No. There is only one fuse or circuit breaker for the whole ring. The two ends of the ring final circuit are joined together at the single circuit breaker. Having two as you described is explicitly prohibited.
John
On Saturday, November 2, 2019 at 3:48:09 AM UTC-4, snipped-for-privacy@downunder.com w rote:
n assumption that the same size wire and so the same current capacity would be used. I believe in the UK circuits can be typically 9 or 13 amps, so s maller than the 15 or 20 we typically use.
) with a local fuse inside the plug that depends upon the load. It can be u p to 13A.
he US
Must be fun when the one breaker trips and everything in the house goes off, including all the lights.
I would expect that both fuses must blow at the same time. With a ring, the current would be about evenly split between the two sources. As soon as one fuse blows, the current in the other fuse would double and it will blow. Are you still really using fuses, not breakers? Here for new work, circuits for living space have to be on AFCI breakers now too, for arc fault protection.
That makes sense. If there were two, both would blow at about the same time due to over current anyway. One would go, the current in the second would double, and then it would blow too.
Except of course it doesn't.
Traditionally each floor in a suburban house has one ring main for the sockets and another for the lights. High current devices have a dedicated spur from the distribution point.
Except the presumption is wrong.
Depends on the age of the installation.
Never heard of AFCI breakers, but that's my ignorance.
Even among those commercial operations most of the small ones will only have 120/240V wiring, two-phase 180 degrees. 208V three-phase is pricey, needs a special transformer and is typically only used in larger places or ones with a high electric energy demand.
Klaus, in the US you will usually see ground distributed to 240V outlets even though it is often not used by the equipment that is plugged in. So there are four connections, 120V phase 1, 120V phase 2, neutral, protective ground. What you need to keep in mind is that such outlets are generally fused at much more than the usual 15A or 20A. So the cable from the outlet to the fuse in your pump circuitry must be rated for the highest expected circuit breaker current rating.
Older homes can have 240V three-prong outlets where you don't have neutral, for example for dryers and in the kitchen for a free-standing oven/range. AFAIK that is no longer allowed for new construction in many states.
Hardwired equipment such as a built-in kitchen oven or range often does not have neutral either but there you cannot legally connect anything else without having an electrician run cable and a new outlet.
-- Regards, Joerg http://www.analogconsultants.com/
an assumption that the same size wire and so the same current capacity woul d be used. I believe in the UK circuits can be typically 9 or 13 amps, so smaller than the 15 or 20 we typically use.
in) with a local fuse inside the plug that depends upon the load. It can be up to 13A.
n the US
I was going by what someone who lives there posted. And even by what you say, if it's a one floor house, then all the lighting circuits go out. In the US you'd lose one lighting circuit, not all of them.
,Again, I just went by what the other poster claimed, so I guess he's full of baloney.
I said for "new work". And that's what the code is, you have to comply with current code for new work it doesn't depend on the age of what's already there.
Google broken?
It's not really a special transformer, but more transformers for light/medium capacity 3 phase. If you're comparing 240/120 split-phase to 3 phase you;d be talking about light capacity 3 phase. To get that here in the US, typically they use two transformers, while for split-phase you only need one. For medium capacity 3 phase, they use three transformers. You see that on street poles all over. How much that added cost affects you as the customer, will depend on the actual power company, but somebody has to pay for it, one way or the other. Which is one reason that 3 phase into homes makes no sense to me.
You will see ground at all receptacles installed for about a half century here in the USA, unless they violated code.
It's actually the other way around. Prior to a few decades ago in the US it was permitted and common practice to use the neutral in a dryer or similar connection as the equipment ground too. Since then a four wire circuit that has an EGC is required for new circuits.
Not so sure about that. I've never seen an oven, range, etc circuit that didn't have a neutral. There probably are some, but I don't think it's common.
To clarify the above, while I haven't seen ovens or ranges that don't use a neutral, what you say is true of other circuits, eg water heaters, well pumps and the like. The issue with ovens, ranges, dryers, etc is that every one I've seen has some 120V requirement, eg light bulbs in older units and electronics in modern ones. They could use 240V bulbs and run the electronics off 240V, but for whatever reasons they don't seem to do so.
I have often wondered, why you have three separate pigs in the pole to get 3 phases. Why don't you use a true 3 phase transformer ? Since some of the flux cancel out in a true three phase transformer, the total amount of iron is less than for three separate single phase transformers.
IDK, but my guess would be that one transformer of the same capacity as the three separate ones would be so heavy that it would be a balancing problem on the pole and they don't want leaning, falling over poles.
Yes, that's what happens.
There's usually enough light from other sources that you aren't blind, but you need a torch to replace the fuse wire in the holder.
Fuses rarely go nowadays. OTOH at my mother's house a breaker seems to pop whenever an incandescant light fails. I don't understand that.
Let's say mistaken in this case.
Irrelevant to whether I had heard of them :)
It seems that we don't need them here because we have lower currents due to higher voltages.
Not sure what you mean by "small". A "small" hospital? I suppose a retail food store could be small and the ones I've been to were small but had 208 volts at the car chargers.
I think you don't realize how pervasive 3 phase power is in the US. Why wo uld it take a special transformer? It's three phase on the distribution li ne, three phase on both sides of the transformer.
