# Do I really need a 20amp supply?



## RogerM (12 Aug 2010)

I'm thinking of buying a bandsaw that Axminster says requires a 16amp supply. This is the Axminster Plus AP4300T/1 which is rated at 1500W (6amps), or the Jet JWBS-16 MK2 rated at 1900W input (8 amps), 1100w output, for which Axminster recommends a 20 amp supply. The only other piece of kit that I will have running at the same time is the dust extractor at 750W (3 amps). I am familiar with the concept of a greater current being required on start up until the motor is turning to create a back emf. The bandsaw will be the only piece of kit requiring an uprated supply as I run my t/s and p/t successfully off the 13amp ring. 

I am a simple person!  The garage has it's own dedicated 13amp ring running from an old style (30 years old) consumer unit (also in the garage) with fuses rather than MCBs. As the ring cable is rated to take 13 amp, that must mean that as a ring it could handle twice that at the socket. So arithmetically at least, surely all I need do is add a piece of 5amp and 2amp fuse wire in the same holder as the existing 13amp, and hey presto - I have a system that would take a transitory load of 20 amp before settling down to around 9 amps continuous. Hey - I might even put my hand in my pocket and buy some 20amp fuse wire.

Or if that doesn't suit, how about wiring in to the immersion heater supply which we never use with a new suitably sized circuit? 

Please note this idea comes from one who at school 40 years ago instigated an experiment that involved wrapping silver foil across the terminals of a 3 pin plug with the winner being the one who created the longest soot mark up the wall without putting all the lights out. I came in a close second behind a lad who went on to become an electrical engineer. And a very fine one!


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## woodbloke (12 Aug 2010)

Roger, yes I'm afeard so, for that Jet b/s (which is the one I'm interested in) you will need a 20A supply (confirmed by the technoweenies at Axminster) The reason is that when the cast iron wheels spin up to begin with, it generates a 'blip' in the mains, which then settles down once it gets going. 

However, all is not not lost. On Bob9fingers advice I recently changed the old Volex CU in my 'shop (with 16A ring main and 6A lighting type B breakers) for a Wylex 8 way (from screwfix) CU complete with Wylex 16A and 6A breakers (as before) *plus* the addition of two 32A type 'C' breakers, one for the bandsaw and the other for the p/t. Cost was around £70 or so for the new CU and breakers and took around an hour to fit in the 'shop - Rob


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## Mike.C (12 Aug 2010)

Roger I have the Axminster Plus AP4300T/1 (brilliant piece of kit, and so quiet) and it certainly needs a 16amp circuit.

IMHO as Rob says you really do need a new CU, one that comes with a RCD and allows you to do a spilt load. This will let you to put everything except the lights on the RCD side, which means that if the system is tripped you are not left in the dark.

Cheers

Mike


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## wobblycogs (12 Aug 2010)

I've just been through exactly the same thought processes with my Jet P/T which states it needs a 16A connection. After blowing a number of 13A fuses trying to get it to run off a regular plug I wired it up properly to a spare 32A Type B breaker (I'm going to get a 20A Type C when I get a chance) and I've not had any problems since. 

I'm curious about your ring main though, I'm guessing its pretty old from the figures you give. A modern ring would be on 2.5mm csa cable which will handle 20A giving a safe maximum ring load of 32A. What you could probably do is wire a 20A junction box into the ring and spur a 16A or 20A socket off that. If your junction box is a of the re-wireable variety though I'd recommend replacing it with a new 17Ed one which shouldn't cost much and will be much safer over all. Note, I'm not a sparky, wire at your own risk 

Edited to correct typo of 1.5 mm to 2.5mm.


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## jhwbigley (12 Aug 2010)

These are the thickness wire are used in my instalations 

32 amp Ring main 2.5 mm

16 amp on 4mm

32 amp on 6mm


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## RogerM (12 Aug 2010)

Interesting. I've just been ferreting about around the fuse box and 13amp sockets. I have a 2.5mm ring feeding two double 13amp sockets, one of which is in a position where it is never used. This is just for the garage. The fuse holder shows 240volt 30 amp. Not sure whether it is in fact 30 amp fuse wire in there as I've never blown it. 

