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Member postings for Toby

Here is a list of all the postings Toby has made in our forums. Click on a thread name to jump to the thread.

Thread: Consumer units -how do they work?
06/01/2017 10:04:21

A common problem, yes modern RCDs and MCBs are more sensitive and quicker acting than a good old fuse. It just highilghts you had a problem but did not know about it before the board was replaced......

 

Edit: to expand on that, according to my data a 30A rated 3036 fuse (your old fashioned fuse board) will typically run continuously at about 55A and will need 87A to blow in less than 5 seconds.

A 32A type B MCB will take a bit over 45A continously but that rises to 160A to trip in less than 5 seconds.

Edited By Toby on 06/01/2017 10:19:44

Thread: removing the head/table from a meddings MF4?
06/01/2017 09:06:31

Thanks Mike, and thanks for the manual by email, it is very much appreciated.

Cheers,

Toby

Thread: Consumer units -how do they work?
06/01/2017 07:58:15

you are correct Rob, the individual (narrower) switches are over current breakers (called MCBs or miniature circuit breakers) and the one at the end (normally double width) is an RCD (residual current device or earth leakage breaker). The RCD being in series with all the MCBs.

The RCD is almost certainly 30mA rated so is specced to trip if there is 30mA flowing to earth for more than 200ms or 40ms if more than 150mA. Often the actual leakage required to trip it is as low as 20 to 25mA.

This leakage is measured as a difference between the line and neutral currents, the assumption being that what is "missing" must have flowed to earth. So the trip can be caused by either a line to earth fault or a neutral to earth fault (neutral is rarely at exactly earth potential).

There are two main reasons why this can happen.

1) a capacitive link between live (line or neutral) and earth. This can be just capacitance in motor windings or it can be caused by a fault.

2) a low resistance to earth from the line or neutral, normally caused by a fault or breakdown in insulation. Quite often caused by damp or water ingress. Or, in the case of a motor a short (or partial short) of a winding to the motor core.

Unfortunately these things are hard to find without specialist test kit. You need to be able to measure insulation resistance at at least 250V and also measure mA leakage currents with peak hold to detect startup pulses.

One thing to watch is that it might not be just the fan that is causing the problem. There could be (in fact probably is...) a general earth leakage from other devices on the affected circuits. Most electronic goods have noise filters on which cause a small earth leakage. It might be that your "background" leakage is say 20mA and it works fine. But plug in something with an additional 5mA leakage and it suddenly trips. This can unfortunately make fault finding harder!

All that said, I would start with the basics:

1) a visual inspection of all the wiring, switches, control circuits and the motor. Any sign of damage or contamination by water or dirt, oil etc?

2) If you have a multimeter, check the resistance from line and neutral to earth, with the unit switched on(but obviously not connected to the mains!). If there are any electronics inside that will complicate things so you might have to disconnect various bits and test them in isolation. Also make sure it is really switched on. Any no volt release switches will obviously complicated things. Any resistance less 2MOhms is suspicious in my view (although you need to be down to around 10kOhm to cause a trip).

3) call an electrician although be prepared for the electrician to say "the fan is faulty, replace it" so you might be better off with an appliance repair man.

I hope this helps.....

Toby

Thread: removing the head/table from a meddings MF4?
06/01/2017 07:15:24

btw, I have been looking at pictures online, is the head bolt the one circled in red in this picture?

06/01/2017 07:05:23

I'll be transporting it in a van so there is enough space to transport it whole but there will not be enough head room to carry it upright so it will have to be laid flat.

As you say it will be pretty top heavy so I like the idea of dropping the head rather than removing it. I have a sack truck so I reckon (with the head dropped) it will be easy enough to get it to the van. Getting into the van will be the challenge although a mate has agreed to lend me his engine hoist.

I assume that, if the head and table are down as far as they will go, I will be able to manage the top end of the column safely with the bottom either on the sack truck or lifted by the hoist.

Mike: Thanks for the bolt info, the parts leaflet would be very useful, I'll send you a pm.

05/01/2017 20:01:44

Thanks Nigel,

This one does not have a foot switch which makes things easier. It is also looks like it hasn't been used much so I am hoping nothing will be too stuck. I will go prepared though!

No hurry (I will not be picking it up before Saturday, probably monday) but bolt sizes would be great! Plus if you could confirm the head bolt location?

Good idea on the jack!

Thanks!

