Drawing Pump Schematic

dronai

Member
D
Join Date
Aug 2011
Location
Calif.
Posts
145
Another Electrician was trying to come up with the controls for a 2 level pump Non PLC relay controls with floats.

He wants to have a tank with 100 gals minimum, and have it stop pumping liquid in after the tank reaches 450 gals.

I tried to draw it up, but I'm stuck on how can I keep the low level pump from cycling, after the high level stops it ? Is this right ?

Pump with start stop.PNG
 
Hi

From the way I see your drawing the Low pump will be on straight away after you lose your high level. Yes this can be done with relays but think about using both normally open and closed switches. For the time and money you will spend on drawings and relays would you not use a small Plc like a logo or pico or somti g in that range


Donnchadh
 
A double pole, double throw relay (DPDT) with one set of contacts used as a latch, will do pump-up control with a pair of level switches:

For some reason, the site's image inserter is not working.

Here's the link to the graphic showing the wiring connections
http://tinypic.com/r/2pq5awi/6
 
You only need CR1 and CR2. Leave the CR1 start stop as it is. Duplicate it for CR2 on a new rung but substitute the float switches for the start and stop buttons. Finally, operate the pump on a third rung using CR1 and CR2.
 
Last edited:
Here is my attempt adding another relay. The pump will initially turn on when the low float falls off. The pump will continue until the high float makes. It will then turn off and stay off until the level again falls below the low float.

Pump Up.jpg
 
zppxt.jpg

34dqzw1.jpg
 
Here is our Controls guy at the electrical forum explains.
"
No need for a relay.

Assuming tank fill.

LL float is NC, opens on level rise. LL NC contact in series with starter coil.

HL float is NC, opens on level rise. HL NC in series with starter coil and LL NC

Starter NO aux. contact seal-in goes around LL float.

At drop to 100gal, LL contact closes, starter closes, seals in around LL contact so that when water enters and raises LL switch, pump continues to run. Runs until HL contact opens, which drops out the starter until LL closes again."
__________________
I then tried to Draw what he explained

Jreaf2.PNG
 
with a little revision here is for the pushbutton version. now when startbutton is pushed and low level is bellow (n/o contact closed when level is below) then pump will start and hold itself (selfholding connection) until stop button pushed or high level reached (n/c contact open above high level)

pump_on n/o contact you can take from motor starter

also the second rung is now obsolete.

EDIT:
connect startbutton and low flt in parallel if you would like to start pump on either start button or low flt

EDIT 2:
generally float switches have c/o contact and contactor usually have 1 n/o aux contact, so no cost to add

Jreaf2.PNG
 
Last edited:
balash said:
with a little revision here is for the pushbutton version. now when startbutton is pushed and low level is bellow (n/o contact closed when level is below) then pump will start and hold itself (selfholding connection) until stop button pushed or high level reached (n/c contact open above high level)

pump_on n/o contact you can take from motor starter

also the second rung is now obsolete.

EDIT:
connect startbutton and low flt in parallel if you would like to start pump on either start button or low flt

EDIT 2:
generally float switches have c/o contact and contactor usually have 1 n/o aux contact, so no cost to add
Click to expand...

Seems like there are a few ways to do this control. 2nd rung is obsolete ? Is that because on a ladder control drawing, you don't need to show the pump motor itself ?

kenvandenberg said:
dronai, CR4 resets when low level relay opens
Click to expand...

Ok, I didn't see that.
 

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