Using a float switch to turn a pump off

I want to rig up a float switch that will turn off my air conditioning water pump if a hose breaks and it starts to flood the bilge.*

It would have to be 120 v and be rated for a wet area. Any suggestions??

If a hose that's connected to an open below-waterline thru-hull breaks, water outside the boat is gonna seek its own level INside the boat through the hole in the hose whether any pump in that line continues to run or not. So I can't see what good a float switch will do.

The outlet for the pump is usually above the waterline.* If the hose comes off the above waterline thruhull or breaks above the waterline a cut off switch would work.* We use both high and low cut off switches on pumping stations.* The floats may be a little large for you, but they work on line voltage.* Go to a plumbing supply that has a good supply of pumps.* They should point you in the right direction.* Here's a link to one source.* Do a google search for pump float switches.

http://www.liquidlevel.com/?gclid=CMvHxaum8KcCFcZw5QoduB9mbA

HeadMistress wrote:
If a hose that's connected to an open below-waterline thru-hull breaks, water outside the boat is gonna seek its own level INside the boat through the hole in the hose whether any pump in that line continues to run or not. So I can't see what good a float switch will do.

Click to expand...

Correct and I think as least a portion of the air conditioning plumbing is below the water line. If a hose comes completely off a fitting that is below the water line there is nothing I can do and the boat will be lost. However I think a hose coming completely off a fitting is far less likely than a split or pin hole leak that with the ac pump shut down can be managed by the dc bilge pumps, as long as dock power remains connected to power the batt charger.*

*

Don,

Rule and probably others make a 120 v pump with intergral switch. I'm considering this, but this will still not stop the air con pump. Not crazy about drilling another hole in the side of the hull though.*

What do you thing of this switch:*http://www.drillspot.com/products/109203/Dayton_3BY74_Normally_Closed_Float_Switch

Tim, you have the right idea, using a float switch for a septic tank.* Check the amperage on the a/c pump, because that is what will determine the suitability of any switch - the voltage is not important.* The reason they say the float switch on the link you provided is 120 volts is because of the plug.* It's rated for 10 amps, whatever the voltage. Here's a slightly larger one is you need the reference:

http://www.grainger.com/Grainger/DAYTON-Float-Switch-3BY70?Pid=search

If you want the deluxe solution, use a keel cooler for a closed loop system with coolant rather than pumping sea water through the boat.

Delfin,

Yes but I think I need a normally closed switch - correct? ie the air con pump is allowed to operate as long as the normally closed switch is, *well closed. When the water rises the switch opens, removing power from the pump.*

To reduce all this 115v from the bilge I'm thinking of installing a relay and using a 12v bilge pump switch. I need some help here, but the basics is a 12v bilge pump switch connected to a battery the other lead going to a relay with a solenoid. When the bilge pump switch closes it activeates the relay which removes power to the air con pump.

Will this work??

Will this work??

Installing a brand new high quality discharge hose will probably work better , with no electrolisis .

You might think about using the float switch to power a 12V alarm.

FF wrote:
Will this work??

Installing a brand new high quality discharge hose will probably work better , with no electrolisis .

Click to expand...

********* I think Fred has the right approach, install new hoses and clamps and maintain them in this condition.

********* If you like a lot of electrical devices,* after the float switch shuts down the AC pump have it close an electric water valve at the Seacock.

********* To take this one step further install a simular system on every normally open thruhull.

**********Once you have all this equipment in play, you will probably have more issues than just maintaining hoses, and keeping your insurance paid up.

JohnP

**********

*

I can't recall ever hear of or reading about a boat that went down because an A/C hose broke.

So while I conmmend the forward thinking I am not sure the occurance of failure is a biggie.

Ok, what you want is a "latching" relay. This is a relay that moves from one position to the other by applying power to a set of contacts. It won't move back to the original position until power is supplied to another set of contacts in the relay.

In your application, the power to the AC water pump would run through a set of contacts in the relay. There is no power applied to the relay coil at this time. You use a normal bilge pump float switch on 12 volts DC to activate the coil to disconnect the power to the AC water pump if the bilge fills with water. If the bilge empties to the point that the float switch connected to the relay goes back to the off position, the relay WILL NOT go back to it's original position turning the AC water pump back on. To move the relay back to the normal position requires momentary power to another coil within the relay (think of this as a manual reset button). This is important as the switches that others have suggested will restart the AC water pump in the water in the bilge goes back down!

