Electrical tests procedure on gas boiler

martineire

Quick question regards electrical test procedure on a gas boiler. I've isolated the power via removing fuse from spur but the problem is when doing my earth continuity, short circuit test and resistance to earth checks I'm getting different resistance reading when the spur switch is turned on and off. Fuse is removed and all clocks and stats are calling for heat but with the spur switch on I'm getting difference reading than when it's switched off?? Earth continuity is grand it's less that 1 OHM but with the other two tests I'm getting confused and need advice

Fuse out with switch on

Live and neutral= 187 OHMS
Live and earth =186 OHMS
Earth and neutral = 000.7 OHMS

Fuse out with switch off

Live and neutral= 183 OHMS
Live and earth= OL
Earth and neutral= OL

My live test I'm getting

Live and neutral= 231V
Live and earth= 231V
Earth and neutral= 17V

Any advice and help thanks

tomdempsey200

martineire wrote: »

Quick question regards electrical test procedure on a gas boiler. I've isolated the power via removing fuse from spur but the problem is when doing my earth continuity, short circuit test and resistance to earth checks I'm getting different resistance reading when the spur switch is turned on and off. Fuse is removed and all clocks and stats are calling for heat but with the spur switch on I'm getting difference reading than when it's switched off?? Earth continuity is grand it's less that 1 OHM but with the other two tests I'm getting confused and need advice

Fuse out with switch on

Live and neutral= 187 OHMS
Live and earth =186 OHMS
Earth and neutral = 000.7 OHMS

Fuse out with switch off

Live and neutral= 183 OHMS
Live and earth= OL
Earth and neutral= OL

My live test I'm getting

Live and neutral= 231V
Live and earth= 231V
Earth and neutral= 17V

Any advice and help thanks

lol

what are you trying to determine with the tests?

martineire

tomdempsey200 wrote: »

lol

what are you trying to determine with the tests?

Resistance to earth test and short circuit test on gas boiler. My question really relates to the resistance to earth test as I should be achieving a reading of infinity but as u can see I'm picking up a resistance with the switch on spur turned on and no resistance (infinity) when switched off. Why is this?

brightspark

You don't say what test voltage you are using, could it be a neon indicator in the spur?

martineire

brightspark wrote: »

You don't say what test voltage you are using, could it be a neon indicator in the spur?

I'm just testing the appliance when isolated with my multimeter, there is no neon in the fused spur (old spur) I think by just Removing the L N E SL from boiler terminal strip and then test the boiler independent is the way around this. This way I wound be picking up any strange reading from the source.

tomdempsey200

what are you trying to determine exactly?

is there a problem with the mains supply or operation of boiler?

martineire

tomdempsey200 wrote: »

what are you trying to determine exactly?

is there a problem with the mains supply or operation of boiler?

Theses test that I'm performing are standard tests that have to be preformed on a gas boiler before you service that boiler. The four tests to be completed are earth continuity, short circuit, resistance to earth and polarity. Three tests are done with the boiler isolated and obviously polarity is a live test. Theses tests are testing the boilers internal components and wiring looms within the boiler itself and not the source. Tests are being completed with a auto range multimeter. No problem with supply or boiler but checks have to be completed prior to service

tomdempsey200

martineire wrote: »

Theses test that I'm performing are standard tests that have to be preformed on a gas boiler before you service that boiler. The four tests to be completed are earth continuity, short circuit, resistance to earth and polarity. Three tests are done with the boiler isolated and obviously polarity is a live test. Theses tests are testing the boilers internal components and wiring looms within the boiler itself and not the source. Tests are being completed with a auto range multimeter. No problem with supply or boiler but checks have to be completed prior to service

is this from an RGI manual?

not having a go but it seems a bit ridiculous having gas service personnel attempting electrical tests with a multimeter

there was a poster here recently with a major RGI blunder on main bonding

martineire

tomdempsey200 wrote: »

is this from an RGI manual?

not having a go but it seems a bit ridiculous having gas service personnel attempting electrical tests with a multimeter

there was a poster here recently with a major RGI blunder on main bonding

Yep your right it is but the tests do have to be completed and any faults rectified. Example poor boiler earth can cause problems with boiler flame rectification hence that's why it's important to do an earth continuity test on boiler conponents.

tomdempsey200

it might be best to scan and post the relevant RGI section on electrical testing

and the correct test procedure can then be outlined

but tbh its all a bit silly due to the inadequate electrical training and test instruments

brightspark

martineire wrote: »

Yep your right it is but the tests do have to be completed and any faults rectified. Example poor boiler earth can cause problems with boiler flame rectification hence that's why it's important to do an earth continuity test on boiler conponents.

Surely the reason for earth continuity testing is primarily to protect against electric shock!

The tests you describe sound similar to those used in PAT testing, i.e. a periodic test to ensure the equipment is still complying with the standards as designed and built by the manufacturer.

I'm not sure that a standard multimeter is appropriate for some of your checks, as the current and voltages used to test properly are not available from a multimeter. (But maybe what you are calling a multimeter is actually a multifunction tester?)