Could this be as simple as taking a spur off one of the existing sockets (or a junction box) using 4mm cable to a new 16amp socket with an RCD? From a pragmatic standpoint I'm struggling to see how this would do any harm.


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## wobblycogs (12 Aug 2010)

I'm pretty sure you would struggle to spur 4mm cable from one of the existing sockets as it would be too tight. It's hard enough getting an additional bit of 2.5mm in there for a regular spur. A 30A junction box from screwfix is 71p (a 20A is 101p - more really is less) so it's hardly going to break the bank and is a neater solution. 

An RCD socket would be a good investment but you really should consider replacing the main fuse box so the whole place is protected. It sounds like your power requirements are pretty modest so something like the Volex 2 Way RCD CU @ £32 would probably cover your needs (although it doesn't provide the benefit of split load obviously) 

Ideally you want a friendly sparky to bring his testing kit round to check the RCD. Occasionally the earth connection on old installs isn't terribly good and occasionally it can result in an RCD that doesn't trip in the required time. If you were closer I'd check it for you.

Edit, just noticed MK do a 2 way garage unit for just £31. The MK stuff is generally nice to work with too.


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## woodbloke (12 Aug 2010)

wobblycogs":3c3pq9v8 said:


> the Volex 2 Way RCD CU @ £32 would probably cover your needs (although it doesn't provide the benefit of split load obviously)


Should you wish to Roger, my Volex CU plus all the breakers is available for the exchange of a moderate amount of vinovouchers. It's the one shown here. Either post or collect from Salisbury if you fancy a run out one day (could give you a demo on veneering if you fancy?) PM if interested - Rob


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## RogerS (12 Aug 2010)

No-one else has mentioned it yet but *Part P?*


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## wobblycogs (12 Aug 2010)

If you wire it as a new 20A circuit you would need to get it checked and signed off. A spur from an existing ring is a (oddly enough) a permitted modification but I'd have to check the regs to be sure about this case as I have a niggling feeling that the spur has to be to a single, fused, 13A socket.

Obviously replacing the CU would very much come under part p.

Having said that, it's not rocket science...


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## RogerM (12 Aug 2010)

woodbloke":1n7hffc1 said:


> Should you wish to Roger, my Volex CU plus all the breakers is available for the exchange of a moderate amount of vinovouchers. It's the one shown here. Either post or collect from Salisbury if you fancy a run out one day (could give you a demo on veneering if you fancy?) PM if interested - Rob



Aaaggghhh! No! Travelling from Plymouth, Axminster would be on the way! Get thee behind me temptation!  PM to follow.


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## tjwoodms (12 Aug 2010)

all motors will draw approx 3 times the current stated on the plate on start up and the settle down once up to speed ususaly about 2/3 of that stated on the plate when running with no load.


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## OLD (12 Aug 2010)

I have a ring cct. in the garage that has a 20 amp fuse and feeds the table saw (blue plug and socket unfused) and very little else, works fine for me. The protection is there for a 16amp m/c and anything plugged in to the ring is protected at 13amp or less to a max combined load of 20amps so the cct is running at a lower load than originally designed for.


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## andycktm (12 Aug 2010)

I'm not an electrician,but i think people are getting carried away with the 32amp breakers.
You've got a motor that requires say 8 amps running(forget startup for a minute)
When its running where's the protection if your allowing it 32amps anytime.
If it can only ever handle 18 amps say for startup and it decided to take 20amps due to say a fault and you've a 32 amp trip on.......


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## wobblycogs (12 Aug 2010)

I suspect you are reffering to the fact I have my P/T on a 32A breaker at present. I fully agree it should be on a 20A Type C as 20A is what the cable is rated at but I didn't have such a beast to hand so I stuck it on a 32A Type B temporarily.

