This check is carried out on all Class I home equipment throughout PAT Testing. The aim of the check is to examine that there’s a good connection between the Earth pin on the plug and the case of the equipment. A very good connection is outlined as having a resistance of lower than zero.1 ohms (or 100 milliohms).
The Earth Continuity check is usually known as the Earth Bond check or the Earth Resistance check. In impact all of them measure that there’s a good connection between the mains plug and the Earth level. The traditional approach to perform this check is to plug the equipment right into a PAT Tester and clip the Check result in an appropriate earth level.
When the check is completed, if the resistance measured is lower than zero.1 ohms, then there’s a good earth connection and the equipment is taken into account protected. When finishing up this check throughout PAT testing, there are a selection of sensible issues to be considered.
Earth level on equipment
In an effort to perform this check, it will be significant after all to clip the check result in an appropriate earth level. If this isn’t executed, then there isn’t a return path for the present throughout PAT testing. This can end result within the equipment failing the check.
Discovering an appropriate earth level will include expertise. It’s important to get a very good connection to the Earth level. Rusty steel or scaling on kettle components might forestall a very good low resistance connection. If so then rotate the connector and use the enamel of the crocodile clip to scrape away the rust or the scaling to get a very good connection. It’s also acceptable to clip onto a screwdriver and use this to connect with an Earth level.
The Golden Rule is: When testing Earth Continuity, for those who do get a failure initially, don’t instantly fail the equipment. Be sure you have a very good connection and check out PAT testing once more. If vital strive a unique Earth level as not all steel elements may be linked to earth.
PAT testing – Class I Plastic home equipment
On some Class I home equipment it is probably not attainable to entry an exterior earth level if the equipment is completely enclosed in plastic. For instance there are a lot of electrical followers in use which fall into this class. This presents us with an issue as a result of if we cannot join the check result in an earth level, there isn’t a circuit made and the Earth Continuity check will fail.
On these home equipment, it is very important acknowledge that their development makes them safer than standard Class I steel home equipment. In addition to having an Earth connection, they’re basically enclosed in plastic giving them an additional layer of security. The best way to hold out PAT testing on these home equipment is to nonetheless perform the Insulation Resistance Check. If this passes, then document this go on the Tools Check Report and make a remark to the impact that the earth Continuity check couldn’t be carried out as a result of plastic enclosure.
PAT Testing – Check Present
The particular person finishing up the testing can use one of many two choices under.
Possibility 1: Use a check present of 1.5 instances the fuse fitted within the plug as much as a most of 25A. For instance, when testing a kettle with a fuse of 13A, a check present of 25A ought to be used. When testing a lamp fitted with a fuse of 3A, a check present of round four.5A is used. The present is generally utilized for a interval of between 5 and 20 seconds. This check ought to NOT be used on IT or different tools the place there are digital elements in use. The massive currents flowing within the earth conductor have been recognized to induce surge voltages which have broken digital elements.
Possibility 2: Use a check present of between 20 and 200 mA. While this check is being carried out the cable ought to be flexed to carry out any apparent faults. That is very protected check and can be utilized on ALL Class I home equipment together with IT tools.
PAT Testing – Check Limits
As talked about above, to go this check, the Earth Continuity resistance must be lower than zero.1 ohm when PAT testing is carried out. As that is from the pin on the plug to the Earth level, an allowance might be made for the Mains lead that’s used on the equipment. For instance, a Class I lamp has a 5m mains lead (present capability of 3A) connected to it. The overall resistance of this lead is zero.195 ohms. To this one would add the zero.1 ohms for the equipment itself to provide a restrict of zero.295 ohms. When testing this lamp for earth Continuity, if the resistance was say zero.22 ohms, then one would go the equipment. Say a PC has a 5m cable of present capability 13A. The overall resistance of that is zero.078 ohms. The go restrict for this PC can be zero.1 + zero.078 which is zero.178 ohms.
If the equipment has a brief mains lead, then this won’t contribute rather a lot to the earth resistance. For instance a 1m cable for an electrical hearth would have a resistance of solely zero.015 ohms. When utilizing a PAT Tester with a show, the consumer will be capable to work out whether or not the equipment passes or fails whereas taking the size of the mains lead under consideration. On Cross / fail PAT Testers, there may be an computerized allowance made for the mains lead. Usually the restrict is about to round zero.25 ohms to permit for as much as 5m of mains cable. On some Cross / Fail PAT Testers, permission will also be made for longer cables, say when testing 10m or 20m extension leads.