Powering an electric dive compressor

[a64pilot]

Originally Posted by boatbod

Wire the motor for 240vac and your current will be half.

Number of watts will be the same, ain't no such thing as a free lunch

[a64pilot]

Exemption tanks, (3442) working PSI tanks should have burst disks that burst at 5250 PSI, and even that leaves a wide safety margin. That is from memory, so it may be slightly off.
However it's not all that uncommon for an exemption tank's valve to have a burst disk meant for a low pressure tank, it works just of course they blow at lower pressures.
The purpose of a burst disk more than anything else is if a tank is in a fire, I have no idea want tank pressure could get to if it didn't have a burst disk in a fire.

[BigBeakie]

Hookah is lovely until something unexpected happens, such as swarms of small whalers at Chesterfield Reef ( between Oz and New Caledonia) chewing on the hose. And as you surface they keep grabbing the hose and pulling you down. Then you have one of those "Ah hookah, seemed like a good idea at the time" moments.

[boatman1]

Good heavens, Mr Beakie, what in all that's holy is a "small whaler" that drags a poor unsuspecting diver down and down into the abyss? That a first! Scuba still has its' place (ie, entering a modern wreck with a still intact cabin structure , "bounce" dives down to the limits of ccompressed air) but for most applications, in 10 fathoms or less depth, the hooka sure has appeal.

[HopCar]

"Small Whalers" Capt. Ahab with dwarfism?

[dwedeking2]

Originally Posted by boatman1

Good heavens, Mr Beakie, what in all that's holy is a "small whaler" that drags a poor unsuspecting diver down and down into the abyss? That a first! Scuba still has its' place (ie, entering a modern wreck with a still intact cabin structure , "bounce" dives down to the limits of ccompressed air) but for most applications, in 10 fathoms or less depth, the hooka sure has appeal.

[Nani Kai]

Originally Posted by Sawbonz

I have emailed and await a response from the distributor. We shall see, but my experience doing similar hasn't always been fruitful.

It is not a hookah setup.

Compressor mounting is planned for a forepeak, though on this boat it has been suggested in a lazarette at the stern so as to be close to where the tanks are kept.

Bauer shows its JRII-ELY/115 SCUBA compressor (yachting package) at 2.9SCFM (2.5 FAD), with a 2HP motor at 1500rpm requiring 1.5KW. I am not an engineer by any stretch but it seems to me the 9KW your genny puts out wouldn't have any issues.

In outfitting a Leopard 45 (excellent choice btw) with a compressor, I would first figure out the minimum SCFM I was willing to accept. Then I would find reputable manufacturers that make electric models meeting that requirement. From those models I would select for weight and dimensions to correspond with my chosen install location. Once I settled on a model(s) I would contact the manufacturer's tech department to determine electrical specs and installation advice. I usually have better luck with phone calls than emails.

I would hesitate before locating the compressor in a lazarette. The #1 consideration for any SCUBA compressor is keeping the air intake as far away as possible from hydrocarbon exhaust. If the Leopard 45 has the same set up as the Leopard 444, the genny exhausts roughly amidships, above the water line between the hulls. With the bow into the wind that exhaust comes aft. If your compressor is in a forepeak then it's upwind of the exhaust.

It would be great to see the final install if you get a chance.

[Captain Bill]

I decided to pass on the dive compressor and got a hookah. I still carry 4 tanks for those occasional dives where the hookah is just not appropriate such as wreck dives. In the past 4 years we've actually used the tanks only 4 times. I use the hookah quite a lot. I opted for the gas powered hookah. Since 90% of my diving is at less than 30 ft I really like the 2.5 hour per tank bottom time I get on the hookah. Ten minutes on the surface and I have another 2.5 hours of bottom time. I do admit that now that I'm in my 60's I never go more than 3 tanks per day(7.5 hours). We also use it for unassisted drift dives by leaving the compressor in the dinghy during the drift. There's no chance of getting separated from the boat. We have done 3 mile drifts and seen some pretty spectacular stuff. If you are a couple alone on the boat it is pretty hard to have a dive buddy and someone on the surface following your bubbles.

