Powering an electric dive compressor

[Sawbonz]

We hope to sign the contract on a Leopard 45 this week and will outfit the boat with a compressor. I don't wish to have the noise, maintenance or fuel consumption of the gas or diesel models and a place that installs dive compressors has told me that a 9kw generator isn't enough to power the compressor. Huh? I have read here that several are doing it, though a search is not specific on how you are wiring the electric one.

In addition I plan to have two 3kw inverters on an lithium battery bank and lots of solar. Can you tell me how to get the oomph needed to start the electric motor on the compressor so that I can start sourcing parts and planning?

[HopCar]

Google "hard start kit". Works for air conditioner compressors.
Look on the compressor label for LRA. This will give you an idea of the amps required for just a fraction of a second to get the compressor moving.

[Sawbonz]

Thanks. I am already planning on a "soft start" but the dive shop said that wasn't enough to get it going which I find hard to believe. Also, I haven't purchased a compressor to look for the label as I want to do the planning before the purchase.

[john61ct]

Do some googling about running a full-size air conditioning setup off batteries.

That big a load is really pushing the limits of "mostly solar", and if you need to run a genny anyway you may be complicating things and overspending for little benefit.

How many hours a day will the compressor be running? Setting startup surge aside for now, put a Kill-a-Watt on your intended compressor setup, get a ballpark (conservative) AH per day figured.

You may find even maxing out your space on panels, best you can hope for is reducing your generator usage a bit, and having some choice about the timing of your run hours.

[Sawbonz]

I have, but I am in the same boat as before (none until next year! Lol). The only reason I mentioned the batteries and solar is that I know there is a way to use the inverters to supplement the generator's constant output. How exactly to do that is what I am after. Google is of little help as no one appears to have asked the exact same question I am trying to ask.

Again, I couldn't do a Kill-a-watt without having the compressor, which I won't buy until I have the answers to the questions I am asking here so that I don't have to do it twice. Thanks for the input.

[DotDun]

I would be surprised if a 9kw generator would not start the dive compressor. Post the compressor specs....

The measured in-rush of a motor isn't necessarily what's required to start it. They will start, albeit a few hundred milli-seconds slower, on a lower in-rush.

[Olddan1943]

Originally Posted by Sawbonz

We hope to sign the contract on a Leopard 45 this week and will outfit the boat with a compressor. I don't wish to have the noise, maintenance or fuel consumption of the gas or diesel models and a place that installs dive compressors has told me that a 9kw generator isn't enough to power the compressor. Huh? I have read here that several are doing it, though a search is not specific on how you are wiring the electric one.

In addition I plan to have two 3kw inverters on an lithium battery bank and lots of solar. Can you tell me how to get the oomph needed to start the electric motor on the compressor so that I can start sourcing parts and planning?

==========

Couple of questions before I recommend you contact the compressor's manufacturer, asking for the starting amperage.

1. Is this a hookah set up? If so, I suspect your current situation is more than enough.
2. IF you intend to have compressor large enough to charge SCUBA tanks, two questions, 1. where are you going to mount the compressor 2. what is the weight of the compressor. I cant even find a space to store my Brownie Third lung 120vt compressor.

IF you are using this only as a hookah unit, Brownie's makes 12vt units.

[john61ct]

Sorry I'm confused. If you know you're running a big genny to power the compressor, why not just use a known-good direct fuel powered type?

I assumed you wanted to just run off the batteries, for quiet or "green PR".

The huge and pricey marine inverter/charger units like Victron's do have built-in circuitry, that passes through shore (genny) power when available, then if the load is greater than the mains supply, ramps up input from the bank. When the load drops, automatically goes back to pass-through and charging mode.

I'm sure you can find a compressor supplier with a good returns policy.

[lifemiles]

I have a gas-powered compressor for my tanks, and I am sure the 5 HP gas engine could be replaced with an equal or maybe slightly bigger electrical motor. since the torque on the electrical motor is much higher you may want to clutch the connection between compressor and motor, so that once your e-motor is spinning, you can (slip) clutch your compressor on. e-motors startup amps will not be high in that case, so no problems running it off your inverter.