If these tests are part of a regular service do you have to use a calibrated meter?

brightspark

martineire wrote: »

Resistance to earth test and short circuit test on gas boiler. My question really relates to the resistance to earth test as I should be achieving a reading of infinity but as u can see I'm picking up a resistance with the switch on spur turned on and no resistance (infinity) when switched off. Why is this?

Because when the switch is on you have continuity from the neutral through the neutralising link at the meter to the protective conductor (earth)

brightspark

tomdempsey200 wrote: »

it might be best to scan and post the relevant RGI section on electrical testing

and the correct test procedure can then be outlined

but tbh its all a bit silly due to the inadequate electrical training and test instruments

Perhaps since they restrict access to gas appliances to their members the RGI need to ensure that their members are as competent on electrical testing as they are on gas. And that they insist on the appropriate calibrated test equipment.

martineire

brightspark wrote: »

Because when the switch is on you have continuity from the neutral through the neutralising link at the meter to the protective conductor (earth)

But with the switch on and fuse removed i am testing between L and E. Not testing neutral so how am I getting a reading between L and E? They shouldn't be meeting and I should be getting a reading if OL. Like I am with off. Sorry if I'm not understanding. Just trying to make sense of it all.

brightspark

martineire wrote: »

But with the switch on and fuse removed i am testing between L and E. Not testing neutral so how am I getting a reading between L and E? They shouldn't be meeting and I should be getting a reading if OL. Like I am with off. Sorry if I'm not understanding. Just trying to make sense of it all.

Because the neutral and earth are joined at the meter!

When the switch is off the neutral of the boiler is isolated from the mains neutral which is connected to the earth.

When it's on you are measuring the complete path from the spur back to the meter...and then back to the neutral of the boiler.

brightspark

tomdempsey200

martineire wrote: »

short circuit, resistance to earth

is that the way they're worded in the manual?

do you have the excerpt from the manual?

martineire

tomdempsey200 wrote: »

is that the way they're worded in the manual?

do you have the excerpt from the manual?

Ill post a link up later for you and you can have a look

martineire

brightspark wrote: »

Because the neutral and earth are joined at the meter!

When the switch is off the neutral of the boiler is isolated from the mains neutral which is connected to the earth.

When it's on you are measuring the complete path from the spur back to the meter...and then back to the neutral of the boiler.

ah thanks it makes perfect sense now thanks for clearing that up. So really when I have the fuse removed from the spur and the switch turned off on fused spur. That's the L and N from boiler isolated from the main circuit. Only the earth is still connected then to the main circuit. So when I'm doin my resistance to earth test if my result is OL I know the boiler is ok but if I was getting a resistance I would then have to disconnect the earth to the boiler and check again at the boiler terminal with earth removed to verify if the fault is coming from the main circuit or the boiler it's self. Am I right in saying that? I know a proper resistance to earth check is meant to be done with a megger sending 500V DC through the circuit and one I'm doin is a much simplified version.

tomdempsey200

the resistance to earth test is probably
something akin to the IR PAT test i presume

i'd like to see how the manual describes it

short-circuit test? dunno about that

earthing and polarity ..i would test at the boiler4 pin female connector(if there is such a thing)

martineire

Here is the link http://boilerfaultfinder.com/electrical-safety-checks/

Please give me your taught on the tests, and proper way to do them.

Thanks

brightspark

martineire wrote: »

ah thanks it makes perfect sense now thanks for clearing that up. So really when I have the fuse removed from the spur and the switch turned off on fused spur. That's the L and N from boiler isolated from the main circuit. Only the earth is still connected then to the main circuit. So when I'm doin my resistance to earth test if my result is OL I know the boiler is ok but if I was getting a resistance I would then have to disconnect the earth to the boiler and check again at the boiler terminal with earth removed to verify if the fault is coming from the main circuit or the boiler it's self. Am I right in saying that? I know a proper resistance to earth check is meant to be done with a megger sending 500V DC through the circuit and one I'm doin is a much simplified version.

martineire wrote: »

ah thanks it makes perfect sense now thanks for clearing that up. So really when I have the fuse removed from the spur and the switch turned off on fused spur. That's the L and N from boiler isolated from the main circuit. Only the earth is still connected then to the main circuit. So when I'm doin my resistance to earth test if my result is OL I know the boiler is ok but if I was getting a resistance I would then have to disconnect the earth to the boiler and check again at the boiler terminal with earth removed to verify if the fault is coming from the main circuit or the boiler it's self. Am I right in saying that? I know a proper resistance to earth check is meant to be done with a megger sending 500V DC through the circuit and one I'm doin is a much simplified version.

Why are you even testing with the spur switched on? Leave it switched off for your testing, you are over complicating the issue.

Please don't go disconnecting earths, there is no need to, just leave the spur switched off. If your meter indicates a live or neutral fault to earth with the spur switched off it must be within the boiler or the cable feeding the boiler from the spur

I'm not convinced that you should be even carrying out these tests until you gain some competence. Are you fully qualified or still doing an apprenticeship?
Regardless I think you need someone to physically demonstrate the correct procedures as it is very difficult to explain every detail here.

Like TomDempsey I too would like to know exactly what the RGI specify for the electrical test.