Many of these relays have 2 sets of contacts. So to separate AC units could run though this one "high water sut down system". Depending on the size of your AC unit, the amperage of the compressor may be too high for the relay, so I would put the relay on the water pump only. Marine AC units have a high pressure shut down for when they get insufficient cooling water, such as a clogged intake or dead water pump. So the AC unit should shut down when the water pump stops.

Here is a link to a latching relay that runs on 12 volt DC and will run two 120 volt AC 1/3 HP pumps.

*

Latching Relay

*

Ted

timjet wrote:
Delfin,

Yes but I think I need a normally closed switch - correct? ie the air con pump is allowed to operate as long as the normally closed switch is, *well closed. When the water rises the switch opens, removing power from the pump.*

To reduce all this 115v from the bilge I'm thinking of installing a relay and using a 12v bilge pump switch. I need some help here, but the basics is a 12v bilge pump switch connected to a battery the other lead going to a relay with a solenoid. When the bilge pump switch closes it activeates the relay which removes power to the air con pump.

Will this work??

Click to expand...

Tim, yes, all the septic float switches are NC, designed to open when the float moves up past hortizontoal and turn the pump off.*

If you want to avoid vac in the bilge, which now that you mention it seems like a darn good idea, then a standard NO Rule float switch or Water Witch could provide 12vdc coil voltage to an icecube relay when it makes.* Just fuse the + 12vdc from the battery for the coil voltage of the relay (1 amp will usually do), and get a relay with contacts rated for the starting amps of the a/c motor.* You could place the relay wherever you can get to the hot side of the feed to the motor, wiring it to the NO contacts of the relay.* If you want get fancy, buy a double pole relay and wire an alarm to the other pole contacts so that if the float switch snaps on, an alarm goes off.* I can tell you about one memorable occasion when I wish I had this on my boat.....It involved my granddaughter flushing her panties down to head....

https://www.grainger.com/Grainger/OMRON-Square-Base-General-Purpose-Relay-6C873?Pid=search

Of course Fred's advice to ensure you are on top of hose inspection is well taken.

*

Thanks Ted and Delfin for the info. That relay you posted Ted looks like something that can be used in a wide variety of applications.

What surprises me is no one has addressed this issue on their boat which leads me to the conclusion that jleonard is correct, a air con plumbing leak is just not enough of a common occurrence to justify a fix. And Ted is right about the system shutting down if a loss of cooling occurs, I forgot about that.

I'm going to contact BoatUS insurance when I have some time and ask them if they have any historical data on ac plumbing leaks.

Concerning Fred's advice about plumbing inspections, I cannot see let alone get to some of the air con plumbing lines especially near the overboard drains.*

*


-- Edited by timjet on Monday 28th of March 2011 09:55:25 AM

I cannot see let alone get to some of the air con plumbing lines especially near the overboard drains.

"IF the Hand offends thee , cut it off"

Or since you are now living on prayers , it might be wise to remodel the hose setup in advance of the sinking problem?

FF wrote:


Or since you are now living on prayers , it might be wise to remodel the hose setup in advance of the sinking problem?

Click to expand...

********* FF,* You took the words out of my mouth, improving accessabilty would be better than an automatic shutdown approach.* JohnP

*

One of the first things I did when I bought my boat was to replace every hose coming from a seacock with new, wire reinforced hose. The boat was 15 years old when I bought it, so I wanted to make sure I had a baseline for hose life and know that everything there was good. Ditto for all the rubber hoses on the engine.

Ya gotta love people who cruise that can't think out of the box...dangerous in my mind.

A running ac unit scares me enough to go to an air exchange ac system rather than water cooled...and yes I know about new hoses and double clamps...and even watertight compartments around systems that can sink you.... most rec boaters don't even know what I'm talking about.

I have been dabbling wuth the same cutout idea...just haven't located the right relays that I want to use...but it's a great idea as a backup to a well thought out, well maintained pumping system/lines.

Even if it's a neanderthal 12 volt ram system that throws a 110 ac system switch.


-- Edited by psneeld on Saturday 15th of October 2011 05:49:47 PM

It is far harder on any switch to cut DC than AC.

So any float switch that was DC rated for the running amperage of the pump would work just fine.

If you are determined to add another layer of complexity, here is a simple way to use an inexpensive 3PDT relay to allow a float switch to shut off the airconditioning circ pump.

