Why is my gas alarm going off at 3am!!

[bluedragon]

Serious replies only please

In the last week or so our Plastimo Gas Alarm goes off more or less every night at around 03.00. I'm trying to eliminate all the usual suspects in the bilge (gas of course, H2 from battery charging, diesel or solvent fumes, even methane from the holding tank!). But WHY OH WHY does this only happen at night, within a period of about an hour, regular as clockwork it seems. That has me completely beat!

My wife says it's because the boat is closed up, but if we leave it closed during the daytime nothing happens.

Has anyone ever had a similar occurrence or a feasible explanation?

In the past few weeks we've a) changed the gas bottle - but it vents out directly overboard b) had a leak from the holding tank pump which went down into the bilges c) have left the fridge running all night (unusual for us) d) a few months ago fitted a second house battery e) been on 24 hrs mains power in the marina. I can argue a case however unlikely for one of these to be the cause or a contributory factor...BUT why only at night at 03.00

 

[VicMallows]

Can we first establish please that this is quite definitely a GAS DETECTOR ...and not a Carbon Monoxide detector or anything else.

Where exactly is the detector (or its sensor(s)) located. ?

 

[ProDave]

Eliminate a genuine gas leak by turning the gas off at the cylinder overnight.

If it still goes off, it's not a gas leak.

 

[VicS]

Plastimo gas alarm ??

The EvrSafe ISS-1040 gas detection system ?

Carbon monoxide alarm ?

Handheld gas detector ?

The first presumably.
It detects a variety of toxic and flammable gases with 4 detectors in different locations.

Does it not tell you which sensor has caused the alarm and what gas it thinks it has detected?

 

[billcowan]

Must be the Vindaloo and Newcastle Brown the.

 

[marklucas]

Just a theory

I've had this happen to me on a yacht once - it's a bugger finding the permanent power line and in-line fuse at 5AM!

So at night only, the boat is relatively sealed up and there are people on board. So CO2 is being expelled into the boat. This is heavier than N2 or O2 so displaces them first, the other flammable gases that will be detected will only get pushed out if they're lighter and the N2 / O2 concentration gets low. The flammable gasses concentration goes up ...

Now I have only seen this happen after cooking dinner for 14 people on a 37' yacht who were all on board for 4 hours. But as previously advised, check and double check you haven't got a serious leak, but then try increasing ventilation.

Let us know if it works.

 

[Steve Clayton]

Just maybe......
http://answers.yahoo.com/question/index?qid=20080202074253AAxLs2L

 

[nigelmercier]

BUT why only at night at 03.00

For the same reason that the batteries in regular smoke detectors always fail at the same time, because it is the most annoying

I don't know the Plastimo, but my Pilot alarm sounds briefly if the power is interrupted.

 

[bluedragon]

AGAIN!! Last night at 02.50

It's uncanny how the time is always more or less the same. And this time the sensor was out of the bilge and hanging on a hook about 9" above the cabin sole with the boards in place. Definitely no smell of gas or anything else either. The unit says "Plastimo LP Gas Alarm for Boats" so I guess that's what it is. If I switched-off the boat power and then on again the alarm would go off again, but if I powered down until 07.00 and then switched-on it was fine the whole day until 03.00 again. But today it wouldn't reset itself at 08.00. So the fuse is now out! Can't take any more disturbed nights. It's got to be a faulty unit / sensor, but how does it know to go off at 03.00?? Really weird...

 

[Norman_E]

.... but how does it know to go off at 03.00?? Really weird...

Because it knows its got you rattled!

 

[ProDave]

It's uncanny how the time is always more or less the same. And this time the sensor was out of the bilge and hanging on a hook about 9" above the cabin sole with the boards in place. Definitely no smell of gas or anything else either. The unit says "Plastimo LP Gas Alarm for Boats" so I guess that's what it is. If I switched-off the boat power and then on again the alarm would go off again, but if I powered down until 07.00 and then switched-on it was fine the whole day until 03.00 again. But today it wouldn't reset itself at 08.00. So the fuse is now out! Can't take any more disturbed nights. It's got to be a faulty unit / sensor, but how does it know to go off at 03.00?? Really weird...

Did you do as I suggested and turn the gas off at the bottle to confirm beyond doubt that it was not a real gas leak?

 

[ben_m]

I had exactly the same problem - turned out it was going off due to low battery voltage, it only ever happened at anchor at 0100 - changing to an LED anchor light and repalcing the battery helped!

 

[SimbaDog]

The only time mine has ever gone off was about 06.00hrs & it was due to low battery voltage!

 

[pmyatt]

It's uncanny how the time is always more or less the same. And this time the sensor was out of the bilge and hanging on a hook about 9" above the cabin sole with the boards in place. Definitely no smell of gas or anything else either. The unit says "Plastimo LP Gas Alarm for Boats" so I guess that's what it is. If I switched-off the boat power and then on again the alarm would go off again, but if I powered down until 07.00 and then switched-on it was fine the whole day until 03.00 again. But today it wouldn't reset itself at 08.00. So the fuse is now out! Can't take any more disturbed nights. It's got to be a faulty unit / sensor, but how does it know to go off at 03.00?? Really weird...

Night Flatulence ?

 

[daveyw]

Did you do as I suggested and turn the gas off at the bottle to confirm beyond doubt that it was not a real gas leak?

And burn off the excess gas in the line using the cooker.

 

[FistralG]

Battery

I had exactly the same problem - turned out it was going off due to low battery voltage, it only ever happened at anchor at 0100 - changing to an LED anchor light and repalcing the battery helped!

The only time mine has ever gone off was about 06.00hrs & it was due to low battery voltage!

Can be the only logical explanation for it happening so regularly at the same time. During the day the battery is being topped up by normally activities. In the wee small hours the battery has been drained sufficiently for the voltage to drop below the critical level for the gas alarm.

Check your battery.

 

[VicMallows]

Can be the only logical explanation for it happening so regularly at the same time. .

Certainly a plausible explanation; but not conclusive. I would first want to establish that his particular alarm does indeed sound under low voltage conditions. Might need to take temperature into account as well.

Just being thorough.

Vic

 

[bluedragon]

Been on mains power, so low battery should be not an issue...but what about some kind of voltage spike in the night??

No it's not gas. Bottle has been turned off and there is zero smell. I understand the human nose is more gas sensitive than these detectors anyway.

The missus reckons we should get a canary like in the old days in the mines, but it's a bit difficult fitting a cage into the bilge

 

[ColdFusion]

Try putting a candle in the bilge. It will go out if there isn't enough oxygen

 

[VicMallows]

I understand the human nose is more gas sensitive than these detectors anyway.

The missus reckons we should get a canary like in the old days in the mines,

I don't know about all noses, but most certainly true of my wife. She also has an amazing sensitivity to alcohol in the tiniest concentrations.

Slight problem with the canary: you knew if the methane level was too high because the canary died ... humans then had enough time to get out. I do still have a genuine gas testing lamp (still in use in the 1960s) .... you judged the methane level by the colour of the flame.

Vic