It entirely depends on the connector. Some have a neutral pin, some don't. Standard 120 volt outlets here have a neutral pin and a ground, but becau se our 240 volt line is two hots, the NEMA 6 series of connectors have no n eutral, only a protective earth ground.
Probably more common are the NEMA 14 series connectors which include a neut ral and a ground for 120/240 volt applications meaning it can provide both
120 and 240 volts. That's the only reason to include the neutral, to provi de 120 volts.
This is not accurate. The TT-30 connectors used for older dryers have a ne utral, but no protective ground. They are deprecated, but not required to be removed. It is now expected such a connection would include a separate protective ground for the frame of the appliance. No new appliance will su pport this connection method.
Ranges are typically hard wired without a connector. Dishwashers I believe are now required to be on an outlet, at least that is what I was told. Th ey are also 120, not 240 volts.
Bottom line is for a 75 watt device there is no reason to consider 240 volt s for US usage. Here appliances use 120 volts unless there is a compelling need for higher power than can be found in a typical outlet, 120 volts, 15 amps. For "continuous" loads the current must be derated to 80%. Not sur e if your pump would be a continuous load or not, but 75 watts is well with in the 80% rating.
If you try to sell a 240 volt pump here it will be a specialty product requ iring a special wiring run to bring power to it.
-- Rick C. ----- Get 1,000 miles of free Supercharging ----- Tesla referral code - https://ts.la/richard11209
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n an assumption that the same size wire and so the same current capacity wo uld be used. I believe in the UK circuits can be typically 9 or 13 amps, s o smaller than the 15 or 20 we typically use.
main) with a local fuse inside the plug that depends upon the load. It can be up to 13A.
in the US
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Not sure lower current buys you anything. You still have a similar amount of power to fuel an arc fault and the higher the voltage, the easier it is to arc. It doesn't take all that much to start a fire.
Lol! The things people say out of ignorance.
An AFCI breaker detects dangerous conditions that are not detected by eithe r GFCI (RCD in your country?) or overload breakers. If a wire is worn or c hewed by rodents or just a loose connection, it will generate a dangerous a rc with local heating. This device detects the transients in current consi stent with faults but not normal operation.
In your country they appear to be called arc-fault detection device (AFDD).
The need for them has nothing to do with current, it is a safety device, no t a regulator.
-- Rick C. ----+ Get 1,000 miles of free Supercharging ----+ Tesla referral code - https://ts.la/richard11209
,
il food store could be small and the ones I've been to were small but had 2
08 volts at the car chargers.would it take a special transformer? It's three phase on the distribution line, three phase on both sides of the transformer.
It depends on what you call special. In the US light capacity 3 phase, they typically get 3 phase using just two pole transformers. Nothing reall y special about them, they just have to be the right ones. For higher capacity then they use three separate pole transformers. You see see both of those commonly used. But the fact that you need two transformers for light capacity 3 phase is another argument for why it makes no sense for homes.
s oe e
t. Standard 120 volt outlets here have a neutral pin and a ground, but bec ause our 240 volt line is two hots, the NEMA 6 series of connectors have no neutral, only a protective earth ground.
It's actually properly called the "equipment grounding conductor".
utral and a ground for 120/240 volt applications meaning it can provide bot h 120 and 240 volts. That's the only reason to include the neutral, to pro vide 120 volts.
y
neutral, but no protective ground. They are deprecated, but not required t o be removed. It is now expected such a connection would include a separat e protective ground for the frame of the appliance. No new appliance will support this connection method.
That's not true. Dryers and such sold today support being used with either an old 3 wire cord and receptacle or the newer 4 wired cord and receptacle. If they didn't people would have to run a new circuit just to replace their appliance.
That's not true either. Ranges are typically free standing and connected with a cord.
Dishwashers I believe are now required to be on an outlet, at least that i s what I was told.
That's not true either.
They are also 120, not 240 volts.
lts for US usage. Here appliances use 120 volts unless there is a compelli ng need for higher power than can be found in a typical outlet, 120 volts,
15 amps. For "continuous" loads the current must be derated to 80%. Not s ure if your pump would be a continuous load or not, but 75 watts is well wi thin the 80% rating.quiring a special wiring run to bring power to it.
Indeed. The "seems" in my statement indicates my ignorance and lack of understanding of that contention.
I merely saw the statement in the wackypedia article.
Here is a small 20/0.4 kV three phase transformer feeding four LV lines
Larger ones 100-300 kVA are installed between two poles.
NO, they will not,
Got any sense ? Put it this way, when one blows there is no current there to blow the other.
Simple enough ?
None of this is relevant because ring final circuits in the UK NEVER have two fuses or circuit breakers. It is forbidden. Socket outlets can be on either ring circuits, usually protected with 32A circuit breakers or radial circuits where the circuit breakers are typically 20 or 32A depending on the thickness of the wire used. Lighting circuits are usually radial, and often have a tree structure. They are separate from socket circuits and are typically protected at 6A with no additional fuses in the appliances. John
They do have three-phase transformers, at least in our area.
[...]-- Regards, Joerg http://www.analogconsultants.com/
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