2391 practical assessment

[andy1984]

got my 2391 practical next week guys and got some queries on a few things?

1, in the assesment is it acseptable to measure the R2 values to the (earthed) screws on the switches instead of taking the fronts off? this is assuming you dont have to do the R1+R2 measurment (which our tutor told us we might not have to)

2, whats the best way of avoiding the dimmer on the IR test? is it to take the front off and chocolate block?

3, with the motor circuit will the starter hold in when pressed (thus putting voltage to the 32A socket outlet) and allowing you to take EFLI measurments?

4, how do i avoid the neon in the IR test?

5, oh and on the first EFLI test our tutor told us to plug our meter in to the socket but not test when you find the switch combination with the missing earth, but my megger test meter automatically tests when voltage is detected so surrely its guna fail me?

thanks in advance
its a great site with some knowledgable people

 

[RF Lighting]

got my 2391 practical next week guys and got some queries on a few things?

1, in the assesment is it acseptable to measure the R2 values to the (earthed) screws on the switches instead of taking the fronts off? this is assuming you dont have to do the R1+R2 measurment (which our tutor told us we might not have to)

No.
The screws will only be earthed if the switch is mounted in a flush steel box, which it probably will not be on a test board.
You will need to get an R1+R2 value for each circuit.

2, whats the best way of avoiding the dimmer on the IR test? is it to take the front off and chocolate block?

Yup.
The only way infact. You need to connect both the feed and switch wire together when you remove the switch to make sure you test the entire circuit.

3, with the motor circuit will the starter hold in when pressed (thus putting voltage to the 32A socket outlet) and allowing you to take EFLI measurments?

If the circuit is live, the DOL starter will hold in regardless of wether a load is connected to it or not.

4, how do i avoid the neon in the IR test?

Disconnect the neon if you can, if not remove the switch and link the wiring out

5, oh and on the first EFLI test our tutor told us to plug our meter in to the socket but not test when you find the switch combination with the missing earth, but my megger test meter automatically tests when voltage is detected so surrely its guna fail me?

Not sure on this one. Does the college or one of your mates have a loop tester you can borrow?

 

[andy1984]

thanks RF

thats a great help cheers. ill have to look into the loop tester thing i think, potential banana skin!

also
1, is it accseptable when testing I.R to open all cb's ( having taken precautions of removeng neons, dimmers etc) to test the whole board and circuits as one rather than individual circuits?

am just thinking of saving time, 1 and half hours dunt seem very long

oh and also when testing the motor starter and socket outlet for I.R im going to have to open the starter up also and test from bottom of contacter to get all the circuit in. am i right in thinking this?

thanks again

 

[andy1984]

sorry another question. are you allowed to remove wires? ive heard conflicting views on this. my way of testing the R1+R2 would be to take the phase out of the cb and terminate it in the earth, therefore being able to measure at the outlet.

any views on this? or being its a test board can i leave both where they are and measure them individually and then mentally add them up?

so many ways of doing things!

 

[RF Lighting]

1, is it accseptable when testing I.R to open all cb's ( having taken precautions of removeng neons, dimmers etc) to test the whole board and circuits as one rather than individual circuits?

you can test the whole installation as one, but you need to make sure all the MCBs are on, and you will have to remove any RCDs or RCBOs as these must not be IR tested. If a low reading shows on the IR test, you can turn the MCBs off one at a time to find the problem circuit. This saves time too.

oh and also when testing the motor starter and socket outlet for I.R im going to have to open the starter up also and test from bottom of contacter to get all the circuit in. am i right in thinking this?

It depends on the starter, but you will probably have to open up the starter and link across the contacts or wedge the actuator in the on position.

are you allowed to remove wires? ive heard conflicting views on this. my way of testing the R1+R2 would be to take the phase out of the cb and terminate it in the earth, therefore being able to measure at the outlet.

any views on this? or being its a test board can i leave both where they are and measure them individually and then mentally add them up?

You are allowed to remove wires. The normal way is to remove the live from the MCB and connect it into the earth rail, then carry out a continuity test(s) at the other end of the circuit.

As this is on a test board, you can carry out a continuity test by connecting one lead of the tester to one end of the earth wire, and the other lead to the other end. This is known as the long lead method. (don't forget to 'null' your test leads first)

This result should be written in the R2 coloumn of the form, not the R1+R2 coloumn.

R1+R2 is the resistance of phase and earth.
R2 is resistance of earth only.

 

[andy1984]

sorry to be pain people but got a few more questions if thats ok

help so far is much appreciated.

1,is it allowable to measure R1 and R2 individually using long lead method and then mentally add them up to get R1+ R2? (long lead method being easy cos its a test board.

2,how do i get R1+R2 for a motor starter circuit? its a starter with a 3 phase socket outlet. am i going to have to bridge the phases to take the contactor out on each phase?

if yes do you test each phase to earth and record the highest as R1+R2?

3,theres a single pole mcb feeding a CU on the test board. is the R1 +R2 value measured to the earth terminal in the CU and where the phase terminates in the incoming rcd Terminal? is this the end of the circuit?

 

[comms]

1. Just add a link at furthest point of circuit between phase & earth, then test at DB between earth bar and circuit phase conductor, this will be your R1+R2.

2. bridge L1 to earth push in contactor take reading at DB do same with L2/E & L3/E, these are the R1+R2 for each phase. Each reading is recorded on the test result schedule.

3. Link between mainswitch phase & earth on single phase CU, at 3 phase DB take reading between earth bar & phase conductor supplying the sp cu.