Sump pump control circuit 2

[vanskat]

From a reliability standpoint the low level electrodes on our sump pumps tends to get corroded after a short period of time primarily due to the type of material/chemicals that are routed to the sump pit.
The cumulative effect is that the pump never shuts off and continuously runs empty (pump life issue). I was considering modifying the control circuit to include a timer along with the high level electrode. Based on the volume of the sump pit I would set a running time after which the pump would shut off. In the event that flow to the pit is increased the high level electrode would restart the pump.
Any views?

 

[peterb]

It's possible that your answer may be to look at a different type of level switch. They are available in encapsulated designs that may be more suited to your working conditions than an electrode type of sensor. Check this link as an example:

http://www.orenco.com/eps/eps_floatSwitchAssembly.asp

 

[djs]

Another option, although more expensive is to use a non-contact level sensing system. We use ultrasonic level measuring systems in quite a few applications to start and stop pumps involving corrosive and/or coating type liquids. In any case I would assume that the cost of a pump would be less that the cost of a U/S level meter.

 

[BJC]

Look at the radar switches that are available. They are getting cheaper and using them for corrosive fluids is their forte.

 

[peebee]

I agree with peterb. Most applications I've seen like this use something similar, they're typically constructed like a mercury switch embedded in a sealed float. Maybe you can't use mercury anymore, though, I don't know.

 

[janerik]

Another option is to monitor the torque of the motor. When the pump runs dry, the torque will reach alarm level and can be stopped. The great advantage is that you put this equipment in the motor control cabinet, so it will not be affected by a hostile environment.

 

[mickstar51]

Have you considered a flush line for cleaning your level probe(s)? I have utilized a tubing tap off the sump pump discharge piping to backwash under capacitance level probes in storm water sumps. The backwash stream will minimize material bridging from the sump to the probe.

 

[jraef]

All fine suggestions, but in direct answer to your question, yes installing a timer such as this is a common practice for pumps that can only stand a certain amount of dry-run time. Just use an Off-Delay timer with the coil in parallel with the starter coil. Then use a N.O.T.O. (Normally Open, Time to Open) contactin series with the seal-in (latching) part of your control circuit. The contact will close immediately with the starter, sealing in the circuit around your start electrode. If the stop electrode works, it shuts off even of the timer is still active. If the electrode fails, eventually the timer expires and the contact re-opens, shutting down the pump.

Then investigate a sensing system that works more reliably.

Subvert the dominant paradigm... Think first, then act!

 

[jbartos]

Suggestion to vanskat (Electrical) Feb 12, 2002 marked ///\\From a reliability standpoint the low level electrodes on our sump pumps tends to get corroded after a short period of time primarily due to the type of material/chemicals that are routed to the sump pit.
///Essentially, I agree with those postings suggesting a noncorrosive float to control the float switch, because of this control approach simplicity.\\The cumulative effect is that the pump never shuts off and continuously runs empty (pump life issue). I was considering modifying the control circuit to include a timer along with the high level electrode. Based on the volume of the sump pit I would set a running time after which the pump would shut off. In the event that flow to the pit is increased the high level electrode would restart the pump.
///There could be many unnecessary starts and stops wearing out the motor and contacts.\\Any views?

 

[buzzp]

Assuming this is a squirrel cage induction motor, monitor the power to the motor driving the pump. The power will tell you when the pump is dry, dead headed, or any other flow problems. If the motor is larger (like 15HP or higher) then you can probably just monitor current and get the same results. No problems with corroded floats or anything else either. There are many vendors to choose from, one is Load Controls Inc or maybe SymCom, Inc.

 

[jbartos]

Suggestion: Certain types of pumps do not like to be running without any fluid. They get damaged soon.

 

[buzzp]

These monitors can come with trip times as quick as one second. No damage to a pump, that I have ever heard, can be done in only one second. I suppose there are a few but for the most pumps, no damage will occur.

 

[Bemac]

Try using low pressure/vacuum switches. Use PVC tubing to connect the switch to a solid tube of suitable material that is held in the sump. You could use two switches, one at low level the other at high level and use your existing system. Or just the high level, and a timer as you mention in your info.
Their are switches available that will detect a differential pressure of 0.072 Psi. They are being used in the Steel industry type "Sumps" with excellent reliability, and very cost effective.

 

[PUMPDESIGNER]

If simplicity, durability, and no moving parts are required:

We make our own solid state level sensors that are far superior to anything that you could possibly purchase.
We use a bolt or piece of metal for each set point. Choose any metal you like, titanium, hasteloy, 316 stainless, etc. Cheap because all you need is two small bolts. We set this bolt through the side of a PVC or Polyethylene pipe leaving only the head of the bolt exposed on the outside of the pipe. Connect a single wire to each bolt, then pot the whole thing with an expanding water proof expoxy. Connect this to an impedence type sensor available from anyone $100.00. The sensor will last virtually forever.

Many may think this weird to make something, but the truth is that it allows us to make something higher quality than what could be purchased, and cheaper too.

We originally designed this for a utility looking to replace sump level detectors that were always being interefered with by debris.

Richard Neff Richard Neff
Irrigation Craft

 

[peebee]

Nice idea, Pumpdesigner. Have you ever had problems from long-term buildup of corrosion, dirt residue, etc?

 

[don01]

hi all
good one there pump designer, you bring back memorys of using pvc conduit stainless steel "clothes line wire" and fibreglass to make level, ph and such probes as a apprentice in acid and fertiliser plants.

With the idea of a timer I would be concern about relying on that alone
a) over running when empty will not enhance the pump and or seal life
b) if it's a sump pump then it will get surges both short and long

If acheivable another simple solution is the bubble tube using a needle valve, rotameter and pressure switch wth a bit of a differential much as Rodmill has described. You can add a guage to indicate the level. (use 2 and a differential guage for density.)

All the best
Don

 

[labster]

pumpster: Great idea. Not to be a knothead, but where might I find such an impedence switch?

 

[PUMPDESIGNER]

Carlo Gavazzi is just one of many hundreds of companies that make them. We have used Gavazzi for years, have not had one single failure, and that is sure because if one failed the customer would definitely come to us for replacment.

Our contact is Ken Wagner at 847-465-6100
We use model S196156115

Did not send you to their site because their website looks like they spent a million bucks on it and got screwed, cannot find anything.

PUMPDESIGNER

 

[jbartos]

Suggestion: Visit

http://www.tycovalves-la.com/NA/YAWMC-0454-US.pdf

etc. for more info