I need a low consumption (amps) air compressor with a fairly large air reservoir (say 100lts)

[Piero]

Now, I am not saying the post I will copy in, is correct, but I found this on an other forum, The chap replying to a similar question did test his own air compressor, his reply I will copy and paste below


Pasted "
Just ran up my 3hp CompAir for you.

Motor plated at 15A for full load (it's 20years old) General Electric old skool moving coil clamp meter.

Inrush on the needle peeks at 25A, running current is 10A from Zero psi.

A brand new motor would be made today with a much higher efficiency, but the pump being new would be stiffer to turn.

SOD

Lathe power requirement varies according to design.

A 6inch chuck is a heavy lump to accelerate a 4inch is not

Gear drive has large losses, a belt drive has not

How long is your piece of string?

 

[voipio]

So, based on start current being six times run current, the Shhh type of compressor might actally be ideal, almost maxing out the Anker 767 surge capacity on start up, with a small margin. Question is, what else might be running off the battery bank at the same time?

 

[sako243]

Fuses are quite slow blow in nature. A typical 13A fuse will handle much more surge, in fact a 13A fuse is supposed to withstand 1.6x the rated current for 30 minutes (BS 1362). It only blows at much higher currents (1.9x ish).

Why does a 13A fuse not blow at 13A?

The rated current is the current that it can pass without not overheating the plug. A 13A fuse will allow a current of 20A to pass without blowing.

www.pat-testing-training.net

 

[carbon]

if 6 times the run current was true, would that not make most air compressors pop there 13amp fuses

I work mostly with pressure washers and use a digital current clamp meter when testing but the sample rate isn’t fast enough to detect the maximum peak current but I still can see currents in excess of 25 amps at start up with some motors. When a motor capacitor completely fails the fuse usually lasts up to about 1 second, looking at the chart in the above post the fuse will then handle about 80 amps before failing.

 

[MetalMonkey]

exactly,

it was a question NOT a education

I was looking for help and suggestions, as you said, My question still remains the same.

some people cant simply reply and help, they have there own needs of curiosity that needs to be meet

Generally the more relevant information you can supply to start with, the greater the accuracy of the responses you will receive.
Especially when you want a solution which is outside the norm for a seemingly arbitrary reason.

A lot of people may think they need something, but they often don't - or just haven't considered or been aware of an alternative - that is the benefit of having a variety of replies.
For example - I find a hand held cordless blower is just the trick for dusting stuff off quickly without the hassle of getting the air line out. However, it is not much use for blowing up a tyre...

 

[Piero]

I work mostly with pressure washers and use a digital current clamp meter when testing but the sample rate isn’t fast enough to detect the maximum peak current but I still can see currents in excess of 25 amps at start up with some motors. When a motor capacitor completely fails the fuse usually lasts up to about 1 second, looking at the chart in the above post the fuse will then handle about 80 amps before failing.

I was actually shopping for a clamp meter with inrush mode, it would be interesting if nothing else

 

[sako243]

A lot of people may think they need something, but they often don't - or just haven't considered or been aware of an alternative - that is the benefit of having a variety of replies.

That is extremely valid. At my old company it was known as the Roger effect. Basically our technical authority in the group was the first contractor our clients had ever had turn around to them and say hang on... Are you sure you want to do that? Or more often - are you being morons?

The end result is it (usually) ended up costing a bit more initially but they got a far more capable and versatile system built out of it. Over the years it trickled down such that junior engineers would often do the same thing - question what they actually wanted and propose alternatives.

 

[GRW]

I've got a 100L Clarke job with a belt drive. It's a few years old (& in the workshed so I cant recall details).
What I can say is that it's surprisingly quiet, and what noise it does make isn't harsh or irritating - way quieter than the bloody racket the direct drive things make.
All in all a cracking little unit, handy (it's on wheels with a pull handle) & does its job well.
Never considered the start load, as it's always fired up easily with no drama.

 

[GRW]

dont quote me on this, but in the back off my mind, it was 3 x the run current, my power station has a 2300 watt amp max output, BUT does have a 3300 what surge rating, I am not happy to test that on a battery, as its a massive demand in such a short time, mains and the like has nothing to damage, but at £3,200 for the power bank, I really would not want to see it smoking

Is this "power station" off the Solar Array basically just an Inverter unit?

If it is, then I'd check to see if it has a stated max motor size that's allowed to be started off it (some US-made Inverters for off-grid systems used to state this - e.g. a Trace/Xantrex 3kW Inverter/Charger stated a max 1hp motor).
Where we had off-grid properties (single inverter) with workshops and/or borehole water pumps, then we'd have those items on a separate circuit to the battery-inverter-generator circuit, so these bigger items could only be supplied directly off the generator output.

If I've interpreted the "power station correctly, & on that basis (& given the pre-mentioned approx. 6x transient start current) - then no way would I be wanting to start a compressor off a 2.3kw inverter directly.

 

[GRW]

As an add-on.... the 6x starting for 1ph motors is a rule of thumb, as there is the factor of whatever the motor is driving.
A motor that spools-up with virtually no load on it may well take less than 6x (& what inrush there is will be for a very short duration).
Something with a lot of weight/drag on the motor (e.g. an old-school Wadkin Planer or suchlike) might push the transient to say 10x, & for longer duration.

 

[brightspark]

If this is the absolute maximum then it may rule out anything with an induction motor. From when I was at college, single phase induction motors need approx six times the run current to get them to start. A compressor may be a bit better as it won’t be staring at full load but something to consider.

i clocked my 3hp motor running at 12,5amp flc and 55 amp starting

 

[Piero]

i clocked my 3hp motor running at 12,5amp flc and 55 amp starting

interesting

 

[jonclancy]

I've got two of these. One stopped pumping after 10 years so I bought another, took the old one apart and it was just a broken valve about £10 these compressors are sometimes running 5 hours a day often one or two hours non stop. Amazing for a cheap Chinese thing.View attachment 393220

Sorry to hijack, but it’s kinda relevant..

SGS will be stocking a slightly down-rated version of this compressor at around half the cost. I like the space saving design, and think it’ll be good enough for my needs (future spraying, air dusting, tyres etc). It’s only a 50L reservoir, and the OP was after 100L, but what’s the opinion of the eperts here please?

SGS 50 Litre Oil Free Direct Drive Vertical Air Compressor - 4.3 CFM, 2HP, 50L

Introducing NEW Air Compressor from SGS - with vertical 50 Litre receiver tank is ideal for DIY and trade applications such as spray-painting, tyre inflation, nailing and stapling. Upright design.

www.sgs-engineering.com

Currently using a borrowed Bambi slient (oil lubricated) fridge style thing. Expensive new and less oomph.

Ta.

 

[Smallfry]

dont quote me on this, but in the back off my mind, it was 3 x the run current, my power station has a 2300 watt amp max output, BUT does have a 3300 what surge rating, I am not happy to test that on a battery, as its a massive demand in such a short time, mains and the like has nothing to damage, but at £3,200 for the power bank, I really would not want to see it smoking

Start up current is 3X run current. Thats what I learned too.