Thread: Generator to run Bosch 1800W Mitre Saw

Generators tend to be heavy. You may want one on wheels, or put it on wheels. Asume you will be drawing the maximum 2400w for each item you plug in.
As I have no experiance you may be best talking to a dealer, e.g. Honda.

Originally Posted by Rickey Herb

We are shortly about to commence building our new home and as we wont have any power during construction are looking at buying a generator to run a few power tools.

Can anyone recommend a generator that would run a 1800W Mitre Saw. It needs to be reasonably portable as we will need to cart it back and forth for a while until we have a secure storage area.

I already have the mitre saw. Most of the generators I have looked at such as the MTM Inverter Generator Silent 4.4kVA PRO SINEWAVE POWER have dual outlets where only half the total output is available at each outlet. I am aware that I will probably need more than 1800 watts to fire up the Mitre Saw.

Any advice appreciated.

Thanks, Rick

this site might help you Generators | FAQ | Power Equipment | Honda MPE
also, IMO it's worth spending significant extra dollars for a quiter unit

also when selecting a generator for a building site I'd allow for the other items which might also be running off the generator -- e.g. a camping fridge, electric kettle, water heater, air compressor, etc

Good advice from Ian and a useful link, although one or two of their figures may be a little suspect. For example, they refer to a 2 HP motor and the current as 1100 watts.

Ahem, 2HP is 1500 watts! However the priciples are OK. Not a good idea to run the generator at it's maximum all the time. You need some in reserve for the continuous running as well as starting.

You need to differentiate between universal motors, which are the most common motor for hand-held tools, and induction motors which power fixed machinery such as larger table saws etc.

The induction motor draws up to four times it's normal running current when it starts, while a universal motor hardly draws any more then the normal running current at start up.

Take a 3KVA generator. It may start a 2400W (3.25HP) circular saw (although this would be close to it's maximum with no room for anything else), but a 750W (1HP) bench grinder, which uses an induction motor, may have the generator bouncing across the floor as it tries to keep up with the demand.

I hope this hasn't confused you. Just look at what you anticipate using. Your 4.4KVA will be good for most equipment on a building site (with the exception of a welder).

Regards
Paul

Thanks everybody for your advice. The problem is that a 4.4kVa Generator that produces around 3000 watts only has 1500 watts available at each outlet as there are two outlet plugs. If there was only one outlet I wouldn't have a problem.

Rickey, we must be looking at different units
using the link I posted, I clicked on "Power saw" and got a power range of 1500 - 2000W accompanied by a list of 7 Honda generators.
As far as I know, even if a genny has a double plug outlet, the plug is fed by a single cable -- so you can run one high current draw appliance, or two lower current draw appliances.
Honda's EM30 series of generators appears to have the specs you're looking for, but if the genny will be the sole power supply on your building site, I'd be inclined to go for a larger unit so I could run some lights and other stuff (possibly a heater) once the framing is completed and you move inside or work after dark.

Hi all,

the saw will draw 1800 Watts at nominal load. At that moment it will return 1100-1200 Watt in drive power (the rest is blown out as heated cooling air and there is also loss in the gears, bearings and commutator friction). 1200 Watts is about 1.5 hp. I wish there would be some medicine to forcefeed into all people claiming that electric power intake is the same as net real hp output, which simply is not and never will be true. The Americans (boasters as they are) once thought this up, to make their machines sound tougher and to conjure up figures that look cool in brochures.

During acceleration from zero rpm just after switch-on, the Amp intake of electric motors can reach a peak of up to five times nominal load value, meaning that for a very short period the saw may draw up to 9000 Watts, which may trip the generator's safety cutout. Overloaded machines will also exceed their nominal input; an 1800 Watts machine can stand 2000 Watts throughflow for a minute or so and up to 2500 Watts for a few seconds. For this reason reputable generator set manufacturers like Bosch, advise 3 kVA output (not 3kW of the petrol motor, but real generator output) as a minimum to drive such a load without generator field coil overheating. 4kVA (approx. 4000 Watts) is even better.

The division into two outlets will probably mean that each outlet has its own fuse system of approx. 10 Amps. In gensets meant for a wide range of users this is often done to avoid severe Amp peaks of hungry appliances, connected by people without expert knowledge and training . But the two outlets may also share one 15 Amp fuse and the rating for each outlet may have been labeled with a 2000 watts max per outlet merely to avoid people getting too enthousiastic. The genset's manual may explain a bit more on this; else ask your dealer. It is also possible that the generating part has two separate field coils (and therefore two separated generating groups, each with its own fuse), both responsible for generating half of the total output. If so, there's little you can do apart from accepting the two fused groups, which cannot be connected in parallel without risk of severe damage.

If there is only one coil group responsible for the total output and there is one fuse for both outlets, just plug in the saw. If there is one coil group and a separate fuse for both outlet, a bit of tinkering could give you one outlet with a bigger fuse. Provided you have the knowledge and skills to do this the proper way, of course.

greetings

gerhard

Thanks Gerhard and Ian. I appreciate the time you have spent providing this advice. Plans are on hold for a moment whilst I recover from an unscheduled eye operation following an accident with an occy. Prognosis is good but no building for a while,

Regards

Rickey

Originally Posted by gerhard

snip
It is also possible that the generating part has two separate field coils (and therefore two separated generating groups, each with its own fuse), both responsible for generating half of the total output. If so, there's little you can do apart from accepting the two fused groups, which cannot be connected in parallel without risk of severe damage.

gerhard
by this do you mean that the generator might be two phase?

I've seen 15kVA 3-phase generators and understand that it's possible to get a 3-phase unit under 10kVA, but I don't think I've every heard of a 2-phase generator.

hi ricky.
i hope your eye has healed up.
how did you go with the generators?

with regards to building a new house in victoria...

there is a qld housing $10,000 grant for people buying or building new homes under $600,000.
this grant is eligible to buyers who sign a building contract between august 2011 and january 2012.

is the victorian government doing anything similar to what the qld government is doing?

justin.

Hi Justin - eye is not too good. Having my second operation tomorrow to relieve the pressure in the eye. Will need a further operation at a later date to replace the lens and remove a cataract.

Ended up buying this BBT Inverter Generator Camping Caravan Outdoors 4.4Kva | eBay

Very pleased to find that it will run the 1800w Bosch Mitre Saw without a problem.

I'm not aware of the Vic Govt providing anything similar grant wise but will investigate.

Regards, Rickey

good luck with the operation.
or, break a leg as they say in show business!

looks like you got a good deal on the generator.

all the best, justin.