Is changing from three phase to single phase worthwhile?

[hfwtrade1]

Dear sir

I am not an electrician but more a motor mechanic and would appreciate it if you can provide me with some answer on the following question. Will you save on a monthly electricity bill from Pretoria Municipality, if you change from a three phase electrical installation to a single phase installation? This will also have to take into account that two 5Kw three phase electrical motors need to be changed to 5Kw single phase electrical motors. The single phase 5Kw electrical motors still need to deliver the same workload as the three phase motors did.
Regards

[LuX10N]

Depends on what your requirements are. In Mossel Bay, single phase prepaid meters have no monthly municipal fee, whereas a 3ph meter has a monthly fee of R 3800 alone.
I'm sure this applies to direct connections too (where you get a municipal account each month).
Many domestic installations here, have converted to single phase to save on the hefty monthly charge.
Some houses with multiple geysers etc, that is too much for a 60A single phase supply, installed relay systems, that switches off some heavy loads when the it draws too much, to stop the mains from tripping.

Seeing as your refering to motors, I'm guessing this is for a commercial/industrial installation. Again, it depends on what your requirements are. A single phase line is usually only 60A supply. So if your equipment or motors draws more than 60A (in total) on nominal work load, then it won't be practical.

To put in in context, a single 5KW motor will draw 21A.

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[ians]

This is an interesting question.

I have a customer who is complaining about a R7000 monthly bill for a single phase standard 3 bedroom house ... which sounds really over the top ... so he has requested a quote to go "off grid" ... however I am told (which I need to verify) Eskom charges a R2000 monthly fee before the meter starts turning.

In this case ... we need to do 2 things ... first thing is to get at least 6 months of eskoms bill ... verify the figues ... and investigate ( Eskom was on site in the area 2 weeks ago ...calibrating meters ... a bit strage ... what I believe they were doing was checking for solar installations turning the meter backwards and broken seals on meters) ... the reason they check for broken seals on meters ... if you take the red wire from the rght and swop it with the red wire on the left at the bottom of the meter ... your meter will run backwards ... or if you drop out the bridge piece on some meters ... it stops the meter ... the clever okes are fitting old solar panels to justify the drop in the bill.

How they catch people tampering with the meter ... the average consumption in a standard 3 bedroom home is around 28-30 kwh per day ... if you bill drops to 15 - 20 kwhr per day ... you are flagged for investigation and meter recalibration ... they are going to start feeling the losses as more and more solar installtions are completed ... which is going to hit them in the pocket ... and we know how people respond when they start feeling it in the pocket.