Where to Buy a Simple, Inexpensive Control Relay

Hello

A water company has a pump that they are concerned about. As of right now, it is controlled manually and is monitored by a 4-20mA transmitter. If the water level of the tank reaches > 2' it risks running dry. They want the pump to shut off if it reaches 2' or less (or X mA). I need a controller to simply turn off the pump if the water level dips below XmA.

The controller needs a simple 4-20mA input and a simple 120VAC output to control the starter.

Does anyone know a cost effective controller for this type of application?
I am having a hard time finding one.

Thank you very much for your suggestions!

There are dozens of vendors who make DC alarms.

The transmitter's 4-20mA is the input to the alarm module.

The alarm module trips at the point you set it up for.

Here's a whole page of DC alarm modules:

http://api-usa.com/signalconditioners_alarms.php

The ones with the pins at the bottom plug into a socket. The socket is purchased separately for less than $10 (USD).

danw said:

There are dozens of vendors who make DC alarms.

The transmitter's 4-20mA is the input to the alarm module.

The alarm module trips at the point you set it up for.

Here's a whole page of DC alarm modules:

http://api-usa.com/signalconditioners_alarms.php

The ones with the pins at the bottom plug into a socket. The socket is purchased separately for less than $10 (USD).

Click to expand...

Thank you!

One of the Omega process controllers should work dandy. The model CNi16-AL doe $210 has 2 relay outputs that can be set for a variety of puposes including High/low, above/below, band, latch/unlatch, normally open/ normally closed.

http://www.omega.com/pptst/CNI-AL.html

Inexpensive? >>> Since the level is already monitored, why not use a low level float switch?

Lancie1 said:

One of the Omega process controllers should work dandy. The model CNi16-AL doe $210 has 2 relay outputs that can be set for a variety of puposes including High/low, above/below, band, latch/unlatch, normally open/ normally closed.

http://www.omega.com/pptst/CNI-AL.html

Click to expand...

Thank you for the link

I agree with JRB and Lancie1- a float switch if water level is stable. Link.
With the 4-20mA signal, you can use a Process Controller for under 100 USD. Just because it says Temperature Controller, doesn't mean you have to use it for temperature. In this case, all you want is the Alarm function.
Link.

keithkyll said:

I agree with float switch if water level is stable. Link.
With the 4-20mA signal, you can use a Process Controller for under 100 USD. Just because it says Temperature Controller, doesn't mean you have to use it for temperature. In this case, all you want is the Alarm function.
Link.

Click to expand...

Thanks Keith

A float switch is not the most practical for this application. It would be 100x easier just to use the existing 4-20mA signal of the transmitter. All I would have to do is run a circuit from the controller to the pump starter.

Thanks for your help!
Very much appreciated

kandymann said:

Thanks Keith

A float switch is not the most practical for this application. It would be 100x easier just to use the existing 4-20mA signal of the transmitter. All I would have to do is run a circuit from the controller to the pump starter.

Thanks for your help!
Very much appreciated

Click to expand...

I agree that a setpoint relay is a good solution for this application. Ideally, it should be one that features an adjustable deadband, to prevent unnecessary cycling of the pump motor. Alternatively, you could install a timer if you find that you need a longer off-cycle for the pump.