The circuit is wired so that when the high level float switch is opened, the relay coil is de-energized and opens the 120VAC circuit to the pump. The relay contacts are shown in the normally open condition and the circ pump is OFF. A pilot light is provided to show when power is supplied to the* circ pump.

A momentary contact (normally open) RESET switch is used to enable restoration of power to the circ pump after a high level shutdown. Notice that with this circuit, if your automatic bilge pump lowers the water level below the high level point the circ pump will not restart by itself and repeat the flooding/pumping process until someone shows up at the boat.

The relay can be mounted behind the circuit breaker panel and the reset and pilot light can be installed on the panel face for easy access. Loss of DC power will shut down the circ pump. To restore normal operation press the reset button.

*

(forgot to mention that the relay and base together will cost about $25 at Newark Electronics)


-- Edited by RickB on Sunday 16th of October 2011 09:14:54 AM

Thanks for the nice schematic and source...but considering the average AC raw water system...the small level of complexity is worth it

.......... Tim, yes, all the septic float switches are NC, designed to open when the float moves up past hortizontoal and turn the pump off. ............

Click to expand...

I have never seen, nor heard of a float switch in a septic tank and I lived in a home with a septic tank for 23 years. Any pump for a septic tank would have to pump sewage and where would it pump it to?

Perhaps people are thinking of a "sump", commonly installed in basements to collect seepage or rain waiter and the float switch that operates the pump or "sump pump".

Regardless, it seems to me that making sure that all hoses and underwater fittings are high quality and well maintained would be sufficient to protect the boat. Shutting the seacocks would be an added assurance. Sinking of boats because of air conditioning hoses coming loose or breaking doesn't seem to be a common cause of boats sinking.

Once we start thinking of 12 volt switches operating relays to switch 120 volt circuits, latching relays, and reset switches, we end up with a lot of fault posibilities and something only the original installer can understand. And remember, if you shut off the water flow to the AC unit, you should be thinking about shutting it down as well so as not to damage it. That's another relay (or contact). And don't even think about using the same relay to switch 12 volt and 120 volt circuits.

rwidman wrote:

.......... Tim, yes, all the septic float switches are NC, designed to open when the float moves up past hortizontoal and turn the pump off. ............

Click to expand...

I have never seen, nor heard of a float switch in a septic tank and I lived in a home with a septic tank for 23 years. Any pump for a septic tank would have to pump sewage and where would it pump it to?

Perhaps people are thinking of a "sump", commonly installed in basements to collect seepage or rain waiter and the float switch that operates the pump or "sump pump".

Regardless, it seems to me that making sure that all hoses and underwater fittings are high quality and well maintained would be sufficient to protect the boat. Shutting the seacocks would be an added assurance. Sinking of boats because of air conditioning hoses coming loose or breaking doesn't seem to be a common cause of boats sinking.

Once we start thinking of 12 volt switches operating relays to switch 120 volt circuits, latching relays, and reset switches, we end up with a lot of fault posibilities and something only the original installer can understand. And remember, if you shut off the water flow to the AC unit, you should be thinking about shutting it down as well so as not to damage it. That's another relay (or contact). And don't even think about using the same relay to switch 12 volt and 120 volt circuits.

Click to expand...

*But I wonder what the percentage is for boats that have A/C running with no one onboard?* Sure the easy answer is turn it off when leaving...but not desireable in certain situations.* The number may be quite high.* Most boaters are paranoid about leaking/loose hoses when running...isn't that why most of us have top quality seacocks?* So why not at a dock where the a/c pump is happily filling your boat and keeping it's cool the whole time??? (pun intended)

As far as only the original owner knowing the system...on larger older boats that can go fo a lot of system if the owner isn't niceenough to pass along basic schematics and even nicer parts lists with supplier info.

As far a a few more relays...heck between fridges, a/c units, diesel heaters, etc...etc...a few more neanderthal relay set ups that are safety related seems a small price.* Otherwise why would we want trawlers???* I'd go back to free wind, slickers, iceboxes, compass and a watch, hand pumps, etc...etc/...ya know like when I started cruising 40 years ago!!!



-- Edited by psneeld on Wednesday 19th of October 2011 07:57:12 AM


-- Edited by psneeld on Wednesday 19th of October 2011 07:58:07 AM

rwidman wrote:
I have never seen, nor heard of a float switch in a septic tank

And don't even think about using the same relay to switch 12 volt and 120 volt circuits.

