Hi guys,

I have a jacuzzi on my non-essential loads and since the solar system was installed it keeps tripping, the circuit breakers on its mini DB get hot and it trips, a 30amp switch also melted that the power flows through to get to the mini DB, anything come to mind that could cause this or is the solar just a coincidence and its something else wrong? 

It is a large load, its around 5kw with the motor and heater running 

Edited December 14, 20213 yr by MakoShark

Well if it is really only 5kW then the total amps should be around 5000/230 = ~22 Amps.  So theoretically it shouldn't be from overload.  But circuit breakers are thermal.  They have a bimetal (two metals) strip that heats up, the two metals respond different to the thermal expansion causing the whole thing to bend a specific way which then trips the breaker.  So some heat is expected

How did you measure 5kW?  Have you had a clamp meter around the wire to check the amount of amps?

Do you have an earth leakage on the hot tub?  Legally you MUST have an earth leakage on a hot tub, it is a wet zone.  It is highly unlikely that much current could be flowing into the earth but that is another possibility.  However if you have an earth leakage that wouldn't be what is happening.

Quote

a 30amp switch also melted

Is it maybe some kind of cheaper brand or something?  Circuit breaker shouldn't melt, the whole principle of operation is for it to get hot and then trip.

What wire thickness is running into the 30a breaker?

Did you double check that the wire is properly tightened into the circuit breaker?  Loose connections get super hot.

Edited December 14, 20213 yr by Gnome

22 hours ago, Gnome said:

Well if it is really only 5kW then the total amps should be around 5000/230 = ~22 Amps.  So theoretically it shouldn't be from overload.  But circuit breakers are thermal.  They have a bimetal (two metals) strip that heats up, the two metals respond different to the thermal expansion causing the whole thing to bend a specific way which then trips the breaker.  So some heat is expected

How did you measure 5kW?  Have you had a clamp meter around the wire to check the amount of amps?

Do you have an earth leakage on the hot tub?  Legally you MUST have an earth leakage on a hot tub, it is a wet zone.  It is highly unlikely that much current could be flowing into the earth but that is another possibility.  However if you have an earth leakage that wouldn't be what is happening.

Is it maybe some kind of cheaper brand or something?  Circuit breaker shouldn't melt, the whole principle of operation is for it to get hot and then trip.

What wire thickness is running into the 30a breaker?

Did you double check that the wire is properly tightened into the circuit breaker?  Loose connections get super hot.

Thanks for the reply:

How did you measure 5kW? - I can see on the inverter it draws 5000w, its a 4kw element and the motor draws about 1000w

Do you have an earth leakage on the hot tub? - Im not sure, there is a breaker in my main DB and a sub-DB where the mains \ jacuzzi heater on that trips and not the main DB breaker

Is it maybe some kind of cheaper brand or something? - It was a switch that was rated 30a that melted, it had been working like that for around a year since I purchased the property with no hassles, this only started after the essential loads change was made, after it melted I joined the cables as I dont need a switch there and thats when the breakers on the sub-DB started tripping but assume there was an issue to cause the switch to melt in the first place

What wire thickness is running into the 30a breaker? - Its pretty thick, I dont know the exact size though, it has around 5 individual strands of around 1mm id guess in each wire sheath

Did you double check that the wire is properly tightened into the circuit breaker? - I havnt but can check this 

Edited December 15, 20213 yr by MakoShark

On 2021/12/14 at 4:13 PM, Gnome said:

Well if it is really only 5kW then the total amps should be around 5000/230 = ~22 Amps.  So theoretically it shouldn't be from overload.  But circuit breakers are thermal.  They have a bimetal (two metals) strip that heats up, the two metals respond different to the thermal expansion causing the whole thing to bend a specific way which then trips the breaker.  So some heat is expected

You are perfectly right. At least that's the way it should be. However, I opened this South African breaker after it tripped several times without obvious reason. I have done this on various breakers in various countries. But on this one I cannot find/identify the bi-metal element, only the magnetic tripping coil. Can you help me?

and in tripped condition:

8 hours ago, Beat said:

You are perfectly right. At least that's the way it should be. However, I opened this South African breaker after it tripped several times without obvious reason. I have done this on various breakers in various countries. But on this one I cannot find/identify the bi-metal element, only the magnetic tripping coil. Can you help me?

 

and in tripped condition:

 

Yeah CBi call it "Hydraulic-Magnetic".  More info here: https://cbi-lowvoltage.co.za/content/hydraulic-magnetic-principles

Whether or not their claims are true is the question, since if it were truly thermally independent I don't get why other companies wouldn't use it.  There must be a drawback that makes other manufacturers use both approaches.  +their newer ranges always use the bi-metal + hydraulic so I think this is some SA company magic snake oil BS that they save money on.

Edited January 5, 20223 yr by Gnome

30 minutes ago, Gnome said:

Yeah CBi call it "Hydraulic-Magnetic".  More info here: https://cbi-lowvoltage.co.za/content/hydraulic-magnetic-principles

Whether or not their claims are true is the question, since if it were truly thermally independent I don't get why other companies wouldn't use it.  There must be a drawback that makes other manufacturers use both approaches.

Thank you Gnome for the info. We never stop learning.

The reason other manufacturer do not use this principle might be that it requires a relatively high precision (expensive) manufacturing process. And that's where the performance inaccuracy comes in.

12 hours ago, Gnome said:

if it were truly thermally independent I don't get why other companies wouldn't use it.

CBI: "Features

• Always holds 100% rated current independent of ambient temperature"

In my opinion, this is not an asset but a disadvantage. Why?

