Nereus or Pilot gas alarm

Leighb

Leighb

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I have read various old threads concerning gas alarms and a number suggest that the Pilot system which is much cheaper is pretty unreliable as the sensors fail if they get even a bit damp - such as from condensation!!! - this makes them "unfit for purpose" in a marine environment I would have thought?

Have they improved at all, as some of the threads relate to 2 or 3 years ago? If not I guess I may have to spend a good bit more on the Nereus system.
 
Buy the Nereus. While others fail if exposed to the slightest amount of moisture, the Nereus sensors cope well with getting wet, dusty and generally contaminated without failing. About as bulletproof as gas alarms and in particular, gas alarm sensors, get.
 
Leighb said:
I have read various old threads concerning gas alarms and a number suggest that the Pilot system which is much cheaper is pretty unreliable as the sensors fail if they get even a bit damp - such as from condensation!!! - this makes them "unfit for purpose" in a marine environment I would have thought?

Have they improved at all, as some of the threads relate to 2 or 3 years ago? If not I guess I may have to spend a good bit more on the Nereus system.
Click to expand...

You might also look at the Nasa Gas Monitor. The sensor is at least splash proof

http://www.nasamarine.com/product/gas-monitor/
 
How do people actually use these gas alarm systems? Do they leave them on 24/7, so that a gas leak whilst the boat was unattended will sound an alarm? Or do they switch them on when arriving at the boat? If the latter, the very act of switching the power on may be dangerous if there's been a gas leak. And, it takes a few minutes before the alarm will detect gas, so do people stand in the cockpit waiting for the system to start up?

Edit: I note that the Nasa Gas Monitor's instructions say to wire it to a "permanent power supply", but it only draws 30mA. The equivalent Nereus draws 60mA.
 
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pvb said:
How do people actually use these gas alarm systems? Do they leave them on 24/7, so that a gas leak whilst the boat was unattended will sound an alarm? Or do they switch them on when arriving at the boat? If the latter, the very act of switching the power on may be dangerous if there's been a gas leak. And, it takes a few minutes before the alarm will detect gas, so do people stand in the cockpit waiting for the system to start up?

Edit: I note that the Nasa Gas Monitor's instructions say to wire it to a "permanent power supply", but it only draws 30mA. The equivalent Nereus draws 60mA.
Click to expand...

We leave our twin Pilot switched in to the main batteries - it comes on when we turn the batteries on and thereafter it remains on. We never leave the boat with the gas 'on' - it is shut down at the bottle outside the cockpit.

So the risk is there, I suppose, at first entry, but I suggest pretty low, and after that, the monitor has it covered.
 
The NASA sytem is good value, but lacks an important feature - as far as we are concerned. It has no facility to connect to a remote solenoid valve to shut off the supply in the event of a leak. This feature also means you can remotely switch the gas supply on and off without having to go out into a cold/wet cockpit. :D

We had the Nereus system in our last boat and it worked faultlessly for 9 years, and went off on two occasions and on one of them gave us immediate notice of a major leak at the bottle which had just been changed. I would like this again, but our budget is limited and some things are more desirable than others so am looking for more economical alternatives.
 
pvb said:
How do people actually use these gas alarm systems? Do they leave them on 24/7, so that a gas leak whilst the boat was unattended will sound an alarm? Or do they switch them on when arriving at the boat? If the latter, the very act of switching the power on may be dangerous if there's been a gas leak. And, it takes a few minutes before the alarm will detect gas, so do people stand in the cockpit waiting for the system to start up?

Edit: I note that the Nasa Gas Monitor's instructions say to wire it to a "permanent power supply", but it only draws 30mA. The equivalent Nereus draws 60mA.
Click to expand...

The gas system will be shut off at the bottle when the boat is unattended. The only , unlikely, risk is a leak from the bottle but since that is in a gas locker any leaking gas will drain overboard.

On arrival switch on the main battery isolator. Sparks from the contacts are only really likely when switching off, far less likely when switching on. A decent quality isolator is ignition protected anyway. The alarm will then power up. When it has gone through its start up process and been "tested" with the test buttonthe gas can be turned on at the bottle after checking all appliance gas taps. At this point the Alde will indicate any leaks on the system.

