IR testing when SPD are in circuit.

[john h owen]

Hi not sure I have all the information on how to do a IR test in a circuit with surge protective devices in circuit all the information I have is to disconnect the SPD's and test at 500v dc or short out the SPD's and test between LN to cpc conductors at 250v dc

 

[brucelee]

hi mate
you are right you either disconnect the item and carry out a ir at 500v d.c. if its low voltage or if you cant disconnect the item then just connect line and neutral together and test between this join and earth at 250 v dc but should still be a minimum of 1.0M/ohm if lower than 2.0M/ohm then further investigate to find the cause of the low reading

 

[nz175963c]

With surge protection devices fitted they will provide protection to the circuit during a (IR) test, the test voltage will cause the protective components inside a surge protector to divert unwanted energy from the protected line.[SUP] [/SUP]This was know in the past as clamping voltages. By clamping the voltage in a circuit, this indicated better protection, but can sometimes result in a shorter life expectancy for the overall protective system. Generally you find that by applying a test voltage of 500v DC to a nominal rated circuit of 230v AC, will cause the clamp to give mis-direction in the readings in the (IR) test, so whoever told you to disconnect them during a test, gave you sound advice.