Anyway, if your motor draws 8A while running the initial draw for a few fractions of a second will be much greater than this. As I understand it, in theory at least motors draw infinite current at zero RPM and the current draw drops as the motor spins up to it's working speed at which point you have it's base load. Since their will be a heavy draw for a short while at spin up you put motors on either a Type C or D breaker, both of which will handle a higher instantaneous tripping current (e.g for type c it's 5 to 10 times it's rated current) and generally will have a longer trip time than Type B.

As for using a 32A breaker in general it's probably not as bad as it appears as long as you are sensible about not overloading the cable (assuming it's 4mm). The fuse / breaker is there to protect the cable from over heating and burning the house down due to excessive current draw not to protect the machine from a fault. 

If there is a short curcuit in the machine, for example, the PFC can easily be in the kA range for a few milliseconds till the breaker trips or a bit longer before the fuse blows (fuses are generally very slow). This sort of short term heavy draw wouldn't be enough to damage the cable. You could probably contrive a situation where there was a fault in the machine that caused a long term draw between 20 and 32A but I think we are talking highly unlikley.


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## woodbloke (12 Aug 2010)

andycktm":2k0ugedc said:


> to take 20amps due to say a fault and you've a 32 amp trip on.......


Axminster told me that the 32A type 'C' breaker would be fine with the Jet. The other thing is that there's no 20A type 'C' breaker sold by Screwfix...32A is the closest - Rob


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## wobblycogs (12 Aug 2010)

You might have to shop around a bit for a Type C breaker that fits your CU as they aren't as common as Type B. I'd be really surprised if you couldn't get one for a modern CU though. A 32A Type C will work but really you shouldn't have a breaker reated higher than your cables maximum safe limit if you can avoid it.

Having said that... when I moved into our current house I found a piece of 1mm lighting cable running a 3kW immersion heater. The cable reached about 50 to 60 deg C after an hour or so of being on - just touchable. Although this sounds hot it's actually still under the specified cable limit of 70 deg C for regular cable. Yes, I would be terrified if any of cable reached anything like 70degC and I changed that circuit straight away. For reference it was suface mounted so had passivle air cooling which is probably why it hadn't melted.


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## wobblycogs (12 Aug 2010)

I suspect this is what you are looking for Rob:

Wylex 20A Type C £5.80

http://www.neweysonline.co.uk/wylex...400v-ac/1050154415/ProductInformation.raction


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## ondablade (12 Aug 2010)

I've had some experience with stock 3pin 13A plugs which suggests that maybe it's not just about the cable and breakers - that plugs too don't seem to have a lot of spare capacity over their nominal rating.

In my innocence i ran my 2.2kW Robland combo saw off a 13A socket. It should draw around 10A when running. i.e. well below the rating of the socket.

Despite this it was the plugs/sockets (it happened in more than one plug socket combination) that caused me some bother.

At one level all was OK - it blew the stock 13A fuse once or twice under sustained load, no doubt because i forced it too heavily. (typically in rip cuts i think it was) On the other hand it didn't pop the 16A fuse fitted in the control panel. Perfectly as it should be you might say.

More ominously though it occasionally stopped during start up - it'd pop the reset on the contactor (?) in the saw's own panel. During the initial phase of start up before releasing the button in run mode i think it was.

Eventually i figured out that this seemed to be the result of some sort of minor arcing inside the socket - there were burn marks on one of the plug pins. A new socket and plug solved the problem for short while i ran the machine before selling it after this.

It may to some degree have a been a vagary of the specific sockets i had, but it brings two points to mind:

1. Despite 10A being the nominal full load current, the short duration start up surge seemed well able to cause problems on a 13A socket - without blowing fuses.

2. It suggests that 2.2kW on a saw motor is getting a bit above the upper limit for a 13A socket - regardless of whatever wiring is used.

