Temperature alarm system

[Briankinley2004]

I am in the process of designing a secondary temp alarm system for my 12V71's as I don't trust my aging 12 point Hatteras alarm. Lauderdale Speedometer sold me a couple of 200 degree switches and an alarm. I was originally thinking of how to make the circuit using normally open switches but they sent normally closed per my ohm meter. I am thinking of putting a relay up in the bridge near the alarm that would be connected to the "off" terminal on the relay. When one of the switches opened due to overheat it would shut off the voltage and open the relay which would power the alarm. Question one is does anyone have another idea or way this is normally done? Also I would be getting the power from the 12 volt converter in the bridge, original to boat. Does anyone know if this convertor works when the key is off or does the key need to be on? I really dont want the relay to pull 12 volts when the engines aren't running thus prefer a source "hot" only when keys are on. Any suggestions appreciated

 

[jrbrein]

I replaced the temperature sending units on my 6-71 N's and added mechanical gauges where I could easily see them.
I am also planning to add exhaust temperature alarms on my exhaust elbows just slightly downstream of the shower heads. I will be using normally "open" switches, a separate Exhaust Alarm panel with a loud alarm and a strobe since I have poor hearing. The power (or "+") for this will be coming from the key switches for each engine.
The hardest part of all this will likely be the wire runs.

I understand what you are trying to do but it just seems more complicated. But, I do not have much experience with relays!

Jon

 

[racclarkson@gmail.com]

I found an exact match to the standard alarm that screws right in it’s place that wakes the dead. Came from Radio Shack if there are any left.

 

[Briankinley2004]

Normally open would have worked better for me but 205 deg was lowest I could find. The 200 deg is still too hot for the engines to get in my opinion but Lauderdale speedo advised to use them and they come highly recommended. Trouble is they are normally closed. I have mechanical gauges in E R and this is how I found out my electric ones weren't working right. They were reading 180 and 190 when the ones in E R were reading 140 which would be right for a cold start at 5 minutes of idle.

 

[Gusshr]

I just added 200 normally open switches to the main exhaust after both inboard and outboard exhausts meet (the large combined exhaust in the engine room). I connected them to the Maretron system through the NMEA2000 switch sensor they have "SIM100". I used this system because I can view the alerts on the flybridge and in the salon on the screens with no extra wiring.

I am not sure if I have selected a correct location (after both the exhausts meet for each engine) versus just after the water injection on only one of the exhausts???

I got the sensor from a warning system kit that is 12v that I bought online, but I did not like their schematics which is running 12v up to the heat switch only to loop and then get back to the panel, and the struggle would be which station to put it on (upstairs or downstairs). A better design is to ground one arm of the sensor to the engine block, and the other one run up to a 12 V buzzer and light, so that when the switch closes it would supply ground to the rest of the circuit and your buzzer and light turn on. This way you run a single wire to both stations (same wire could supply multiple stations). Thats how I would do it if I did not have the Maretron system.

 

[jrbrein]

Here are 200 degree F switches made by Aqua Alarm:

http://aqualarm.net/exhaust-engine-monitors-c-5/

I would place my switches just after or close to where the shower head ships in raw cooling water into the exhausts from each engine. I want to run a ground wire from the battery (-) to the switches and continue that ground wire from the switches to the Alarm panel and the circuit gets completed at the panel with a (+) wire from the key switches when the temperature hits 200 F, the switches close and alarms sing!

I like simplicity...hard wires and corrosion control with BoShield or whatever you like.

Jon

 

[Gusshr]

Here are 200 degree F switches made by Aqua Alarm:

http://aqualarm.net/exhaust-engine-monitors-c-5/

I would place my switches just after or close to where the shower head ships in raw cooling water into the exhausts from each engine. I want to run a ground wire from the battery (-) to the switches and continue that ground wire from the switches to the Alarm panel and the circuit gets completed at the panel with a (+) wire from the key switches when the temperature hits 200 F, the switches close and alarms sing!

I like simplicity...hard wires and corrosion control with BoShield or whatever you like.

Jon

so you just randomly select one of the two exhausts of each engine and put the sensor on that exhaust?

