And there was me thinking that if two conductors have the same electrical potential, the potential difference is zero. And thus there is no energy transfer (First law of thermodynamics). And thus there is no relevance to power or power factors. 
10mm cable for shower - Why?
- Thread starter Handyman
- Start date
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I suppose if manufacturers made these shower units with switches, thermostats and wiring that were far more substantial, the units would last forever and put electricians and plumbers and shower manufacturers ( and myself )out of business.Washing machines,dishwahers etc have all suffered from vastly underated components which are designed to fail just after the guarantee expires .Watchdog cant always be wrong. I blame Maggy Thatcher, I dont know why,but my dad always did, so it must be her fault.Ha Ha
AdamW said:And there was me thinking that if two conductors have the same electrical potential, the potential difference is zero. And thus there is no energy transfer (First law of thermodynamics). And thus there is no relevance to power or power factors.
Don't menion thermodynamic laws. I have a running argument with someone (a creationist) who argues that evolution violates the the 2nd law. I have explained, in vain, that it doesn't.
B
Big_Spark
AdamW said:And there was me thinking that if two conductors have the same electrical potential, the potential difference is zero. And thus there is no energy transfer (First law of thermodynamics). And thus there is no relevance to power or power factors.
Adam, whilst the potential difference between two conductors may be zero, thus at the same potential, that can change due to conditions and thus the PD will be +/- zero
The Neutral of a circuit and the Earth should have the same potential difference, but this DOES NOT make them the same conductor.
The First Law of Thermodynamics is irrelevent in this context...but not irrelevent to electrical circuits in general in case someone wanted to point that out..
I am busy with a quote at the moment, but when I have done this I will write a plain and simple explanation that will allow this to be clarified so everyone is clear.
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B
Big_Spark
Your Both wrong.
It is a matter of semantics in one case, however, electrically you are both incorrect.
I will explain it later when I have time free to type a full explanation.
It is a matter of semantics in one case, however, electrically you are both incorrect.
I will explain it later when I have time free to type a full explanation.
FWL_Engineer said:
What you originally said was:
Now, if they have the same potential, the potential difference MUST be zero. In which case in the Earth frame of reference then neutral DOES equal zero. Now, I know that in real life power supplies neutral doesn't = 0 with respect to earth, but I just thought I should perform my duty as a pedantFWL_Engineer said:
With respect to the evolution thermodynamics thing, it could be worse: some (perhaps all) states in america are only allowed to teach evolution as "a theory" and have to give equal weighting to creationist theory. What next? A european electrical college describing earth as "a theory" and giving equal weighting to flimsy inadequate cables?
AdamW said:With respect to the evolution thermodynamics thing, it could be worse: some (perhaps all) states in america are only allowed to teach evolution as "a theory" and have to give equal weighting to creationist theory. What next? A european electrical college describing earth as "a theory" and giving equal weighting to flimsy inadequate cables?
It wouldn't suprise me.
As I said, I'm having a running debate with someone about evolution vs. creationism. Arguing with him is like wading through treacle.
When it gets to the point that I have made a convincing argument against his, he brings in everything else to confuse the issue again.
I.e. "based on this and that, according to Jenkins, taking into account the rotation of the moon.....
, evolution is therefore impossible".... Jesus!Are there any creationists on this site, just out of curiosity?
Seeing your recent post about SWA to the guy powering his studio made me wonder if you ever got an answer from the IEE about this?
FWL_Engineer said:
B
Big_Spark
I did speak to the IEE about this, the reason I stated as possible for the difference in volt drop is correct, and the volt drops listed in the regs are for 3 phase 400V cables.
If 3 or Multicore cables are used for single phase supplies then you should use the volt drop figures for 2 core single phase cables.
There is nothing that tells you this in the Regs book, but the IEE state this is the correct route to go.
If 3 or Multicore cables are used for single phase supplies then you should use the volt drop figures for 2 core single phase cables.
There is nothing that tells you this in the Regs book, but the IEE state this is the correct route to go.
OK.
What's going on to make this happen? Lower voltage drop implies lower resistance. Lower resistance implies greater current carrying capacity.
But 3/4 core cables used for 3-phase have lower VD and lower capacity.
¿que pasa?
What's going on to make this happen? Lower voltage drop implies lower resistance. Lower resistance implies greater current carrying capacity.
But 3/4 core cables used for 3-phase have lower VD and lower capacity.
¿que pasa?
FWL_Engineer said:
Odd - this guy claims that all of the houses on his estate have borrowed neutrals: http://www.screwfix.com/talk/thread.jspa?forumID=23&threadID=7021&messageID=68973#68973
and this guy confirms what I thought, i.e. that there was a time when it was, if not common practice, not unheard of.. http://www.screwfix.com/talk/thread.jspa?forumID=23&threadID=7021&messageID=69294#69294
What about the rest of you pros out there - how widespread is this insidious practice?
When is somebody going to step in and do something about this? Given that an increasing number of dwellings have two bathrooms and potentially, therefore, two electric showers, how are normal domestic supplies going to cope? There is a very high chance that both showers could be running simultaneously, along with a kettle, a toaster the cooker and maybe even electrical heating on a winter's morning. Let's say around 160A. Okay, so a 100A BS88 fuse will handle 200A for around 25 minutes, but is it a good idea to regularly overload your service fuse like that? And are all consumer units and fuseboards built to deal with that current draw?
Might we soon have to regulate what type and size appliances are allowed, as they do in many countries less well endowed with electrical supplies? Householders treat leccie like kids treat toys - they can do what they like until something breaks. I sometimes shudder when I encounter the years of bodged additions to ancient installations and marvel that the houses are still standing.
I'm with B-A-S here - somebody stop B & Q from selling electrical kit to DIY-ers, please - showers and downlighters a priority!!!
Might we soon have to regulate what type and size appliances are allowed, as they do in many countries less well endowed with electrical supplies? Householders treat leccie like kids treat toys - they can do what they like until something breaks. I sometimes shudder when I encounter the years of bodged additions to ancient installations and marvel that the houses are still standing.
I'm with B-A-S here - somebody stop B & Q from selling electrical kit to DIY-ers, please - showers and downlighters a priority!!!
I
Igorian
I've just bought an electric shower (9.8KW@240V, 9.0KW@230V) and although I have used 10mm TWE, the installation instructions say that 6mm TWE is ok?
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