Strange power Trip

[nellymcl]

So we have been coming home to find occassionally that the power has tripped.

We have now narrowed this down to receiving a phone call. Yes i know that sounds strange but today the power tripped as soon as i rang the house phone.

Not all the time but seems to be just during the day occassionally.

Any thoughts?

 

[Iggifer]

What kind of phone do you have? One with a mains supply or a standard phone that just plugs into the jack?

 

[deadshort]

I think it's just a coincidence. The telephone line does not, or should not be connected to mains wiring.
Post a pic on your consumer unit (fuse box) please.

Thanks,

DS

 

[JohnD]

The incoming phone line has an earth IIRC on the armour, that is not supposed to be connected to the electrical earth of the house. I once connected mine to the metal back-box after redecorating, and BT flagged up a fault during automated testing, send a man who disconnected it and explained it should be isolated. I have an idea I found the armour twisted into a pigtail and taped up loose, which would normally be poor practice.

There was no G&Y connection, it was just a metal box in a dense concrete block wall.

Any chance of something like that?

 

[bernardgreen]

The incoming phone line has an earth IIRC on the armour,

A phone line does not have an Earth, neither do domestic phone lines have metallic armour. Some aerial ( overhead ) drop cables have three ( or 5 ) strain wires which are steel and have no electrical function. Most often these have a yellow sleeve and may be mistaken to be an Earth conductor. They should be not connected to anything.

It is almost 99.99 % certain to be impossible for an incoming phone call to trip a mains protection device.

There is a very slim chance that if the yellow strain wires were connected to the CPC of the mains wiring and the earth leakeage breaker was an old voltage operated VOLCB then voltage capacitively induced on the strain wires during ringing could be enough to raise the CPC voltage high enough to trip a VOLCB.

 

[securespark]

A phone line does not have an Earth

Not quite true. I have come across hundreds of phone lines with an earth wire attached to a nearby pipe.

My 1968-built house that I lived in before moving here had a subterranean armoured cable coming into the house. We had an issue with a crackling line and I suspected the joint box outside. When the engineer came to sort it, we chatted about phones and stuff and he mentioned the armour was grounded.

 

[bernardgreen]

An Earth is needed when

1) the line is a party line where two different subscribers share one line. The earth is used to inform the exchange which of the two subscribers wants to make a call. Pressing the "Call Exchange" button connects one side of the line pair to earth and this enables the exchange to identify which subscriber wants to use the line. For incoming calls ringing voltage is applied to one of the pair and Earth to select which phone bell rings.`

2) a private exchange uses Earthed A and / or Earthed B signalling to the exchange.

3) surge suppression / lightning arrestors are fitted to a line considered at high risk of lightning strikes or accidental contact with power lines.

 

[crystal ball]

Assuming it is an RCD tripping, when I get called to random tripping problems I check the fridge/freezer, shower and outside lights, the usual suspects IMHO

 

[ban-all-sheds]

Earthed phone line with a dodgy earth... dog tied up outside to the telegraph pole¹... TT supply, also with a flaky earth, earth rod next to telegraph pole... sorted.

¹ Why do we still call them that?

 

[nellymcl]

Ok it's been a while but we are seeing the issue again. In the afternoon, no one in, come home and the main rcd has tripped. How on earth (excuse the pun) do you figure out what's doing it!!

 

[333rocky333]

post a pic of this main rcd, if poss.
if your flush with cash it may be worth investing in single rcds for each circuit

 

[nellymcl]

Hi 333rocky333
I have put an image in my post. The main RCD is the RCCB in the middle.

 

[deadshort]

Mm, been there, done that, have the RCCB tested. I have replaced two on these Crabtree units due to nuisance tripping. Your electrician will have the equipment required to ramp test the RCCB.

Kind regards,

DS

 

[nellymcl]

Great. Thanks. I am getting in touch with a local electrician in the morning to come and check. Do i ask for ramp checks to be done?

 

[JohnW2]

Do i ask for ramp checks to be done?

You could, but one would hope that a competent electrician would not need to be asked/told!

I suppose that, pragmatically, if it appears that (s)he is not going to undertake such tests (or maybe not even test the RCD at all), you might want to 'mention it' to avoid wasting time!

Kind Regards, John