Simplified version? it's the wrong tool for the job. (And 500V may or may not be an appropriate test voltage depending on the equipment.)

Testing for faults to earth with a regular multimeter on ohms will not detect a breakdown in insulation, any fault you may find with a multimeter would probably have been sufficient to have blown the spurs fuse anyway (unless a Neutral-Earth fault)

A multimeter is also poor at checking earth continuity due to the very low currents used.

brightspark

martineire wrote: »

Here is the link http://boilerfaultfinder.com/electrical-safety-checks/

Please give me your taught on the tests, and proper way to do them.

Thanks

Those tests are just for fault-finding, e.g. if the boiler isn't firing. They don't appear to be proper safety tests to ensure the boiler is electrically safe, though they would highlight complete failures.

Didn't see where the requirement to test resistances with the spur switched on was located?

tomdempsey200

those tests are mostly nonsense

3 of them are wrong

2 of them are flat-out hazardous

brightspark

Is that app/website approved by RGI?

It seems to have been produced in response to

Far too many gas safe registered heating engineers are unable to accurately diagnose and repair faults on their customer’s boilers. Research commissioned by an independent professional body within the industry, proved that many gas engineers were unable to demonstrate vital skills to carry out fault finding on boilers. Research commissioned by an independent professional body within the industry, proved that many gas engineers were unable to demonstrate vital skills to carry out fault finding on boilers

http://www.emergencyplumber.uk.com/plumbing-news/boiler-fault-finder-app/



That last sentence would make me wonder if it really is worthwhile having a law that says only registered gas installers can work on boilers, if so many of them lack VITAL skills that a step by step instruction app was required

martineire

The app is an example that I'm showing u. I've completed all my training recently, The earth continuity, system polarity, resistance to earth and short circuit tests have to be carried out prior to servicing a boiler regardless if the boiler has a fault or not. The boilers that I was working on and performing the tests on in the training centre didn't have double pole spurs. The had a single pole (no switch just a fuse). The problem I was having here at a boiler was I was isolating the boiler by removing the fuse from spur but I left the switch on hence i was getting reading from the main circuit until I switched the switch off aswell and I was just wondering why and where I was getting the resistance reading from.

brightspark

Is there a code of practice outlining the required tests etc?

tomdempsey200

it's hard to see much value in the so-called short-circuit or earth-resistance tests with a multimeter

other than that a loop impedance tester would check supply at boiler
..polarity on both lives and earthing

there's certainly not much to be said for that test procedure

martineire

Lad the the problem I was encountering was only on the resistance to earth check Irrelevant as ye say it is I'm just interested in understanding why I was getting a resistance reading with the switch on. I'm not sure I still quite understand because I have the fuse removed from the spur so that's the live isolated from the main circuit. Now when I'm doing the resistance to earth test I am testing between Live and Earth. Now correct me if I'm wrong but as I understand by having the spur switch on but the fuse is still removed I have Neutral from the boiler connected to the main circuit but by having the switch off with fused removed I am now breaking the Neutral from the main supply, Correct??

Now this is where I'm getting confused. When I'm doing my resistance to earth test I'm testing between Live and Earth. Now ye guys are saying I'm getting a resistance reading when the switch is on because the Earth and Neutral are connected at the meter so that is creating a circuit hence that is why I'm getting a resistance as opposed to having the switch off (neutral broken) and not getting a resistance (testing boiler only). But with the switch on and fused removed I'm probing the Live and Earth terminals at boiler, how is that creating a circuit through my multimeter regardless of the Earth and Neutral connected at meter because one my probes is in the Live terminal at boiler which is broken (fuse removed) and the other in the earth terminal but how is the creating a circuit through my multimeter so that I'd be is pick up a resistance?

2011

martineire wrote: »

The four tests to be completed are earth continuity

From the distribution board to the boiler and from the boiler earth terminal to all conductive parts? How low a resistance do you require to pass the test?

short circuit

Do you mean earth fault loop impedance test?
What value are you deeming to be a pass?

resistance to earth

From the boiler to the MET (main earth terminal)?

Three tests are done with the boiler isolated

If the boiler is isolated the 2nd and 3rd tests will fail as the readings will be infinity

Theses tests are testing the boilers internal components and wiring looms within the boiler itself and not the source.

In general they aren't.

Tests are being completed with a auto range multimeter.

"Auto range" is a feature of many multimeters from cheap and nasty to professional test meters.

But with the switch on and fuse removed i am testing between L and E. Not testing neutral so how am I getting a reading between L and E? They shouldn't be meeting and I should be getting a reading if OL. Like I am with off. Sorry if I'm not understanding. Just trying to make sense of it all.

Ok, now I'm really worried.

No offence but from reading your posts I am concerned that you may put yourself or others at risk. Electricity is dangerous enough at 230V but in this case you have the added danger of gas.
There very good reasons that only RGI are permitted to service boilers.

Please seek professional training if you wish to service gas boilers.
If you have any electrical questions that you would like assistance with while doing a suitable course feel free to post them here.
We are willing to help, but it would be unwise for you to attempt to get all of your gas boiler service training from an internet forum.