Fireboy CO Monitor Replacement

Nodak7

Nodak7

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Sep 28, 2008
1,256
Hunter 41DS Punta Gorda, FL
I recently replaced my Fireboy CMD4 - MR CO Monitors (3) due to a required end of life (5 years) replacement. I purchased and installed three (3) replacement and supposedly upgraded Fireboy CMD5 - MD CO Monitors. The install went well and I thought successfully. However, for some reason after a couple of days they began to alarm for no apparent reason. Like sitting at the dock with absolutely nothing running on the boat. I reset them and within a few hours they begin to alarm again. Right now they are disconnected since they will just begin to alarm for no apparent reason. Which is a safety concern. But it just seems to be a nuisance alarm right now. Has anyone else had this issue with the new Fireboy CO Monitors or is it just me?
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
22,929
CAL 35 Cruiser #21 moored EVERETT WA
I have there Propane detector. It was alarming when I ran the auxiliary engine. I replaced the sniffer. No more false alarms.

Your problem is different.
Just to be on the safe side, how certain are you that there is not a real issue. I would get one of the less expensive battery home units and see if it alarms.
The Fireboy manual says the alarm can be triggered by chemicals in the air or off gassing of new plastics in the boat.

Thus the suggestion of trying a different CO alarm. We occasionally have decomposition gas issues bubbling up from the marina bottom mud.
 
Nodak7

Nodak7

.
Sep 28, 2008
1,256
Hunter 41DS Punta Gorda, FL
jssailem said:
I have there Propane detector. It was alarming when I ran the auxiliary engine. I replaced the sniffer. No more false alarms.

Your problem is different.
Just to be on the safe side, how certain are you that there is not a real issue. I would get one of the less expensive battery home units and see if it alarms.
The Fireboy manual says the alarm can be triggered by chemicals in the air or off gassing of new plastics in the boat.

Thus the suggestion of trying a different CO alarm. We occasionally have decomposition gas issues bubbling up from the marina bottom mud.
Click to expand
Thanks JS! That was my next plan to get another CO Monitor and check to see if indeed there is something going on. It just seems strange that the old ones never went off and these seem to continually go off. Just wondering if anyone else has had this issue with these monitors. I will know today if there is anything to this I hope! Thanks
 
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Davidasailor26

Davidasailor26

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May 17, 2004
5,588
Beneteau Oceanis 37 Havre de Grace
Was your battery charger on at the time of the false alarms? Battery off-gassing has been a reported cross-sensitivity for CO sensors in past threads.
 
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Nodak7

Nodak7

.
Sep 28, 2008
1,256
Hunter 41DS Punta Gorda, FL
Davidasailor26 said:
Was your battery charger on at the time of the false alarms? Battery off-gassing has been a reported cross-sensitivity for CO sensors in past threads.
Click to expand
Thanks David! I did consider this as a possibility since we have a solar system but these alarms were also going off after dark as well!
 
Scott B

Scott B

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Sep 20, 2006
2,952
Hunter 33 Georgian Bay, Ontario, Canada
Nodak7

Nodak7

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Sep 28, 2008
1,256
Hunter 41DS Punta Gorda, FL
Scott B said:
I have the exact same problem. Replaced with Fireboy couple years ago and kept going off. Only thing I can think of is the batteries off gassing and the detectors being too sensitive.

If you Google problem with CO detector and lead acid battery charging, many articles come up about battery charging and CO detectors.

Click to expand
Yeah Scott my thoughts were it has to do with the batteries being charged. But the off gas for that is hydrogen gas. The Fireboys may see that as CO! Not certain. My batteries (6 lead acid) are not sealed up and vent to the cabin. With the solar system whenever there is sunlight they are getting a charge so it could explain the issue. But a number of times it was in the middle of the night. No genset operation or sunlight and they still went off. A mystery! Thanks
 
Scott B

Scott B

.
Sep 20, 2006
2,952
Hunter 33 Georgian Bay, Ontario, Canada
Nodak7 said:
Yeah Scott my thoughts were it has to do with the batteries being charged. But the off gas for that is hydrogen gas. The Fireboys may see that as CO! Not certain. My batteries (6 lead acid) are not sealed up and vent to the cabin. With the solar system whenever there is sunlight they are getting a charge so it could explain the issue. But a number of times it was in the middle of the night. No genset operation or sunlight and they still went off. A mystery! Thanks
Click to expand

The articles I found all point to the CO picking up H2 from the batteries.

Lead-acid batteries produce Hydrogen when charging.

Carbon Monoxide detectors use something called a "Metal Oxide Semiconductor (MOS)" sensor, which detects a variety of gases including Hydrogen.

A MOS sensor calibrated for CO will give a false positive in the presence of Hydrogen gas at ~10% of the actual value. So, that ~85ppm reported of CO was in reality ~850ppm of Hydrogen gas.
 
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MikeHoncho

MikeHoncho

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Dec 28, 2015
1,897
Laser, Hunter H30 Cherubini Tacoma
most Co sensors have a cross-sensitivity (that’s what this condition is called) to hydrogen. All though they tend to have similar cross sensitivity amounts, each sensor manufacturer has a individual spec. Your detector should have the spec for ppm when alarming.
Comparing toxicology to flammability is a little interesting. Flammable gasses are , in most instances, toxic way before they are flammable. Co IDLH is 1200ppm and my meters (not detectors) alarm at 35ppm but Co’s lower explosive level is around 120,000ppm which is around 12% in atmos. Hydrogen isn’t toxic but is a asphyxiant and is obviously flammable. It’s LEL is 4% in atmos. That’s 40,000 ppm which tends to not be a problem unless it’s confined in a poorly ventilated area.
 
Justin_NSA

Justin_NSA

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Jul 7, 2004
8,481
Hunter 30T Cheney, KS
My new Kidde CO alarm was doing the same thing. Never figured it out. My batteries and charger are in separate, isolated aft lockers.
 
Nodak7

Nodak7

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Sep 28, 2008
1,256
Hunter 41DS Punta Gorda, FL
Justin_NSA said:
My new Kidde CO alarm was doing the same thing. Never figured it out. My batteries and charger are in separate, isolated aft lockers.
Click to expand
It truly is a mystery. I did purchase another CO monitor and it has not alarmed since I put it in the boat. The only think I can think is these are very very sensitive to hydrogen off gas from the batteries being charged by the solar panels. Three of these are located in different parts of the boat. Two are well away from the batteries and one is fairly close. I hate to disconnect them and rely on this cheaper.
 
MikeHoncho

MikeHoncho

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Dec 28, 2015
1,897
Laser, Hunter H30 Cherubini Tacoma
Nodak7 said:
It truly is a mystery. I did purchase another CO monitor and it has not alarmed since I put it in the boat. The only think I can think is these are very very sensitive to hydrogen off gas from the batteries being charged by the solar panels. Three of these are located in different parts of the boat. Two are well away from the batteries and one is fairly close. I hate to disconnect them and rely on this cheaper.
Click to expand
There are a ton of other cross sensitivities with these along with they do fail from contamination and just failed components. A actual C0 meter start out in the mid to high $100s as a reference.
 
Nodak7

Nodak7

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Sep 28, 2008
1,256
Hunter 41DS Punta Gorda, FL
MikeHoncho said:
There are a ton of other cross sensitivities with these along with they do fail from contamination and just failed components. A actual C0 meter start out in the mid to high $100s as a reference.
Click to expand
Well these are about $110/each. I guess I didn't consider them cheap but higher end!
 
MikeHoncho

MikeHoncho

.
Dec 28, 2015
1,897
Laser, Hunter H30 Cherubini Tacoma
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