Powering an electric dive compressor

[Palarran]

Originally Posted by stgermain45

Can someone here recommend a make and model of single phase soft starter for my application? Yesterday, I purchased a Bauer Junior II dive compressor (JRII-E1-2HP). I went with the 115V version with 2HP motor as my plan is to wire it through my 2.5KW inverter (Mastervolt Mass Combi 12/2500-100) to power share with the 8KW onboard generator (Fischer Panda mini-8) when the load is ramped up. The boat is 100% wired for 115V and I'm choosing the simpler route of keeping the dive compressor 115V as well, despite marginally slower tank fills compared with the 3HP+ 3-phase compressors. I won't be running other large draw items like the water maker or air conditioning units when filling a scuba tank. In the compressor shop, we tested the startup on the Bauer and the inrush current was right around 100A. The draw was in the low teens after the initial inrush which will ramp up a bit as the tank fills.



Back to the soft start. I've seen the EasyStart recommended on this forum quite a bit for air conditioning units. I contacted Micro-Air yesterday and they did not recommend any of their soft starters for a dive compressor. Maybe a CYA thing, I don't know - but I don't see much in the way of published specs on their website.



Since this is a single phase application, I'm looking for a soft starter and not a VFD. Any tips would be appreciated!


Thanks,

Chris

Man, I think you need to just try it first and see if there is a problem with it starting. I have a Junior II also (230v) and can start it off my 8kva without a problem. In fact, the generator can run the compressor and my watermaker (230v 40gph) also at the same time.

Read how many people have had zero problems starting them - why not just try it.

[BigBeakie]

We could not start our Bauer Poisidon PE100, which is very similar to the Junior, on the either the Victron Multiplus 3000 or the 5000. It was close on the 5000, but no go.

We found a great company here in Australia who specialise in power sources, and their soft start is in every Dometic AC unit. They had another unit for heavier duty applications, and we tried it with our compressor....BINGO.

They also used their lab ocilliscope to measure the in rush current before and after using their device. The compressor had an inrush of 65 Amps at 230V. After installing their smart soft start, the inrush is in the low 20's Amps, a huge difference.

Their device is not a capacitor based system, it is electronic wizardry that "learns" the operational characteristics of whatever device it is connected to, and self configures to give the best results. After 4 or 5 starts, it operates at optimum performance for both performance and safety. It will not force a start if there is something wrong, as in a locked rotor condition, or excessive belt slipping etc., so it is a step above the other soft starters we looked at, including the EasyStart. Other devices without this safety protection can damage your inverter!

And it is very reasonable for what it does, a couple hundred Aussie pesos.

Since we took the PE100 to them for testing, they were able to put it in the same electrical box of the compressor. A nice neat installation.

We're delighted to have found this. The company is Hyper Engineering P/L located in Wollongong NSW. Speak to Rudra on +61 2 4229 2069.

[stgermain45]

Really great info folks. Thanks!

Looks like the 115V model SureStart from Hyper Engineering only covers up to a 1.75HP motor. Maybe there is a "heavier duty" model, like you referenced. I'll contact them.

Still digging around to see what the options are, whether single phase VFD like transmitterdan recommended or soft start. And maybe I'll find I don't need one...Definitely not opposed to wiring it up without one and seeing what happens. I like money enough to keep it in my pocket!

Thanks,
Chris

[stgermain45]

In case it helps anyone with a 115VAC wired boat, I'll follow up with my experience. All said, my 8KW Fischer Panda generator outputting 115V didn't skip a beat with the inrush current powering a 115V 2HP Bauer Junior II portable compressor. It's advisable to open condensate drains on manual drain systems like mine to ensure the motor starts without load.

I initially bought the Hyper Eng Sure Start to reduce inrush, given the great recommendation here and the US distributor support convincing me the HP rating had some "fudge" and would work...but it would not start the motor due to its start capacitor being unable to handle the high inertia required. The Aussie engineering group later confirmed this for me. This is the 115V single phase version I'm referencing (there is a 230V 1-phase unit that can handle higher HP). Incidentally, I've decided to reuse it for one of my air conditioning units and see if the inrush is low enough to run aircon off the inverter. Speaking of the inverter, the manufacturer tech support (Mastervolt) highly recommended against trying to power share the dive compressor load with generator and inverter, even in the case of paralleling two inverters. I decided to heed that advice for the dive compressor and not wire it through the inverter. Ultimately, my original grand plan of reducing startup loads and power sharing resulted in simple wiring to the AC panel with no soft start or VFD. I'm definitely guilty of overthinking things at times.

FWIW- in my research I found a single phase 120V input, 1ph/3ph 220V output VFD by a company called ATO. General wisdom would be to opt for a 3-phase motor compressor going this route as also recommended here, but it would be an option either way with a 1ph or 3ph motor. Model# GK3000-SP1S1-004 (5HP). It's not a recommended practice to take single phase VFD output, but their engineering support advised it would work well to effectively eliminate inrush at either 1-phase or 3-phase output. No firsthand experience with the product, just passing info along. I could be wrong, but I didn't see any 120VAC input drive options rated at 2HP+ from the reputable players like Eaton, Schneider Electric, Fuji, etc or products from Grainger and McMaster Carr. 220V boats have a lot more options.


Regards,
Chris

[BigBeakie]

Sorry to hear the difference between the 115V and 220v was a show stopper, Chris. But you can do some battery charging and watermaking while the tanks are filling on the genset, I guess.


Sent from my iPad using Cruisers Sailing Forum

[rcontrera]

Originally Posted by stgermain45

... my 8KW Fischer Panda generator outputting 115V didn't skip a beat with the inrush current powering a 115V 2HP Bauer Junior II portable compressor.

Great report, Chris!

The 7 KW minimum genset recommendation from Bauer was based on your Junior II 115/2hp motor. The standard 3hp motor would be a bit of a stretch and would most likely damage other onboard electronics that are running at the same time.

Take good care of your compressor (change oil and filters regularly, keep it clean, keep it cool, apply wax to all painted parts OFTEN, etc.) and it will last you a long time.

[Sawbonz]

My update... We installed a Nardi Atlantic 100 compressor, 230v 3 phase. Our boat is 120 volts, so a transformer steps it up to 230 and then a frequency drive ramps up from about 15 hz to the 50 hz required by the compressor. This unit also has an auto Purge and sure drain system which eliminates trying to start against a lot of pressure. I think total load is 28 amps.

Yes, I did end up going with a 6kw generator, but this system works just fine on my inverters! I have two Multiplus units in parallel which is plenty for the dive compressor and more.

So, smart design of the system makes it possible to do a lot of things that I was told were not possible.