Click to expand...

Two strikes ...

Float switches are very common in marine sewage systems as well as shoreside sewage transfer systems.

What? Are you worried that some mysterious event will cause a crossover or something? That is no more likely than adjacent contacts shorting out within the relay case. If we were to take your position we would use separate relays for each phase or line in the circuit and all relays would be single pole single throw.

RickB wrote:rwidman wrote:
I have never seen, nor heard of a float switch in a septic tank

And don't even think about using the same relay to switch 12 volt and 120 volt circuits.

Click to expand...

Two strikes ...

Float switches are very common in marine sewage systems as well as shoreside sewage transfer systems.

What? Are you worried that some mysterious event will cause a crossover or something? That is no more likely than adjacent contacts shorting out within the relay case. If we were to take your position we would use separate relays for each phase or line in the circuit and all relays would be single pole single throw.

1.* If you say so, but those aren't "septic tanks".

2.* I worked in electronics and electricity and what you are proposing would be a NEC code violation, at least in the USA, on land.* Now it's your boat and there will be no inspection so you are free to do what you want to it.

This thread seems to be an excercise in how to solve a problem that doesn't exist, and to show complicated ways of performing a simple task.* Have fun with it, there's no need for me to be here.

rwidman wrote:
This thread seems to be an excercise in how to solve a problem that doesn't exist, and to show complicated ways of performing a simple task.* Have fun with it, there's no need for me to be here.

Click to expand...

If you are afraid of the building inspector, use two relays.

You are correct, it is an exercise in solving a problem that doesn't exist but that hasn't stopped boat owners from doing a million similar things. People like to tinker and if they ask for a way to do something there is usually a way to do it.

I don't believe fuel polishing systems are necessary but I don't have any problem helping someone design one if they ask. Contribute or not, it's your choice but if you have a simpler way of doing what the OP asked for then what's the harm in sharing that knowledge, even if it is just tinkering.

Everyone here has a boat but I suspect only two or three have any need for marine transportation so should we stop talking about boats?

And who says it isn't a problem??? Like I posted before..I personally don't know of anyone who sank from a bad hose/ thru hull but I'm currently replacing all of my seacocks/thru hulls because they are 25 years old. Without destructive testing there is no easy way to determine the metalurgy of the thru hull portion which again with a proper seacoch isn't all that important...why...because I can afford it and going through all the bottom work it seems crazy to reinstall 25 year old bronze that's been underwater all that time.

One more time...anyone actually know the percentage stats of boats sinking that leave a/c running when no one is there???? I didn't think so....

psneeld wrote:
it seems crazy to reinstall 25 year old bronze that's been underwater all that time.

One more time...anyone actually know the percentage stats of boats sinking that leave a/c running when no one is there???? I didn't think so....

Click to expand...

Not as crazy as replacing them 50 years before they might show signs of erosion or corrosion.

If you are asking about boats that sank* - because - the a/c was on probably o one can tell you because no one has ever heard of that happening. It is a statistical outlier.

"But I wonder what the percentage is for boats that have A/C running with no one onboard?"

IN FL or the rest of the south in summer , I would assume 100% of the liveaboards that can pay for the electric.

*

Remember HEAT is way different from cooling.

*

A heater can easily pump air that is 150+ deg warmer than the cabin , so the response is rapid.

*

Most air cond will deliver air that is 35 deg or so , which takes way longer to effect the cabin temperature. 100F inside -35 F is only half the effect of heat.


-- Edited by FF on Thursday 20th of October 2011 04:40:57 AM

"Once we start thinking of 12 volt switches operating relays to switch 120 volt circuits, latching relays, and reset switches, we end up with a lot of fault posibilities and something only the original installer can understand. And remember, if you shut off the water flow to the AC unit, you should be thinking about shutting it down as well so as not to damage it."

That ciruit is probably among the least complicated control circuits on the boat. There is no latching relay used or required and the item described fails safe, nothing runs. It can't get any simpler. And if having to push a reset switch is too complex a task, then what must if be like to turn on a chart plotter or use a radio?

Uh, if the discharge hose from the a/c circ pump failed and was pouring water into the bilge the a/c controls will shut it down pretty quick on high pressure ... by using its own low voltage control system to power a relay most likely.

*

*





-- Edited by RickB on Thursday 20th of October 2011 05:18:40 AM