I'm wiring the shop now for my Hammer machines. The conclusion i've drawn from the experience is that it seems to be as important to build some slack into the sizing of the plus and sockets as it is in the rest of the circuitry - that electrical componentry maybe does not have a great deal of spare capacity...


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## wobblycogs (12 Aug 2010)

Very interesting Ian. Personally, I would wire in a 16A or higher circuit for anything that drew 10+ amps a long period. A 13A socket should be able to cope but like you I've found that you can occasionally get some arcing although I've only found that with cheap plugs and sockets. We didn't have central heating for a while so were using 2kW fan heaters - the plugs on some got quite warm due to the contact resistance.


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## Eric The Viking (12 Aug 2010)

ondablade":4uk9srmd said:


> In my innocence i ran my 2.2kW Robland combo saw off a 13A socket. It should draw around 10A when running. i.e. well below the rating of the socket.
> 
> Despite this it was the plugs/sockets (it happened in more than one plug socket combination) that caused me some bother.
> 
> ...



It's one of the big advantages of the 16A and 32A socketry: no fuses in the plugs. Furthermore the round pins make a much better mechanical connection than the rectangular pins of the 13A series (which are actually pretty poor in comparison). It all works to stop the plugs heating up, which in turn stops the grub screws working loose through repeated hot/cold cycling, which reduces arcing, which makes them safer. 

Since fuses typically go at twice their rated current (continuous), they can get pretty warm beforehand. I used to own a 3kW fan heater - the plug used to get too hot to touch. You will sometimes see sockets in older houses with scorching round the live socket, often in kitchens and bedrooms. It's heat conducted through the live pin, which is closest to the fuse, when that socket was either used for a kettle or a fan heater.

IIRC, the history of 'ring mains' goes back to a shortage of copper after WWII. Previously, with the 2A, 5A, 15A series, sockets were individual spurs wired back to the fuse box ("consumer unit") and separately fused. This is expensive in both copper and installation time, so the ring main was introduced as a cheaper alternative.

There are experts on here (and I'm not one(, but IIRC, breakers trip earlier than Fuses (the type C has a time delay specifically for motor surges etc.), so that a 20A breaker goes at that current, whereas a 20A fuse goes at 40A continuous. Fuses will thus tolerate surges more readily, but they warm up significantly (proportional to current squared), and if used near their rating for any significant length of time they also weaken (somewhat like lightbulb filaments), and blow at a lower-than rated current.

I think that's correct. Someone will be along in a min, if I'm wrong.


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## Jake (12 Aug 2010)

ondablade":e9nljzko said:


> I've had some experience with stock 3pin 13A plugs which suggests that maybe it's not just about the cable and breakers - that plugs too don't seem to have a lot of spare capacity over their nominal rating...



Could be voltage drop problems - how are your sockets fed? 2.2kw shouldn't give a 13A socket a problem. 

(It wasn't a double with another machine - extractor eg - running off it?- the 13A rating is for the faceplate, not each plug that can go in it)


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## ondablade (13 Aug 2010)

Over here in Ireland we seem to get more like 220V on single phase mains Jake, with the possibility of pretty drastic drops below that if you are at the end of a line fed by a transformer, and there's been extra houses put on the line. 

Our (effective monopoly) service provider contracts to supply between 207 and 254V - to EN50160 they say. But i've often heard of it going lower. It sounds like wiring should probably be sized to handle the currents generated at the lower end of the supply voltage range(?)

My voltage in recent years is i think pretty good (but i've not checked), there was a new transformer installed quite recently. But maybe 220V is quite low compared to the 230/240V (?) you guys reportedly seem to get.

I didn't realise that fuses could let the current get so high above their nominal rating without blowing, it means i guess that my 13A socket could indeed have been fairly heavily loaded. 

Interesting that it arced though, that surely would be a voltage rather than a current determined phenomenon.

Interesting too on the ring main bit Eric, i've been reading up wiring recently so i could wire my shop and rather wondered at how it came about. :wink: I guessed that maybe it was something to do with the English tendency to be 'economical'.

