I finally got around to wiring up my fuel vapor detector and CO monitor..

Now I'm having problems with false alarms from the fuel vapor detector.

It is suppose to detect gasoline and propane. I have not gasoline aboard at
this time (will have gas for the dingy OB while cruising) and the only
propane is in a tank on the stern rail for the MAGMA BBQ. Not even hooked up
at this time..

Seems the alarm goes off after I run my diesel engine for about 20 to 30
min. However this false alarm happens about 10 min. after I secure the
engine.

The Fuel Vapor Detector sensor is located in a dry location about 18 inches
from the bottom of my engine room bilge sump. This is the lowest point in
the boat for gas or propane fume to accumulate.

I can't imagine why I'm getting fumes off my diesel that would set off the
alarm. The alarm is intermittent and continues to go off/on for about 30
min. or until I pull the fuse.

I have tried running a elect fan, directed towards this bilge area, but it
doesn't seem to purge any fumes. I have checked to make sure the sensor is
dry, no loose connections, etc.

Could this be the result of a bad sensor??

Steve
s/v Good Intentions

jSteve,

Ideally you would check the area with a lab instrument to see exactly
what you are dealing with (fire dept's may have something). At the very
least I would buy (you can always return it most places) one of the home
CO2 detectors with readout to verify if it is CO2 or not. I think you
can now get them for propane and maybe gas but am not sure.

Regards, Ron

Steve wrote:

Now I'm having problems with false alarms from the fuel vapor detector.

The things will detect nearly any hydrocarbon and are sensitive to
moisture if mounted low in the bilge.

Your engine probably vents crankcase fumes and diesel vapors into the
engine compartment ... the time delay sounds about right for the engine
to heat up and start "fuming" as well as increasing the local humidity.

Can you adjust the sensitivity or relocate the sensor?

Rick

I think I'm going to have to relocate that damn thing.

I just came back from a day with the family. Light to no wind so we motored
for several hours. With in 20 mins from leaving the dock, the gas/propane
detector went of and on, just as I discribed.. I finally pulled the fuse..

I really don't want to move it but there is no way to adjust the
senseativity.. The main bilge is where I would most likely get vapor from
gas or propane, when I have it aboard.

I'm sorry now I ever even installed the thing.

Thanks Rick,

Steve

Steve wrote:

I really don't want to move it but there is no way to adjust the
senseativity.. The main bilge is where I would most likely get vapor from
gas or propane, when I have it aboard.

Well, you could always wire the power supply so that the detector is
"off" when the engine is running.

What kind of air supply and ventilation is provided for the engine
compartment? You could also remount the sensor so that it is in "fresh
air" being drawn to the engine when it is running. It sounds like there
isn't much air flow around the sensor even when the engine is running.

You could route an induction hose from the engine air inlet to a low
point in the bilge. That would provide positive ventilation for the
lower bilge so that you might never reach LEL in the event of all but a
huge leak. Put a "suck-in" door in it up high so that a flooded bilge
won't choke off the engine.

Just a couple of ideas not based on seeing the installation ... they are
worth what you paid for them.

I'm sorry now I ever even installed the thing.

Sometimes having too much information can be problem. 8-)

I used to fly mail across the mountains of Montana in the middle of the
night and we used to talk about what we would do if we were ever forced
down in bad weather. The concensus was that we would turn on the landing
lights until we saw something we didn't like then turn them off.

What you don't know will probably kill you but at least you won't be
worrying so much about it.

Rick

I finally got around to wiring up my fuel vapor detector and CO monitor..

Now I'm having problems with false alarms from the fuel vapor detector.

Have had a Zintex fuel vapor detector in the engine compartment
operating almost continuously for over ten years now. The sensor has
a limited life span (and limited shelf life) and fails safe; mine
started falsing at six years and required replacement. Essentially
they become more sensitive as they degrade and signal unnecessarily
when vapors are below 20% LEL. The factory said they last longer when
continuously powered up; expect 3-5 years when used intermittently.
Although yours is new; maybe that's the problem, an old or defective
sensor.

I find it hard to believe the problem is hydrocarbon leakage from the
engine if there's no falsing while the engine is running.

Splash water or immersion quickly poisons the sensor; has yours gotten
wet in the past? I faintly recall shortening the sensor cable is a
no-no; that might cause falsing. Prior to coughing up $60 for a new
one can you test your sensor by borrowing a dockmate's and seeing if
the problem persists?

Also, be aware the detector is very sensitive to hydrogen, so wet-cell
battery gassing will trigger it if there's a route from the batteries
to the engine compartment. A 13.8v float voltage triggers mine after a
few hours on a calm day, 13.4v doesn't.

If you're running a 3 stage regulator and the batteries are fully
charged before engine startup, the regulator will quickly reach the
14.4v acceptance phase and vigorous gassing will start. Takes a while
for the concentration to build up at sensor height because hydrogen is
lighter than air. If your blower is on while the engine is running,
it might adequately vent the hydrogen until you shutdown the engine.
I asked the factory about this and they said hydrogen is much
"stickier" than big molecule hydrocarbons and it takes a while for the
sensor to flush itself if a high hydrogen concentration triggered it.

Of course, if you have gelcells or AGMs that's not the problem g.

Is it a new boat? New fiberglass offgasses components that set off these
false alarms. Bad news is that there isn't anything you can do about it
except let the hull "age".

"Steve" wrote in message
...
I think I'm going to have to relocate that damn thing.

I just came back from a day with the family. Light to no wind so we
motored
for several hours. With in 20 mins from leaving the dock, the gas/propane
detector went of and on, just as I discribed.. I finally pulled the fuse..

I really don't want to move it but there is no way to adjust the
senseativity.. The main bilge is where I would most likely get vapor from
gas or propane, when I have it aboard.

I'm sorry now I ever even installed the thing.

Thanks Rick,

Steve

you might try contacting the mfr. to see whether it's defective, oversensitive
Joel Albert
Potomac, MD
))

The Self Life my be the factor here. I purchased the CO and the Fuel Vapor
detectors over 5 years ago, along with some other boat equipment as Boat US
was closing it's store in Seattle.

Never realize that might be a problem..

I will get the mfg and model number and see it I can get a replacement
sensor.. I think the brand name was Aqua..(something or other) I don't see
them listed in any of the current catalogs (not a good omen).

Steve
s/v Good Intentions