This sort of thing really annoys me

sailorman said:
we have CO2 & fire
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CO, presumably?

We have that and LPG, no fire. Must admit that smoke alarms didn't occur to me, but I can't see any obvious reason why I should have them in the house (and I do) but not in the boat. I suppose I'd need one in each cabin, and they are ugly...

Pete
 
Fire alarm in each sleeping cabin and engine room. CO alarm in three cabins and LPG alarm in galley/saloon. They all cost peanuts and they represent the two biggest dangers to life on a boat - fire and CO. Some people pay twice the cost of a budget liferaft 'just in case' even though statistically there's no chance of using it but maybe skimp on a £4 alarm. Every second counts in a fire on board.
 
I had a gas alarm - on my 2nd boat. Made and presented by crew who also was an electronics patent agent.
Housed, appropriately in a Guiness can, it was mounted, in the bilge, underneath the HP Gaz bottle/burner.
When tested it worked a treat.
We (me, 2 boys aged 5 & 7 and their sister 14), sailed from Poole to Weymouth, there we rafted up about 5 boats out, at the Cove.
To our extreme embarrassment, every 15-20 minutes the alarm started and howled away at us until disconnected.
After the 5th time we discovered the reason, about 4-5 minutes after a car had started on the street above, the alarm would go off - we didn't wait to find out if it did the same for a diesel as it did for a petrol- engined car.
Of course back then. in the 1970s cars still used crude carburettors and chokes.
 
Big John said:
"We've fitted gas so need a gas alarm. The 'marine' units are insanely expensive, even NASA charge about £65 yet claim it uses inexpensive parts. So then I come across this:"

Not wishing to be a kill joy but non of the units shown have a separate "sensor" which in the case of LPG, which is heavier than air, has to be mounted in the lowest position to be able to detect any gas in the bilges etc. Ok for CO as that does lurk every where and the unit can be about 1metre above the floor level. These also have problems if mounted in a draft area eg open door/window.
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Bobc said:
As Big John says, you need the gas sensor to be in the bilges because LPG is heavier than air.
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For the Trio.....

http://www.ebay.co.uk/itm/MOTORCARA...g=20140407115239&rk=10&rkt=30&sd=271160699983


And additional sensors

http://www.ebay.co.uk/itm/like/2711...1=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108&ff19=0


You can have up to 3 sensors.

I have one mounted below the stove for any gas leaks, the other two are mounted mid level in the sleeping cabins so they get any CO.

Works for me. I specifically didn't want to have a gas alarm, and a seperate CO alarm, having had the excellent (but now impossible to get) Dualwatch gas/co alarm on a previous boat.
 
Thanks for the links, Comrade. Looks very useful.

3 external sensors means that there are 4 sensors in the system altogether, yes? One is built in to the main unit?

So, main unit in saloon with it's own sensor there, one sensor in each of two cabins, third sensor somewhere low down specifically for LPG-related leaks around the gas installation?

Does the main unit have some indicators to tell you what sort of gas it has detected?
 
Saguday said:
Thanks for the links, Comrade. Looks very useful.

3 external sensors means that there are 4 sensors in the system altogether, yes? One is built in to the main unit?

So, main unit in saloon with it's own sensor there, one sensor in each of two cabins, third sensor somewhere low down specifically for LPG-related leaks around the gas installation?

Does the main unit have some indicators to tell you what sort of gas it has detected?
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The main unit does not have a built in sensor but for my application the location of the low down sensor for LPG is also on the main "route" for the sources of CO so I hope it would also pick up a CO build up.
 
blackbeard said:
From time to time, as seems a good idea, I get down on all fours and have a good sniff.
Effective, reliable, unaffected by moderate amounts of damp, uses 0 amps, and costs £0.
If I'm asleep the gas will be firmly turned OFF at the regulator.

Need to be careful though - my crew has no sense of smell (not uncommon).
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Careful, yes. Carbon monoxide has no smell. Nor does LPG unless mercaptane is added, which is required in most countries, but not all.
 
prv said:
The "smell of gas" is methyl mercaptan, yes, added so that you can detect a leak. Butane on its own doesn't really smell.

Pete
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Back in the 1980s I visited the British Gas terminal at Bacton on Sea. That was where gas from the North Sea was piped ashore and where they added the smelly stuff. Methyl mercaptan is so volatile and so smelly that everywhere on the site you could smell it. They were constantly receiving calls from the public telling them they has a gas leak. Of course they hadn't but, no matter how big they made the flanges on the pipework joins, a small amount of the stuff always found its way into the open air.
 
Comrade Red said:
The main unit does not have a built in sensor but for my application the location of the low down sensor for LPG is also on the main "route" for the sources of CO so I hope it would also pick up a CO build up.
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Hmm. This is the bit on their site that confused me:

"Simple use once wired in its just a case of turning the device on for peace of mind, the alarm has an in-built sensor making them totally standalone."

They refer to the 'alarm' and the 'sensors' separately so this suggests there is a sensor built in to the main unit??
 
Angele said:
Back in the 1980s I visited the British Gas terminal at Bacton on Sea. That was where gas from the North Sea was piped ashore and where they added the smelly stuff. Methyl mercaptan is so volatile and so smelly that everywhere on the site you could smell it. They were constantly receiving calls from the public telling them they has a gas leak. Of course they hadn't but, no matter how big they made the flanges on the pipework joins, a small amount of the stuff always found its way into the open air.
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Mercaptan doesn't burn in the engines of LPG cars, so the exhaust smells of leaking gas, which can be unsettling at first.
 
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