Generator for my tools - advice required.

[archersam]

Hello helpful people, been very quiet at my end as too many conflicting priorities to be getting much made so no postings but have been watching what you been up to ;-)

Am temporarily moving my workshop and need some advice. I will be storing it in a unit that has no electricity connection. Whilst I do not intend to spend lots of time at the place there are some items that I need to be making/finishing so I will need power for my tools:
- T/S
- P/T
- pillar drill
- router
- bandsaw
- sander and associated power tools.

Can someone give me some advice on what to look for in a petrol generator?

Is somethign like this going to be of any use:
- http://cgi.ebay.co.uk/2-8KVA-PETROL-GEN ... 286.c0.m14

Noise should not be a major issue as it is in the middle of nowhere.

Thanks v.much.
Sam

 

[wudbutcher]

from an electrical point of view it depends on the electrical size of your power tools ie how much power they consume. The geny you have a link to is is only 2.8kva (approx 2.8kw) so assuming it will comfortably supply this much power and non of your tools are bigger than 2.8kw it will work fine. Another point to remember is that 2.8kw is the total amount it will supply so if you need lighting, heating, kettle etc then you will have to take these into account as well (bear in mind most kettles consume at least 2kw so you will have to down tools to put the kettle on).
One more thing are all your tools single phase or not? if you have three phase machinery then you need a three phase genny

Hope this helps not adds to confusion

 

[archersam]

hey wudbutcher, yep that helps. Thanks v.much. I always stop work when the kettle is boiling.........

 

[9fingers]

Take care!
The classic mistake of mixing Kva and Kw has been made.

Gennys produce Kva ie 240 volts at a number of amps. The load may well not have a power factor of 1 and so the useful kW output will likely to be less.
The only time Kva = Kw is running fillament light bulb or electric fires etc

Generators are also mainly specified to sound better than they really are.

First of all most have some sort of low voltage DC output for battery charging

This needs to be subtracted from the Kva total. So lets say we have a 2.8kva genny with 13.8 volts DC at 20 amps. This is 276va to be subtracted.

so the 240 volt output is a max of 2524 va

max current is therefore 2524/240=10.51 amps.

This current has to supply the starting current for your tools. The heftiest requirement is likely to be the TS or P/T

10 amps will possibly start a 1.5hp or 1.1kW motor.

Loads of power to run it but if it won't start it won't run.

Sorry to dampen your hopes but I suggest that you get a demonstration of the genny powering your tools before you buy.

Bob

 

[archersam]

Thanks 9fingers that is really useful and was talking to a friend last night who was trying to explain something similar but seeing it in writing makes more sense!

As I am saving my monthly workshop costs I may consider renting one that way I know if it is not powerful enough I can upgrade it without too much hassle.
Sam

 

[wudbutcher]

i agree with all your points 9fingers you will notice that I did put approx. I did not want to get into th detail of power factor, apparent power, inductive loading, inrush etc on a woodworking website. The point I was trying to make was be carefull as this unit may well not meed your needs.
Maybe I did not spell this out.

 

[9fingers]

Hi Wudbutcher,

I did not mean to imply any criticism of your post. I quite agree that the concept of power factor is not easily understood by non techies- it sounds like mumbo jumbo and folk switch off.

Combining the general over specification by the sellers of these low end gennys with the lack of electrical understanding, it is easy to end up with failure.

I reckon the OP is best served by renting where he will get a better rated genny and possibly a quiet one and the opportunity to upgrade if needed.

Bob

 

[laird]

To put it in perspective Sam I have a 2.8Kva genny for power cut use. It copes with the central heating pump (and boiler ignition, a few lights, the fridge, a microwave and a couple of fish tank aerators. There;s not a load of power left. Non of these needs big power up surges.
Phil

 

[SVB]

I am also after a geny for use on board a boat.

I found this site very useful and relevant here as they give an overview on motor starting power and VA / Kw.

http://www.justgenerators.co.uk/pages/which.htm

BRgds

Simon.