270ltr 2x4kw tandem on 13/16amp supply..

[Domeo_jones]

Could you do it.... and most importantly costs...

So hello again all you lovelys... been kind if shifted over here from the brew room...
So I was looking at big 3phase compressors like 7.5hp for blasting and noticed massive CFM and pretty cheap. Also motors run quieter and smoother om 3phase But the supply... so then looked into vfds... not so cheap and potential issues eith restarting the pumps..
So.... I thought how about if I build a 2x 4kw 270 ltr compressor using vfds and usual house hold supply... .possibly 16amp..

So.... let's go... tell me I can't do it or it might get expensive and I'll have to do it.. lol

 

[daleyd]

2 x16a supplies?

 

[brightspark]

so what comps are u going to use single or 3 phase and why is the limit 16 amp ???

 

[hotponyshoes]

I have got a single phase compressor with 2 motors/pumps. 4hp each I think.
That needs 20a minimum. And that's with a staged start-up.

 

[Domeo_jones]

2 x16a supplies?

Was just thinking the 16amp in the garage... so single...

 

[Domeo_jones]

I have got a single phase compressor with 2 motors/pumps. 4hp each I think.
That needs 20a minimum. And that's with a staged start-up.

What compressor is it... any pictures or details... costs etc... sounds perfect... 20amp... I only have 16amp at the moment... how did you get 20amp?

 

[Domeo_jones]

so what comps are u going to use single or 3 phase and why is the limit 16 amp ???

I wasn't sure. Hence asking... I'm thinking single as I already have a 16amp supply. Blue plug... but my eyes are opened to vfds so now 3 phase is possible

 

[brightspark]

whats stopping you putting a bigger feed from the house to the garage . if your going to be doing blasting what size jet are you going to run 2x 14cfm comps will run nicely on a 3mm jet after that its a 6mm jet and would need a minimum of 75cfm of air

 

[Ruffian]

No chance.
4kw with 230v is 17.4amps
So even one is pushing a 16amp supply.

32amp supply is going to be much more like it. For a tandem 4kw.

 

[tigdlo]

I think most 4kw 1ph to 3ph inverters will need a 32a supply, on a domestic supply I think it would be best to power them on seperately due to the inrush current and starting the motors in stages, then it may work.

I did call my DNO to talk to them about running high power equipment like big inverter drives for old transformer tigs and was told if it started dimming the neighbours lights they are within their rights to lower the cut out fuse to 60a...

 

[steviec_lj]

In a word, no.

16a is around 3.5kW.

You’ll need some clever timers and switching to get 2no 4kW motors to start on a single 16a supply, after uprating the cable and putting a 20a D type MCB in its place. Not really good practice.

You could maybe squeeze them on a single 32a supply, as long as both motors don’t kick in at the same time.

Same with putting a VFD on a 16a, you’ll be limited to the 16a it’s plugged in to.

 

[daleyd]

Was just thinking the 16amp in the garage... so single...

So, no matter how hard you try you aren’t getting 2 x4 kw out of 1 x 16amp supply.

If it’s single phase supply (I assume it is) then you are even further from where you want to be - a 3 phase 4 kw motor will take something like 14 amps per phase but the input to a 4kw vfd running on single phase would be much higher, I’d guesstimate on needing at least a 32 amp supply

A 4 kw single phase motor has a full load current of something like 27 amps.

 

[hotponyshoes]

What compressor is it... any pictures or details... costs etc... sounds perfect... 20amp... I only have 16amp at the moment... how did you get 20amp?

I don't think even my twin one will be enough for proper blasting. I have a 2nd compressor (single pump, 3hp?) connected up as well and need them all running for the shot blasting cabinet.
There is a 100a supply in the workshop,, originally had 2x 16a points for 2 compressors. Had to change a breaker to a 20a for the twin pump one.

 

[hotponyshoes]

What about a engine driven compressor rather than electric?

 

[brightspark]

op hasn't said yet what blasting gear he intends to run that's the governing factor on size of comps as I said theres a jump from 3mm to 6mm and your not going to get 75cfm of anything electric its a diesel one needed

 

[Domeo_jones]

op hasn't said yet what blasting gear he intends to run that's the governing factor on size of comps as I said theres a jump from 3mm to 6mm and your not going to get 75cfm of anything electric its a diesel one needed

Well, ideally just 3mm sand blasting, just thinking about bigger cfm for speed

 

[brightspark]

Well, ideally just 3mm sand blasting, just thinking about bigger cfm for speed

I run one double 14cfm comp with 2x 2.5kw motors it can run a 3mm jet all day long .builds up pressure and cuts in and out when im running it it has 2 contactors run through a timer to stagger the start up I think its about 30 amp supply

 

[Domeo_jones]

I run one double 14cfm comp with 2x 2.5kw motors it can run a 3mm jet all day long .builds up pressure and cuts in and out when im running it it has 2 contactors run through a timer to stagger the start up I think its about 30 amp supply

Brilliant... ebaying right now..

 

[RWD3M]

I run one double 14cfm comp with 2x 2.5kw motors it can run a 3mm jet all day long .builds up pressure and cuts in and out when im running it it has 2 contactors run through a timer to stagger the start up I think its about 30 amp supply

Sounds like you have the same one as me:



Great piece of kit running off a 32A MCB and serves all my needs from paint spraying (supporting an air fed mask), blasting, various air tools etc... Not all at once of course

 

[brightspark]

Sounds like you have the same one as me:

View attachment 261910

Great piece of kit running off a 32A MCB and serves all my needs from paint spraying (supporting an air fed mask), blasting, various air tools etc... Not all at once of course

very similar. as said good machine 28cfm and a big tank .mine was second hand and outside on the scrap heap paid 75 quid for. it rewired it 1 motor was knacked so put a new one on for 120 quid and it works fine the garage asked me to fix for them and I said I didn't know anything about them so they scrapped itim a lying git and knew all about them with the contactors and timer was easy to fix