Don’t know if it helps to understand the difference of a MCB to a RCD, here’s my take-
A Circuit breaker (CB) or miniature circuit breaker (MCB) is the fuse of the system and is looking for overloads i.e. too much current being drawn down the line/live conductor. The main function of the MCB is too protect the cable it is serving; if a cable draws more current than it is rated for, it will overheat and catching fire is a real possibility.
One solution for a MCB tripping is to change it for a C curve, this allows a certain amount of surge current above the rating of the circuit breaker for a small period of time. This is helpful when you just have problem with high starting currents of machines. To note if you change to a C curve CB the maximum allowable Zs (earth fault loop impedance path) is reduced, which mean cable runs/length for a given C.S.A of cable are reduced, you are definitely into electrician’s territory of testing to make sure it is safe.
A Residual Current Device (RCD) is a device which looks at the current following in the line/live and the neutral conductors, this should be equal. Most final circuit RCD’s are rated at 30mA which means this amount that can flow to earth (and by earth, this can be the earth in the cable, or you holding onto the live conductor and touching the floor!!!) before operating the RCD, and the RCD operates because it sees the current is missing. The reason for 30mA is that this value is considered the safe amount of current that a human body can handle without any damage.
Certain machines leak a little current to earth, computers are a known culprit, they can leak up to 5mA. In a large household where there is 3 computers, washing machine, kettle, fridge etc all on at the same time the combined earth leakage can be quite high, so one more machine could be too much and cause nuisance tripping. In this case there is no problem with any of the equipment it is just a combined earth leakage that is a problem. This is where 17th edition boards are good as they have two RCD’s and the house circuits are split up to try and help avoid this problem. You could also put every circuit onto its own RCD (known as a RCBO) but this comes with a big pricetag for the RCBO.
Some RCD’s even though rated for 30mA actually operate at lower value, testing will show any problems.
If you have a socket that isn’t RCD protected (sometimes the freezer isn’t) then try the machine on that socket to see if the machine operates, if it does then the earth can be metered and the value can be measured. If it is high then you could contact the manufacturers and get their opinion. You could move the lathe onto a non-RCD circuit but this just disguises the problem rather than solving it.
I hope I haven’t rambled on to much and it is of some help.
Cheers
David
A Circuit breaker (CB) or miniature circuit breaker (MCB) is the fuse of the system and is looking for overloads i.e. too much current being drawn down the line/live conductor. The main function of the MCB is too protect the cable it is serving; if a cable draws more current than it is rated for, it will overheat and catching fire is a real possibility.
One solution for a MCB tripping is to change it for a C curve, this allows a certain amount of surge current above the rating of the circuit breaker for a small period of time. This is helpful when you just have problem with high starting currents of machines. To note if you change to a C curve CB the maximum allowable Zs (earth fault loop impedance path) is reduced, which mean cable runs/length for a given C.S.A of cable are reduced, you are definitely into electrician’s territory of testing to make sure it is safe.
A Residual Current Device (RCD) is a device which looks at the current following in the line/live and the neutral conductors, this should be equal. Most final circuit RCD’s are rated at 30mA which means this amount that can flow to earth (and by earth, this can be the earth in the cable, or you holding onto the live conductor and touching the floor!!!) before operating the RCD, and the RCD operates because it sees the current is missing. The reason for 30mA is that this value is considered the safe amount of current that a human body can handle without any damage.
Certain machines leak a little current to earth, computers are a known culprit, they can leak up to 5mA. In a large household where there is 3 computers, washing machine, kettle, fridge etc all on at the same time the combined earth leakage can be quite high, so one more machine could be too much and cause nuisance tripping. In this case there is no problem with any of the equipment it is just a combined earth leakage that is a problem. This is where 17th edition boards are good as they have two RCD’s and the house circuits are split up to try and help avoid this problem. You could also put every circuit onto its own RCD (known as a RCBO) but this comes with a big pricetag for the RCBO.
Some RCD’s even though rated for 30mA actually operate at lower value, testing will show any problems.
If you have a socket that isn’t RCD protected (sometimes the freezer isn’t) then try the machine on that socket to see if the machine operates, if it does then the earth can be metered and the value can be measured. If it is high then you could contact the manufacturers and get their opinion. You could move the lathe onto a non-RCD circuit but this just disguises the problem rather than solving it.
I hope I haven’t rambled on to much and it is of some help.
Cheers
David
