Installed or portable in 42' sailboat?

[Fishpie]

A good friend of mine has just bought a Valiant 42 and will be bringing her down to Ft Lauderdale in November.
He wants to spend 5 to 6 weeks over Christmas doing a Bahamas, T&C, (DR maybe) and Cuba loop back to Ft Lauderdale.
I have been invited on the trip and we both want to do allot of diving.
He wants to have a compressor onboard.
For this trip there will only be 2 divers onboard, but the expected maximum on future trips would be 3 divers, making 3 dives each, every other day. About 10 tanks to be filled every 2 days. There will be 6 tanks onboard.
The boat has a 5 kw ac generator.
I have seen another Valiant with a Rix installed in the engine compartment. I don't know if this was a SA6, but I think that this boat also had the 5 kw Westerbeke.
The preference for this new install would be for a permanently mounted compressor run by the boats generator.
BUT
I have a whole shed load of questions.

Would it be better to have a small portable Bauer Jn since it can be run on deck which will be cooler than in the engine room?
If this is the situation can he get an electric Junior and run a dedicated outlet from the generator for the compressor?
Will 5 kw be enough power to run a SA6? (or eveen the Junior)
I am not certain, but I don't think that a bigger Bauer (Mariner/Oceanus) will fit in a Valiant???
What filtration system/set up is recommended for use in hot humid conditions?

Many thanks in advance.

 

[CraigAClark]

An SA6 uses a 5 hp motor, if I recall correctly. That would require a minimum of 20Kw generator to start it straight up. You might get by with a 12.5Kw using a frequency drive. I have been dealing with yacht/boat installations for over 20 years. When it comes to generator sizes requirements, this is how things generally go in relation to 230VAC,60Hz, single phase: 2hp minimum 6Kw, 3hp minimum 8Kw, 5hp minimum 20kw and 7.5hp minimum 25Kw. Starting at 25Kw and up, generators are available in 3 phase.

If you get a Junior II, you might get by with a 2hp version, but you won't know for sure until you actually try it. Sometimes, when you are right on the cusp of the requirement, you might be able to change the capacitors in the motor to tweek you over the start-up load. You'll have to check with the motor manufacturer to be sure.

Craig

 

[dannobee]

Sort of a hijack but maybe it will help.

Craig, is it very common to run a hydraulic drive off of the main engine to run compressors? Or how would one run a compressor on a boat without a gen set or with a smaller gen set?

 

[Fishpie]

Ok.
Looks like the permanent install is out......I don't see the owner pulling out a perfectly good Westerbeke with less than 700 hrs just to put in a bigger one to run a compressor.
That leaves the portable option.
Gas or electric?
He'd prefer not to have to carry around extra jugs of petrol......but if it can't be avoided, oh well.
As for the electric route.
Would it be advisable to run a permanent, dedicated outlet wired just for the compressor and have some sort of "soft start" on the electric motor?
Is there a better (longer lasting, cooler running) option than the Jn II?

A third option.
I do have an old 3 point something cf single phase Mako sitting in my back room. I picked it up at a yard sale 6 years ago and never got it overhauled. It runs and pumps but would need a complete overhaul to be trusted (it'd probably need a better filter system too).

Would it just be cheaper and simpler to get a brand new,bog standard, Jn II gas version and have done with it?

 

[CraigAClark]

Sort of a hijack but maybe it will help.

Craig, is it very common to run a hydraulic drive off of the main engine to run compressors? Or how would one run a compressor on a boat without a gen set or with a smaller gen set?

I've only seen it done a couple times. If I remember the cost of the pump, reservoir, motor and selector valve was very expensive, costing more than the compressor itself. The other solution is gas or diesel. The noise and vibration however, can drive you crazy on a small boat. I know that people put compressors in the engine room, but that is the worst environment for them,IMO. If they are day trippers (returning to port each day), some will use shore power to run the compressor.

Craig

 

[CraigAClark]

Ok.
Looks like the permanent install is out......I don't see the owner pulling out a perfectly good Westerbeke with less than 700 hrs just to put in a bigger one to run a compressor.
That leaves the portable option.
Gas or electric?
He'd prefer not to have to carry around extra jugs of petrol......but if it can't be avoided, oh well.
As for the electric route.
Would it be advisable to run a permanent, dedicated outlet wired just for the compressor and have some sort of "soft start" on the electric motor?
Is there a better (longer lasting, cooler running) option than the Jn II?

A third option.
I do have an old 3 point something cf single phase Mako sitting in my back room. I picked it up at a yard sale 6 years ago and never got it overhauled. It runs and pumps but would need a complete overhaul to be trusted (it'd probably need a better filter system too).

Would it just be cheaper and simpler to get a brand new,bog standard, Jn II gas version and have done with it?

Frequency drives are your friend!

Craig

 

[Fishpie]

So maybe a SA6 with a VFD motor/controller can be run with a 5 kw gen set???

 

[Fishpie]

Craig.
I just re-read your first post......and answered the question.

If I understabd you correctly....a Junior with a VFD motor can be run from a 5 kw gen set, but anything bigger would be questionable.

 

[CraigAClark]

Craig.
I just re-read your first post......and answered the question.

If I understabd you correctly....a Junior with a VFD motor can be run from a 5 kw gen set, but anything bigger would be questionable.

The standard, stock Junior II is 3hp, single phase, 230VAC, 60Hz. You might be able to swing that on the 5Kw, but I was thinking more of the 2hp version. When a frequency drive is used with a single phase supply (they are really for 3 phase use), it is oversized, in this case probably one for a 5hp, 3 phase would be used. The motor on the compressor is changed to a 3 phase motor, in basic terms the drive creates the third leg of power to turn the motor.

Craig

 

[Fishpie]

Thanks again Craig.
Let's see if I am understanding you correctly.
I will be able to run the 115v 2hp version of the Jn II with no mods directly from a 5 kw gen set.
To reliably use the 3hp version (with the higher output) I'd need to use a frequency drive.
There is no way that a 5kw gen set will ever power a 5 hp motor with all the fancy controllers and drives in the world.

This leads me to yet more questions.
Once the compressor is up and running, do you think I will be able to charge the house bank at the same time?
Which would you recommend SA-3 or Jn II?.....not to put you on the spot or anything!
As I see it the Rix has the advantage of not burping out an oily mess every 15 mins and doesn't need a filter stack.