Current Sensing Switch for Elk M1

[rbejr]

I had a problem a few weeks ago where some debris got caught in the float switch on my sump pump and it ran dry for many hours (possibly a whole day).  So, I want to hook a current sensing switch up to my Elk M1 to monitor when the sump pump turns on. I think I could use a combination of a current switch and a float switch (something like the sump bobber) to alert me if there was a problem (i.e. the sump bobber isn't tripped AND the current switch is, so there must be a problem).  It looks like the float switch is pretty straightforward, it just wires directly into an input on the M1.  However, I'm unsure of how to hook up the current switch.    I was planning on taking a short extension cord and placing this over the hot wire then wiring the output to an input on the M1.  Is that all I need to do or is it more complicated than that?
 
One sensor I saw is made by Veris Industries and is called a Hawkeye 908.  I'd post a link to it but since I'm a new member I'm unable to do that.  Is this something that would be compatible with the M1?
 
 
Any help would be greatly appreciated.  Thanks in advance,
 
 
Rich

 

[tmbrown97]

Welcome Rich!
 
You got it - those current switches are pretty easy - you set them for the voltage that makes them trip then hook them to a zone on the M1.  One thing to note - I believe a pump running dry will actually draw less current than one operating normally, so be sure to adjust for extra sensitivity - and if for some reason you aren't getting enough current to detect, you can loop the hot wire one or more times to increase the sensed voltage.  The possibilities are endless - like knowing when the dryer finished, when the AC is on, etc.

 

[BraveSirRobbin]

I would consider using one of these current sensors for this application. 
 
http://www.functionaldevices.com/building-automation/display.php?model=RIBXGTA
 
http://controlscentral.com/eCatalog/tabid/63/CategoryID/377/ProductID/313949/Default.aspx?SkinSrc=[G]Skins/_default/No%20Skin&ContainerSrc=[G]Containers/_default/No%20Container
 
http://ribrelays.wordpress.com/tag/ribxgta/
 
http://www.simplycontrols.com/functional-devices-ribxgta-enclosed-split-core-ac-sensor-75-150amp-adjustable-terminals.html
 
 
You just place it over a hot wire by separating it from the (three) bundled cable going to the pump, or via an extension cord and separating the wires in it at a small area.
 
This will provide a contact closure at an adjustable current threshold (trip) level.  It also has trip indicator LED's to help easily set this up.
 
Not sure how you think you are going to monitor the float switch, especially if it already has AC voltage/current present on it.  I would consider adding a second float switch just to monitor the water level with the M1.

 

[rbejr]

Thank you both for your replies.  I have been reading through the forum for a long time but this is the first real HA project I have attempted in many years.

 

[BraveSirRobbin]

IF you need any help, let us know!

 

[swaggy]

Not to hijack this thread but I believe my question is still relevant to the original poster.
 
BSR's links to the RIBXGTA reminded me about the need to monitor my sump pump. I wanted to confirm that using a device such as the RIBXGTA does NOT require me to expose the bare hot wire from it's insulation. My understanding is you only need to separate the hot/load wire from the bundle (thus cutting into outer appliance or extension cord insulation) and put the current sensor around it.
 
On another note, are there any fully integrated "in-a-box" solutions for monitoring current on an AC load? Perhaps one that fits neatly into a 1gang box and is safely tucked away? I am aware of Brultech and TED but those products are made for a different purpose.
 
Thanks.

 

[tmbrown97]

That is correct - you do not need to expose the copper - just separate it enough from the bundle so that it passes through the current sensor alone.
 
I am not aware of any nicely bundled solutions - these tend to be for industrial applications, but I'm sure you could come up with something if you're creative.

 

[BraveSirRobbin]

Another nice thing about the one I linked to is it is a split core, meaning you don't have to cut the wire itself to pass it through the sensor (it 'clamps' around the existing wire).

 

[swaggy]

Thanks for the confirmation. According to data sheet, the RIBXGTA has NO contacts, any way to convert it to NC?

 

[BraveSirRobbin]

Well, the contacts are 'closed' when the current is 'above the threshold', so in your monitoring your sump pump, I believe it would act as a normally closed right?  You would just have to adjust the threshold to a little over a minimum (detection) setting.
 
I actually have one of these at home I could play around with if you would like.
 

 

[swaggy]

Thanks BSR. I probably should've clarified in my previous post what I want. I would like the contacts to open when "in alarm", in other words when the current is above threshold (meaning pump is running) and to be closed when below threshold (meaning pump is not running). It's really a preference as I can have it work either way with the OmniPro, was just curious if there's a way to adjust from one to the other.

 

[tmbrown97]

Doesn't look like you're going to be able to switch it.
 
One concern I had with the RIBXGTA is that it has a set zone voltage it'll learn and look for - with a 15% variance it'll tolerate.  While that may be OK, a normally running pump will have a certain amount of amperage it pulls - but one that's running clogged will consume more power, and one that's running dry will consume less (IIRC) - I'd be quite tempted to put an ammeter on that pump and test in all 3 conditions to see what kind of current swings you see.
 
Since you're looking to check a couple of things, I'd probably choose one with a lower detection level that just closed and didn't have a set range - because for your application, it sounds like you always want to know when it's running - not just when it's running in ideal range (it would defeat the purpose if gave the same indication as being off because it was running dry).

 

[swaggy]

I do remember reading about that on this forum. Is running dry that common of a problem? I have a Zoeller pump and was told it's a reputable brand that should last a long time. This is my first home with a sump pump so not sure what to expect.

 

[sic0048]

I do remember reading about that on this forum. Is running dry that common of a problem? I have a Zoeller pump and was told it's a reputable brand that should last a long time. This is my first home with a sump pump so not sure what to expect.

 
Liquids running through a pump act as a heat sink, so running the pump dry will cause the pump to run hotter.  If the impeller is metal, the risk of damage is much lower than with a plastic or rubber impeller which can be ruined by running dry.  I would be surprised if the impeller is anything BUT metal in good quality sump pumps.  That being said, there are other parts like bushings and bearings that will last longer if they run cooler.  So while the effects won't be immediate, running a pump dry will likely cause premature failure of parts eventually.

 

[swaggy]

Liquids running through a pump act as a heat sink, so running the pump dry will cause the pump to run hotter.  If the impeller is metal, the risk of damage is much lower than with a plastic or rubber impeller which can be ruined by running dry.  I would be surprised if the impeller is anything BUT metal in good quality sump pumps.  That being said, there are other parts like bushings and bearings that will last longer if they run cooler.  So while the effects won't be immediate, running a pump dry will likely cause premature failure of parts eventually.

 
What you are saying makes sense. What I am asking is how likely is it that a pump will run dry? One way this could happen (that I can think of) is the float switch getting stuck in the ON position after the water level has receded.
 
One way I am thinking of monitoring for this condition is with a GRI2600/GRI2800 in the sump basin at or below the low water threshold, so something like this:
 
IF low_thresh_water_sensor NOT_READY AND pump_is_running THEN pump_running_dry