Now you are safely up and running. The alarm will sound if any leaks develop.

The instructions for the Pilot alarm say to connect directly to the battery isolator so that it automatically powers up when the isolator is closed. It draws 90mA in standby.
 
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pvb said:
How do people actually use these gas alarm systems? Do they leave them on 24/7, so that a gas leak whilst the boat was unattended will sound an alarm? Or do they switch them on when arriving at the boat? If the latter, the very act of switching the power on may be dangerous if there's been a gas leak. And, it takes a few minutes before the alarm will detect gas, so do people stand in the cockpit waiting for the system to start up?
Click to expand...

Mine is off when I am away from the boat. When I arrive, the first thing I do is to go below and turn on the batteries, the gas alarm and the lights. Any crew with me wait on deck while I do this. So, if the whole thing goes BOOM, it is probably only me who gets 3rd degree burns. The sacrifices I make for my crew.....

Seriously, with the gas always off at the bottle when I am not on board, the chance that gas had somehow made its way below is very low indeed. Plus, I would like to think I would notice the smell of gas having come on board from the fresh air if it had reached a concentration where it was explosive.

For me, the gas alarm becomes the principal defence against a slow leak that might not be noticeable when remaining below decks and when the gas tap might be on.

I have the Nereus, which replaced the one that the boat was supplied with when it stopped working (because the detector got damp or whatever). Had it 4 years now and it is still working fine. (Last tested by a gas engineer this time last year).
 
I fitted a Nereus single sensor to my last boat and it worked faultlessly for 6 years, including detecting 2 leaks from faulty regulators. Gas was always off when I wasn't on board and the arrival procedure was to switch domestic battery on, then gas alarm. I then waited until the alarm had gone through start up before switching anything else on.
My new boat comes with a Pilot Monitor which will be changed in the next few days for a Nereus combined gas and CO alarm.
 
I fitted the Pilot twin sensor and combined solenoid system because it a) automatically shuts off the gas at the solenoid in the event of gas being detected and b) I thought it was good value for money. Wish I knew then about the apparent lack of waterproofing of the sensors! but so far so good - coming up to a year since installation and both sensors mounted where they should not get wet.

The gas is always turned off via the solenoid after use and turned off at the bottle when leaving the boat for more than a few hours.
 
bitbaltic said:
No-one's mentioned the Haztec, which we had profesionally fitted by our marine gas fitter. Seems fine to me, apparently also MCA approved.

http://www.whayward.com/Details.cfm?ProdID=644
Click to expand...

Another recommendation for the Haztec. We've had a twin sensor + solenoid shutdown system for 16 years and it has behaved flawlessly.

Interestingly the instruction manual specifically mentions that after a period of non-use, the sensors will need to warm-up (i.e. dry off?) which may take a couple of cycles of turning on and waiting for the green light and solenoid open to function.
 
Our alarm is normally on all the time - but the boat is on shore power permanently and we spend three or four days on it every week. On those few occasions when we are away for longer periods, we will isolate the batteries which will disconnect the alarm, but we then use a hand-held gas pen to check the bilges before we power things back up again.
 
Thanks for the various replies, I had not heard of the Haztec, which surprises me slightly since Will Hayward did the new gas installation on my last boat 9 years ago!

It sounds promising, but makes no mention of the waterproofing of the sensor which seems to be the failing of the Pilot system? Certainly more reasonable priced than the Nereus.
 
A significant consideration is current consumption since the gas sensor is left on all the time when we are aboard.
For reference (manufacturers' data):
Nereus WG 100 L 60mA
NASA gas monitor 30mA
Pilot Mini 12V 90mA
Waeco MSG150 100mA (1.3W)

Does anyone know about the Haztec? I can't find any data for current consumption.

While looking into these gas alarms, I found this kit which actually runs off 9V but is supplied with a mains power supply. It claims to use 50mA. I can't find any information on water resistance but for £36 it's a lot cheaper than most of the alternatives.

Derek
 
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