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Old 31-07-2015, 11:04   #16
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Re: Raw Water flow sensor switch alarm

Isn't a temperature gauge supposed to do all this stuff Why overcomplicate life or boating?
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Old 31-07-2015, 11:27   #17
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Re: Raw Water flow sensor switch alarm

Yeah, it should, but if motoring for 8 hours with the AP on.... often easy to forget to check it. How many times do people check the gauge on a long motor? 10 minutes is all it takes to have an issue...
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Old 31-07-2015, 12:43   #18
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Re: Raw Water flow sensor switch alarm

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Originally Posted by kevins View Post
I am thinking about putting a flow sensor/switch/alarm inline between the raw water intake pump and the heat exchanger. Has anyone done this? Any luck. I believe it will help me recognize an overheat before it happens.

any thoughts?

thanks
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Hi Kevin,

With wet exhaust systems there are two basic ways to monitor the presence of sufficient cooling [injected raw] water: water flow (as you describe) and external temperature of the exhaust hose.

I chose the external monitoring method for simplicity and cost effectiveness. (No sensors inside the caustic exhaust hose environment- its bad enough on the outside...)

Another reason I chose this approach is because flow of raw water at the injection point does not necessarily mean enough water is being injected to keep the exhaust tubing at desired temperature. [e.g., What if your exhaust elbow is constricted and not allowing enough water to be injected...? A not uncommon problem prompting annual inspection and cleaning of our exhaust injection elbows as part of our PM process...]

I bought 3 submersible thermistors [extreme environment waterproof and potted] from the manufacturer for about US$10/each and put one on each engine and generator wet exhausts, with one for a spare...

For details regarding this DIY approach, read the excellent article John Lewis wrote last year published in Ocean Navigator magazine.

I hope you have fun with your project.

Cheers!
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Old 01-08-2015, 16:22   #19
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Re: Raw Water flow sensor switch alarm

We installed Aqualarm. Our notes might be helpful
https://sites.google.com/site/sinbad...heating-alarms
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Old 02-10-2015, 15:45   #20
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Re: Raw Water flow sensor switch alarm

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Isn't a temperature gauge supposed to do all this stuff Why overcomplicate life or boating?
The temperature gauge -- even if you're staring right at it! - will start to hint at the problem only after your impeller is already destroyed and your exhaust hose has started to melt down, if raw water flow is cut off by a plastic bag. Especially with engines (like mine) with a large coolant capacity and large thermal inertia. Don't ask me how I know!

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Old 03-10-2015, 00:34   #21
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Re: Raw Water flow sensor switch alarm

I have pondered on this for years and inspiration on a cheap reliable technique is yet to strike.

My Yanmar had an over temperature alarm which only ever went off at the most inconvenient time (usually because I had forgotten to open a valve) one is then in the position of deciding whether to continue to run the engine until you can get an anchor down or get enough sail up to sail out of problems. Opening the valve is not an option if one wishes to avoid a cracked head and it generally took about twenty minutes for the engine to cool down before it could be started again. Never had an exhaust hose or the plastic waterfall device burn out as they seem to retain enough water to prevent this.

One of the cheap differential pressure switches installed between the pump output and the inlet to the mixer may do the trick.
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Old 03-10-2015, 01:01   #22
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Re: Raw Water flow sensor switch alarm

Onan gensets have a flow sensor after the raw water pump and before the heat exchanger. Its just a simple pressure switch.
It generally trips and stops the genset a few seconds after starting when the impeller is shredded...which usually happens every 150 hours or so.
Its a good avoider of overheating...but I still don't understand why the impeller shreds itself ...there's another thread on here about that specifically.
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Old 03-10-2015, 11:45   #23
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Re: Raw Water flow sensor switch alarm

The cheap version is to put an inexpensive "snap disc" thermostat on the water mixing elbow, attached to a 12V alarm or light.. if you loose water this will go of pretty quickly. $15 at Graingers.
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Old 03-10-2015, 11:52   #24
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Re: Raw Water flow sensor switch alarm

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Isn't a temperature gauge supposed to do all this stuff Why overcomplicate life or boating?

We have been using a aqualarm flow alarm for the past 20 years and it's been terrific.

By the time the engine overheat alarm goes off its already to late. Damage could be done especially with the aluminum components on today's newer engines. The flow alarm tells you way before the engine temp alarm fires off thus maybe saving you big bucks in repairs.

For those folks saying it's just another thing to break ..... that is a true statement but after all these years many of them full time cruising we can say it's cheap insurance and has paid for itself a couple times.

Safe sailing

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Old 03-10-2015, 13:43   #25
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Re: Raw Water flow sensor switch alarm

The gui I
Quote:
Originally Posted by RaymondR View Post
I have pondered on this for years and inspiration on a cheap reliable technique is yet to strike.

