Working on a job today which included a very simple new lighting circuit.
The lighting circuit a very short run from a distribution board to a single switch position, which then supplies a single luminaire.
The customer wanted a dimmer switch to control the fitting.
To crack on and perform the dead tests, the dimmer was disconnected and the line conductor joined through. The R1+R2 measurement was 0.28 ohms. Polarity checked and insulation resistance measurements taken... all good.
The dimmer was then reconnected and a Zs measurement taken at the end of the circuit.
The dimmer was causing the reading to be >2000 ohms. Is this normal, or acceptable, as it makes you wonder what you happen in the event of a fault on the load side of the dimmer?
With the dimmer bypassed again the reading is fine (approx 26 ohms, on TT system).
So, with my "tin hat on", I guess the following are open to question as well:
Maybe the R1+R2 should have been performed with the switch in place. To speed things up with the insulation resistance testing it was bypassed for all dead testing.
Some say it is dangerous to perform Zs measurements on a light fitting as you have access to live terminals and therefore calculating the value is sufficient and a preferable option.
The light fitting doesn't have any exposed conductive parts and is well out of reach. I didn't actually unpack it and put it up, it is most likely double insulated, one of those self-contained flexible LED strips. It was supplied with a 13A plug which was replaced with a flat 3-pin plug and socket, the socket being the end of our circuit and where the measurements were taken.
I welcome any thoughts.
The lighting circuit a very short run from a distribution board to a single switch position, which then supplies a single luminaire.
The customer wanted a dimmer switch to control the fitting.
To crack on and perform the dead tests, the dimmer was disconnected and the line conductor joined through. The R1+R2 measurement was 0.28 ohms. Polarity checked and insulation resistance measurements taken... all good.
The dimmer was then reconnected and a Zs measurement taken at the end of the circuit.
The dimmer was causing the reading to be >2000 ohms. Is this normal, or acceptable, as it makes you wonder what you happen in the event of a fault on the load side of the dimmer?
With the dimmer bypassed again the reading is fine (approx 26 ohms, on TT system).
So, with my "tin hat on", I guess the following are open to question as well:
Maybe the R1+R2 should have been performed with the switch in place. To speed things up with the insulation resistance testing it was bypassed for all dead testing.
Some say it is dangerous to perform Zs measurements on a light fitting as you have access to live terminals and therefore calculating the value is sufficient and a preferable option.
The light fitting doesn't have any exposed conductive parts and is well out of reach. I didn't actually unpack it and put it up, it is most likely double insulated, one of those self-contained flexible LED strips. It was supplied with a 13A plug which was replaced with a flat 3-pin plug and socket, the socket being the end of our circuit and where the measurements were taken.
I welcome any thoughts.
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