Fault finding. This one has me beat!

[Paul.M]

Call out today for a nice customer, loads of shops that I look after but this fault was in his own home. Details:-

4 Bedroom detached on a single phase supply. Kitchen has been fitted a few months ago and "Kevin the kitchen fitter" also did the electrics! No earth sleeving on any of the outlets, none of the chrome sockets were earthed to the backbox (ok they all had a fixed lug eyelet but still???). Out of 10 sockets/SFU, 5 of them were wired wrong and reverse polarity was the result! The RCD tripping fault was due to a loose termination for the combi boiler, that is fixed but the RFC still needs looking tomorrow, I had enough at 7pm on a Sunday night. Split the ring, made it into a radial and put in a 20A MCB as a temporary measure over night so they can have hot water and the fridge freezer can be used again.


Me question is this:- Whilst live testing I got a reading of >65 Hertz from the RFC??? Dropped down to <45 Hertz for a few seconds and then back up to >65 Hertz??? Single phase supply to a domestic property and it does not have a PV set up and I have a constant 50 Hertz at the incomer and CU. I am really scratching my head on how this could be? Reverse polarity at sockets can not effect Hertz and the Hertz output from the power stations are very closely monitored within a 0.3 (I think) so how can this be???

Any help on this would be great, I hate not knowing why and I really hate fixing a fault without knowing how the fault was created. (had it a coupe of times, fixed a fault whilst poking around and dont know how?)

What am I missing or forgetting? Ripping my hair out thinking about it lol.

 

[Leesparkykent]

Dodgy multi meter?

 

[Paul.M]

Dodgy multi meter?

Calibrated a few months ago and checked the results against my Chauvin Arnoux meter (very precise bit of kit).

Me and my friend were thinking this was an electrical wind up for a Dom Jolly tv show with Tony Cable sat in the loft flicking control switches! Way too many faults for a simple kitchen install, this chaps reputation is going to be mud by the end of the week in the "local community". He really needs to stick to kitchen fitting and not electrics, the word will get around very fast in the circles he works within.

 

[Darkwood]

Batteries in meters can give all sorts of obscure readings if they are drained or got a reactive/resistive contact point...

Get new batteries and buff up and respring the contact points..

Or your meter is knacked!

 

[pennychew]

Out of interest which meter are you using? Don't think I have one that shows the frequency

 

[Bobster]

So both of your meters showed the same 65Hz?

I'm presuming this house has a DNO supply?

If the meters are in fact correct, it's most likely that something connected to the RFC is generating 'noise' and that is fooling your meter. I can't see it being a DNO issue as those Hz figures would mean real trouble.

Edit: just to add, most MFT's range for measuring frequency is 45 - 65Hz

 

[Darkwood]

If meter checks out and its DNO supply then it would all point to harmonics or similar noise generated by a local business or possible if you have a large amount of electronic driven devices throughout all the house ..like led lighting....

I get this issue with my meters on machinery sometimes with harmonics been the culprit but never seen it domestic.

 

[Marvo]

Maybe the loose termination was causing the weird reading.

 

[Pete999]

Thats a strange one Paul, I bet that hertz you brain thinking about it, sorry couldn't resist.

 

[Paul.M]

Batteries in meters can give all sorts of obscure readings if they are drained or got a reactive/resistive contact point...

Get new batteries and buff up and respring the contact points..

Or your meter is knacked!

By that stage the MFT had worked over time so the batteries getting charged every ten minuets may have been the issue. Been back today, checked and re-terminated 3 sockets and everything checks out fine.

Out of interest which meter are you using? Don't think I have one that shows the frequency

Metral MI 3000, 3 years old. Put it on Volts setting.

So both of your meters showed the same 65Hz?

I'm presuming this house has a DNO supply?

If the meters are in fact correct, it's most likely that something connected to the RFC is generating 'noise' and that is fooling your meter. I can't see it being a DNO issue as those Hz figures would mean real trouble.

Edit: just to add, most MFT's range for measuring frequency is 45 - 65Hz

Both meters have a range of 45-65 Hz. It could have been the batteries or noise from something else in the house. Incoming supply tested at the same time showed 50Hz.

If meter checks out and its DNO supply then it would all point to harmonics or similar noise generated by a local business or possible if you have a large amount of electronic driven devices throughout all the house ..like led lighting....

I get this issue with my meters on machinery sometimes with harmonics been the culprit but never seen it domestic.

With the multiple faults, loose connection and dying batteries, it all makes sense. It was harder than the 2391 exam lol.

Maybe the loose termination was causing the weird reading.

Phil took a pic of the readings (my phone is still broke, need to fix that) I'll ask him to send it over and post it up.

Thats a strange one Paul, I bet that hertz you brain thinking about it, sorry couldn't resist.

:rofl: Yes it did Pete lol. Soon as one fault were found and fixed, another 2 faults popped up due to all the reverse polarity. Every socket checked, random spurs and hidden sockets. Great fun for a Sunday afternoon & evening.

 

[Knobhead]

There’s a gospel choir singing near by.

On the subject of frequency Dynamic Demand