Zs for awkward lights

[NoSparks]

So the last light on the lighting radial is a pendant but the rose is all painted up .
The previous two lights are those B&Q fittings that takes upto 10 mins to dismantle and 20mins to re-install. the first light on the circuit is a chandalier.

We've all been there, so what did you do to measure (R1+R2) and Zs?

a) Smash the pendant and put up a new one (at your own cost)

b) Spend half an hour or so taking down one of the B&Q fittings (Remember your on a fixed price job so time is hitting your pocket)

c) Take a reading from the pendant, connecting to the earth at the switch (if there is one)

d) Take a reading from the switch using a Nutral from another local circuit to power the meter

e) Declare a limitation that you can't measure Zs for the circuit

f) Somthing else ................................... (please fill in the blank)

 

[Spudnik]

If we are going buy the EAWR then technically we should not be working live so calculation is the way to go.

However, depends on the client really.

I would go with a) but i would also inform the client why it needs to be replaced and charge a minimal amount.

 

[Guest123]

Hi.

I would go with option 1.

However calculating Zs is a permitted method. So in this instance I would measure the R1+R2 at the switch and obviously you will already have your Ze and then calculate the Zs for that circuit and note it on the test from as "Calculation method used for circuit 1 L1" or what ever the circuit number is.

Another option is a 2 wire test instrument.

Hope this helps.

 

[demolution4o]

R1+R2 from the switch and Zs by calculation
if u don'thave rcd u can measure Zs aswell

 

[NoSparks]

That's interesting.

Since Zs = (R1+R2) + Ze

Then (R1 + R2) = Ze - Zs


So as far as I can make out, measuring Zs at the switch amounts to the same as measuring (R1+R2) and adding Ze.

The real situation is that using either of these methods, the resistance of the cable between the switch and the light is not included.

Sorry a little off topic here but I would be keenly interested in the time others would take to adopt method a). Personally I recon (I'm thinking allowed here) 5 mins to obtain permission, 4 to get the dust sheet and tools in place. say 2 to smash the rose cover and remove the base, say 7 to mount the new base, 4 to reconnect the wires. 4 to tidy the tools and remove the dust sheet, 5 to get the vacuum and clean the residual. Assuming no problems about 30 mins or 20% extra time for the PIR. How would you manage?

Geoff

 

[tomasi]

Ask the client if they will pay for the new rose and installation,
if no, measure at closest available point and list the rose as a limitation and the circuit that supplies it
is only tested to the closest available point

alternatively measure the supply voltage at the intake position,
fit a lamp in the rose of high wattage and then switch on and measure the volt drop at the intake
deduct one voltage reading from the other and use ohms law.
loop impedance testers only basically calculate volt drop any way to produce a reading.
Easier if the load is much heavier though,i would basically put it down as a limitation if the client wont cough up.

 

[DHES-LTD]

Just do R1+R2 and Zs at the switch using 2 lead method.