Two engines, one heat exchanger... ?
I want to add another, smaller generator to my boat.
Existing and new sets have indirect water cooling.I have only one heat exchanger and the expense of
adding another seems a little high. So I was wondering if anybody tried adding a second
generator to the heat exchanger of another engine,
with two Y connectors at the exchanger?
Engines would have a shared indirect cooling system.
Does this work? Do I need to install one-way valves at
the outlets to the cooler to avoid cooling water to run
through the inactive engine, or is that not an issue?
Cooling capacity should be ok for both engines since the
exchanger was sized for a bigger engine (bigger than my
'big' generator) but I intend to run only one genset at
a time anyway. Thx, Al |
franc
Jan 8
2006
|
| Why install a second genset and only plan on running one? Is it for
relibility? If so does sharing a cooling system really make sense? How much do you save
over the entire cost of installing a genset???? |
Rick
Jan 9
|
| Thje conclusion I drew was that he was installing a smaller 2nd genset. I
could see that as generators have a minimum fuel consumption based on their
maximum output. If you use a large one to just get a few hundred watts you
are wasting fuel because even at little or no load the generator engine
still has to turn a set rpm to maintain the 60hz output. It will do it at
a lower throttle opening but you are still turning a bigger engine and a
bigger alternator. There is a fixed overhead load in the size. It is more
efficient to run a smaller one if all you need a little power. |
James
Jan 9
|
| James got it right. I have a 16KW generator and am adding a 5KW unit. I
mainly want it so I can load it at 75% when charging my batteries. Will
save me money on maintenance in the long run since running the big one
at max 25% is not healthy for the engine.
But, yes, I also want the second generator as a backup. Running my main
engine just to charge batteries is the last thing I want to be forced to do.
The super-sound-proofed 5KW 1500rpm genset set me back 4K euros
(slightly used), should give me more than 15000 hours of charging.
Adding another one of these coolers would probably cost at least that
too. Drydock, work hours, etc. So sharing the cooler makes a lot of
sense financially, I think. Al |
franc
Jan 9
|
| That's a hell of a lot of electrical power you got going there :-) I'm
thinking pretty big boat. I'll look you up for a tour next time I'm around
there, haha. The med or the atlantic? |
James
Jan 9
|
| What difference does it make if he's only running one at a time? Did you
even read the post you replied to? |
James
Jan 9
|
| I don't think I need to do anything on the raw water side since the
cooler consists of a bunch of rods outside of the boat in a cut-in of
the hull, hence raw water circulation is simply 'natural' and can't
fail. Expensive to install, so that's the reason for the question.
Each engine has its own rubber vaned pump for coolant cirulation, so if
I follow your story I would need to do absolutely nothing except Y the
exchanger and that would be quite simple cheap and fast... correct? I
suppose there wouldn't even be a problem if both engines were to run?
I just realized that I will also need to make sure that both coolant
overflow tanks are fairly close together (boat movements) and at the
same height. I actually have another, unused, heat exchanger which is a flat
compartment welded against the (8mm steel) hull, which I would like to
use but I have no idea about its cooling capacity - if there is some
kind of formula (cooling capacity per surface unit) I'd be interested...! Al |
franc
Jan 8
|
| Yes, I would expect the rubber vaned pumps to provide enough of a seal when
not running to prevent significant backflow. I would recomend some testing
to run both engines in this arrangement. Differences in the pump outputs
could cause one or the other to not have enough coolant flow. Best course
would be to try it in a controlled situation and watch the temp gauges and
overflow tanks. To calculate the cooling capacity involves the surface area as well as the
material, thickness, and temp differentials. A trial run would be more
practical. |
James
Jan 8
|
| Your present heat exchanger, while it might be big enought to handle a
larger engine, it's probably not big enought to effectivly cool two
engines. |
Capt
Jan 8
|
| You may have to add a couple check valves to the sealed coolant side
depending on the type of pumps. A rubber vaned pump will prvent backflow
when it is not spinning. A regular metal vaned pump such as is used on a
marinized car engine will not. You don't give any specifics but I presume
you also have a way to provide the raw water flow no matter which engine is
running? Normally a pump on the engine also provides the raw water flow to
the heat exchanger. If you are also planning to Y the raw side as well the
same issues about check valves would apply. I have not seen appropriate
check valves for this application but I suspect they are available. They
would need to open with minimal forward pressure so check valves designed
for use in a pressurized water supply may not work. On the other hand the
check valves would not have to provide a perfect seal. The additional
complexity in plumbing may make it not worth while. There is something to
be said for simple. "franc" <nml@nml.nm> wrote in message |
James
Jan 8
|
