Using a float switch to turn a pump off

[timjet]

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??

[HeadMistress]

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.

[Moonstruck]

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=CM...FcZw5QoduB9mbA

[timjet]

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.

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.*

*

[timjet]

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/10...d_Float_Switch

[Delfin]

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.

[timjet]

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??

[FF]

Will this work??

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

[Keith]

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

[JohnP]

FF wrote:
Will this work??

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

********* 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

**********

*

[jleonard]

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.

[O C Diver]

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

[Delfin]

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??

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/OM...873?Pid=search

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

*

[timjet]

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

[FF]

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?

[JohnP]

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?

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

*

[Keith]

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.

[psneeld]

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

[FF]

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.

[RickB]

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