question

[dingledong]

3 phase heater no neutral. in the fuse board itsd been wired up as 2 phases and neutral , why does it work ??????:thinking:

 

[mattmoo1974]

Its running at 66%

 

[Rockingit]

various explanations - what kind of heater is it?

 

[mattmoo1974]

If its got no netrual its balanced load. 2 phases are running 2/3 of it and the one with the netural is doing jack
A random guess i mite add...........

 

[dingledong]

hmmm i changed it back to 3 phase i'll have to ring up the company and see if its blowing out more heat ??

 

[johnboy6083]

so in other words, one of the coils has been wired to the neutral, and the other 2, each have a phase to them?

if so, then the heater will still work, as you have effectively shared a neutral between 2 single phase loads, albeit through a higher impedance.


any 3ph 4wire system uses this principle, as the max current that can flow in the neutral is equal to one phase. (harmonics muddy the water slighlty)

 

[dingledong]

but its not a 3 phase 4 wire system its just a 3 phase 3 wire system

 

[mattmoo1974]

Some ppl think the blue/black has to go to netural

 

[Rockingit]

Some ppl think the blue/black has to go to netural

Most likely explanation!

But surely the type of heater has to be relevant, too? I'm making an assumption its a big blower with a 3ph fan motor inside - if it's a diddly little halogen or IR then the 'balanced' theory starts to fall apart.

 

[BlueToBits]

hmmm i changed it back to 3 phase i'll have to ring up the company and see if its blowing out more heat ??

Based on what you have described, I would agree that Matmoo has probably the most likely explanation. However, it may be wise to fully understand what's really going on before re-connecting the 3rd phase, particularly if its an old unit. For instance, someone may have replaced 400v control gear with 230v or the elements themselves may have been changed for 230v.

 

[johnboy6083]

but its not a 3 phase 4 wire system its just a 3 phase 3 wire system

i know that the heater shopuld be wired as a 3wire load ie balanced, but what im saying, is that the way in which you say it has been wired, uses the same principle of a 3ph 4 wire system.

 

[Knobhead]

If it was 1KW per phase the output would be 1.66KW with the way it was wired instead of 3KW.
View attachment 9373

 

[benji]

give us a photo/sketch or if it,s got 3lines going to it could it not be star

 

[Deleted member 26818]

You say, it's 3 phase, but is it?
A lot of 3 phase heaters, have single phase elements, each being supplied by just one of the phases.
Obviously they then require a neutral.
How many elements are there, is there any single phase control gear?
Sometimes with 3 phase machines, there is a transformer, and neutral connections are connected to the star point of the transformer.
I've also seen some machines (mostly eastern European, where they have a 5 pin plug, TPN&E, yet inside the machine, the N & E are connected together.