3 phase domestic installation issues

[Karl Atkins]

Hi, I have been out to a property 3 times in the past week to a country pile with a 3 phase supply that keeps blowing it's 100amp distributor fuse.

The property has a pool house, a large garage with power, stables with power and a wooden annex type space also with power.

I have taken off every accessory in this huge place and can't find any obvious issues.

At the board I have measured a PFC of 1.19 kA and a PSCC of similar.

Nothing trips in the board when the dist fuse goes, I've not done a lot of work with 3 phase so unsure where to go from here.

Any advice much appreciated.

 

[Dillb]

I would be lookimg at fitting a power analyser, then reading the data from that, which should help you find the issue.

 

[Baker1988]

It sounds like the property has a high demand and may be useing more that 100A which is causeing the fuse to overload and blow, might want to get a clamp meter and check how many amps it is pulling.

 

[Des 56]

If they are using the 3 phases,check the balance

 

[dmxtothemax]

Sit down with the customer, try to analyze the situation,
Try to establish a pattern to it,
When does it blow ? What time of day or night ?
What is likely in use ? What was recently turned on ?
Don't forget automatically controlled loads too,
Like pumps and water heaters.

 

[telectrix]

you have 3 DNO fuses. is it the same phase that blows each time?

 

[Pete999]

you have 3 DNO fuses. is it the same phase that blows each time?

What he said^^^^^^^^^^^^^^^^^^^

 

[Karl Atkins]

you have 3 DNO fuses. is it the same phase that blows each time?

Yes same one every time, this is the board, as you can see pretty busy in there.

 

[davesparks]

Why have you taken off every accessory? Was that a random attempt at finding something by guesswork?

Do you carry out any testing or approach this in a logical manner?

 

[Pete999]

Why have you taken off every accessory? Was that a random attempt at finding something by guesswork?

Do you carry out any testing or approach this in a logical manner?

What Dave said

 

[Karl Atkins]

Why have you taken off every accessory? Was that a random attempt at finding something by guesswork?

Do you carry out any testing or approach this in a logical manner?

Evidently otherwise I wouldn't have been able to post the PFC and pssc. Do you have anything constructive to add such as the logical approach you would take?

 

[streamer]

It is unlikely that any accessory is causing a main fuse to blow, more likely to be an overload. Has anything been added recently?

 

[Karl Atkins]

It is unlikely that any accessory is causing a main fuse to blow, more likely to be an overload. Has anything been added recently?

They say not but then having said that I found a whole floor via the loft they hadn't even mentioned to me! Everything is in old colours except for 2 circuits, 1 of which is lighting and the other I'm not sure at this stage as it's not labeled, hence one of the reasons for looking at all accessories.

 

[davesparks]

Evidently otherwise I wouldn't have been able to post the PFC and pssc. Do you have anything constructive to add such as the logical approach you would take?

The logical approach of take is to think about what might cause a cutout fuse to blow without any mcb operating.
So either a fault between the cutout and the DB, am overload, or loose connections/overheating of the cutout.
Therefore randomly removing accessories is a waste of time and the customers money.

Why measure the PFC and PSCC? Did you carry out any other tests?

 

[Andy78]

Taken off all accessories in a place like that ? That would take me a week I reckon. Wouldn't even consider that in the event of a phase loss.

Overload would be my first thought at that place and I would check the load balancing and take some measurements.

What bearing do old coloured cables have on this ?