AM2 Fault finding failure. Bonding splan motor circuit

[Pete286]

Hi everyone. I sat my AM2 last week and passed everything except the fault finding.
They just tell u pass or fail not what u got right or wrong etc. I struggled on the faults I'll explain below. I know the faults will be different next time but would still like to know how to approach these problems and what the faults actually could have been.

Bonding fault: 'engineer has been struggling to get continuuty on main bonding conductors'
Had sepearse gas and water main bonding. Was hidden behind trunking between the bird and clamps on pipes. I disonnected them and tested end to end. Had continuity. I tested from what was saying gas at the disconnected board to the clamp side of water and still had continuity. I said therefore it is a short circuit. Could it have been crossed polarity?

2nd fault: boiler and pump are continuously running.

3rd fault: motor will not start. I checked from board to starter end to end continuity N L1 L2 L3 and from starter to motor end to ends. All belled out ok. I wasn't sure how to test bewteen the contactors within the Dol.

All these faults have to be wiring faults and only found with continuity meter no IR.

If anyone has any other common faults for these 3 above please share

Cheers

 

[Joenicholson1996]

3rd fault:
Fault seems to be in starter.
Physically push in the contactor and test continuity between all contacts ( I.e between 1 and 2, 3 and 4, 5 and 6)
Make sure the A2 of coil has continuity with main neutral incomer into starter.
Same goes for the A1 side of coil, ensure the coil gets a supply by proving all contacts for latch (read this when contact is physically pushed) and buttons read through when pushed. Stop button may have welded in so read through that this reads open when pushed and closed when not. Ensure overload hasn’t tripped and that the overloads are set to the motors running current.

 

[gazdkw82]

Belled out?


Low ohms continuity you mean?

 

[magnoliafan89]

In regards to the bonds. Did u test end to end . I had this fault too but i had continuity between the bonds but thats because they both went into a metal box. When i tested between one end of the water to the other i found no continuity so put this down as a break in the cable

 

[Wilko]

Hi - on your bonding fault - it may be they didn't like you removing the bonding without isolating the installation?

 

[gazdkw82]

You should always disconnect bonding conductors from the MET because of parralel paths

 

[ipf]

What is your current state, qualification and jobwise.

These are suggestions so thinking cap required.

1. What has polarity got to do with earth continuity?

2. Stat or control cct problem.

3. Motor winding test to begin with....then control cct.

 

[Sintra]

If you are a trainee why not join the Trainee Forum by applying HERE

 

[chris gray]

The polarity part did cause my eyebrow to raise

 

[davesparks]

Bonding fault: 'engineer has been struggling to get continuuty on main bonding conductors'
Had sepearse gas and water main bonding. Was hidden behind trunking between the bird and clamps on pipes. I disonnected them and tested end to end. Had continuity. I tested from what was saying gas at the disconnected board to the clamp side of water and still had continuity. I said therefore it is a short circuit. Could it have been crossed polarity?

2nd fault: boiler and pump are continuously running.

Cheers

You're not making complete sense here, but it sounds a bit like you have a bond labelled as gas which is actually connected to the water? In which case the problem is incorrect labelling.
I'm not sure what you mean about polarity?

Read the circuit diagram for the boiler controls to identify which components actually control the boiler, this will tell you what could have failed to cause the boiler to fire constantly.

 

[Martin Scott]

Fault 1
you say you had continuity on the bonding, if so you may want to consider the fault may have been a high resistance fault.

For the AM2 the wiring faults are either Open circuit (which can be on any conductor in the circuit) , Short circuit, Short to Earth (Earth fault) High Resistance. & reversals. If you find an open circuit check it is the only one in that circuit as reversals may lead you to believe you have an open circuit, if you find two open circuits check that the wires are not reversed.

Fault 2
If the pump and boiler are constantly running, there may a short circuit or reversal on the control wiring, for AM2 Faults there are clues in the wording of the faults you are given, these point you to where in the circuit you should be looking, with the heating system (which is an S Plan with a solar element to it) if your not familiar with heating systems use the diagram (its wiring by numbers/colours) check for continuity following each wire until you find your fault.

Fault 3

Again there are clues in the wording of the fault for example if the contactor is chattering and will not hold in it would suggest you may have an open circuit on either A1 or Neutral to the coil which holds the contactor in once its been activated.

