Cooling a diesel generator

[Theo]

My sister is thinking of having a diesel genny fitted under the side bench in the boatman's cabin. Obviously it needs to be cooled. Can its water cooling be plumbed into the same skin tank as the propulsion engine? I can see possible problems with the cooling water's choosing to flow through the propulsion engine rather than the skin tank but do one way valves exist which would prevent this?

 

Nick

[John Orentas]

As long as both engines are fitted with pumps I can't see a problem, just connect them both to the skin tank. No need for valves I think but probably seal off the lower header tank.

[Theo]

As long as both engines are fitted with pumps I can't see a problem, just connect them both to the skin tank. No need for valves I think but probably seal off the lower header tank.

 

 

Not entirely convinced about this, John, though I am sure that it would be OK if both engines were running. Since the cooling water pump is centrifugal can't the water just back through the stopped one even with minimul pressure?

 

Nick

[bottle]

Even if it did back through the stopped engine/generator, what is the problem.

 

The heat would still be dissipated and the stopped engine/generator would be pre-warmed and easier to start and maybe even reduce engine/generator wear.

 

There are units sold to pre-warm engines, especially in cold climates.

[Gary Peacock]

Two solutions we would use is to either raw water cool the genset or preferably weld a flared skin tank onto the outside face of the swim.

 

The only boat I have seen sharing the same skin tank did work but for some reason suffered a lot from overheating with the main engine after the gen set was added even when it wasn't running.

[Theo]

Even if it did back through the stopped engine/generator, what is the problem.

 

The heat would still be dissipated and the stopped engine/generator would be pre-warmed and easier to start and maybe even reduce engine/generator wear.

 

I am sure that you are quite right, Bottle. Why didn't I think of this?

 

 

There are units sold to pre-warm engines, especially in cold climates.

 

It seems from the Mikuni manula that this is just what my CH boiler was designed for!

 

Nick

[NB Alnwick]

Even if it did back through the stopped engine/generator, what is the problem.

 

The heat would still be dissipated and the stopped engine/generator would be pre-warmed and easier to start and maybe even reduce engine/generator wear.

 

There are units sold to pre-warm engines, especially in cold climates.

 

What a brilliant solution! Generating enough juice to start the big old lump while warming it up ready to start at the same time!

 

Must have one . . .

[Blake]

My sister is thinking of having a diesel genny fitted under the side bench in the boatman's cabin. Obviously it needs to be cooled. Can its water cooling be plumbed into the same skin tank as the propulsion engine? I can see possible problems with the cooling water's choosing to flow through the propulsion engine rather than the skin tank but do one way valves exist which would prevent this?

 

Nick

I am that sisiter! We would like to use the skin tank to cool it (One already fitted that cools the engine. this would mean that the genny would have to be fitted on the near (port ) side as the skin tank is on that side. However the heating fuel tank is on the other side so we would have to cross over or under the prop shaft. What would be the best way of getting the fuel over the other side of the boat (We have an 8' boatmans cabin and a 6' engine room

[GLYN FORSTER]

I am that sisiter! We would like to use the skin tank to cool it (One already fitted that cools the engine. this would mean that the genny would have to be fitted on the near (port ) side as the skin tank is on that side. However the heating fuel tank is on the other side so we would have to cross over or under the prop shaft. What would be the best way of getting the fuel over the other side of the boat (We have an 8' boatmans cabin and a 6' engine room

Hi there one thing to bear in mind is that the skin tank may not be big enough to cool both gen and engine running at the same time, most built in generator are raw water cooled through a heat exchanger anyway so wuldnt cause a problem.

[Theo]

Hi there one thing to bear in mind is that the skin tank may not be big enough to cool both gen and engine running at the same time, most built in generator are raw water cooled through a heat exchanger anyway so wuldnt cause a problem.

 

I cannot think of any reason for running both generator and propulsion engine at the same time. Blake, the NB in question, has a 230V alternator which would do the job of the generator. The reason that Victoria wants the additional generator is to provide a source of electricity which is significntly quieter than the main engine.

 

Nick

 

Edit.

 

I suppose that all is not lost even if they connect up to the single skin tank and it is not successful. They can try it out and if it does not work properly then they can try another method.

 

As for the raw water cooling idea. I would prefer not to follow that route. Theodora has raw water cooling for the propulsion engine and I have found it a bit of a chore and a rather uncertain chore at that, to add antifreeze to the mud box and then run the engine for a time which is hit or, more probably miss to get the antifreeze to the necessary parts.

 

Nick

Edited January 5, 2007 by Theo

[DHutch]

Alternativly, you could add another skintank, eather just the same as the other one, but on the otherside. Or if thats not easy, place its on the outside as gary is suggesting.

[Smudge]

I'm sorry if this is a stupid question but is there a particular reason a gennie is needed?

Our boat builder suggested we have travel power instead as a gennie is only another engine and we already have one of those!