My Yanmar had an over temperature alarm which only ever went off at the most inconvenient time (usually because I had forgotten to open a valve) one is then in the position of deciding whether to continue to run the engine until you can get an anchor down or get enough sail up to sail out of problems. Opening the valve is not an option if one wishes to avoid a cracked head and it generally took about twenty minutes for the engine to cool down before it could be started again. Never had an exhaust hose or the plastic waterfall device burn out as they seem to retain enough water to prevent this.

One of the cheap differential pressure switches installed between the pump output and the inlet to the mixer may do the trick.
Opening the valve will not create a problem. These are fresh water cooled, so cold water is sent to the heat exchanger, not the cylinder head.

Provided, of course, your impeller is still intact. If not, then the question is moot anyway.

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Old 03-10-2015, 14:39   #26
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Re: Raw Water flow sensor switch alarm

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Originally Posted by Cheechako View Post
The cheap version is to put an inexpensive "snap disc" thermostat on the water mixing elbow, attached to a 12V alarm or light.. if you loose water this will go of pretty quickly. $15 at Graingers.
I've done exactly this. I wired the temperature switch in series with the engine high temperature alarm. When either the engine high temperature switch opens (usually the water pump / alternator belt has broken or when the temperature switch on the cooling elbow opens (usually because I failed to open the raw water seacock), the alarm sounds. The temperature switch is held against the cooling elbow with a radiator clamp. I got my switch out of a broken coffee maker. In its original life it shut the heating element off if the coffee maker overheated.
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Old 03-10-2015, 15:45   #27
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Re: Raw Water flow sensor switch alarm

Yah, put them on a couple of 12V generators I built. Available in different temp versions. I wonder if they are available adjustable?
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Old 03-10-2015, 16:21   #28
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Re: Raw Water flow sensor switch alarm

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I've done exactly this. I wired the temperature switch in series with the engine high temperature alarm. When either the engine high temperature switch opens (usually the water pump / alternator belt has broken or when the temperature switch on the cooling elbow opens (usually because I failed to open the raw water seacock), the alarm sounds. The temperature switch is held against the cooling elbow with a radiator clamp. I got my switch out of a broken coffee maker. In its original life it shut the heating element off if the coffee maker overheated.
Have you checked that it works? Or have you worded your post incorrectly or perhaps I have misunderstood it .

I understand what you want to achieve and I think it should read "I wired the temperature switch in series parallel with the engine high temperature alarm. When either the engine high temperature switch opens closes (usually the water pump / alternator belt has broken or when the temperature switch on the cooling elbow opens closes (usually because I failed to open the raw water seacock), the alarm sounds."
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Old 03-10-2015, 20:31   #29
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Re: Raw Water flow sensor switch alarm

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Have you checked that it works? Or have you worded your post incorrectly or perhaps I have misunderstood it .

I understand what you want to achieve and I think it should read "I wired the temperature switch in series parallel with the engine high temperature alarm. When either the engine high temperature switch opens closes (usually the water pump / alternator belt has broken or when the temperature switch on the cooling elbow opens closes (usually because I failed to open the raw water seacock), the alarm sounds."
Good catch. Thanks. Complete brain fart on my part. You are correct.

I have had high temperature alarms from both the engine temperature switch and the cooling elbow switch, so it does work. In addition to the two temperature switches, there is a momentary switch, also in parallel, which serves as a test switch for the alarm horn and engine temperature light. The mixing elbow temperature switch is mounted on the metal exhaust pipe that leaves the U style mixing elbow on my Yanmar 3HM35F just above the exhaust hose going to the water lift muffler. I've been impressed with how fast the temperature rises when the raw water flow stops.

And another error; the temperature switch must have been the one that turns on the 'ready' light on the coffee maker rather than the overheat switch that turns off the power to the unit.

[I have been working from memory because my old copy of AutoSketch will not run under Windows 10, and I can not currently open the .skf wiring diagrams that I drew using AutoSketch. I'm having a hard time justifying the $265 cost of the current version of the program -- AutoSketch 10.]
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Old 03-10-2015, 21:20   #30
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Re: Raw Water flow sensor switch alarm

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...... In addition to the two temperature switches, there is a momentary switch, also in parallel, which serves as a test switch for the alarm horn and engine temperature light. The mixing elbow temperature switch is mounted on the metal exhaust pipe that leaves the U style mixing elbow on my Yanmar 3HM35F just above the exhaust hose going to the water lift muffler. I've been impressed with how fast the temperature rises when the raw water flow stops......
Yes, the test function is important IMHO. Even then, the is no easy self test of the high temp switches themselves without taking it out and testing it off the engine. I tested mine recently and while I found it was operating correctly, I found the thermostat wasn't . It had failed half open and being a raw water cooled engine (2GM20), there were no external signs that it had failed. Raw water volume (flow) remained the same but the engine must have been running cooler.

I am now planning to fit a temp gauge (with built in user settable alarm) on the exhaust for the reasons you have noted and one on the head.
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