The Hammer machines i'm wiring for next week are all 3kW single phase - which comes out at about 14.5A at 207V.

Which rather begs the question of whether or not 16A sockets would be OK. I've for safety more or less decided to go for 32A sockets and wiring - also to cover against the possibility of in future running larger stuff. e.g. it's looking like i'll be running a 4kW bandsaw on a rotary inverter which definitely will go well above 16A. 

Interesting territory...


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## RogerS (13 Aug 2010)

Eric

Reading on some of the trade forums there does seem to be a bit of a groundswell back to radial circuits.


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## RogerS (13 Aug 2010)

ondablade":3awysyea said:


> .....it's looking like i'll be running a 4kW bandsaw on a rotary inverter which definitely will go well above 16A.
> 
> Interesting territory...



That'll make the neighbours' lights dim


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## Eric The Viking (13 Aug 2010)

ondablade":1ovdwocp said:


> Over here in Ireland we seem to get more like 220V on single phase mains Jake, with the possibility of pretty drastic drops below that if you are at the end of a line fed by a transformer, and there's been extra houses put on the line.



Universal problem! I once worked for a short while in the HImalayas. Between us and the xfmr was a blacksmith who made steel window grilles. Every time he struck an arc... we ended-up having to start video editing sessions at 2AM.



> Our (effective monopoly) service provider contracts to supply between 207 and 254V - to EN50160 they say. But i've often heard of it going lower. It sounds like wiring should probably be sized to handle the currents generated at the lower end of the supply voltage range(?)



It doesn't work quite like that. 

Your machines consume a certain power at a specified voltage, but they are just loads. No magic happens! The energy/sec (power) they consume is proportional to the voltage. If that drops, so does the power of the machine. Thicker wiring won't really help, except insofar as its own resistance will be lower, so you waste a bit less warming the wires up. 

The wire thicknesses specified for lighting, ring mains, etc. take the resistance of the load into account: light bulbs have high resistance, so the 'contribution' of the wiring to the overall load is small - you can use thinner (higher resistance) wire as a consequence. 

For machines, the load resistance is small, and the currents are large, and the wiring's resistance could otherwise become a significant proportion of the total. That's why you need thick wire. 



> My voltage in recent years is i think pretty good (but i've not checked), there was a new transformer installed quite recently. But maybe 220V is quite low compared to the 230/240V (?) you guys reportedly seem to get.



Actually ours is as iffy. The rules for supply were changed by those idiots in the EU some years ago, to 'harmonize' electricity supply. They compromised on a _nominal_ 230V. The official range, IIRC is -5% +10% (of 230V). (after Googling to check) Wrong! it's [insert whole basket of fruit!] changed AGAIN:



> Voltage tolerance of 230 V +10%/−6% (216.2 V to 253 V), widened to 230 V ±10% (207 V to 253 V) in 2008. The system supply voltage remains centered on 240 V.
> http://en.wikipedia.org/wiki/Mains_power_around_the_world



This has two serious negative implications (nb: this is bordering on politics, rather than engineering!): Firstly 207V is low enough to damage some designs of motors (some refrigeration pumps, for example), and secondly, the upper limit was raised. Over-voltage shortens the life of filament bulbs significantly, and can affect other components (for electrical/electronic devices where the internal voltages are proportional to the supply current). In the old days you could force the supply authority/company to alter the voltage tap on the local substation, to correct matters. Now they just laugh at you (from personal experience!).

The third implication is perverse: inattentive Far Eastern manufacturers, for whom we are 'just another Western market', look at the spec., and design to 230V, _not_ 240V. The result is lightbulbs that blow early, as they can be operating at 253V rather than the 230V they were designed for. The lifetime of a filament anything falls off very rapidly with overvoltage.