[magnetman]

I'm sorry if this is a stupid question but is there a particular reason a gennie is needed?

Our boat builder suggested we have travel power instead as a gennie is only another engine and we already have one of those!

 

My theory is that the main engine is for moving the boat forwards along the canal and racking up hours on it using it for electricity means that if it breaks down (which becomes more likely with more running hours) you won't be able to move the boat OR get power. Which is bad. Whereas with separate units the genny breaks down you can still get power from the engine and move the boat as well, to a location where the genny can be fixed.

 

A small generator is also likely (not certain?) to be more economical to run than a 40hp diesel engine.

Edited January 8, 2007 by magnetman

[bottle]

I'm sorry if this is a stupid question but is there a particular reason a gennie is needed?

Our boat builder suggested we have travel power instead as a gennie is only another engine and we already have one of those!

 

Hi Smudge

 

For a start there is no such thing as a stupid question, but some of the answers maybe.

 

In my case the boat will be 'all electric' so a3.5Kw 'Travel power' would not be big enough, my generator will be about 7 to 9 Kw 'Onan'

 

Also as Magnet man says by having both if one breaks down I will at all times have some electricity but not always motive power (can always get the wife to bow haul)

[Smudge]

Ok, point(s) taken... but, we liveaboard ours and only have to run the engine for about 2 hours (in winter) a day to provide us with enough electricity for the rest of the day, in summer we can get away with less if we're not pootling about. Having said that we are going to be looking at wind generators when we go to the boat show so that, hopefully, we can get away with running the engine even less!

Oh, and our unit is only 3.5Kw and there are 3 of us living on there full time, 4 at the weekends, so if you take into account the kids tv, our tv/video, washer/dryer machine (again, kids, so lots of that!), heater bulb in the terrainium that's on constantly and all the rest of the 'crap' that you have, i don't think we do too bad!

[Theo]

Ok, point(s) taken... but, we liveaboard ours and only have to run the engine for about 2 hours (in winter) a day to provide us with enough electricity for the rest of the day, in summer we can get away with less if we're not pootling about. Having said that we are going to be looking at wind generators when we go to the boat show so that, hopefully, we can get away with running the engine even less!

Oh, and our unit is only 3.5Kw and there are 3 of us living on there full time, 4 at the weekends, so if you take into account the kids tv, our tv/video, washer/dryer machine (again, kids, so lots of that!), heater bulb in the terrainium that's on constantly and all the rest of the 'crap' that you have, i don't think we do too bad!

 

I would suggest that there can be a number of reasons why you would want a separate generator.

 

1. The size of the generator's engine can be matched to the electrical power output. This means that you don't get the problems associated with running a diesel on very low load.

2. The diesel generator can be very thoroughly sound insulated so running the washing machine is not accompanied by the racket of a JD3.

3. I suspect that the fule efficiency of running a propulsion engine just to generate electrical power is rather low so by having a dedicated machine you will do less environmental harm.

 

Nick

[Smudge]

so running the washing machine is not accompanied by the racket of a JD3.

 

sorry Nick, 'nother 'stupid' question.... what's a JD3? our travel power unit makes no sound whatsoever so it can't be that, can it?

[bottle]

Hi Smudge

 

The 'JD3' is an engine based on 'John Deere' tractor engine sold by Beta marine, it sounds like one of the old type of engines fitted to narrow boats 'thump', 'thump', 'thump',

[Smudge]

oooohhh! i see! (it's Mrs Smudge btw! haven't got round to logging myself in!)

 

we just have a routine... get in from work, start engine, put washing on, by the time a washing/drying cycle has done the batteries have enough charge in them for the rest of the night. We have to run the engine anyway as we don't have shore line hook-up, it's very basic where we are! but it works for us, so....

[magnetman]

so what's the BD3 then?

 

 

washing/drying cycle. Call that basic? Sounds like mod cons to me...

[Theo]

Hi Smudge

 

The 'JD3' is an engine based on 'John Deere' tractor engine sold by Beta marine, it sounds like one of the old type of engines fitted to narrow boats 'thump', 'thump', 'thump',

 

 

It sounds delightful. the builder made it sound even better by fitting what looks like a silence but is, in fact a resonator. It makes it go "thunk" instead of "thuck".

 

Nick

[Smudge]

washing/drying cycle. Call that basic? Sounds like mod cons to me...

 

ok, where we are MOORED is basic, we are very well set up onboard, but we intended to be when designing it

[bottle]

so what's the BD3 then?

 

 

A typing error

 

Just had a quick look at the 'new Beta Marine web site and cannot find the JD3, they have a BD772 but this is a three cylinder high revving engine where as the JD3 was three cylinder low revving.

Edited January 8, 2007 by bottle

[magnetman]

A typing error

 

Just goggled it and (oo) the BD3 is based on a 3 pot Lister rather than the John Deere.

[bottle]

Just goggled it and (oo) the BD3 is based on a 3 pot Lister rather than the John Deere.

 

I knew that??????????