[Brains]

Re: Earth Loop Impedence Test Equipment

Understood – thank you. I always continue to learn something about this industry. 🙂

Thanks for shedding light on this. The Dishwasher was certainly not one of the cheapies I see regularly featured on Whitegoods.

[Brains]

Re: Earth Loop Impedence Test Equipment

Shane

This is what I thought. I am well aware of the cheap timeswitches. However, the timeswitch is integral with this particular dishwasher (not a plug-in cheapy)- By virtue of the integral timeswitch the manufacturer is encouraging off-peak use – any comments?

[Brains]

Re: Earth Loop Impedence Test Equipment

Simonb

Thanks for the reply… so just following another thread (not generally associated with loop testing as such)…. does the manufacturer of any (washer / tumble dryer etc) machine specify that they can be run unattended or at night? We have a dishwasher from a well known manufacturer that has a timer on it. Mrs Brains normally sets it to work at about 3am so that we can benefit from cheaper electricity (economy 7). (As you probably can gather, I normally don’t repair wet goods – I focus on electric cookers, microwaves, electrical installation etc).

[Brains]

Re: Earth Loop Impedence Test Equipment

Ooops – made an error. For 230V circuits when testing at 500V lower limit is 0.5Mohm not 0.25Mohm. Only for SELV circuits is the lower limit is 0.25Mohm.

If you look in the latest IEE site Guide page 73, it gives you all this good stuff. 🙄

When carrying out Periodic Inspections, fixed loads & lamps are normally disconnected or switches are opened. Personally, I like to do a quick check in case there is something nasty brewing as mentioned above.

[Brains]

Re: Earth Loop Impedence Test Equipment

Wow – look like I opened a can of wiggly worms!

The 0.25Mohm is in any combination measuring across the different bus-bars at the Consumer Unit. This limit value is based upon the fact the all the circuits are in parallel. So, if one or more are down in value, clearly it impacts the whole installation. I always measure from the bars to earth then investigate the individual circuits.

Typically, if I am doing a periodic (electrical installation) inspection, I switch on the appliances & carry out an insulation check . I recently came across a Whirlpool tumble dryer where the element wiring & terminations were at the point of melting & breaking down & the insulation was way low.

You are right in what you say that whoever looks at it last, may be held accountable if something horrible goes wrong. This is why I always ‘eyeball’ the insides of an appliance & record all the test data on a test sheet I put together. I know it takes a little longer, but, I for one, want to sleep at night.

At the end of the day, I guess we have to record all the data just in case something does go wrong. At least, we can then be reasonably ‘comfortable’ that best efforts were applied.

I once had a car whereby a junior idiot in a garage fixed it & the thing failed – went into the back of another. Had to take the garage to court etc with the help of the AA. Another tale for another day.

It is becoming more difficult in the whole electrica industry. oh well…. only another 10 years before I hang up the megger 😆

[Brains]

Re: Earth Loop Impedence Test Equipment

Simonb

Be very careful if you allow the insulation to fall to 0.25Mohm. You can affect the complete installation. Also, if the appliance is connected to an RCD controlled circuit and the insulation failure is neutral to earth, the RCD will not reset causing the user to go ballistic. (Had a problem like this a couple of weeks ago).

The minimum insulation value allowed by IEE Wiring regs (for an installation) is 0.25Mohms. It is generally accepted that if the total insulation value at a bus-bar of a Consumer Unit is less than 2Mohm, investigation should be undertaken.

Hate to teach you to suck eggs, but, insulation failures can lead to fires.

Also, be careful with the soft tester as you describe. Key to popping the fuse or tripping the MCB within the required disconnection time is the value of the earth fault loop impedance. In other words, use a decent tester (I know they cost the earth but what choice is there really 😉 )

[Brains]

Re: Samsung M1714

Dave

Again – many thanks. When I eventually find the fault, I’ll post on one of the forums. Maybe it will someone else.

