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For two nights in a row now I've had CO detectors trip. I've got the regular pair of built-in Xintex units and those did not trip. I also have a Kidde battery operated residential unit and a handheld one. The first night those tripped and read 47. Both reading the same numbers lent some creedence to their accuracy (and questioning of the Xintex units...) In neither case was their any external engine source of CO anywhere nearby. And when I exited the cabin the levels dropped off to zero. The first time I shut off the AC entirely. The second time I just turned off the cooling but left the fan running. Both times the level dropped once the system stopped running.

The common element in both cases was running the AC constantly for about 6 hours, down to an interior temp of 72F. We'd got to the boat the first night around 9 and turned on the AC. The second night we returned to the slip also around 9 and cranked the AC. Both times from shore power. At 3am the sensor went off, so that's 6 hours both times. We had it running for about 4 hours off the genset and no sensors tripped.

There's no breakers being tripped. Nor do we smell any sort of burning odor. I have not yet opened the access panel to examine the AC control unit. We did have one replaced last year due to a short inside it that singed some wiring. But we smelled that RIGHT AWAY.

We've never had this problem in the past. We've cranked the AC overnight many a time before without such issues.

So what gives here? How is running the AC for 6 hours generating CO (or causing CO detectors to "think" that's the case)?

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-Bill Kearney, 2005 348 Vista

The following is information from Xintex manual regarding installation DONTS - Where NOT to install your CO Sentinel and nuisance alarms conditions. At the end of this reply is a service to repair/test the unit. I have seen others on this site comment that do this annually to optimize their protection ...

-DO NOT install a CO Sentinel near a hatch or porthole through which seawater could be spilled on the device.
-DO NOT install in locations where the normal ambient temperature is below 4.4°C (40°F) or exceeds 37.8°C (100°F).
-DO NOT install in locations where temperature, moisture, and/or ultraviolet light affect the operation.
-DO NOT mount within one foot of corners or other ‘dead’ air spaces.
-DO NOT locate CO Sentinel within 5 feet (1.5 m) of any cooking appliance or in direct airflow from air conditioning or heat vents.
-DO NOT locate CO Sentinel in close vicinity of curtains, pillows, or other obstructions.

Nuisance Alarms

Although the CO Sentinel will detect only carbon monoxide in a normal environment, studies have found that unusually high concentrations of chemicals and/or vapors will affect the sensor.
The device may be triggered by any number of hydrocarbons at very high levels. These include toluene, isopropyl alcohol, methyl ethyl ketone, mica, and many adhesives.

Many of these chemicals are the result of outgassing in new boats. While these may be considered nuisance alarms, levels high enough to create an alarm condition are also hazardous. Treat these “nuisance” alarms as an actual carbon monoxide alarm condition. Evacuate and ventilate the area. Before, during, and immediately after working with any chemicals, make sure enough fresh air ventilation is available.

Limitations

• This carbon monoxide alarm is designed to detect carbon monoxide gas from ANY source of combustion. It is NOT designed to detect smoke, fire or any other gas.
• The CO Sentinel will not detect carbon monoxide that is not in the vicinity of the alarm. Carbon monoxide in other rooms or areas will not be detected. Alarms mounted near obstructions or in ‘dead’ air spaces will not detect carbon monoxide.
• The CO Sentinel does not guarantee or imply that CO poisoning will not occur. Do NOT use the CO Sentinel as a replacement for ordinary precautions or periodic inspections of equipment. NEVER rely on alarm systems to save your life, common sense is still prudent and necessary.
• The audible horn on the CO Sentinel meets UL requirements; however, the horn may not be heard in remote areas.

FACTORY RE-CERTIFICATION AND WARRANTY RENEWAL PROGRAM

Because of the unique sensor and circuit design characteristics of a carbon monoxide alarm, it is not possible to field test the CO Sentinel. The Xintex Recertification and Warranty Renewal Program provides peace of mind by offering factory re-certification and a new one year warranty.

Return the CO Sentinel to the factory, prepaid, along with your check or money order for $25.00* at any time to take advantage of this program. This service includes complete testing of circuitry and sensor. Repairs, re-calibration, or sensor replacement are included. In addition, you will receive an additional 12-month limited warranty. This offer does not include replacement or repair of units that have been damaged through misuse, carelessness, misapplication, altered or otherwise been destroyed as a result of fire, collision, or sinking. Should the returned CO Sentinel require repairs from misuse as described above, you will be notified of the cost prior to repair.

