Lockdown Learning - The recommended basic electrical safety checks you should perform

welcome to one and all welcome to another session of lockdown learning today we are going to talk about the recommended basic electrical safety checks that should be performed before you work on an appliance that contains electricity before I begin on the technical stuff I just like to say thanks to all you people that have given us positive feedback regarding these lockdown learning training sessions as a business boxer we are committed to helping you guys in any way shape and form that we can so thank you so with regard to today's basic electrical safety checks in previous videos we've already covered a couple of the items I spoke to you in previous videos about safe isolation and that incorporated the use of earth loop impedance testers and I also spoke to you about ensuring the case wasn't live using a device such as this a non-contact voltage indicator if I may just take the opportunity to mention there are lots of these types of test equipments available if you're purchasing one of these or maybe you already have one of these in your toolbox then I would recommend that you just have a look on the side of it and see what is the recommended working voltage range for your test equipment now as a human being if we submit it to a voltage once it gets above a hundred volts that's when it becomes potentially lethal to a human being so a suggested range a working range for one of these would be a range from 100 volts let's say up to a thousand volts also in the previous videos I mentioned to you about the use of this type of device which is an approved voltage indicator in which we would you to confirm that we have performed safe isolation and there is no electricity at the appliance in conjunction with this remember you should prove that the device is working using something like this which is called a proving unit so I'm gonna take those areas as already covered and now we're going to look at the remaining tests which form part of the basic electrical safety checks and for this we can use the multimeter so the first test we're going to perform is a test that's called earth continuity this is the earth continuity for the appliance we're going to measure ohms resistance so we would select on the multimeter alumns resistance and then we would measure from a known earth source so outside the appliance a known earth source to an earth source of the appliance which may be the metal casing not painted bare metal or it could be the earthing strip which is part of the incoming mains terminal strip and when we perform this test we're looking for a resistance reading which is less than 1 ohm that confirms that the appliance is adequately earth what we would do then inside the appliance we would repeat that test from the earth terminal which we've just confirmed is definitely connected inside the appliance it's recommended that you perform this earth continuity test in five different positions and in each case we're looking for a resistance value of less than 1 o if we say that that passes we have a value of less than 1 ohms what we would perform next is called a short circuit test to perform the short turkey test any switches for the appliance must be turned on so the boiler stack should be up the room thermostat for example should be up we're not turning the power on the power remains turned off so witness switch is turned on we would now use the multimeter to measure the resistance between the live and the neutral terminals and we now at this point are looking to see an ohms resistance value of more than 20 ohms if it's less than 20 ohms then in the appliance somewhere there is a short circuit we would stop work and we would then investigate inside the boiler the cause of the short circuit to give you one example if you were working on a back see let's I do otech and you perform this test you're looking for a resistance reading that's good at between about six and eight hundred ohms so if we say that test passed then the next test we need to perform as part of this basic electrical safety check procedure is called resistance to earth still with the meter measuring ohms resistance only this time we're going to measure the resistance value between the live terminal and the Earth terminal we are now looking to check that all of the electrical insulation inside the appliance is good and now we're looking for a massive reading a reading that should be more than 1 million ohms now if you have an auto-ranging meter such as mine and you perform this test and you're absolutely confident that these probes are in contact with those terminals and you see a value on the screen as o L then you know you've got a huge resistance value it's a pass because the meter cannot measure the value it is definitely more than 1 million ohms so those three tests earth continuity remember less than 1 ohm sure circuit should be more than 20 and resistance to earth should be more than 1 million those tests have all been performed with the power off they are commonly called the debt tests because there's no cower if they all pass we've confirmed that the appliance is safe to connect to the electrical supply so now we could put the power onto the appliance and the next stage is to confirm that the power supply is being delivered correctly so now we're going to measure a voltage so now on my multimeter I would need to select volts ac and I'm going to confirm the incoming power supply to the appliance is wired up the right way round we would measure between the live and the neutral we're looking for a voltage reading that's between 207 and 253 so for example let's just say 240 volts we would then measure between live and earth we're looking for near enough the same reading so in my example 240 volts we would then measure between neutral and earth we are allowed between neutral and earth a voltage of up to 15 if you had those readings then you have confirmed that the appliance is correctly connected to the live the neutral and the earth if for example we measure between either neutral and we have 240 volts and then we measure between live and Earth and we have zero volts but when we then go from neutral to earth we now have 240 volts then we have already discovered that the you have what they call reverse polarity the power supply is coming into the boiler along the neutral wire remember some appliances will not work on reverse polarity so those tests are the basic electrical safety checks they are your first steps to fault-finding so I hope you've enjoyed this video there are more videos to follow so stick with us and we're going to try and give you as much information as we can practically do so look after yourself take care and I'll catch up with you on another video

Channel: Baxi - sustainable heating and hot water solutions

Views: 26,784

Keywords: Lockdown Learning, Baxi Training, Multimeter, Boiler

Id: 3mljWv4Tgys

Length: 9min 10sec (550 seconds)

Published: Thu Apr 23 2020