Running the generator all night

[techmitch]

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I believe the greater danger is from CO being drawn into the sleeping area from the A/C air intakes on the side of the boat as opposed to CO seeping into the cabin from the engine room. Our detectors have gone off from that source on very still nights as well as during a thunderstorm when the was lots of air movement, some of it resulting in CO getting sucked into the cabin when the boat was moving around a lot. Also the diesel guys who idle their engines in the marina letting things "warm up" set off the detectors when our boat is running A/C down below, so there is a risk to diesel as well. It is less than gas, but still there. The storm event was kind of a freak occurrence, but I was surprised by how long it took for the detector to return to standby. This took perhaps 5 minutes with hatches opened to let fresh air inside. We did that in pouring down rain.

"A/C air intakes on the side of the boat"???

 

[sbw1]

"A/C air intakes on the side of the boat"???

Yes. It's not a closed system. When you run the a/c there is a vent somewhere that exhausts some air from the cabin. On our boat is is below that radar arch on the port side. On the opposite side is the intake. If you place a piece of tissue next to it the tissue is drawn up against the vent. Air exchange keeps the cabin from become stale.

 

[techmitch]

View attachment 98149
Yes. It's not a closed system. When you run the a/c there is a vent somewhere that exhausts some air from the cabin. On our boat is is below that radar arch on the port side. On the opposite side is the intake. If you place a piece of tissue next to it the tissue is drawn up against the vent. Air exchange keeps the cabin from become stale.

Interesting.

 

[stephenm27]

View attachment 98149
Yes. It's not a closed system. When you run the a/c there is a vent somewhere that exhausts some air from the cabin. On our boat is is below that radar arch on the port side. On the opposite side is the intake. If you place a piece of tissue next to it the tissue is drawn up against the vent. Air exchange keeps the cabin from become stale.

There’s no such A/C intake on a 2009 310. It is very much a closed system. Perhaps your Tiara is different than SR.

 

[sbw1]

Our SR 370 Express had two exhausts. One was for the shower so moist air had a place to exit and allow the cool air to move freely into the area and keep that small space comfortable while also exhausting toilet odors using a fan motor The galley vent was a second vent although I don't remember that detail. That probably served as a passive A/C exhaust vent as well. The other a/c exhaust vent for the berth was a clam shell on the port hull side by the v berth. I believe the fresh air intake for system was though the top of the sliding door to the salon. So not a closed system in that SR. Maybe your SR ventilation is different than the system used on the bigger boats. It would be unusual and not desirable to eliminate air exchanges as a part of any system's design. It would be sort of like putting your car A/C in recirculating mode all the time and having your windows fog up on the inside. That is generally not a good thing.

 

[stephenm27]

Indeed, passive air exchange can occur via both the head exhaust fan route and galley exhaust fan route. Our 310 had both as well. Boat cabins are notoriously not airtight. However, since the A/C system is not expelling air to the outside, nor drawing supply air from the outside, there is little to no "makeup" air required via an "intake".

If, on the other hand, you turned on the head or galley exhaust fan, makeup air is definitely necessary and would be drawn from the route of least resistance. That said, I still wouldn't classify these as "A/C intakes".

Moral of the story: run multiple CO monitors, maintain the generator and use due caution whenever sleeping while it's running.

 

[sbw1]

Indeed, passive air exchange can occur via both the head exhaust fan route and galley exhaust fan route...............
Boat cabins are notoriously not airtight. However, since the A/C system is not expelling air to the outside, nor drawing supply air from the outside, there is little to no "makeup" air required via an "intake".

I'm not sure that is entirely accurate. Our 370 Express definitely discharged air through the clamshell vent on the side of the hull. So much so that the hull would have condensate on the outside of the hull by the vent when the a/c was cranking. You could also feel the air being discharged through that vent. All that air was being replaced by intake air which I believe was coming through the top of the slider and through exhaust vents for the head and galley.

 

[Alex F]

View attachment 98147
I believe the greater danger is from CO being drawn into the sleeping area from the A/C air intakes on the side of the boat as opposed to CO seeping into the cabin from the engine room. Our detectors have gone off from that source on very still nights as well as during a thunderstorm when the was lots of air movement, some of it resulting in CO getting sucked into the cabin when the boat was moving around a lot. Also the diesel guys who idle their engines in the marina letting things "warm up" set off the detectors when our boat is running A/C down below, so there is a risk to diesel as well. It is less than gas, but still there. The storm event was kind of a freak occurrence, but I was surprised by how long it took for the detector to return to standby. This took perhaps 5 minutes with hatches opened to let fresh air inside. We did that in pouring down rain.

My 420DB doesn't draw air from the outside and 320DA didn't as well.

Very still night is a rare occasion and this is probably the only time when I wouldn't run gas genny myself. If there's no natural airflow, then there's no way to have CO move away from the boat.

Your example of diesel engines is not applicable here. You just can't compare low CO diesel generators to a big diesel engines. Especially scenario at the dock where the boat doesn't follow (swing) with the wind direction. So, of course it's expected for CO detectors to trigger, if next to you boat idles in a slip blowing smoke for a while.

Going back to the question related to overnighting on the hook, over the years I've spent quite a few nights with no wind and not once my CO detectors went off from my generator. Having said that, I feel very comfortable running my genny over night. Gas genny is not an issue, as long as you have some breeze to move that CO away from the boat.

 

[sbw1]

My 420DB doesn't draw air from the outside and 320DA didn't as well.

Very still night is a rare occasion and this is probably the only time when I wouldn't run gas genny myself. If there's no natural airflow, then there's no way to have CO move away from the boat.

Your example of diesel engines is not applicable here. You just can't compare low CO diesel generators to a big diesel engines. Especially scenario at the dock where the boat doesn't follow (swing) with the wind direction. So, of course it's expected for CO detectors to trigger, if next to you boat idles in a slip blowing smoke for a while.

Going back to the question related to overnighting on the hook, over the years I've spent quite a few nights with no wind and not once my CO detectors went off from my generator. Having said that, I feel very comfortable running my genny over night. Gas genny is not an issue, as long as you have some breeze to move that CO away from the boat.

Sounds like you are good to go. Sleep well.