Selecting the Right Cable Gauge for a 3.3kW STIHL Pressure Washer Over 30m Distance

Colleagues, I am asking for help. I have a STIHL pressure washer. The 3.3 kW engine burned out. The website stated that it burned down because the extension to the washer, about 30 meters long, was made of a 3x1.5 kw cable. Is it possible?

Total rubbish, the cross section of the wires in the extension cord cannot cause the motor to burn out.

spinacz wrote:

Total rubbish, the cross section of the wires in the extension cord can not cause the motor to burn out.

I would argue. Take into account the voltage drop (1.5mm kW is not enough for this power), throw in poorly twisted plugs / sockets and it turns out that the motor gets, for example, 150V instead of 230V. How will the engine behave when the voltage is lowered? It will be weaker + load as for full power = more heat, less cooling. It is only a matter of time before the winding burns out.

Well, you're right, buddy, maybe I wrote too sharply, but I suspect that the contact you are talking about with a poorly twisted than a burnt engine would get stoned sooner.

With this length it must be 2.5mm square. I had a similar case. For the future, buy a karcher washcloth - on this cross-section and with this length of the extension cord you will not start at all, and at 2.5mm sq. It flies like this doll.

I do not have this washer, it is on the site, but what do you think can be the nominal current with such a large single-phase 3.3kW motor.

Probably around 14A.

14A, assuming that cos phi = 1 and it certainly is not ... for such a motor, the rated current will be about 18 A

I propose to calculate the voltage drop on a 1.5mm cable and a length of 30m. I understand it's a copper cable. I guarantee it's not 80V.

I recommend the site Link , there is a formula for calculating the minimum wire diameter for a given voltage drop. According to my calculations, 3x2.5 mm2 is enough for this washer with your assumptions and the efficiency of the 3.3 kW motor is 0.81.

That 3X 2.5mm is no doubt and if the service saw a 3X 1.5mm extension cord and the washer is under warranty, they will not recognize this warranty, and what was the cause of the engine burned, you can only guess.

The question was whether the 1.5mm cable damaged this device. In my opinion, a 10% chance of it. And what the cable should be, the producers probably know better. And the fact that the website did the topic in its favor in 3 minutes is a different matter.
Even if they were sure it was their fault, it would be easier to push it onto the customer.
But unfortunately the user has no chance of defense in this case.

But why is there not a word about it in the manual. The user does not need to have an electrical education and know that the extension must use a 2.5mm square cable.

I may be wrong, but the important thing is whether this 30-meter cable was developed. because if it was not fully developed, a coil could be created.

hmm, and what will happen when such a coil is created?

Note that there are two cores in the coiled cable and if the device works correctly, one wire will "flow" into the device and the other will "flow out" ... and thus the induced magnetic fields cancel out ...

Hello colleagues
You are too deep about the extension cord.
The 3.3kW motor with single-phase power is a bit big and strange (unnormalized) power (it can take about 20A). For single-phase power, the largest typical motor is 2.2kW.
But the question is different: why is the motor in the device not protected against overload (motor switch, thermal relay).
When the supply voltage drops, the motor consumes more current - when the rated value of the motor is exceeded, the protection must switch it off. In this way, it is not allowed to operate in abnormal conditions and damage the engine.
So, either there is no security or it is malfunctioning.
Don't get in the service - it's not an extension cord.

ergonus wrote:

Note that there are two cores in the coiled cable and if the device works correctly, one wire will "flow" into the device and the other will "flow out" ... and thus the induced magnetic fields cancel out ...

Magnetic fields cancel out, but a coiled cable can transfer 40% of what is unrolled If you let go of 10 through such a coil, you have a nice heater
But why did you tell the service technicians that you worked on an extension cord?

and are you sure the washer is single-phase? whether the cable cross-section for the extension cord is specified in the manual

If the washer was 3-phase, how would it be connected to a 1-phase extension cable?
Of course I am, but you have to get a bit of work and want it very much! With this 3.3 KW, I would be wondering
Maybe the type of washer we'll find out?

The discussion on this topic becomes pointless, so I am asking you to close it, because it will not bring anything in anyway.

Okay, colleagues, I am very glad that you answered my question so spontaneously. There is no doubt that the installation should be changed to 2.5 kw. I will do so and thank you once again and close the topic. Hi