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Old 10-16-2011, 03:58 PM   #21
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RE: Using a float switch to turn a pump off

Thanks for the nice schematic and source...but considering the average AC raw water system...the small level of complexity is worth it
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Old 10-19-2011, 07:34 AM   #22
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RE: Using a float switch to turn a pump off

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.......... Tim, yes, all the septic float switches are NC, designed to open when the float moves up past hortizontoal and turn the pump off. ............
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.
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Old 10-19-2011, 07:52 AM   #23
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Using a float switch to turn a pump off

Quote:
rwidman wrote:
Quote:
.......... Tim, yes, all the septic float switches are NC, designed to open when the float moves up past hortizontoal and turn the pump off. ............
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.
*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
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Old 10-19-2011, 08:47 AM   #24
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RE: Using a float switch to turn a pump off

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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.
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.
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Old 10-19-2011, 08:59 AM   #25
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RE: Using a float switch to turn a pump off

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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.
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.
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Old 10-19-2011, 09:18 AM   #26
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RE: Using a float switch to turn a pump off

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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.
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?
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Old 10-19-2011, 10:06 AM   #27
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RE: Using a float switch to turn a pump off

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....
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Old 10-19-2011, 10:45 AM   #28
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RE: Using a float switch to turn a pump off

Quote:
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....
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.
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Old 10-20-2011, 04:36 AM   #29
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Using a float switch to turn a pump off

"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
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Old 10-20-2011, 05:08 AM   #30
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Using a float switch to turn a pump off

"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
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Old 10-20-2011, 06:49 PM   #31
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RE: Using a float switch to turn a pump off

OK, This thread has become nothing but childish bickering and insults. Carry on if you wish, I am done.
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