We have an Airline hookah and it stores quite easily on the back deck when not in use in it's case. It's smaller than a 40 qt ice chest and we really don't even notice it. The model we have is an older one rated at 4 divers to 85 feet though admittedly I have not used it below 50ft. I think the current ones at rated at 3 divers as ours is a 2 piston model and the current ones are single piston. The hoses and regulators for 4 divers store in about the same space as 2 scuba tanks. I do not recommend the 12v electric models as a substitute for scuba. They are ok for cleaning the bottom or getting a line off a prop but they don't have the capacity to substitute for a scuba tank. They are both depth and endurance limited. The 110V models mean you are limited to diving within 100 feet of your big boat. Recharging is a slow process compared to refilling a 1/2 gallon tank with gas so more than 1 dive to shallow depths/day isn't going to happen.

I looked at small dive compressors before deciding on the Hookah and got the same feedback from the dealers that you are getting. The maintenance issues associated with the HP compressors were also an issue if I was going to use it a lot. The various filters that would have to be acquired and maintained as well as special oils for the compressor all led me to decide of the hookah. I'm not saying the Hookah is maintenance free,, but it is much simpler than the high pressure compressor. I carry gasoline for my dinghy anyway and I now need to do my second rebuild of the compressor in 4 years. The rebuild kits cost $85 per piston and take about 1.5 hours to install on both pistons A definite advantage to having a single piston model. The pressure pop off valves wear and need to be replaced about every 2 years. I have also replaced an outlet hose and a connector hose, but single piston models don't have this hose. I change the engine oil once per year. I take apart and clean the regulators once a year. I follow the manufacturers recommendations on rinse downs after diving and the only part that is rusting is the exhaust and muffler.

[Rumpi]

This is actually simple to do:

Option 1:
Compressor with unloader valve powered by 3 phase motor and VFD. The VFD converts 1 phase from generator or inverter to 3 phase and allows programable soft start. The unloading valve bleeds the pressure and assures the compressor does not start against any significant load. Should start and run of the inverter alone. Up to 3hp VFD's are cheap and you can mount the compressor anywhere in the boat using a dedicated 3phase circuit.

Option 2:
Wire the battery bank for 24-48V and use a DC motor and controller on the compressor. Requires the use of a DC-DC converter for 12V loads. To keep the cables short you need to locate the compressor near the batteries or you use really thick cables to compensate.

So basicly what power are we talking about here? A 2hp compressor can be started and operated at 24V DC without any problems if the battery bank can support it. It can even be done at 12V with a big enough lithium bank. At this power levels there is no difference between a compressor or an electric anchor winch or bow thruster or a non recuperating watermaker.
So the question becomes how big is the battery and what C rates can it sustain? Or you go for option 1 and use the generator, or you do it like many others do and drive the compressor from one of the main engines.

[amandasearle]

Originally Posted by kryg

I have dived may years with tanks, then I tried a hookah diving, what a joy. No tanks to lug a round or store no large compressor taking up space nor fuel to run it or tanks to refill. I got rid of my dive tanks replaced with a 12 volt electric hookah unit that is the size and weight of a tool box, it serves 2 divers easily to 15 meters. and has a 125' hose split in a Y with two 25' hose connected with two regulators.

The hookah runs of the boats battery bank, which is recharge by solar panels while diving!. It is the most amazing economic weight saving solution for sports diving. Even though it is hookah for safety I recommend taking a certified diving course.

I would stay away from buying single hooker air pump, insure to purchase a unit with a double pump output. or a gas powered ones, they are nosy heavy and difficult to setup as well as store.

Happy navigation experiences,

Kryg Skoiern IV

Do you have to keep it charging on the boat while you use it or can you float it and move away from the boat?
We want to use it for two of us to clean the bottom of the hull but also for snorkelling/ shallow diving. How long would the air last on the 12v battery system for two of us?

[Sawbonz]

Originally Posted by Nani Kai

Bauer shows its JRII-ELY/115 SCUBA compressor (yachting package) at 2.9SCFM (2.5 FAD), with a 2HP motor at 1500rpm requiring 1.5KW. I am not an engineer by any stretch but it seems to me the 9KW your genny puts out wouldn't have any issues.