I wouldn't necessarily go for the lithium bank. very expensive and may not be worth the extra money ? if you have the space: there are 1500 aH 2 volt Gell batteries available these days, I have 24 of those on my boat (they weigh 85 kilo each so maybe on a cat you'll want a little less) that run through 3 inverters virtually my whole yacht (130')

[Sawbonz]

Originally Posted by DotDun

I would be surprised if a 9kw generator would not start the dive compressor. Post the compressor specs....

The measured in-rush of a motor isn't necessarily what's required to start it. They will start, albeit a few hundred milli-seconds slower, on a lower in-rush.

That's what I would have thought too, but the shop selling the compressors says no. I need sources to be able to refute that.

[captmikem]

I run a Bauer Utilis 10E with a 220/110 motor off my Westerbeke 7.5KW genset with no problems at all.

I used to run it off a Panda 4200 (which is more like 3KW) and as long as I would let the belt slip a little on start up it ran fine. A big cap (soft start) would have taken care of the start problem.

M

[Sawbonz]

Originally Posted by Olddan1943

==========

Couple of questions before I recommend you contact the compressor's manufacturer, asking for the starting amperage.

1. Is this a hookah set up? If so, I suspect your current situation is more than enough.
2. IF you intend to have compressor large enough to charge SCUBA tanks, two questions, 1. where are you going to mount the compressor 2. what is the weight of the compressor. I cant even find a space to store my Brownie Third lung 120vt compressor.

IF you are using this only as a hookah unit, Brownie's makes 12vt units.

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.

[Sawbonz]

Originally Posted by john61ct

Sorry I'm confused. If you know you're running a big genny to power the compressor, why not just use a known-good direct fuel powered type?

I assumed you wanted to just run off the batteries, for quiet or "green PR".

The huge and pricey marine inverter/charger units like Victron's do have built-in circuitry, that passes through shore (genny) power when available, then if the load is greater than the mains supply, ramps up input from the bank. When the load drops, automatically goes back to pass-through and charging mode.

I'm sure you can find a compressor supplier with a good returns policy.

I think you mean why not get a gas powered compressor? More money to purchase, more maintenance, more fuel to carry and more noise. If something else is what you are asking now _I_ am confused! lol

Those Victron units is what I was thinking but I am certainly not tied to a brand. I am trying to get a basis in electric power so that I truly understand the setup. I have done my googling (if for no other reason than so that I don't have to listen to people tell me to do so ) and read a lot of static web pages that have honed me in a bit. Those remaining holes in my knowledge and others' personal experience doing what I am trying to is what I am looking for here.

Returns may well be possible, but I feel it is always better to plan out and do it once. Labor alone plus boat mods would make it a real bummer to have to do a return. :thanx:

[Sawbonz]

Originally Posted by lifemiles

I have a gas-powered compressor for my tanks, and I am sure the 5 HP gas engine could be replaced with an equal or maybe slightly bigger electrical motor. since the torque on the electrical motor is much higher you may want to clutch the connection between compressor and motor, so that once your e-motor is spinning, you can (slip) clutch your compressor on. e-motors startup amps will not be high in that case, so no problems running it off your inverter.

I wouldn't necessarily go for the lithium bank. very expensive and may not be worth the extra money ? if you have the space: there are 1500 aH 2 volt Gell batteries available these days, I have 24 of those on my boat (they weigh 85 kilo each so maybe on a cat you'll want a little less) that run through 3 inverters virtually my whole yacht (130')

Purchasing the electric motor and requisite power supplies off the bat would be my preference and is what I am really trying to hone in on here.

The lithium question is off topic, though I would love to hear about your setup. If you want to message me I would be interested in what you have to say and we can keep this thread more narrow. :thanx:

[Sawbonz]

Originally Posted by captmikem

I run a Bauer Utilis 10E with a 220/110 motor off my Westerbeke 7.5KW genset with no problems at all.

I used to run it off a Panda 4200 (which is more like 3KW) and as long as I would let the belt slip a little on start up it ran fine. A big cap (soft start) would have taken care of the start problem.

M

Excellent! Is that an old model? Googling gets me a 10 but not 10E. I use HP steel tanks and would want to get the full 3445 psi.

Did you have to make any mods or do you just fire up the generator and turn on the compressor?

Aaaaaand, if the Panda did the job I wonder why the people selling the compressors are trying to steer me in a different direction.....