 

[Gusshr]

Here are 200 degree F switches made by Aqua Alarm:

http://aqualarm.net/exhaust-engine-monitors-c-5/

I would place my switches just after or close to where the shower head ships in raw cooling water into the exhausts from each engine. I want to run a ground wire from the battery (-) to the switches and continue that ground wire from the switches to the Alarm panel and the circuit gets completed at the panel with a (+) wire from the key switches when the temperature hits 200 F, the switches close and alarms sing!

I like simplicity...hard wires and corrosion control with BoShield or whatever you like.

Jon

Also the unit I had was exactly the one sold by aqualarm (but around $30 cheaper), the manual that comes with it shows that I add the sensor actually on the rubber exhaust hose obviously after the water joins the exhaust.

 

[Scarlett]

Another option that I used is to install water flow alarms. The flow sensor goes in the water line just after the water pump, that way if the flow of water stops for any reason the alarm goes off way before an over temp sender would set off an alarm. Aqua Alarm makes these also. They come with an alarm and light panel that shows which engine is setting off the alarm. The other advantage is you do not have to go out and check your water flow at the exhaust on start up. John

 

[Briankinley2004]

I just added 200 normally open switches to the main exhaust after both inboard and outboard exhausts meet (the large combined exhaust in the engine room). I connected them to the Maretron system through the NMEA2000 switch sensor they have "SIM100". I used this system because I can view the alerts on the flybridge and in the salon on the screens with no extra wiring.

I am not sure if I have selected a correct location (after both the exhausts meet for each engine) versus just after the water injection on only one of the exhausts???

I got the sensor from a warning system kit that is 12v that I bought online, but I did not like their schematics which is running 12v up to the heat switch only to loop and then get back to the panel, and the struggle would be which station to put it on (upstairs or downstairs). A better design is to ground one arm of the sensor to the engine block, and the other one run up to a 12 V buzzer and light, so that when the switch closes it would supply ground to the rest of the circuit and your buzzer and light turn on. This way you run a single wire to both stations (same wire could supply multiple stations). Thats how I would do it if I did not have the Maretron system.

Thanks for all the response. Im really wanting to keep it simple and not reliant on electronics or other stuff on the boat. Something that works independently of other items on the boat. Also as stated the sensors I have are normally closed so I need advice on normally closed circuitry. I have exhaust sensors too but want to be able to monitor coolant temps as those are closest to the heads

 

[tonytrakovich]

Here is your basic ladder diagram for that circuit. I do not know what alarm panel you bought. I have included a green power on lamp to show you system is on. Does your alarm have a red fault light? Does it have a buzzer silence switch? In this circuit, if the relay fails you will get an alarm. Circuit should be fused between key switch and alarm circuit.

 

[jrbrein]

so you just randomly select one of the two exhausts of each engine and put the sensor on that exhaust?

No.

Each exhaust shower head has a switch. Port engine panel and a Starboard engine panel.

Each is wired separately.

Jon

 

[Briankinley2004]

Here is your basic ladder diagram for that circuit. I do not know what alarm panel you bought. I have included a green power on lamp to show you system is on. Does your alarm have a red fault light? Does it have a buzzer silence switch? In this circuit, if the relay fails you will get an alarm. Circuit should be fused between key switch and alarm circuit.

Thanks Tony. That’s pretty much what I had in mind but wasn’t sure if it was the best way. The fuse and green lights are good ideas. I didn’t really buy a panel per se. it’s a combo buzzer and light that both activate when 12v is applied. (Cole Hersee 4112). I think I will poke around and find a 12 volt source with key on. I think the actual key circuit is 32 volts but I’m not sure. That was part of my question originally. Thanks for the help

 

[Moonhowler]

My port Murphy gauge is not reading at the helm, and I suspect that recent efforts to run a new transducer cable from the ER to the helm probably resulted in a kinked capillary tube. The wire chases are way crowded/tight, and successfully threading a new sensor and tube from the helm to the ER just doesn't seem likely. There is a capped off wire that looks like it is from a previous electrical gauge, and I'm wondering: IF i can isolate that wire, and it is already run to the helm, would an electronic gauge be able to use that wire as its positive lead, and I could then use a common ground in the ER? If so, I skip all the drama of wire chasing and life becomes much simpler.