Toby

Thread: Boxford
05/01/2017 19:30:25

I don't know if it will help but there are some good pictures of the back of an apron here.

http://www.practicalmachinist.com/vb/south-bend-lathes/1947-model-9a-128005/index2.html

I know that thread is for a southbend but there are only very minor differences between those pics and ones I have of my AUD.

Thread: removing the head/table from a meddings MF4?
05/01/2017 19:13:49

I need to pick up a meddings MF4 and am pretty sure I will have to remove the head and table to transport it. Or rather to lift it as I gather they are not light and I am going to have to do it without a crane etc.

Can anyone advise how the head is fastened to the column on these? It would be nice to be prepared and be sure I have the right tools with me

btw. it is the later, square head style if it makes any difference.

Any advice gratefully received!

Toby

Thread: Electrical help / advice please
20/12/2016 16:26:09
Posted by V8Eng on 20/12/2016 15:54:19:
Posted by Ajohnw on 20/12/2016 10:48:01:
Posted by V8Eng on 20/12/2016 10:23:40:
Posted by Dave C on 20/12/2016 09:57:07:

All work carried out by myself is all surface mounted and clearly visible so everything is clear to see.the workshop is only small, So far I have had no difficulty getting electricians to do the work with the exception that all days I have been offered have been mid week and I work away from home. I have had difficulty getting people available when I am that is my only issue. All my work so far has been looked at and the response I have had is that what I have done so is fine.

I have only asked the question due to me having some time off over xmas. Unfortunately though everybody else also wants a break. I just wanted to progress the job a little further so I can finally power up my machine.

The workshop has planning permission and is all approved and as I say all electrical work will be certified once completed.

Dave

I think you should read this and follow the relevant links on the pages.

**LINK**

Like lots of things on the web that isn't entirely correct. It would take a lot more typing to explain how the building regs aspects work out than what I mentioned earlier. There is another aspect to that as well. In some areas what was called the IEE make recommendations and that may add other things or differ in some respect. Those are generally met too.

It sounds like Dave is ok in respect to his consumer unit. When that is changed a full update is needed. Largely aimed at older houses that don't have rcd's.

Work can be certified too. Were things get complicated is when the direct mains is played with and there is no isolator. Odd really as the main fuses could be pulled instead. Also extending ring mains. Spurs are much less of a problem - a bit strange really if people think that through.

The direct mains aspect makes me laugh a little. It's caused problems as only certain people can do it. So they are fitting a totally separate isolator to feed the consumer unit. This avoids the need to pull the main fuses out which should be sealed. However there will be lot about with no seals. Done by ordinary electricians earlier.

John

-

My apologies, I seem to have posted links to a page that had gone out of date.

Edited By V8Eng on 20/12/2016 16:07:50

I don't think you did. I have had a quick read of that page and I cannot see anything that is incorrect.

I think the thing to clarify is that Part P is just one of the building regulations, like Part L for for conservation of fuel and power and Part M for access and use of buildings. Any work done has to meet all the building regs. So as an electrician I need to ensure correct energy saving (part L), correct height of sockets (part m), structural integrity (part A) etc etc.

Then there is the wiring regulations (BS7671), this is what gives wiring methods, earthing requirements, details current carrying capability etc. This is what is published by the IET (formally IEE).

On top of that the the Electricity and work regs (heath and safety) and other stuff including requirements from the network operators which might actually vary from region to region.

The confusion comes because Part P is often used to refer to the means of certifying (which is actually done against BS7671) and notification which has to be done for some, but not all work - basically new circuits and special locations. A shed is not a special location but this does involve new circuits so will need notifying.

Thread: Cheap 3 in 1 tig welder - any one used one?
20/12/2016 14:20:05
Posted by Ajohnw on 20/12/2016 13:18:15:

Anyway - bad news after a fashion. No idea what country does this but the earth cable was a lot lighter than live and neutral. Might be 1.5mm^2. I think I will change the mains lead. The live and neutral are probably 2.5mm maybe more. I suspect this explains the comment about adding another earth lead.

John

Err, that would be the UK that does that John

Ok, that isn't quite fair but it is true of fixed wiring - your ring final circuit is probably wired in 2.5mm2 L/N and 1.5mm E, assuming it is fairly modern. Some older circuits are closer to 3mm2 L/N and closer to 1mm2 earth in practice. I know, I am sad but have a vernier in my tool box when I am doing electrical work

The earth does not need to be as large as the L/N as it only takes fault currents for short duration, rather than full load continuously. So it is the let through energy that is important, not the continuous rating.

