order to progressively restrict the flow. No electrics involved.
You lost me there.
The electric motor drives the pump. If you restrict the output flow of the pump, doesn't the electric motor "feel" that? If it gets harder for the pump to work against the increased back pressure, doesn't the electric motor need to work harder to keep driving the pump?
Obviously not.
If it WAS a piston pump used to drive water out of my garden hose, I flip the electric switch on, the electric motor drives the pump, water sprays out the end of the garden hose. Now, instead of shutting the pump motor off, if I slowly close the valve on the end of the garden hose, but the pump is still running, either the garden hose eventually explodes or the piston pump becomes fluid locked and forced to a stop, with the electric motor still powered and humming straining to drive the pump. So obviously that cannot be how the CSV system works.
I realize the CSV valve never actually closes fully. It varies the restriction on flow rate to maintain a constant pressure in the lines downstream of the valve. But by choking down the flow rate it raises the back pressure in the line between the pump and the CSV.
Even if it's not a positive displacement piston pump, it's still a pump working against an increased back-pressure. The pump is still being driven by an electric motor that only has a simple on/off switch. Where is the excess water pressure going? Is it leaking back through the pump itself? If the elevated water pressure from the pump isn't escaping anywhere, then it must mean the increased back pressure is forcing the pump to run slower. If the pump is being forced to run slower, that means the electric motor is also being forced to run slower than it wants and it will be straining more and more trying to drive the pump onward. That motor would be drawing more amperage when forced to run slower, not less.
That's the part I'm not understanding.
When you choke a centrifugal pumps output the amp draw decreases.
Sounds right to me since it's not lifting water anymore (or as much I guess). I'm not an expert on every aspect of this just trying to help someone understand.
I'm sure he'll direct you to one of his other long posts where he explains this.
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