When I worked at Bosch we sold 2 generators, a 2.4kva for small power tools and 5.5kva for larger ones such as the 2300 watt 9" angle grinder which happened to be the most power hungry power tool we sold in those days.
The generator module also came from a quality manufacturer. To ensure that each generator complied with its stated output it was very probable that actually the generator was built to a higher kva and downrated on the label. At the time there was no law against that. A manufacturer on a production line couldn't guarantee each generator was exactly 5.5kva without testing and certificating each unit built. So in those days genuine honest manufacturers built in a margin for error.
A 5.5kva generator was also heavy. We mainly sold these into the construction industry and moving them around on site (no wheels) was a 2 man job. The gubbins was in a strong steel frame - you have no idea how they treat equipment on South African building sites.
One of the gutter vac suppliers says that they can run their 1400watt vacuum motor on a 2.0kva generator. This is interesting as motors have a higher starting current. (Some new power tools and appliances have a soft start built in to reduce the initial power surge at start up.)
According to the calculator a starting current for a vacuum cleaner motor can be 3 times the running current.
https://www.sgs-engineering.com/help-advice/which-generator-should-i-order/ Another calculator says 2.5 to 3 times. But I wouldn't rule out what that supplier says as a load of rubbish. I have a 2200 watt Bosch angle grinder which is about 30 years old. 2200 watt is 10amps. On occassion it trips my 15amp circuit breaker in the garage on starting, but not often. Now 15 amps is 3300 watts so the starting current required to start that grinder isn't 2.5 to 3 times the running current. (I'm also allowing for a time lag through the circuit breaker. Not all circuit breakers are identical and some might be slightly more sensitive than others, even from the same production line.) If my grinder did draw 2.5 times its running wattage on startup then it would trip the circuit breaker every time.
So according to that I would need a much bigger gen set to run my gutter vac than a 2.0kva. My Vacuum cleaner motor doesn't have a starting current on the label. I have emailed the supplier and asked them.
I would like to be self sufficient and have my own generator, but gutter clearing isn't my core business. I do it begrudgingly for existing customers. I bought the gutter vac for the safety aspect but don't want to pour vast sums into the service - I just don't fancy falling off ladders doing a gutter clean. We have still had to use ladders to remove the down pipes on a couple of customers houses recently as they were fully blocked and had gardens growing out of them.
So I would probably hire a generator to ensure that the size I was buying did actually work for me. I would take the vacuum unit with me and let the hire company size the gen set for me to hire. If that worked fine I would then buy my own from a reputable supplier.
Just to further complicate matters; how do I know that my vacuum cleaner motor is a 1500 watt? Maybe its a higher wattage motor down rated on the label. In my old Bosch days they did that all the time. (There was no law back then making it illegal to under rate a spec - it was illegal to manufacturer a product with an advertised 800 watt motor that was only 600 watt obviously.)
A new Bosch drilling machine was lauched stating it had a 500 watt motor even although it was manufacturered as a 750 watt motor. Further down the sales line it was then relaunched and promoted with a more powerful 550 watt motor and then later as a 650 watt drill. But the part numbers for the armature, brushes and field coils were the same. The only thing that changed was the label and perhaps some minor cosmetic changes. (The rear handle may have been given a soft absorbant material to absorb vibration which cost a couple of Phennig in those days before the Euro.)
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