Can you safely under run a piston compressor?

[qwakers]

I have a 16mm swa supply from the house to the garage and fully up to date wiring in the garage. Still.wont run reliably from a 13a supply. It also trips a 16a b type mcb on start. As does my compressor. Both are now on c type mcbs.
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[dobbslc]

My workshop wiring is fully compliant with some regs somewhere back in time....

It is backed up with a mcb and 30ma RCD though

 

[brightspark]

My workshop wiring is fully compliant with some regs somewhere back in time....
View attachment 238935
It is backed up with a mcb and 30ma RCD though [/QUOTE mine wasn't compliant in any reg still isn't apart from a new db and a tt supply with earth rod. if I ever sell il just disconnect the wiring inside

 

[dobbslc]

Yeah I'm on a TT supply too....17-21 ohms over the last year or so if you're wondering!

 

[brightspark]

Yeah I'm on a TT supply too....17-21 ohms over the last year or so if you're wondering!

that's decent. as long as its under 200 will be ok. never bothered testing mine possibly do it within the week and see what it is should be good as its soil and clay and a high water table

 

[daleyd]

I have a 16mm swa supply from the house to the garage and fully up to date wiring in the garage. Still.wont run reliably from a 13a supply. It also trips a 16a b type mcb on start. As does my compressor. Both are now on c type mcbs.
..

You must have either a very low voltage or some other issues if you can’t run a 2hp motor from a 13a supply. A 3 Hp I can understand being near the limit but 2hp is well within.

 

[Country Joe]

Mine is a 3hp 1ph "ABAC" compressor, and runs fine from a domestic (13a) supply.
It hasn't tripped (as far as I remember) in the last 14 years.

All the Best,
CJ

 

[qwakers]

You must have either a very low voltage or some other issues if you can’t run a 2hp motor from a 13a supply. A 3 Hp I can understand being near the limit but 2hp is well within.

nope. all tested and ok’d when i bought the place.

 

[Jbo2231]

Dont forget a lot of 3hp single phase 13amp plug compressors also use capacitors to help start the motor. If you're retrofitting a new 3hp motor on to an older compressor that used to have a 3ph motor on it I think the start up surge would just about exceed a normal ring main 16a mcb depending on the motor.

 

[fizzy]

I doubt you'll get a 3hp motor to run on a 13a supply. My 2hp motor blows a fuse on every 3rd or so startup... I've had to stick it on a 16a commando plug.

My Clarke 3hp has run fine for years on a normal 13amp supply - I even use it on an extension reel.

 

[qwakers]

i wonder if the main issue is its a 1950’s 230/415v motor? and just not as efficient as the current crop?

 

[daleyd]

i wonder if the main issue is its a 1950’s 230/415v motor? and just not as efficient as the current crop?

That doesn't sound like a single phase motor? What is the start mechanism? Most modern motors have capacitor start, I have an old GEC motor on my drill that has a split phase start where it has an extra winding which is switched out by a centrifugal switch when up to speed.

 

[qwakers]

it is, its single phase or 3 phase. it has 2 caps in it. s’all i know, cap’n!

 

[daleyd]

That may explain it - if its single/3 phase I can only imagine it's actually a 3 phase motor that someone has added capacitors to to allow it to run on single phase. This will probably reduce the efficiency and power of the motor somewhat but can be a solution if you don't have 3 phase.

I've never heard of a motor that could run on either single or 3 phase - but that's not to say they don't exist, just that I've not come across them...

 

[Reman]

I remember someone once telling me that you can run a 3 phase on single phase by using a couple banks of exactly calculated capacitors and a few other components to retard 2 of the phases, But he also said that all the components usually end up costing more than getting a replacment 1 phase motor because the bigger the motor the more beefy the capacitors you need to use. He said it only makes sense to do it if you work on the industry and can scrounge the parts you need.

 

[daleyd]

I remember someone once telling me that you can run a 3 phase on single phase by using a couple banks of exactly calculated capacitors and a few other components to retard 2 of the phases, But he also said that all the components usually end up costing more than getting a replacment 1 phase motor because the bigger the motor the more beefy the capacitors you need to use. He said it only makes sense to do it if you work on the industry and can scrounge the parts you need.

I've heard of it being done for smaller lightly loaded motors, eg coolant pumps on lathes etc. (Though I've never done it myself). I don't think it's really suitable for things that are quite demanding in terms of power.

 

[hermetic]

Wire a 16a single phase blue socket for your compressor, and fit a 32a C type mcb in the house to supply the garage. I have a 60+ 3 phase supply, and the lights still dip when I am using my single phase compressor. Single phase motors are very inneficient, and the dipping is also due to power factor. Also make sure your earthing is effective over the whole installation. Most important!! I also fried a capacitor, and eventually the motor, but replaced it with another single phase 2860 rpm motor, but this time with 2 capacitors, and it does start more briskly. Infortunately, the latest crop of Chinese motors are woefully inneficient, unless you got for a brand like TEC, which are designed and specced in the UK, but built in China, the Italian motors that Clarke and the like used to sell werem't that bad, but they probably sell Chinese ones now. Modern motors are neither good nor efficient unless you buy very good quality ones!! The actual efficiency of motors has changed very little over the years, and the modern idea of rating a motor in Watts, insted of HP is a marketing ploy that makes undersized motors look more powerful.