Testing generators

[Laxt44]

I've put a small garage unit in to run a couple of lights & a plug powered from a generator. When I came to test my KT65 meter would not function correctly & would only show 110 volts being supplied from the generator. My multimeter proved it was 240 volts. Using my KT65 on a normal house supply & it works fine. I've also tested the KT65 on another generator & had the same problem. Has anyone had similar problems? Please advise. Thanks

 

[Knobhead]

Let me guess, it's a site generator.

Not suitable for what you’re trying to do. In fact downright dangerous.

 

[gnuuser]

Let me guess, it's a site generator.

Not suitable for what you’re trying to do. In fact downright dangerous.

i agree with tony
most site generators are designed with portability in mind. and if not installed correctly will skew readings and present dangerous conditions.
from what i can see about the kt65 it is designed with the UK. electrical system in mind
and unless your generator was manufactured in the UK it will most likely not be suitable for your intended use

 

[Engineer54]

i agree with tony
most site generators are designed with portability in mind. and if not installed correctly will skew readings and present dangerous conditions.
from what i can see about the kt65 it is designed with the UK. electrical system in mind
and unless your generator was manufactured in the UK it will most likely not be suitable for your intended use

The generator will almost certainly be manufactured for use in the UK, it's just that they are unsuitable for much more than site lighting and hand tools etc. Most of these tiny gen-sets will have a single phase floating earth arrangement and will rely on the speed vs load for voltage output, having no AVR.

 

[gnuuser]

thank you this info is what i suspected but not quite sure of

 

[Laxt44]

The generator will almost certainly be manufactured for use in the UK, it's just that they are unsuitable for much more than site lighting and hand tools etc. Most of these tiny gen-sets will have a single phase floating earth arrangement and will rely on the speed vs load for voltage output, having no AVR.

Thanks guys. Both generators are from machine mart & are Clark's. The latest one is a fg4050es, I installed an earth electrode rod and got a reading of 125 ohms (with temporary rods) installed electrode rod to earth block,
I am concerned because can't get a Ze, PFC, any Zs and RCD, readings, is there a meter that would do theses test or is it because the generator supply, would it be safer not to go through the garage fuse board
thanks for your help it very much appreciated

 

[Engineer54]

The problem lies with the floating earth arrangement, on normal generators there will be a winding N-E, connection, which is not the case in this instance. All you are doing with the earth electrode you have installed is earthed the frame. It can be adapted, but you would need to know what you're doing. Is it really worth it??

To be honest, if all you want from this generator is to power up a socket(s) and a couple of lights in a garage, just leave the thing as it is, it should be fine for electric hand tool etc, just not anything that has sensitive electronics.

I bet if you look in the manual, it will have a disclaimer of some sort or other stating that the genset is not suitable to power household installations or appliances...

If there is no mains supply to the garage you could go through the Garage CU via a suitable plug and socket arrangement. (female plugtop on genset lead). At least it will then still be portable...

 

[Knobhead]

If you are to use this unit the MCB’s and switched should be DP. Otherwise what you assume is the neutral is live and unprotected.

I do wish people would leave these things alone to do their specific job.

 

[Marvo]

With the type of generator you have rather just earth the chassis with your existing rod and use trailing leads, don't connect it up as a permanent installation.

 

[Laxt44]

If you are to use this unit the MCB’s and switched should be DP. Otherwise what you assume is the neutral is live and unprotected.

I do wish people would leave these things alone to do their specific job.

What I'm seeing then, is because of the floating earth, is the reason I am not getting the results on my test meter. As it's been put through a 16 amp plug into a garage unit, there is a potential of the earth being live when the generator is running. I have connected up 3 x 5 ft single tubes & a double plug. It is a container being used as a small workshop. To correct this system, I need to remove the rod & garage consumer unit & then fit DP switch for the lighting & for the plug. Or the best thing would be for my mate to buy a decent generator that hasn't got a floating earth - can you recommend a 5 kva generator suitable for the installation that I've done? Cheers.

 

[mechelec]

Speak to the manufacturer. Some will advise linking the neutral and earth at the plug and installing earth rod. This will allow downstream RCD's to operate which won't with a floating earth system.

 

[Laxt44]

Speak to the manufacturer. Some will advise linking the neutral and earth at the plug and installing earth rod. This will allow downstream RCD's to operate which won't with a floating earth system.

Just looked through the book - there is a place on the frame & recommends it should be earth to rod. It doesn't mention anything about a floating earth, bit obviously that's the case - that's all it really says. I will contact the manufacturer & see what they say. Thanks.

 

[Engineer54]

Speak to the manufacturer. Some will advise linking the neutral and earth at the plug and installing earth rod. This will allow downstream RCD's to operate which won't with a floating earth system.

Don't think that's an option with a floating earth arrangement, but i'll stand to be corrected if i'm wrong...

Just looked through the book - there is a place on the frame & recommends it should be earth to rod. It doesn't mention anything about a floating earth, bit obviously that's the case - that's all it really says. I will contact the manufacturer & see what they say. Thanks.

That earth rod connection will not afford a functional earthing system, in the true sense of the word.

Yes contact the manufacturer as to what they recommend with regards to earthing. Nothing they can do about the genny not having an AVR though, unless it's available as a retrofit option.

Myself, if all that is wanted from this genset is a bit of lighting and a couple of sockets for tools etc, then don't muck about with it hook it up as has been suggested in other posts...

 

[mechelec]

Don't think that's an option with a floating earth arrangement, but i'll stand to be corrected if i'm wrong.

i have done this several times as advised by Honda and some lesser known manufacturers. The point is it ties the earth (chassis, earth pin in socket and rod) to the neutral and creates in effect a TN-S system. You need the wiring diagram as it will not work with some. As I said previously speak to the manufacturer.

I would not want to connect anything voltage sensitive though due to no AVR. Some power tools with electronic control can be susceptible to badly maintained generators. Ie over revving causing higher frequency and voltage spikes.