GENERATOR IN A LOCKER

[Komuuk]

My boat has a 40 cubic foot locker, accessed through a deck hatch in the stern. Long before my time, it housed a built in diesel generator. I have just fitted it out with shelves and racks to stow various bits of equipment, including a Honda EU20i silent petrol driven portable generator.

As an experiment, I started the generator in the locker and, with the hatch open, the noise level in the cockpit was at an acceptable level and couldn't be heard at all below decks.

The original 2" diameter through hull exhaust fitting is still in place and this has led me to speculate whether it would be feasible to use it for some kind of forced air extraction system so that the generator could be run with the hatch closed. There is a nearby dorade box which could be used to funnel fresh air into the locker.

Any thoughts, tips or cautionary advice would be gratefully received.

 

[WindermereColvic]

Sounds abit dodgy but i can’t really visualise 40'cubed, i would try and fit a direct connecting pipe from the exhaust to the skin fitting, and then use the forced air system, bilge blower or whatever to deal with the petrol fumes. Matt

 

[exfinnsailor]

Carbon Monoxide springs to mind .. Be very careful .. I think I would have a carbon monoxide warning device on board just in case .. If you can run the exhaust to the outside fine but make sure you have no leaks .. Carbon Monoxide like all gasses will get everywhere .. /forums/images/graemlins/frown.gif

 

[VicS]

I agree it does not sound like a sensible idea, at least not without a very serious air extraction system. The genny will always be partly breathing its own exhaust fumes.


40ft³ is just over 1m³

 

[tcm]

Hi newbie! It sounds ok to me. The inlet in locker for new cold air shd be as low as poss, outlet as high as poss. You could praps use metal ducting to lead exhaust up and out.

 

[Pete7]

I would be more worried about the build up of petrol vapour in an inclosed space with a hot engine and generator running.

We have a Honda 20i but put it on the side deck with exhaust down wind of any hatches into the boat when using it.

Pete

 

[sarabande]

I think the difficulty is ensuring that exhaust fumes get out without mixing with air in the enclosed space. The Honda is susceptible to back pressure in the exhaust system, so any extended exhaust will affect the running, and life of the genny.

Heat build up can be countered by a forced draft fan, but you'll be losing say 150 watts at 240v to run a good fan. If you want to put one in, set it up as an extract fan, not an input one.

Re-fuelling the genny in the locker will be a bit of a risk. It should be filled in open fresh air where petrol fumes can drain away easily.

There's also an issue with making the sides, floor, and lid of the locker into a fire-resistant box.

40cu ft is OK for a genny space designed from the start to be one (roughly 4x3x3), but it might be easier to use it as a store, and put it into a box in which you run it on deck, and lower it into the locker when finished and cool.

 

[vyv_cox]

I can imagine that an Eberspacher type concentric exhaust could work OK in this application. Exhaust gas goes down the centre, about 15 mm diameter, and air comes in around the outside, around 30 mm diameter. In your case you could probably increase these dimensions to fit the 2 inch hole, so maybe a 1 inch exhaust down the inside.

You would need to make a fitting for the inboard end to take the air from this pipe, then maybe put a small fan on the end.

 

[sarabande]

agree, a fan assisted exhaust (either by extraction in line, or injection towards the exit) would be a good way to get the gases out.

 

[saltwater_gypsy]

Will this little model fit in???Its the mini 3.5kW one.

 

[Komuuk]

Many thanks for your replies. I was thinking along the lines of a 'Y' connector with the exhaust going to one of the arms, an extractor blower connected to the other arm, blowing out through the hull fitting, which is about 20 cms below the bottom of the generator. In view of tcm's reply, it would be easy enough to route the air intake to the very bottom of the locker.

It would be almost impossible to hermetically seal the generator exhaust to the exit pipe without major surgery which would certainly void any warranties but I am sure that it could be constructed in such a way that some 'fresh' air would be taken in with the exhaust fumes.

I know that I have to watch out for back pressure but I am not sure about its effects or what to do about it and I hadn't taken Pete 7 and Sarabande's comments on petrol vapour into account.

Plan 2 was always to put it into a deck locker - as I want to built two anyway. The boat in question is a Vagabond 42, by the way. I have never come across another boat of that size with so much space for stowage below and so little easily accessible stowage for deck gear and stuff like the generator.

Thanks too to saltwater_gypsy for brightening my morning.