Wanting advice with undersized generator

[Aksailor14]

Has anybody used Gates PowerGrip® SB Clamps on their boats. These heat-sensitive thermoplastic hose clamps generate even high clamping pressure for use on silicone hoses. I have recently replaced my engine hoses with silicone.
Thanks in advance.

[Force Majeure]

Just get a “power assist” charger/inverter from Victron or TBB. The inverter recognizes the need and will supply AC power from the battery bank to assist the start up of the compressor for a few seconds. Batteries make great capacitors to supply large amounts of current quickly and you already have them. This will take care of the inrush required.

[ericoh88]

Originally Posted by Revelations

We have a Kohler 13 KW single phase 220 volt generator onboard. We also have a Bauer Mariner 320 compressor with a 7 KW single phase 220 volt motor.
...

Variable Frequency Drives,
...

I am not an electrician. I would add VFD to slowly (1 minute) ram up the motor (provided there is no load) and power down gradually ( 30 seconds) . The VFD must be correctly installed and programmed.


Eric

[Briggers]

Originally Posted by Revelations

No, we have not tried it. The generator is onboard, the compressor is in my workshop. Will be several months before we will be able to install the compressor.

If the compressor is in your workshop just put a clamp meter round the live and measure the current, then times amps by volts to find the watts.

If it’s too high, slacken off the outlet connection and test again.

[charlesmoore03]

Check this video out. Not the best but it telss names you can track down
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https://www.youtube.com/watch?v=o1IVgMWhevs

[skenn_ie]

Originally Posted by rslifkin

If the compressor has an unloader so the motor isn't starting with the compressor output pressurized, there's a decent chance it'll work. Personally, I'd try it and see how it does before adding stuff to the compressor to reduce the startup load.

Agreed. As long as the compressor isn't immediately pumping against a full or nearly full tank, I would be surprised if you will have a problem.

[Palarran]

Personally, I'll be surprised if you don't have a problem. Looking at the spec's for that unit, is should draw at least 3 times more power than my old Bauer Jr. II. Bauer's spec's don't actually show that compressor being made without it being a 3 phase motor. Why did you get this compressor or was it from a dive shop? The unit alone weighs 340 pounds vs Jr II at 100. And on a catamaran - death by weight gain.

All the suggestions of VFD controllers and capacitors - clear them out of your mind. The capacitor won't work, and a VFD controller for this size motor will cost more than a new dive compressor.

I don't know if you are trying to run a dive company off the catamaran, but if not, maybe consider modifying your plan. I used to have twin generators, a 12kva and 8kva, along with a Bauer. I removed the 12 and the compressor and it really helped with speed. Now I'm going to remove two sets of the dive equipment and replace the 8kva with a 6kva. All together this will remove 2000 pounds of weight from the boat. It makes a huge difference. Just because you have the space doesn't mean you should fill it.

[skenn_ie]

Is belt-driving the compressor an option ? Get rid of a hefty motor and maybe alternator too ? I think, if I was to install a dive compressor (the thought has crossed my mind), I would belt-drive through a mechanical clutch, from one of the main engines.

[john manning]

A capacitor start single phase motor will not solve your problem. The initial starting current of single phase motors is 5 - 7 times the running current and that is the block you are trying to get over.
The suggestion of unloading the motor is the only thing you can try with your current design. If the pressure unloader idea does not work and your compressor is belt driven you may be able to fit a clutch pulley to the motor to unload on start up.
If your compressor has any electronic controls DO NOT TRY STARTING with an under power genset. Electronic panels can often be destroyed by low voltage or low frequency power.
The way I have solved this problem before is to change the single phase motor. Fitting a three phase motor with a variable speed frequency drive will allow the unit to start. The variable speed drive needs to be a single phase to three phase type (Teco or Siemens sell these) and the motor needs to have a 220V connection to match.

[downunder]

Originally Posted by Palarran

Personally, I'll be surprised if you don't have a problem. Looking at the spec's for that unit, is should draw at least 3 times more power than my old Bauer Jr. II. Bauer's spec's don't actually show that compressor being made without it being a 3 phase motor. Why did you get this compressor or was it from a dive shop? The unit alone weighs 340 pounds vs Jr II at 100. And on a catamaran - death by weight gain.

All the suggestions of VFD controllers and capacitors - clear them out of your mind. The capacitor won't work, and a VFD controller for this size motor will cost more than a new dive compressor.

I don't know if you are trying to run a dive company off the catamaran, but if not, maybe consider modifying your plan. I used to have twin generators, a 12kva and 8kva, along with a Bauer. I removed the 12 and the compressor and it really helped with speed. Now I'm going to remove two sets of the dive equipment and replace the 8kva with a 6kva. All together this will remove 2000 pounds of weight from the boat. It makes a huge difference. Just because you have the space doesn't mean you should fill it.

On the money as its definitely a high capacity compressor compared with the Bauer Jn most of us use. You need to talk with experienced electrician. Running the compressor with a 3phase motor and variable speed drive (VSD) should do it.

[downunder]

Originally Posted by john manning

A capacitor start single phase motor will not solve your problem. The initial starting current of single phase motors is 5 - 7 times the running current and that is the block you are trying to get over.
The suggestion of unloading the motor is the only thing you can try with your current design. If the pressure unloader idea does not work and your compressor is belt driven you may be able to fit a clutch pulley to the motor to unload on start up.
If your compressor has any electronic controls DO NOT TRY STARTING with an under power genset. Electronic panels can often be destroyed by low voltage or low frequency power.
The way I have solved this problem before is to change the single phase motor. Fitting a three phase motor with a variable speed frequency drive will allow the unit to start. The variable speed drive needs to be a single phase to three phase type (Teco or Siemens sell these) and the motor needs to have a 220V connection to match.

[Uncle Bob]

Originally Posted by Cheechako

Did you actually try it? Worse case is a temporary stall, just be ready to flip it off. The initial surge is big, but it may come right out of it.
Also, I wonder what the startup draw would be with all the pressure out of the compressor tank? With no "push back" pressure, wouldn't it be very low? Or an option of a valve on the compressor line to open until the motor runs is an option.
I have an old shop compressor that has an undersized motor, maybe 1 time out of 10 it wont start up, (Tank empty) I have a permanent wrench on the air fitting so I can crack it open and it starts right up when the motor was stalled....

A Bauer Mariner 320 compressor is a high pressure multi stage compressor used for filling diving tanks. On the older models each stage had its own condensate drain which could be opened independently so if the newer ones are so fitted then opening each prior to start would perhaps reduce the load.
Enjoy the diving.

[pbmaise]

You must have a lot of space on your vessel if you want big compressor and a separate generator to run it. In the dive industry, almost no one I know goes with the approach you want to use. My strong recommendation is to sell both of them and buy a compressor with an integral engine.

I have known other boaters who have tried the split route and I read one post that said good rule of thumb is 3 to 1. This ratio is in line with what others have told me.

You wouldn't by chance thinking of locating the compressor inside the vessel and the generator outside? I was thinking along those lines for a long time until a dive shop operator who ran two compressors on a dive boat told me there was zero chance I could eliminate all the heat the electric driven compressors would generate. The problem isn't so much the electric motor. It is the heat released by the air as it is compressed and the water condenses out.