Originally Posted by SV Coronado
For the electric Bauer compressor, what’s the minimum genset size needed to power it? Would something like an Onan 5 kw handle it or would you need a bigger genset?
Short answer, it depends and running a scuba
compressor is not easy or simple
for electric motors you have the running amperage and you have the starting amperage. starting amperage can be over 3 times the running amperage. specifically for scuba compressors on a boat its the starting amperage you have to worry about.
for the BAUER Jr its 3hp and 3500psi if i remember correctly. the BAUER Oceanus is 5hp at 5000psi, its running amperage at 240v is 25A if i remember correctly, but the starting amperage is 40-60amps. that means you could run it off of a 30amp circuit but cant start it. the Bauer Jr is lower capacity, essentially fill a single aluminum
80 within 30 min. i dont have the start amperage numbers but when i looked all this up long ago i believe it was possible to run off a 30 amp circuit
a 30amp circuit is important because if your running off of shore power
, your mostly looking at a 16amp 230v (euro) or using one or two 30a 120v sp cables
into a inverter charger
or auto transformer to get 230/240v. a victron and some other brands are able to boost power from the battery
in addition to the shore power
input which would allow you to use a scuba compressor without a generator
For a generator
you have to look at the power output Watts and convert that to amps and compare that to the starting voltage of the compressor. for the bauer oceanus you may be able to run it off a 5kw generator but more likely you need 6kw or 7kw to meet startup amperage. you have to do the math on the specific equipment
to verify. you can use an easy start device - essentially capacitors to drop the starting amperage.
smaller compressors can use a DC motor
2-3hp, but i havent seen much bigger than that unless your above 24v. those motors get expensive. there is an issue with dc motors and compressor loads due to the torgue below running load speed. i have less knowledge on this but it depends on the controller and you may have to get a bigger motor to be able to start the compressor.
I was told a RIX is better for a sailboat and is oiless where the Bauer has oil
, the oceanus specifically is able to work
at an angle for boats that are rocking. the Rix doesnt have an issue with angles, however i dont have experience with the RIX.
I have a Bauer Oceanus, and dive with HP steel
tanks 4500psi. so i have been working on this issue for a bit. its a complicated problem and your dealing with higher voltage so you absolutely need to make sure this is done correctly to be safe. original 5hp 240v motor went bad, and i just finished replacing the motor and in the process of installing on the boat for the first time - 42ft sailboat. first i had to swap to 240v from 120v for the AC system. i replaced the 240v motor with a 5hp 3ph 230v/400v motor, and running that with a 10hp Variable frequency drive (VFD), you need double the capacity with a VFD in a compressor application. the VFD is programmable and is able to slow start the motor at full torque at close to the running amperage. 3PH is more efficient than 120v/240v single
phase. the motor runs on 14amps but thats with 3 phases and i havent seen what amps it pulls off the 240v circuit into the vfd yet. essentially it will be close to the running 20a if i used the single phase 240v motor. this means in theory with the big battery
bank im putting in that i SHOULD be able to run off battery's for a couple tanks, OR run a smaller more efficient generator like a 4kw, combined with an inverter charger
off a battery.
i have researched, and looked at almost every possibility and what i listed here is essentially the only ways i can find that you can run a scuba compressor on a boat without a large generator. the 3ph motor with VFD has a lot of advantages for a boat and would also be good with a water maker. keep in mind that to make any of this remotely possible i had to make some major changes to my electrical system
and upgrade my electrical equipment
to the next sizes up in capacity. S/V Delos uses a similar capacity compressor to the Oceanus but run it off of a generator, they have a 50ft boat too. a larger compressor than the oceanus specs is going to require even more complexity, $, juice and a bigger generator and is probably in the realm of larger power boats