In outfitting a Leopard 45 (excellent choice btw) with a compressor, I would first figure out the minimum SCFM I was willing to accept. Then I would find reputable manufacturers that make electric models meeting that requirement. From those models I would select for weight and dimensions to correspond with my chosen install location. Once I settled on a model(s) I would contact the manufacturer's tech department to determine electrical specs and installation advice. I usually have better luck with phone calls than emails.

I would hesitate before locating the compressor in a lazarette. The #1 consideration for any SCUBA compressor is keeping the air intake as far away as possible from hydrocarbon exhaust. If the Leopard 45 has the same set up as the Leopard 444, the genny exhausts roughly amidships, above the water line between the hulls. With the bow into the wind that exhaust comes aft. If your compressor is in a forepeak then it's upwind of the exhaust.

It would be great to see the final install if you get a chance.

I agree, it looks to me as if it should work. Why the person selling it would say not....

I'm willing to accept anything that works! How simple is that?[emoji23]

When I get an install I will be happy to post a picture. It's the least I could do.

[a64pilot]

In order to prevent complaints they have to assume you do not have enough sense to power manage your appliances, best way to ensure there are never any complaints is to size the generator to run everything on the boat.
Heck even on shorepower I have to power manage our boat, I can't run all battery chargers, both AC's and heat water, much less make toast.
We had to do the same on our RV.

But we do just fine, just have to look at the amp meter before you turn on a big load is all.

[Sawbonz]

Originally Posted by Rumpi

This is actually simple to do:

Option 1:
Compressor with unloader valve powered by 3 phase motor and VFD. The VFD converts 1 phase from generator or inverter to 3 phase and allows programable soft start. The unloading valve bleeds the pressure and assures the compressor does not start against any significant load. Should start and run of the inverter alone. Up to 3hp VFD's are cheap and you can mount the compressor anywhere in the boat using a dedicated 3phase circuit.

Option 2:
Wire the battery bank for 24-48V and use a DC motor and controller on the compressor. Requires the use of a DC-DC converter for 12V loads. To keep the cables short you need to locate the compressor near the batteries or you use really thick cables to compensate.

So basicly what power are we talking about here? A 2hp compressor can be started and operated at 24V DC without any problems if the battery bank can support it. It can even be done at 12V with a big enough lithium bank. At this power levels there is no difference between a compressor or an electric anchor winch or bow thruster or a non recuperating watermaker.
So the question becomes how big is the battery and what C rates can it sustain? Or you go for option 1 and use the generator, or you do it like many others do and drive the compressor from one of the main engines.

I think you may be the answer I'm looking for!

If a VFD is all that's needed and is cheap to boot it seems like using one to power the more prevalent (I think) 230v 3-phase compressor is the answer. I would mind running the generator to power the compressor instead of an inverter...I just want it to work.

I'm hoping to find an electrical engineer to help draw out a plan for the specifics.

[a64pilot]

Your not running this compressor off of a battery bank, no conceivable bank could handle it.

Phase converters are pretty common for running machine shops and big woodworking tools etc. before I ran three phase power to the barn I had a phase convertor, looked like a panel box and an electric motor, it's the motor or generator maybe that actually makes three phase power, it may be a motor turning a generator, looked that way anyway.

On edit, hat may be old school maybe there is a way to do it with solid state components now, no moving part?
However I believe what I had was actually inefficient, but if you don't have three phase and need it, what are you going to do.

[Sawbonz]

Originally Posted by a64pilot

In order to prevent complaints they have to assume you do not have enough sense to power manage your appliances, best way to ensure there are never any complaints is to size the generator to run everything on the boat.
Heck even on shorepower I have to power manage our boat, I can't run all battery chargers, both AC's and heat water, much less make toast.
We had to do the same on our RV.

But we do just fine, just have to look at the amp meter before you turn on a big load is all.

My RV had a 20kw generator that would run everything. Everything until my wife turned on her hair dryer. That always seemed to be the killer. Hot water heater, 4 cruisairs, lights, chargers, tvs, stove top, washer dryer, water pump....no problem. Dry your hair though.....