Exhaust Temp Alarm

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stownsend

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Afternoon

A very quick query ! I'm knocking together an exhaust gas sensor / LCD / alarm system for a Volvo Penta 2020 with some spare bits I have lying around. The temp sensor will be clipped to the exhaust hose - any ideas on the best temp to set the alarm off ?

I did have a quick search on the forum and tech manuals and by the looks it 90 degrees for the thermostat to open on the cooling system but nothing for the exhaust.

Cheers

Stu
 
pvb said:
Set the alarm at 130 deg C.
Click to expand...

That seems a bit high to me

Even through my engine water temperature runs at about 80 to 90 deg C my exhaust injection elbow only runs at about 60 deg C

I would measure it under normal running conditions and set it about 20 deg C above that measurement.
 
Rogershaw said:
That seems a bit high to me

Even through my engine water temperature runs at about 80 to 90 deg C my exhaust injection elbow only runs at about 60 deg C

I would measure it under normal running conditions and set it about 20 deg C above that measurement.
Click to expand...

I would set it by trial and error. During a good run with the engine at whatever are your normal highest revs see what temperature is being achieved. Then set it 10 degrees higher than that. If it goes off on another long run and everything is OK there's no damage done and you can set it 5 degress higher.

Richard
 
stownsend said:
Afternoon

A very quick query ! I'm knocking together an exhaust gas sensor / LCD / alarm system for a Volvo Penta 2020 with some spare bits I have lying around. The temp sensor will be clipped to the exhaust hose - any ideas on the best temp to set the alarm off ?

I did have a quick search on the forum and tech manuals and by the looks it 90 degrees for the thermostat to open on the cooling system but nothing for the exhaust.

Cheers

Stu
Click to expand...

I monitored a spot on the exhaust injection bend before installing a similar alarm, the temperature was surprisingly low, around 30 - 35 degrees C (rose to 40 - 45 degrees some ten minutes AFTER engine shut down). I choose a bimetallic switch closing at 70 degrees. Note the switch is on the bend, not on the rubber hose. This is on a 20 hp Beta.
 
Thanks for the responses, I've got a couple of temp sensors - one runs up to 125 degrees and the other tops out at 50 degrees so will give both a try and see what readings I get.

The outlay comes to about £7 inc the lCD screen and arduino nano. A bit cheaper than the NASA version !

Cheers

Stu
 
I fitted an alarm system using a 12v aquarium controller switch (about £10) with a sensor strapped to the stainless steel exhaust mixer elbow on our Nanni 35 . This gives a continuous digital readout and I was quite surprised how low the temperature is when the engine is running : around 21-28C. I have currently set the alarm at 35C, which is probably a bit low as the alarm triggers on restart if the engine is still warm from recent running and the exhaust elbow has taken up heat from the engine. However, it is reassuring to see the readout falling quickly as the cooling water starts to flow again.
 
stownsend said:
Thanks for the responses, I've got a couple of temp sensors - one runs up to 125 degrees and the other tops out at 50 degrees so will give both a try and see what readings I get.

The outlay comes to about £7 inc the lCD screen and arduino nano. A bit cheaper than the NASA version !

Cheers

Stu
Click to expand...
Someone else using arduinos on board :cool:
I replaced the fridge thermostat with one, works great. With bluetooth to view/change the settings and an so card to log.
I was thinking of doing the same as you, but also putting a sensor on the stuffing box and logging batt voltage. Is it a ds18b20 sensor you are using?
All that stuff is so powerful and cheap.
And fun :)
 
There was a good article in PBO about this a couple of years ago as a practical project to make an alarm from a basic Maplin kit. I'm not sure if I still have the article and will have a look. I fitted it around a year ago and it has a variable temp setting, I think it is set to around 80c, I think.
 
I went the expensive route and fitted the Nasa kit as I liked how neat it was and had an illuminated large display. Mine is set to alarm at 45 deg c and normally runs about 26-29 c (volvo D130)
 
I also fitted a cheap chinese LED aquarium controller which has been excellent.
They were so cheap I bought 3, one for each engine ehaust and one to measure the engine room ambient temp.

As said above the engines run at around 21 to 35 (depending on time of year, i.e. ambient & sea water temp)
The engine room varies from around 30 to 40ish, but importantly after shutting down heat soak increases everything to around 50 deg C.

Therefore I would set your alarm at around 60 or 65 for best effect and to avoid false alarms when restarting in hot weather, and still allow plenty of early warning of cooling problems.
 
Loving the Arduino, at the moment building a full monitoring system for boats / caravans etc.. using GSM. I had some bits spare so saw the article in PBO but wanted to see the temp on an LCD.

Cheers

Stu
 
I have ordered the vetus temp alarm from ASAP. Heat sensor goes into a drilled hole at top of exhaust hose. I assume it measures the mixed temp of combustion gases and heat exchanger discharge salt water. AS salt water is pulsing I assume this temp can vary - any idea what alarm temp is set at - just interested

Not received the alarm yet but in case instructions are not clear I assume the exhaust hose is drilled as near to the exhaust elbow as possible.. As hose is almost vertical in this position I assume it doesn't matter which side the heat sensor is fitted?

Any advice?
 
Sailfree said:
I have ordered the vetus temp alarm from ASAP. Heat sensor goes into a drilled hole at top of exhaust hose. I assume it measures the mixed temp of combustion gases and heat exchanger discharge salt water. AS salt water is pulsing I assume this temp can vary - any idea what alarm temp is set at - just interested

Not received the alarm yet but in case instructions are not clear I assume the exhaust hose is drilled as near to the exhaust elbow as possible.. As hose is almost vertical in this position I assume it doesn't matter which side the heat sensor is fitted?

Any advice?
Click to expand...

Vetus appears to be set at about 70 deg C according to the ASAP web blurb. The reason for getting the NASA one was that you get a constant read out of actual temp from the sensor and you can set the alarm at what you like - mine is at 50 deg and runs 25-35 deg C in normal conds.
 
I've used N/O thermal switches like this to close an alarm circuit when over temperature is reached.
Mounted with a strap and using a little thermal paste to give a good thermal connection. They are available with various temperature triggers.

http://cpc.farnell.com/microtherm/03en35t044-20-30/thermal-switch-n-o-30c/dp/SN35838

I've got one on my exhaust manifold which sounds a buzzer if the water flow stops and another mounted on the cooling fins on my battery charger.
The charger is in a small locker and when it's charging at a high rate and gets hot, the switch turns on a 3" PC cooling fan to give additional air circulation.
 
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