Include your return shipping or mailing address and telephone number along with the CO Sentinel and mail to:
Re-certification Department
Fireboy-Xintex, Inc.
PO Box 152
O-379 Lake Michigan Dr. NW
Grand Rapids, MI 49534

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2002 Vista 298 VP 5.0Gxi

Excellent notes, but this is not a problem with the existing sensors. It's possible they have gotten less sensitive and they are on my list of things to have reconditioned. I actually have a fresh spare that's never been installed. They DO sound an alarm if there's a high level of CO, like from the dinghy outboard running just outside an open porthole. Just not during these 3am incidents.

The rest of the points aren't quite applicable as there hasn't been any use of chemicals. The boat is now over 4 years old so any outgassing is likely to have completed by now. And probably wouldn't be so closely tied to repeatable behavior like running the AC for 6 hours. If they triggered right after using some sort of cleaner that'd make sense, but that's not the case.

If it was a matter of refrigerant leaking from the AC then that would likely be detectable by a lack of proper cooling. As it stands the system is working as powerfully as it always has. Refrigerant leaks tend to cause the system to stop delivering the same performance, if not cease working outright. That same refrigerant is usually also what lubricates the compressor. No refrigerant means seized compressor and that's not the problem here.

I'm just very puzzled by this. I plan on opening things up tomorrow and give them a thorough looking-over. I can't quite see what would cause a mis-read of two brand new detectors (in exactly the same way) when the only active system is the AC system running for 6 hours. Maybe I'll get lucky and find a way to repeat it tomorrow when I'm on the boat replacing the genset impeller.

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-Bill Kearney, 2005 348 Vista

Bill,

Where is the cold air return? Is it possible there is not a good seal between the intake grate and the duct work, or the duct work has a tear or hole in it and is pulling in bilge fumes? Do you smell a subdued gas smell when the system is on and blowing?

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Brett DiMichele

Don't smell any fumes. A the bilges are clean. I did use some bleach last week to clean out the genset and ac strainers. A small bit spilled into that mid-cabin bilge but I dumped a couple bucket loads of water in there and let the pump clear it out.

The AC system returns air from the grille next to the steps. But as with most boat AC systems there's not a guaranteed return 'system'. Most of it does come through that grille (which was cleaned with plain water back in April) but it'll draw air from anywhere back there.

I'm thinking that if it is something outgassing, what would trigger a CO monitor only when the ambient temp drops to around 72F?

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-Bill Kearney, 2005 348 Vista

I'm not a thermodynamacist so I can't comment on why 72 Degrees F is your magic number. But perhaps it's just the amount of time it takes to get to 72F and the airflow the system is turning over in the amount of time it takes to get to 72 is raising the particulate level enough to trip the Kiddie's. The other issue is that you are using "Residential" Kiddie units, and those are not Time Average Weighted for a boat cabin, your boat cabin's SQ FT is much smaller than even the smallest room in your home and because of this, the averaging of those units is incorrect for in a boat cabin. But... And there's always a but... I would expect the Kiddie's would be LESS sensitive not more sensitive, since they are designed for much larger areas than your boat cabin.

At the very least I would sent the Xintex units in and have them recal'd and I would ditch the Kiddie Residential units and get the correct marine units.

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Brett DiMichele

The use of another sensor (singular) is additive, not replacement. The built-in Xintex sensors do trip, but usually only when there's a typical source of CO, like the dinghy running outside an open porthole. They're not what I'm concern about. They're probably due for recalibration, but that's not the current issue.

The smaller space argument is worth considering. Bear in mind, however, that the sensor doesn't trip when just the circulating fan is running. It only seems to trip if the cooling system is active too. That is, when both the fan and the cooling system are running for six hours the sensor tripped (and the handheld read the same PPM). Shutting off just the cooling system but leaving the fan running saw the numbers drop pretty quickly. This was also accompanied by a rise in temp from 72 to about 78F. That leads me to believe it has something to do with either the operation of the compressor or the resulting drop in temperature, not the dispersion of airborne particulates. I don't believe the air handler changes the path of air flow based on the compressor being operational. So it seems the running compressor is generating a source of particulates that trip a sensor.

I'm going to try running the system today to see if the numbers remain high or go higher after 6 hours. And then take the handheld sensor into the cabinet with the compressor to see if I can pinpoint a source of higher concentrations.

I have a third CO sensor that's never been used and stowed here at home in a ziploc bag. I may swap it with one of those on the boat to see if it activates. I've planned to have the existing ones recalibrated so now's probably as good a time as any to send them off.

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-Bill Kearney, 2005 348 Vista

Bill, I know this is an old post but wondering if you determined what the issue was with your CO alarm and/or AC unit. We have a 2002 348 and seem to be having a very similar issue. The only difference is that I am also getting a bilge like smell circulating through the cabin. I think this may be due to the condensate drain hose and it's routing through the bilge and exit in the stern. Do you have a similar setup? Also, any advice on how to thoroughly clean the AC unit and ducts?

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Heath - 348 Vista
Erie, PA