 

[magnoliafan89]

I can tell you that the bonding issue is as my previous post as i recently done my am2 had that exact fault put that the water bond was open (break in the cable) also thay t passed the fault finding so it mustve been the case seeing as you need 100% on that section

 

[sparky1]

Hi Pete, looks like we are both in the same boat I've passed everything apart from my fault finding which i have taken a few times but don't seem to be cracking it. I've also been taking mine at Leeds Building College nice center and nice guy is Paul the assessor.

just to recap on some things maybe others can help us out hopefully.
There only can be 4 types of fault i.e
~SHORT CIRCUIT
~OPEN CIRCUIT (NO CONTINUITY)
~REVERSED POLARITY (CROSS CONNECTION)
~HIGH RESISTANCE (MORE THAN 0.5 OHMS)

As we know none of the Equipment is faulty.

I believe from reading others feedback Terminology is important for example,
LINE instead of live, open circuit rather than broken cable or lost neutral e.g high resistance and reversed polarity is the correct terms.

Exact Location is important too, i.e
At no 2 socket to fuse spur

At consumer unit to TPN socket

Between these two points etc

From wiring center to controller
ETC ETC ETC

And also the Rectification write up is important too, I did read somewhere that candidates do not record a correct method of rectifying the faults.Maybe we should be writing things like,
Replace cable
Reverse the polarity
Tighten the connection
etc etc etc

SOME OF THE FAULTS THAT WE GET PRESENTED WITH ARE AS FOLLOWS,
1. Before commissioning couldn't get r1+r2 reading on TPN socket outlet

2. Bonding conductor has no continuity

3. 3 phase motor doesn't operate

4. 3 phase motor switch is chattering

5. customer is complaining that they can't always get hot water

6. Ring main keeps tripping the circuit breaker

7. Bonding fault: 'engineer has been struggling to get continuity on main bonding conductors

8. boiler and pump are continuously running

9. etc etc etc

I think new guys like myself it goes without saying we lack in experience and only time and plenty of work will give us that required experience and knowledge especially when it comes to Fault finding but for know i've gone and bought a £20 cheap multi-meter from Toolstation and going to build myself two boards one with a ring main and the other an intermediate lighting circuit to get some practice.

What i would like if you guys could just give me and Pete Im sure he doesn't mind me mentioning him lol is some clarity on the four faults so,

Excuse me if i sound Dumb every day is a school day,

SHORT CIRCUIT,
is when you have continuity between L and N or L and E, N and E obviously you don't want this as the two conductors are touching causing a short?????

OPEN CIRCUIT,
is when you don't have continuity on a end to end test on a conductor????

HIGH RESISTANCE,
is when you get more than 0.5 ohms (obviously here i'm talking about the AM2 test bay as they are only short runs)?????

CROSS POLARITY
is when u check at one conductor end to end it doesn't have a reading but when u touch your test probe from one side to another conductor you get a continuous reading????

Sorry for the long essay guys just determined to get as much info and pass hopefully.

 

[DPG]

The open and short circuit descriptions you gave are right. The polarity one wants a bit of work though. Good to see someone who wants to know why things are done and what the results mean, rather than just writing numbers down.

 

[sparky1]

Thanks mate want to learn and become a good competent installer long way to go though, okay lets just put the polarity definition on hold for a moment lets look into high resistance,
considering your working in a test bay and the runs of cables not too long going to a switch board etc through a resister which they have put in purposely to put a fault on the circuit what would you consider as a high resistance reading??? would you say anything above 0.5 ohms is unacceptable?

 

[DPG]

I would say any fault resistor that they insert would be well above 0.5R. Others may be able to confirm this for certain.

 

[Powellm]

Fault 3. Complete half split technique. Spilt circuit in half and test if the start contactor, emergency stop and overloads all check out and you verify connection at this half you eliminate this side of the circuit. Approach the 2nd half of the circuit as a while new circuit and again half split this if there are normally open switches or contractors. If you find all normal readings to the motor the and all control switches and fuses arc are fine it's the motor. Impressive the examiner even more by pulling out your megger and complete a full winding test for insulation breakdown at 100v then rip out the stator and put a new squirrel in there. Good as gold... all the best next time.

 

[Powellm]

I would also like to apologise to all reading my above the grammar and spelling is horrendous

 

[sparky1]

unfortunately your not allowed an insulation tester (i.e megger) just a cheap DIY tester, this is to really test our knowledge and basic understanding i believe.

so any reading above 0.5 ohms is a high resistance fault is that correct????

 

[sparky1]

Bump