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[wakeyomega]

Hi All
Just looking for a home air compressor (electric) for general jobs, but including grit blast gun. There are loads on the market (Machine Mart, screwfix, halfrauds) Just wondering if anyone can recommend one based on personal experience?
Thanks Pat

[Kevin Wood]

Depends on the intended use IMHO. You can spend as little or as much as you like.

Grit blasting is going to give it a bit of a caning so with a small compressor you will have to do a little at a time and allow it to rest in-between. This is because most small compressors don't have a particularly high displacement and, in addition, won't be rated for the motor to run anything like continuously. If you grit blast for long periods this will be a frustration!

In other words, get the best one you can afford.

I have a Tiger 8/44 from machine mart http://www.machinemart.co.uk/shop/product/details/tiger/path/airmaster-2. It does the job for occasional use and has given no trouble. It does (predictably) struggle with more thirsty tools. It was a lot cheaper when I bought it (85 quid inc vat IIRC).

Not sure I'd regard it as great value at the current price but it's one of the better "entry level" machines I've seen . :-/

Kevin

[wakeyomega]

Thanks for that Kevin

Pat

[Ken T]

I think you will find that about 8CFM is the most you can get from a machine that plugs into a 240 socket. This is not bad, I had problems trying to run a spray gun and air mask from 4CFM, but 8CFM would have been a lot better, close to ideal. Watch cause some compressors don't tell you what pressure the CFM is being delivered at, eg you get 8CFM at a low pressure, but at say 50psi the flow is much lower. Also some of the smaller machine motors are not continuously rated, so they will overheat and the thermal fuse will trip, usually just when you need it most!.

Ken

[Ken T]

Oh yes, don't be put off by a 3phase machine, you can get a 3phase inverter that will run up to 3HP for a reasonable price. Only thing to watch here is that the motor can be rewired to run in delta configuration (240V per phase) as against star (415V per phase)

A 240V 8CFM hydrovane just went for £100. OK it needed some work, but......

Ken

[Andy B]

Oh yes, don't be put off by a 3phase machine, you can get a 3phase inverter that will run up to 3HP for a reasonable price. Only thing to watch here is that the motor can be rewired to run in delta configuration (240V per phase) as against star (415V per phase)

 ......

I'm just a 'multi-skilled' fitter who hasn't fired a multi-meter (at work) in years. But aren't most 3 phase motors intended for use with an inverter for work use too?


(for a multi-million £ firm, we still use a lot of 'Task Units' where now-a-days you'd use an inverter, apparently a 60's answer to variable speed control ..... no idea how they work - they just do!      or they do while they can get the obsolescent spares  :-/ )

[Kevin Wood]

I'm just a 'multi-skilled' fitter who hasn't fired a multi-meter (at work) in years. But aren't most 3 phase motors intended for use with an inverter for work use too?


(for a multi-million £ firm, we still use a lot of 'Task Units' where now-a-days you'd use an inverter, apparently a 60's answer to variable speed control ..... no idea how they work - they just do!      or they do while they can get the obsolescent spares  :-/ )

Depends what you want to do with them. In most cases, you just want them to run at constant speed, so you can just connect it to a 3 phase supply. If you need to precisely control speed and direction then yes, some sort of inverter will be used to control the motor.

In a domestic setting, 3 phase mains is not available, so you need an inverter simply to generate a 3 phase supply from an incoming single phase supply.

3 phase is a more efficient way of distributing leccy than using a single phase system, which is why most of the grid is 3 phase. Individual phases in a domestic supply are used to supply domestic properties but heavier users will have a 3 phase connection.

A 3 phase supply also allows physically smaller AC motors to supply more power. Induction motors can build up a rotating field just by having three stator windings rather than the single phase arrangement where you need a capacitor to introduce a phase shift between wstator windings. There is also a more or less constant delivery of power with a 3 phase supply whereas with a single phase supply this is not the case, and this leads to less vibration with a 3 phase motor.

Kevin

[Andy B]

I'm just a 'multi-skilled' fitter who hasn't fired a multi-meter (at work) in years. But aren't most 3 phase motors intended for use with an inverter for work use too?


(for a multi-million £ firm, we still use a lot of 'Task Units' where now-a-days you'd use an inverter, apparently a 60's answer to variable speed control ..... no idea how they work - they just do!      or they do while they can get the obsolescent spares  :-/ )

Depends what you want to do with them. In most cases, you just want them to run at constant speed, so you can just connect it to a 3 phase supply. If you need to precisely control speed and direction then yes, some sort of inverter will be used to control the motor.

In a domestic setting, 3 phase mains is not available, so you need an inverter simply to generate a 3 phase supply from an incoming single phase supply.

3 phase is a more efficient way of distributing leccy than using a single phase system, which is why most of the grid is 3 phase. Individual phases in a domestic supply are used to supply domestic properties but heavier users will have a 3 phase connection.

