Are bilges connected

You will probably also have to use a relay in addition to the float switch as chances are you will not find a switch rated for the amount of amps a ac pump draws.......

You don't want AC (120V) in your bilge... bad idea! The bilge switch will need to be run to a relay that controls the AC voltage. 120 AC in water travels everywhere (or more hopefully blows the circuit breaker), but if there's a fault the result is that anyone that contacts bilge water risks becoming a statistic.

Bilges should not be connected since you don't want fuel or oil from a possible leak to get into living quarter bilges

Your AC pump may be in the bilge but it is/should be away from water

I don't see the point of your reverse float switch. If an AC water line fails the AC will shut down on high pressure due to the loss of water flow and when it does the pump will shut down as well

Now obviously if the leak is below waterline water will still flow in with the pump off sonyou d be better off adding an extra bilge pump since most production boats don't have enough anyway

Relays...

I'd ask the folks on this thread... http://www.thehulltruth.com/archive/t-108046.html

It is a simple project but many people might hesitate to offer help online because just asking how indicates you might not have the skills or knowledge to work with mixed voltages and the components required to do the job yourself. Please don't take that as an insult. If I went on a flying forum and asked how to start the engine of a specific aircraft, I bet a lot of people would be leery of responding.

If you want a schematic with a suggestion for components, I would be happy to send you one but only with your full appreciation that I have absolutely no control of how you build or install the system, no knowledge of your level of electrical safety awareness, and your complete understanding that if you do it wrong you might hurt yourself, someone else, the boat, and in the end it might not work at all for what you have in mind. Not because the design is faulty but because it was built and installed by someone not skilled in doing so.

This borders on the Nordhavn thing in a way, someone installed something, someone didn't use good judgment, and Nordhavn got poked with a sharp stick. None of us want to be Nordhavn. (except at the bank maybe)

Your bilge area may have 115V AC but those lines should not be anywhere near the bilge water. The simplest setup will likely be a 12 VDC NC relay. Contacts rated 120V ?? amps depending on the design of your A/C system. A high water bilge alarm switch connected to 12V can power the relay and an alarm at the same time. On the AC A/C side you don't want to interrupt the water pump - you need to shut down the whole system. The compressor shouldn't be running without cooling water. So you basically need to turn off the A/C as if the area was satisfied. Ideally it would use the compressor lockout feature to prevent cycling if someone bumped the float switch.

As others have cautioned YOU need to understand what you are doing before you start. I only offer this as a suggestion of one way to do it for someone who could do it another way without my help.

Hi,

Just be careful of the man called Murphy who lurks in the bilge of every boat.

reason it's not discussed is that it is not needed because of the circuitry in the AC/pump system...

again, look at your bilge pumps capacity first. i woudn't be surprised if you boat only has 3, 1500 to 2000 gph pumps which isn't enough.

your AC pump is probably aroudn 1000 GPH on a boat that size so a 2000GPH bilge pump shoudl have no problem keeping up but i'd want a back up.

the best way to add a back up bilge pump, ideall the larger 3700 rule, is to mount it higher in the bilge so that it only comes in if the primary fails or fails to keep up.

float switches are the primary cause for bilge pump failures so test them, at least monthly.

with adequate bilge pumps, regular tests and routine inspectinos of the AC coolling hose and clamps, you dnot' have much to worry about. AC cooling is fairly low pressure... if installed properly, even if both hose clamps fail on a barb, the hose will not pull out without some serious efforts. often, you have to slit the hose to get it off a barb fitting...

On almost every Carver I have been on the forward and aft bilge connect through the stringers and the engine room is sealed off.

Not all systems have that circuitry. Mine would trip the compressors on high head and leave the pump running. Also you could have a failure of a hose downstream of the compressor which wouldn't make any difference to any A/C system since the water flow would be normal.

I agree that the pump volume should be less than any reasonable bilge pump. However I'm sure there are more than a few sinkings due to the A/C system failing. Probably most are related to the A/C failing first and the bilge pump giving up later. Maybe days later.