How long do filament and 'low energy' bulbs last around here? Far less time than they should! I have argued unsuccessfully with the energy supplier. At one point we were 0.5V RMS below the maximum permitted, "but your supply is within spec., sir."! Bring back SWEB and the CEGB!

Worse still, I believe Chinese motor winding companies are keeping cost down by designing to 230V too, hoping they'll get away with it. I have had three, brand-new squirrel cage machinery motors burn out within hours of first use _in the last six months_. The supplier of two of them had a service department full of the wretched things! 



> I didn't realise that fuses could let the current get so high above their nominal rating without blowing, it means i guess that my 13A socket could indeed have been fairly heavily loaded.



Fuses are filaments. They won't last forever above their rated capacity, but yes, if slightly overloaded they can get very hot and still not blow quickly. The arcing you mentioned earlier may well have been screws working loose in either the plug or the socket, caused by repeated heating and cooling (from the adjacent fuse).



> Interesting too on the ring main bit Eric, i've been reading up wiring recently so i could wire my shop and rather wondered at how it came about. :wink: I guessed that maybe it was something to do with the English tendency to be 'economical'.



Not economical: back then, totally skint! We only paid off the final tranche of war debt about two years ago, IIRC.



> The Hammer machines i'm wiring for next week are all 3kW single phase - which comes out at about 14.5A at 207V.
> 
> Which at a nominal 14.5A @ 207V rather begs the question of whether or not 16A sockets would be OK. I've for safety more or less decided to go for 32A sockets and wiring - also to cover against the possibility of in future running larger stuff. e.g. it's looking like i'll be running a 4kW bandsaw on a rotary inverter which definitely will go well above 16A.



Whilst it won't hurt to put in heavier wiring, it doesn't work like that (see above). You must protect the circuit to the manufacturer's recommendation (i.e. the load printed on the machine's plate, or what they specify in the manual, if there's a significant startup surge). Upping the breaker/fuse capacity beyond that doesn't buy you anything, but reduces the safety margin.

Sorry about the rant. Hope some of it helps.

E.


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## ondablade (13 Aug 2010)

Expediency in standards is a bit of a bete noire of my own Eric! Right now I'm in the mood for a rant myself on the topic of political expediency in state regulation of technical topics - see the story below on a plumbing issue that's infuriated me for the past week. My sense is that the market would sort itself out just as well...

It's probably a bit more 'Himalyan' over here, but there's a certain comfort in hearing that we're not alone. 

On electrical loads/sizing of wiring components. I guess my thinking in making sure my wiring, sockets etc (not breakers) have some spare capacity is influenced by how little it took to trigger the socket problems i described - and also dimly by the way motors when heavily loaded draw more current because the inductance (is it? - long time since i was educated on this) falls as they slow. But i guess maybe that in the start up situation they behave mostly as resistive loads, and just draw whatever the nominal V=iR current is.

On lights dimming Roger. I'm crossing my fingers. I'm allowed 62A (increased to 80A with a meter box fuse change) so the 20A or so the saw will draw should be OK (?) What's less clear is that rotary converters it seems can maybe up the current drawn - i don't know why. (on start up?) Can anybody explain the story on this?

ian





PS Optional plumbing/political expediency in state standards rant: 

I've just spent three days and probably €120 between parts and transport trying to get the plumbing fittings for a simple DHW cylinder replacement and relocation - all for the sake of nobody stocking 4no. €4 22mm tube x 1/2in solder ring adaptors.

Think of it. Country with pop of Birmingham decides to go it alone with imperial sized copper tube fittings when the UK and Europe are metric - because there's a tiny factory in Cork making compression fittings that doesn't want to spend the money to change their tooling. 

Yet almost every bit of equipment you buy with copper tube fittings is imported and hence metric. (not much chance of the Chinese or anybody else customising for our market!) 

Being a tiny market nobody bothers to stock a proper range of adaptors, and anyway doesn't know what you mean or what they have in stock - so you have to drive in and trawl their shelves. So quite apart from the extra labour, cost and leakage risk of multiple fittings it turns into a dog and pony show. One from here, two from there....