Regards

Mike

[Brains]

Re: Samsung M1714

Dave

Thanks for the reply. The only other number I can find is:

7JB R2 02375F

Regards

Mike

[Brains]

Re: Earth Loop Impedence Test Equipment

Martin

This is the mis-understanding that most people have. If you don’t have a means of comparing obtained value vs the listed max value, then taking these measurements are a waste of time (please don’t take this the wrong way). You also need to be careful as inappropriate testing can damage an installation or cause inadvertent shock risks to customers whilst carrying out the test.

Robin publish a little booklet called ‘A guide to 16th Edition Testing’. You should be able to get this from any good wholesaler who stocks Robin Instruments. Also, for a user guide on your tester, give Robin Instruments a call. I know they were taken over by Fluke, so you may have to search around. I believe that Robin can be contacted via http://www.robinelectronics.com. Generally, instruction books for testers won’t give acceptable values for EFLI.

The PAT Testing guide you have is not really good enough for this stuff as you are confirming that the appliance is safe (I am sure you know this. Please forgive me if I’m teaching you to suck eggs!). The objective after doing insulation tests is then to carry out an EFLI test. The PAT guide typically discusses bonding resistance values for appliances (also important) & yes, I do use a PAT tester for confirming this after I carry out a repair as well as carrying out an EFLI test either at the outlet or in the case of a cooker or oven at the terminals.

The Wiring Regs book is the only way to get the values you need. The other way (which is the method I sometimes use) is to use a program like Amtech Power software (I also do electrical installation work) which lists the common protective devices (MCBs) & the max EFLI vs. disconnection time. May be you have a friendly electrician who properly understands this stuff that can also help.

After a while, you will get a ‘feel’ for the correct values. But sometimes the value can be too low – this then can cause an issue with the MCB or fuse for other reasons.

Don’t let this scare you – it is always daunting in the beginning. No, gain without pain (or headache) 😆

If you want to learn about testing & how to interpret these values, may I suggest that you contact the local Tech College as these places often run courses on 16th Edition Inspection & Testing.

Let me know if you need further help – I’ll be pleased to help a fellow techie- just send another message on the forum or via e-mail on UKW & I’ll give you my personal e-mail address.

Regards

Michael

[Brains]

Re: Earth Loop Impedence Test Equipment

Martin

Earth loop impedance gives an indication of the impedance under short circuit conditions between phase & earth. This value is important since if it is too high, the controlling fuse or MCB will not trip under a fault condition.

The limiting values are often dependent on the type of fuse or MCB used. Disconnection time requirements as declared by BS7671 (IEE Wiring Regulations) will also dictate Earth Fault Loop Impedance.

The max values are listed in this very weighty document. Also take a look at the IEE site guide.

Also take care when testing circuits controlled by RCDs. They will trip & you will need to use a range specifically designed for RCD controlled circuits.

Let me know if you need any further help.

Good luck with your tester.

Regards

Michael

[Brains]

Re: Earth Loop Impedence Test Equipment

Dave

Latest price is about £750 plus VAT. If a number of people are interested & we can work up a quantity I may be able to get a discount. I got mine heavily discounted on a special deal at the time I purchased it (less than £600 inc VAT).

😀

[Brains]

Wow!! Dissapointed to read that everyone is not checking earth fault loop impedance before closing up the toolbox. Like all of you, I’ve come across high or open earths. This is a real danger. Personally, before I work on an earthed device, I check the earth fault loop. Then check it again when I’m done. There are some cheap testers out there now. So, go on protect yourselves, your employees, your business and the customer – you know it makes sense!!

[Brains]

Re: Earth Loop Impedence Test Equipment

Dave

I’m using an Instaltest 61557. I also have the remote probe which saves having three hands (great when testing earth fault loop at cooker / oven terminals!!)

Regards

Michael

[Brains]

Has anyone looked at installation testers by a company called Metrel? I scrapped my Robin Megger when the lead nulling kept going wrong (important when testing R1+R2 continuity). I have been using this tester now for 18 months. These are distributed by Edmunson Electrical Ltd. They are imported by Alpha Tek in Manchester.

Michael

[Brains]

Re: Motor for Hoover U3340 001

Thank you both for the part number

Regards

Michael

[Author]

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