Unfortunately, for "mobile" wiring it is not possible to guarantee the fixed circuit it will plug into so it is safe to make the earth the same size as the line and neutral. However, if you know you are plugging it into a known circuit (like the aforementioned ring final circuit) then you might consider it overkill to change a cable to higher rating than the circuit it will be plugged in to

Of course I would not be saying you should not change the cable, Just that I would not lose any sleep over it if I was in your shoes.

Thread: Electrical help / advice please
20/12/2016 13:17:15

Excellent, sounds you are sorted then.

Toby

20/12/2016 11:48:30

My first post on this forum as I generally just lurk as I don't know what I am talking about! But electrics is something I do know something about (for my sins I was a registered electrician until recently) so I thought I would comment......

Given the other responses I think some clarification is worthwhile to avoid confusion.

So, as I understand it you have a two gang switch. One gang switching the internal light(s) and one switching the external lights?

If I understand you correctly, the internal light(s) are a standard two core switch line/return to one of the lights so it will simply be line (brown?) to the switch common and switch return (Blue?) to L1.

For the outside lights you have a Line & neutral supply to the switch and line and neutral out to the light(s)? If this is the case then follow Emgee's advice. There is no connection between the two switching gangs/circuits, just connect all neutrals (blue) together, the supply line (brown) to switch common and the light lines (browns) to the switch L1.

To avoid confusing (and perhaps be a bit pedantic!) I have referred to Line above rather than Live as strictly speaking the neutral is also a live conductor (and really can be "live" sometimes). Oh, and when I refer to the "common" of the switch, this is the one the other side from the L1/L2, so marked L in your case?

In case you don't already know this, all line conductors need to be brown, so if blue conductors are uses for switch returns (eg you internal lights) then need to be over-sleeved with brown at the switch and light. Also make sure you connect all the cpcs (circuit protective conductors or earths) together properly (with green/yellow sleeving). I am a big fan of wago push connectors for this sort of stuff.

eg: **LINK**

(although you might not find them worthwhile of you only need a few)

And (a pet hate of mine) don't do what used to be common practice, ie twist all the cpcs together and sleeve them overall. That makes it a pain to work on later. Just sleeve then individually and connect at the terminal block (or wago or whatever).

Also, a question, do you have any cables running over what might be considered an escape route? (ie the main door) If so they really should be supported by non-combustable means. These do not have to anything fancy, just an occasional metal strap would do. The aim is just to stop them sagging enough to catch you (or a fireman) if the cable clips melt.

A few other comments based on other responses so far:

Consumer units are no different in garages/workshops compared to a house. They all should be of a non-combustable (eg metal) material nowadays.

Yes, the work is notifiable, hopefully this is what Dave means by "certified" although strictly they are two different things. ie. the work needs testing and certifying, then notifying to building control.

As to the French switching the neutral, it is certainly against their regulations (as it is ours) but I gather they sometimes ignore it because, well, the French were never big on following regulations

A bit stupid really as it is the best way of killing someone, especially if you have multiple lights on a switched circuit (the neutral of the light fitting will be live even when "turned off" ) smile o

One last comment. This is obviously up to you Dave but I would recommend not energising and using any circuit until it has been tested properly. I know it is tempting to just wire it and use it but, even with the best will in the world, we all make mistakes and the proper test sequence is the only way of knowing it really is safe.

 

Lastly, you have my sympathy trying to get a electrician to help but I have to admit that I too would normally run a mile from the "I am wiring it myself can you just advise and certify it" type jobs. It is too easy for it to turn into a bit of a nightmare to get right and customers don't react well when you tell them it will be more expensive than doing it myself from scratch! On the other hand, customers that do the hard work (digging trenches, making good afterwards etc) are great

Unfortunately I am too far away or I would at least offer some more practical advice.

Sorry, that turned into a bit of a ramble, I hopes it helps...

Toby

Edited By Toby on 20/12/2016 11:49:28

Edited By Toby on 20/12/2016 11:49:47

Thread: CONTACT DETAILS FOR CLASSIFIED ADS
28/10/2016 13:12:21

... access to the classifieds would be nice

28/10/2016 13:12:02

.... to that end.....

28/10/2016 13:11:51

.....and actually started using my workshop again.....

28/10/2016 13:11:21

....and I think it is about time I came out of the woodwork.....

28/10/2016 13:09:44

another lurker here......

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