The idea behind the fuse and the bi-metal triggered breaker is to simulate with exaggeration the temperature behavior of the installation wiring. To blow or trip before it reaches temperature that could melt the insulation.  Current ratings of wire sections are valid at 20 to 25°C ambient. If ambient is significantly higher the cooling effect is lesser, the current carrying wire heats up more. The protective device should take this in account, assuming it is at same ambient as the wiring. Therefore the device affected by ambient temperature, like bi-metal, is a safer protection.

On 2022/01/05 at 11:34 PM, Beat said:

Thank you Gnome for the info. We never stop learning.

The reason other manufacturer do not use this principle might be that it requires a relatively high precision (expensive) manufacturing process. And that's where the performance inaccuracy comes in.

Let's say I have my doubts because the newer and higher kA rated CBi circuit breakers also use bi-metal strips.  I suspect there are reliability, consistency or tolerance issues with it.  Also the SA forum for electricity doesn't speak very highly of CBi (quality wise).  I wouldn't be surprised if that model was created during apartheid and manufactured that way as a cost saving measure or they couldn't even get the parts for the bi-metal strip (SA being isolated).

All manufacturers of circuit breakers use the magnetic disconnect for surge disconnect so adding a damper is a relatively small extra cost, were it superior.

Overall I like Schneider Electric the most.  They even offer 10kA + overload + RCD in a single DIN package.  Pretty demanding specifications for such a tiny package.

 

On 2022/01/06 at 11:34 AM, Beat said:

CBI: "Features

• Always holds 100% rated current independent of ambient temperature"

In my opinion, this is not an asset but a disadvantage. Why?

The idea behind the fuse and the bi-metal triggered breaker is to simulate with exaggeration the temperature behavior of the installation wiring. To blow or trip before it reaches temperature that could melt the insulation.  Current ratings of wire sections are valid at 20 to 25°C ambient. If ambient is significantly higher the cooling effect is lesser, the current carrying wire heats up more. The protective device should take this in account, assuming it is at same ambient as the wiring. Therefore the device affected by ambient temperature, like bi-metal, is a safer protection.

Yep I also thought might be one of the reasons, but the reality is that roof spaces require derating which wouldn't match the wiring anyway.  (I have yet to see a modern install where they install > 2.5mm in roof spaces, yet the still use 20A breakers 🤷‍♂️).

But yeah for sure isn't helping the situation in hot climates.

Edited January 7, 20223 yr by Gnome

To add my 2-cents, just make sure also that all your piping around the Jacuzzi are bonded and earthed to a earth rod in the ground outside. I'm not sure about the codes in SA, but here in Zimbabwe it's mandatory that all pipes are earthed and bonded, it's really a safety issue, not very sure how this would help with earth leakages, but it may save your life in the event of electrical faults, especially near a water body. You can get a copper strip from your local hardware as well as a 1metre earth rod and earth wire and a plumber will be able to make sure all your pipes are bonded, especially those on the hot water copper pipes. And yes I would agree with the comments about getting a good and high quality circuit breaker, it will definitely save you headaches and potentially is life-saving.

15 hours ago, Gnome said:

Overall I like Schneider Electric the most.

Yes I like them too. As a matter of facts, they got such good reputation that a Chinese manufacturer found it worthwhile to produce fake Schneider breakers. Verify what you buy.

15 hours ago, Gnome said:

but the reality is that roof spaces require derating which wouldn't match the wiring anyway.  (I have to see a modern install where they install > 2.5mm in roof spaces, yet the still use 20A breakers 🤷‍♂️).

You are right. I'm surprised anyway that SA rates 2.5mm² wire for 20A. In Europe its rated only 16A.

In general I'm very disappointed about the quality of SA electrical installer. But the worst I have seen is in picture below. Taken right after an inspector has issued the COC!

Note wiring to Neutral on leftmost 10A breakers, besides other wiring errors.

What is the power factor of your pump?

1kw/230vac is not always 4,5 amp. (0,96 vs. 0,25 cos phi)

 

 

Does it make sense?

I ended up sorting this out by adding a slightly bigger breaker, went from a 25a to a 32a...maybe the original was on its way out.

As Murphey would have it... Now the spa leaks 🙄

On 2022/01/14 at 6:35 AM, MakoShark said:

I ended up sorting this out by adding a slightly bigger breaker, went from a 25a to a 32a...maybe the original was on its way out.

As Murphey would have it... Now the spa leaks 🙄

What size wire is beyond this breaker? The breaker protects the wire. Doesn't help the breaker is 32a if the wire is going to melt. 

On 2022/01/13 at 5:48 PM, Mauritius B said:

What is the power factor of your pump?

1kw/230vac is not always 4,5 amp. (0,96 vs. 0,25 cos phi)

 

 

Does it make sense?

I would be seriously impressed if you get a real-world load of 1kW that can do a 0.25 PF continuously...

2 hours ago, P1000 said:

I would be seriously impressed if you get a real-world load of 1kW that can do a 0.25 PF continuously...

Well, examples may not be always "real-world" ones. They are just simply used to clarify an idea.

That was the intention of this example, to highlight the fact that Makoshark is dealing with an inductive load and current may be higher than expected.

As the protection is tripping by overcurrent, the reactive component of the load might explain the issue and it was solved indeed by replacing the protection with a higher rating one.

On 2022/02/10 at 10:15 AM, Mauritius B said:

That was the intention of this example, to highlight the fact that Makoshark is dealing with an inductive load and current may be higher than expected.

As the protection is tripping by overcurrent, the reactive component of the load might explain the issue and it was solved indeed by replacing the protection with a higher rating one.

It could also be helped with a compensation capacitor in parallel with the inductive load. Size to be determined in function of the inductive load.

55 minutes ago, Beat said:

It could also be helped with a compensation capacitor in parallel with the inductive load. Size to be determined in function of the inductive load.

Of course.

Keeping the PF close to 1 is always the best solution.