A few questions for the forumers!

[Gassy_NE]

Had a quick chat with a mate yesterday about the following, could someone please clarify...

- If there is hot water but no central heating (or vice versa) is it more than likely the diverter valve? Poor hot water could be the plate heat exchanger?

- How do you check for earth continuity on a boiler? Power off, one multimeter pin on earth and the other on the boiler case? Not had much experience with electrics.

- How do you test polarity on a boiler? Check between L & N and then L & E, fault present if below 240v?

- Before work is carried out on an appliance do the following tests ALWAYS have to be carried out?
Earth continuity (dead test)
Short circuit (dead test)
Resistance to earth (dead test)
Polarity (live test)

Help with these questions would be great, thanks.

 

[stratobuddy]

Don't forget we are now 230V. not 240V

 

[galaxy_plumbing]

is not exactly 230v as you have AC voltage in domestic grid

 

[Gassy_NE]

Thanks, but is that the full extent of a polarity test?

Can you clarify any of my other points?

Thanks

 

[Howsie]

240 -+ 6% I believe.

 

[galaxy_plumbing]

check 5 points on boiler for earth continuity, resistance no more than 1 ohm. pin on earth an then test various parts in boiler.
turn boiler controls on, check live and neutral, reading more than 20 ohms, if lower than probably short circuit.
live to earth should be more than 2 M ohms
L-N 240 VAC
L-E 240 VAC
N-E 0-15 VAC

 

[stratobuddy]

Since 1 January 1995 (Electricity Supply Regulations, SI 1994, No. 3021) domestic voltage has an asymmetric voltage tolerance of 230 V+10%−6% (253 to 216.2 V)

 

[Howsie]

It may do but it's supplied at 240 in the UK. Won't be lowered for quite some time. PITA really.

 

[gtmspyder]

Surely a bit academic as far as the guy's question realy, if he gets a belt, it's a fair bet he could be dead at any of these voltages.

At the mains connector on the boiler and using a multi meter set to a voltage scale greater than 250v.

Live to earth, the voltage would be between 220 and 250 volts, with one probe on the marked L terminal and the brown wire from the supply connected to that terminal, and one probe on the earth terminal with the green/yellow wire connected to it.

Live,one probe to brown wire terminal and one probe to neutral blue wire terminal, the voltage would be between 220 and 250 volts.

With AC voltage, it does not matter which colour probe goes to which terminal.

You can't realy do an earth test with a multimeter, but to prove that you have an earth continuity of sorts, set the meter to resistance setting, put one probe to the green/yellow earth terminal on the boiler and the other probe on a known earthing point which could be the earth wire behind the faceplate of the socket or fused connection point and read off the resistance scale, this should be less than 1ohm, the lower the better.
Then, one probe on the boiler earthing point green/yellow, and touch the various metal points around the boiler, again, the resistance should be less than 1 ohm.

A much better test for earthing would be obtained using a meggar for insulation testing, or a PAT tester, but these are expensive items of equipment. Also, a meggar is not a friend of electronics, so need to be use with care.

Regards,

BrianT.