Exhaust Overheat alarm install Question

[Dougcole]

Hi All,


I am getting ready to install Aqualarm Exhaust Overheat alarms to my twin Yanmar 4LHA-STP. Installation is pretty straight forward (pulling the wires up to the FB will be a bear as always) but I have one question.


The alarm sensors switches are super simple, they just have two wires, one goes to a 12V source the other goes to the alarm board. I've got good access to a DC buss on my aft ER bulkhead that I can wire both sides into, but I think I'd rather have them pull off of the engine somewhere. Preferably someplace that is only hot when the engine is running. Any recommendations? Maybe on the 12V leg on the strater relay?


Or would it be better to just pull them off of the 12V buss?



Thanks,
Doug

 

[SteveK]

Doug,
Did not understand your description. I ran one wire to nearest ground and the other to the alarm board. The board also needs +/- and the positive needs to be switched. Since I have a master switch for CB instruments that is where I took power. But it has occurred that there may be one time when I do not run up top so will rewire to an ignition switch source.

 

[Dougcole]

The alarm board connects to a ground source on the aqualarm, the sensor (it's just a switch) does not. The wiring diagram shows that you wire from a pos source to the sensor on the exhaust hose and then from the sensor to the alarm board.


The alarm board has it's own Positive source and the aforementioned ground. I'll wire them to a fuse panel I have under my dash, no issue there.



It just seems cleaner to me if the sensor picks up off of the motor somewhere. I don't have to do it that way, I just like the idea of the alarm sensors powering up when the motor is started, no reason to have power running to them all the time.

 

[SteveK]

Yes from that instruction I see the confusion.
The runner to the sensor is looking for a ground source. When the sensor closes the alarm grounds out as in this drawing.
The power supplied feeds the alarm + side waiting for sensor to close.
The green ON light (not shown) shows that it is ready and that light needs an active ground not through the sensor.




But I will now have to review my setup and find instructions that came with it.

 

[DavidM]

The Aqualarm's wiring is a little weird in that DC goes to the switch and then to the alarm board. That means in order to have a source of DC that turns off and on with the engine, I suspect you will have to go to the "ignition" switch or key on the instrument panel and then back to the alarm switches. I can't think of any routine service on that engine that is affected by the ignition switch. Even the alternator output terminal is hot all of the time from the battery.

On a Cummins which has an engage to run solenoid on the fuel injection pump which should work as a source of switched DC, the Yanmar has an engage to stop solenoid that only gets power when you hit the stop switch.

This is contrary to the much simpler Borel wiring in which you power the alarm itself from the ignition switch and then run trigger wires to the alarm switches which close when the temperature is reached and then the wire goes to any nearby ground that completes the circuit.

David

 

[Dougcole]

Yes from that instruction I see the confusion.
The runner to the sensor is looking for a ground source. When the sensor closes the alarm grounds out as in this drawing.
The power supplied feeds the alarm + side waiting for sensor to close.
The green ON light (not shown) shows that it is ready and that light needs an active ground not through the sensor.

View attachment 108328


But I will now have to review my setup and find instructions that came with it.

Thanks Steve, so the setup in your diagram above puts the switch (sensor) in the ground, the aqualarm, at least according to the instructions that came with it, puts it in the pos wire. I assume the Aqualarm grounds through the alarm panel?


I notice that your instructions show to pull off of the ignition. That's pretty much my plan as well, I'd just like to find a convenient place to do it on the engines.

 

[Dougcole]

The Aqualarm's wiring is a little weird in that DC goes to the switch and then to the alarm board. That means in order to have a source of DC that turns off and on with the engine, I suspect you will have to go to the "ignition" switch or key on the instrument panel and then back to the alarm switches. I can't think of any routine service on that engine that is affected by the ignition switch. Even the alternator output terminal is hot all of the time from the battery.

On a Cummins which has an engage to run solenoid on the fuel injection pump which should work as a source of switched DC, the Yanmar has an engage to stop solenoid that only gets power when you hit the stop switch.

This is contrary to the much simpler Borel wiring in which you power the alarm itself from the ignition switch and then run trigger wires to the alarm switches which close when the temperature is reached and then the wire goes to any nearby ground that completes the circuit.

David

Thanks David, that makes sense.


Sounds like the best thing is just to go to the buss on the aft bulkhead.

 

[SteveK]

Doug, I will review and test my setup in a couple weeks when back at boat. The instruction diagram you showed suggests that both the sensor and panel want a + feed. But then both should be switched, why have power on 24/7 at either end.
I will check the panel, leave ground & pos connected and see if sensor terminal is + or -.
I may have done it wrong, no longer sure if your instructions suggest otherwise.

 

[catalinajack]

I obtained power from the output side of my oil pressure alarm switches. As soon as pressure rises enough to turn off the alarm buzzer, the Aqualarm is energized, about 1 second. In my case, very simple and very accesible.

The Aqualarm's wiring is a little weird in that DC goes to the switch and then to the alarm board. That means in order to have a source of DC that turns off and on with the engine, I suspect you will have to go to the "ignition" switch or key on the instrument panel and then back to the alarm switches. I can't think of any routine service on that engine that is affected by the ignition switch. Even the alternator output terminal is hot all of the time from the battery.

On a Cummins which has an engage to run solenoid on the fuel injection pump which should work as a source of switched DC, the Yanmar has an engage to stop solenoid that only gets power when you hit the stop switch.

This is contrary to the much simpler Borel wiring in which you power the alarm itself from the ignition switch and then run trigger wires to the alarm switches which close when the temperature is reached and then the wire goes to any nearby ground that completes the circuit.

David