A 3 phase supply also allows physically smaller AC motors to supply more power. Induction motors can build up a rotating field just by having three stator windings rather than the single phase arrangement where you need a capacitor to introduce a phase shift between wstator windings. There is also a more or less constant delivery of power with a 3 phase supply whereas with a single phase supply this is not the case, and this leads to less vibration with a 3 phase motor.

Kevin

Most motors at work will have an info plate that will show the curerent drawn if it was star or if it was wired delta. I have to admit I have fallen into the trap of just handing the job over to the sparks .... in true Heinz tradition. Sparks have their job & the fitter have theirs and never the twain shall meet  I haven't (been allowed to) wired a motor in years now 3ph or single. 

[Vamps]

I'm just a 'multi-skilled' fitter who hasn't fired a multi-meter (at work) in years. But aren't most 3 phase motors intended for use with an inverter for work use too?


(for a multi-million £ firm, we still use a lot of 'Task Units' where now-a-days you'd use an inverter, apparently a 60's answer to variable speed control ..... no idea how they work - they just do!      or they do while they can get the obsolescent spares  :-/ )

Depends what you want to do with them. In most cases, you just want them to run at constant speed, so you can just connect it to a 3 phase supply. If you need to precisely control speed and direction then yes, some sort of inverter will be used to control the motor.

In a domestic setting, 3 phase mains is not available, so you need an inverter simply to generate a 3 phase supply from an incoming single phase supply.

3 phase is a more efficient way of distributing leccy than using a single phase system, which is why most of the grid is 3 phase. Individual phases in a domestic supply are used to supply domestic properties but heavier users will have a 3 phase connection.

A 3 phase supply also allows physically smaller AC motors to supply more power. Induction motors can build up a rotating field just by having three stator windings rather than the single phase arrangement where you need a capacitor to introduce a phase shift between wstator windings. There is also a more or less constant delivery of power with a 3 phase supply whereas with a single phase supply this is not the case, and this leads to less vibration with a 3 phase motor.

Kevin

Most motors at work will have an info plate that will show the curerent drawn if it was star or if it was wired delta. I have to admit I have fallen into the trap of just handing the job over to the sparks .... in true Heinz tradition. Sparks have their job & the fitter have theirs and never the twain shall meet  I haven't (been allowed to) wired a motor in years now 3ph or single. 

Many years ago when I was a 'Service Engineer' for 'Andrews Heat For Hire' I was called out, near home time to  a breakdown, the problem was not our equipment but in the supply of electricity, a simple fuse problem   keen to get home I was heard to say that I will fix the distribution box, and there was hell on. I was told in no uncertain way that I had to wait for a sparky, waited ages for a 2 minute job.  In those days you could not do another persons job, even if quite able.....

[r1]

i would buy the largest compressor you can afford/have space for/that your electric can run.as you will add more tools as you go along
also if you have a choice of machines that are the same go for the one with the bigger air tank
also be aware that some compessor make a lot of noise

[feeutfo]

i would buy the largest compressor you can afford/have space for/that your electric can run.as you will add more tools as you go along
also if you have a choice of machines that are the same go for the one with the bigger air tank
also be aware that some compessor make a lot of noise

very much so, for domestic use, your neighbours wont thank you, as said size v price will take most consideration once you know your application. I have an 18 litre capacity which struggles with a windy gun and wheel nuts done up to 110nm, a mate had a 24 and upgraded to 36 for that reason, but he uses his much more than i do.

.....which reminds me, its probably due to have the water emptied out of it....hth

[Ken T]

Thats why I like Hydrovane, they are a rotary vane system, not totally unlike the Wankel engine. I remember going to an exhibition, and speaking to the chap on the Hydrovane stand. Next to him was a compressor, running, I didn't notice it it was so quiet. OK, 2nd hand worn ones are noiser but still very quiet.

Ken

[Marks DTM Calib]

Thats why I like Hydrovane, they are a rotary vane system, not totally unlike the Wankel engine. I remember going to an exhibition, and speaking to the chap on the Hydrovane stand. Next to him was a compressor, running, I didn't notice it it was so quiet. OK, 2nd hand worn ones are noiser but still very quiet.

Ken

Good but very expensive and can take some sorting out if they have issues.

13-14CFM is about the max you can get from a 3Hp setup which will run off a 13amp plug

[wakeyomega]

Fascinating stuff guys, thanks for all that. Looks like I might be better off checking out the second hand market for a higher spec in the same budget range.

(And all that talk of 3 phase , Star, Delta etc took me back to my electrical apprenticeship (remember those?) in the mid 60's. Luck for me, the local leccy board made all apprentices redundant as they came out of their time - why lucky? I took a job with a large international computer company the next day and stayed for 30 odd years. But I can still remember most of my electrical theory (although I can't remember what I did yesterday!)

Pat