Dog and pony 2 plays out in a few years when they are belatedly forced to go metric as they inevitably will be, to leave gazillions of legacy imperial piping systems which nobody will want to stock imperial for.

Then you look and discover that the standards organisation is notorious at senior management level for being full of political hacks from the party that has just destroyed our economy. You have to ask why a country this size in the EU has to have a standards organisation at all (it was originally modelled on BSI) - but even buying that why bother if (as you too imply) these decisions are made on grounds of political expediency rather than what's technically and economically for the greatest benefit!! 

These same hacks/clowns having pretty much doubled the labour and other costs of jobs like mine then have no problem going on radio to bleat about the need for national competitiveness and belt tightening. :evil:


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## RogerS (13 Aug 2010)

My rant... window double-glazing standards....especially in old houses. Gradually turn the screw so that the heat loss from the window is reduced...but that then requires thicker wooden frames to carry the massively over-spec'd DGU's which means heat loss goes back up...so increase the size of the DGU...let's throw in argon filling for good measure....So windows have more wood than glass (especially on smaller windows) which looks rubbish.

And the actual heat saving? Wanna guess? 1kw a day ? Nope. 250W a day? Nope. OK...100W? Nope. 3.6watts. I lose more heat when I fart.

oh yeah..throw in a whole load of quango's, inspectors, auditing bodies, ISO9001...

And the houses lose 100x more heat through the walls than the bloody windows in the first place.


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## Eric The Viking (13 Aug 2010)

ondablade":3mklvy1v said:


> I've just spent three days and probably €120 between parts and transport trying to get the plumbing fittings for a simple DHW cylinder replacement and relocation - all for the sake of nobody stocking 4no. €4 22mm tube x 1/2in solder ring adaptors.



Sorry--its probably too late now--but you can still get 22mm->3/4" adaptors here, I think only in end-feed copper (I never use solder ring, as they're too awkward and unreliable). Good plumbers merchants sell them (3/4->22mm) and might post to you. If you can then get imperial adaptors 3/4" to 1/2" you'd be home and dry, (literally!). Alternatively go 22mm end-feed to 3/4" BSP in brass, then screw on an adapter down to 1/2". 

The received wisdom on 1/2" is that you can get away with 1/2" in a 15mm fitting, or thinning down 15mm to 1/2" with emery paper (dodgy with modern thin-walled tube, but hey). Adaptors used to be made but weren't that popular even during the changeover period in the 1970s. I think I may have a whole one (15mm->1/2") somewhere. They used to be indicated with a dab of green paint as they were easily confused with 15mm straight couplers. 15mm compression fittings do work with 1/2" pipe, just about, although I'd be happier with proper 1/2" olives (unobtanium here nowadays). British Standard pipe thread is your friend here, as once you can get as far as BSP thread, you can interconnect metric and imperial fittings fairly easily 

None of these solutions is very tidy, but would be strong and reliable.

Incidentally, the whole world (pretty much) still uses BSP threaded fittings, even in continental Europe, althougn boiler manufacturers often use 'special' fittings with metric threads (I think that's to stiff customers on spares pricing!). 

Thos. Crapper still has much to answer for...


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## ondablade (13 Aug 2010)

Thanks Eric, but I didn't have time to get fittings mail order from the UK - i had the laundry down and the gun to my head. (my double incontinent Mother lives with us, and there was rather a stack of thunder pants and other unmentionables building up ;-) )

I got caught that way because the people i bought the (UK made stainless) DHW cylinder from supplied it with 3/4in nuts and olives.

Then i found that the cylinder connections were actually 22mm compression, and so the search for 22mm fittings and adapters saga started with the clock ticking - the system already drained and the old cylinder removed.

