temperature sensor in the exhaust line

danielefua

danielefua

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The wet exhaust line of my Perkins 4.108 has a sensor that triggers an alarm in case the hose temperature rises above 96°C.
The sensor (a dated - no more available - VDO 30/3/11) is screwed into a short stainless steel hose section at approximately two feet from the engine exhaust.
The sensor is badly corroded as is the s/s hose section itself so I am planning to replace the whole assembly.
I would appreciate if someone could recommend which new sensor should be fitted.
The specs of the present one are:
two poles,
switch, normally open,
6-24V, 100W,
96°C- 92°C,
120° max.
The thread is quite strange because it appears to be M17x1.5 even if I cannot be totally certain.

I understand that the exhaust gases are particularly corrosive so I wonder if I need to get a sensor different from the standard ones used in the cooling water circuit.

Thank you in advance for your help

Daniel
 
A temperature sensor on the outside of the stainless pipe would probably be just as effective and would last a long time?

How about a thermal switch set at, say, 95 degrees?

Tony.
 
NASA Marine do an exhaust temperature monitor, EX1, for about £80. This includes a sensor which mounts in the flexible exhaust via a 5mm hole (which needs drilling in the hose), and is simply strapped in place with tie wraps (supplied) around the outside of the exhaust hose. This connects to a small display unit showing the temperature, and which will sound an alarm at whatever temperature you want to set (default is 85 degrees). http://www.nasamarine.com/proddetail.php?prod=EX1

I've no experience of them, but was pondering a purchase myself.
 
You can use one of the low cost thermal switches from this range - http://cpc.farnell.com/jsp/search/b...nsor&Ntx=mode+matchallpartial&getResults=true
Use a NO switch and wire a piezo buzzer to 12 V through the switch. When the temperature is reached the circuit is closed.
Strap it to the exhaust manifold where the cooling water is injected, maybe with a little thermal paste to ensure a good contact, if the water stops the temperature will rise rapidly and the buzzer sounds.

I use a similar switch to activate a cooling fan in the locker where my battery charger is installed.
 
I fitted two of these two years ago, with surface mounted probes. The alarm is adjustable so I set it a few degrees above the max operating temp - even flat out this never goes above 40C on 255 HP engines.

This one is £16, but they are available cheaper from Hong Kong - EBAY 181006904049
 
superheat6k said:
I fitted two of these two years ago, with surface mounted probes. The alarm is adjustable so I set it a few degrees above the max operating temp - even flat out this never goes above 40C on 255 HP engines.

This one is £16, but they are available cheaper from Hong Kong - EBAY 181006904049
Click to expand...

That would suit me fine if I had the space for the bulky control unit and a very long extension lead to plug into the mains to provide the 220 volts power supply needed! ;)
 
My only doubt regarding outer surface mounted sensors is that they may be too slow in their response. The triggering of the alarm could be too late for the healthy survival of the rubber compound of the exhaust hose.

Daniel
 
danielefua said:
My only doubt regarding outer surface mounted sensors is that they may be too slow in their response. The triggering of the alarm could be too late for the healthy survival of the rubber compound of the exhaust hose.

Daniel
Click to expand...

I agree. I was pondering this earlier. An external one would probably respond fast enough if it was fitted to a section of metal pipe, perhaps?
 
The externally mounted sensor on the Sentry exhaust alarm triggers at 165F, whatever that is in new money, which is well below the point at which exhaust hose would be damaged. It's fitted to the rubber hose just after the mixing elbow.
 
LittleSister said:
Ah, that's better! Is that the type you fitted a couple of years ago? (I ask as the specified 12v +/- 10% would likely be exceeded when alternator charging, etc.)
Click to expand...

This is the spec sheet for the units I have. The spec doesn't mention the voltage tolerance, but not had any issues with the alternator voltage being around 14.4v, after all they only operate whent he engines are running.

https://www.dropbox.com/s/si7p6rh74aoiv30/Willhi Temperature controllers WH7016E.pdf
 
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