Intermittent Circuit Breaker Tripping

[Rolanda Woo]

So this problem has been ongoing for a few months and we couldn't sort it out. I'm trying here to see if any expert from this forum could shed some light on what possibly has been going wrong.

This particular breaker is the one for 4 led ceiling lights downstairs, 3 led spotlights in the bathroom and one extractor fan for the bathroom. The bathroom doesn't have a window as it's in the middle of the house. The extractor fan had been doing a fab job to keep the room mostly mould free by continuously running with its integrated humidity detector.

It started tripping randomly but infrequently in the beginning, but we were able to switch back on the power and the circuit didn't complain. After a while, it became more frequent and we tried to turn off the extractor fan, but it still didn't stop the problem reoccurring.

We then called an electrician company. Their engineer tested all and Sid he couldn't pin down the cause. I did particularly ask him if there's a chance to do with the wiring within the bathroom let humidity go in. He replied that he did check the wiring and confirmed it's intact. But he said only switch off the extractor fan wouldn't disconnect the system entirely. So we agreed that the next more reasonable action was to disconnect the extractor fan all together and see if we could rule it out.

Then in the following 2 weeks, the breaker didn't trip. (I had to use dehumidifier to extract the humidity in the bathroom during the time).

Two weeks after, we concluded the cause must have been the extractor fan and the electrician came to replace it with a new one.

Since then, there was no tripping for about a month and a half until a a couple of weeks ago. This time, it mostly happened at night when I only had the dishwasher, washing machine set on time to do their jobs. The breaker was also refusing to switch back on. We initially thought to try to remove the bulbs from the ceiling lights one at a time just to rule them out. It turned out it did work. But it didn't stop it happening again. So the cause was not the bulbs, even though whenever the breaker refused to turn back on, the first few time it worked if we remove a bulb. But by the end, nearly all bulbs were removed and the breaker still wouldn't turn back on.

We didn't intend to leave the problem forever. But with the experience the first time, we just don't know what to do anymore.

It appears very likely to do with the humidity in the bathroom, but the electrician first time concluded the wirings were intact and humidity shouldn't be the culprit.

We want to sort it out, but since the problem is intermittent, this makes it trickier for anyone who's been called over to look into it.

Can anyone here share some ideas as to what the possibilities are and what the next step should be please?

Thank you.

 

[roys]

What are the exact details of the breaker that trips? Is it an RCBO, RCD or MCB the details you supply will confirm.
Nothing to say you now have another fault or the breaker is knackered after all it’s previous trips.

 

[johnb2713]

Which circuit break is tripping is it an MCB or an RCD? Maybe send a photograph of the consumer unit with the breaker thats tripped.
Have you considered it maybe a faulty circuit breaker?

 

[Rolanda Woo]

One of these black breaker? Are they RCD?

 

[johnb2713]

They look like RCBO's which is good. Maybe the one for the fan and lights is a bit over sensitive / faulty?

 

[SPECIAL LOCATION]

Has the RCBO been tested to confirm it is operating correctly?

I would probably look for an equivalent rating of RCBO already in you CU that's working OK...

Make a temporary swap of the two circuits onto each others RCBO..
Then wait and see if the problem stays with the RCBO or follows the wiring onto the alternate RCBO?

 

[johnb2713]

What he said ^^^^

 

[UNG]

From the OP's description this sounds like the fan is on the end of a long duct and the water vapour that is condensing in the duct is running back into the fan, I have also seen one fan where rain and strong winds driving in the "right" direction forced water down a 3m solid duct and into the ceiling mounted fan
It is usually ceiling mounted fans that give the most problems as the fan cover can act like a bowl holding the water until it builds up and it reaches the power connections and control board
Simple fixes can be ensuring the duct is installed so it falls (slopes) to the outside wall, if there is a drain close by a condensation trap could be installed to catch any condensate and drain it away

Problems like this can also be heavily influenced by the prevailing weather conditions and external temperatures so can be very intermittant or more prevalent at certain times of the year

Another one to look at is the fan performance figures which are generally based on a short duct length and when substantially longer ducts and especially the flexible type are used the performance (flow rate) can degrade quite significantly even on a straight duct throw in a bend or two and it's even worse this makes most of the available 4" / 100mm fans on the market unsuitable for the application as they can't achieve the air changes per hour that are required to meet the building regs

So I would check the mechanical side of the installation is upto spec before doing anything else

 

[mort2376]

Use of insulated ducting can also help with the moisture in the duct issue.

 

[SPECIAL LOCATION]

The bathroom doesn't have a window as it's in the middle of the house.

You didn't say if this fan is a ceiling fan or an in-line fan part way along the duct?

From the OP's description this sounds like the fan is on the end of a long duct and the water vapour that is condensing in the duct is running back into the fan, I have also seen one fan where rain and strong winds driving in the "right" direction forced water down a 3m solid duct and into the ceiling mounted fan...... etc.. etc...

Good observations by UNG...

You need to consider the physical fan arrangements not just wiring connections etc.

As longer duct lengths typically need fans that can move a higher volume of air to reduce build up of condensation problems, which can in poorly designed systems allow moisture to penetrate parts they should not!

Most ceiling, (and wall), fans are designed for short duct lengths.

But longer duct lengths are very prone to condensation where warm moist air inside a duct is passing through a cooler ceiling/loft void with insufficient air flow per minute.