BSP saved my ass as you say, i was able to get from a short 22mm copper pipe stub (cut from a short piece of left over pipe a plumber friend had from back when some places did stock some, i couldn't buy any) to a 22mm x 3/4 BSP adapter, with a 3/4in BSP male x 3/4 copper adapter screwed into it. (whew!) It's bad practice though - so many joints really ups the risk of leakage and the cost.

Having bust a gut to get the 22mm compression fittings, insult was added to injury when it turned out that some of the nominally 1/2in and 3/4in fittings i'd bought were in practice 15mm and 22mm castings with imperial nuts and olives - so it seems the fittings makers are playing games too.

I'd been told of the possibility of using imperial nuts and olives in metric fittings (and other stuff), but was reluctant to do so. But ended up that way anyway on the 1/2in. It seems unwise to me not to properly support the pipe with a good fit in the casting, as any slop risks the olive getting worked as the piping moves with temperature changes.

I'd not used solder fittings before, and we don't get the non filled type over here. That said i took no chances and topped them up with some extra solder. Cleaning (like in all forms of soldering) is so critical to getting a good joint, the gas torch needs a light touch and good timing to avoid overheating the solder too.

Anyway. Talk about the difference between the theory and practice of plumbing. I dug up a training manual put together by our excuse for a national apprentice training outfit (another haunt of political hacks), and nearly wet myself laughing at some of the happy happy stuff they had to say. 

I'm lucky enough that having spent years on machine R&D for Europe and in the US i'm moderately familiar with most of the various pipe and other thread and compression/flare based piping systems. Push comes to shove and i have the reference material to look most of it up. Heaven help the average DIY innocent who sets out to handle a plumbing job though.

The good news is that it all refilled and started up last night with no leaks or other problems.

What's more i lucked into some radiators (new) for my workshop heating on the cheap today too....

Thanks for the moral and other support...


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## Sheik Hans (15 Aug 2010)

I am with you a 100% on the farce of Irish standards ... they are usually low Why they insist on re inventing square wheels when the world already has round ones . The plumbing one near drove me demented here 15 years ago when i was first installing in my first house . I had to bore out Instantor fittings on a lathe and lately i just swage the pipe with a homemade drift . . As for you voltage variations I wouldnt worry too much , they are not so bad these days and i live in Kerry ..... I deal with current and voltage all day on industrial stuff


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## ondablade (15 Aug 2010)

Hi Hans. I guess a set of swaging tools would take the heat out of the situation all right. The voltage has indeed improved, even we we do pay one of the highest rates in Europe for our electricity - as a direct result of the monopoly enjoyed by yet another unreformed state monopoly. (they would of course claim otherwise) 

You'll know all about this as the possibility is being discussed, but heaven help us if the state goes through with selling it off like they did Telecom/Eircom in the case of the phones. 

Having sold that one on they cost many a fortune by encouraging people to buy shares - the consumer was meanwhile left to the tender mercies of the one after the other bleeding returns on the ever more crazy prices they paid for the monopoly - by minimising investment and maximising charges to the consumer.

So much for 'national interest' - in the end it came down to maximising the return for the bureaucracy and to hell with competitiveness.

Are you possibly one of the many Germans living in the South West?


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## Sheik Hans (16 Aug 2010)

Hi Ian I really am going to have to stop wearing my recreational Liederhosen thats twice this year someone has thought i was German ...... 
I'm English . what county are you in ?

I'm interested in the whole single phase machine supply threads /posts as i have found myself sadly lacking in knowledge in this department . I have always wired three phase stuff with no supply restrictions (this weeks jobs is a 120kw motor supply) .So this whole business hasnt really been an issue for me . Now i find myself purchasing machinery for home use and not have what i need So i am learning new stuff even though i am a spark . I'm leaning towards buying a 240v single to 240v three phase inverter drive to power my workshop . Its a hobby shop so i only ever need one machine running at once . I figure a selector switch a few contactors,3 sockets and variable pots will sort out 3 phase for my three machines . i ve used plenty of 3phase drives for speed control but never for this purpose. I'd love to know if anyones tried this approach


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