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new_spark

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Hi

I apologise in advance for lack of knowledge i this subject as I only work in domestic, a mate owns a commercial gym and has a 6 Kw sauna heater which comprises of 3x 2Kw elements.

He asked me to look at it as he has fallen out with his normal electrician over prices, he told me that he has had a few problems with it in the past which is normally related to the elements failing.
The fault as described to me was that it just wasn't working.

I started at the board which is a 3 phase board, the sauna is on a single phase 40A RCBO, which was in the off position, after isolating the supply at the RCBO I traced the 10mm T+E to a 45A DP Switch which was checked and isolated.

I then dismantled the heater and checked continuity on all of the elements, all appeared to be working, then I traced the wiring back from the heater which is some type of heat flex it has 6 cores and earth and appeared to be 3 line conductors and 3 neutrals. I then followed the cable back to a IP enclosure which was on the side of the sauna in quite a humid area, the cover was off and I found the mess in the picture, no wonder the RCBO had tripped!

The contactor is a Moller Dil 1M, it appears to overheated on the neutral supply side which is fed in 10mm T+E going back to the 45A DP switch as mentioned earlier.

My questions are, why would the original installer have fitted a contactor, it's not high voltage switching and more importantly, why has it over heated? The cable sizes would all appear to be correct and judging by the heat damage the RCBO has only blown when the Neutral cable has burnt completely through and broken the link.

I have disconnected the entire supply from the board and removed the contactor, I've told him its beyond me and told him to get the yellow pages out!




[ElectriciansForums.net] 6Kw Sauna
 
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I would imagine the neutral was loose as Glen said, you'll find that 95 times out of an hundred it is always the neutral.

Also it's not high voltage why you fit the contactor, but an high load. As this box is fixed to the unit, was this not part of the manufacturers control system?

I would imagine that the switch which is double pole or even single pole is controlling the contactor coil, so it can switch all 3 elements on via this
 
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malcolmsanford said:
I would imagine the neutral was loose as Glen said, you'll find that 95 times out of an hundred it is always the neutral.

Also it's not high voltage why you fit the contactor, but an high load. As this is box is fixed to the unit, was this not part of the manufacturers control system?
I would imagine that the switch which is double pole or even single pole is controlling the contactor coil, so it can switch all 3 elements on via this
Click to expand...


Thanks for the reply, the smaller flex you see in the pic comes from the timer and is controlling the switching element of the contactor, you may be right in that it is part of the installation instructions but it looks a bit DIY to me the IP enclosure doesn't look big enough to house the contactor perhaps why the cover was off? I wouldn't have thought that the load, 26A, would be classed as a high load?
 
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must admit the wiring in the last pic doesnt look factory fitted.
What rating was the contactor ?
dont suppose it matters now , it needs replacing and he cable re-making off anyway.
 
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Loose neutral in on the contactor terminal inside on the bridge piece , and not on the cable terminal then , never the less thats a lose neutral .
It all looks good to me and factory standard , don't forget it is the thermostat that is switching the load so would you put that 26A straight through it or go through the contactor instead ?
If you go on the net , there are plenty of suppliers about for this sort of kit , i have just brought a new 8KW heater and remote controller like this to replace one on my own sauna , it was a Oceanic which seems to be good i also have a Oceanic steam generator in a shower in the same bathroom that has been going strong for several years now !
 
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dpelectricalltd said:
Loose neutral in on the contactor terminal inside on the bridge piece , and not on the cable terminal then , never the less thats a lose neutral .
It all looks good to me and factory standard , don't for get it is the thermostat that is switching the load so would you put that 26A straight through it or go through the contactor instead ?
If you go on the net , there are plenty of suppliers about for this sort of kit , i have just brought a new 8KW heater and remote controller like this to replace one on my own sauna , it was a Oceanic which seems to be good i also have a Oceanic steam generator in a shower in the same bathroom that has been going strong for several years now !
Click to expand...

Thanks for the reply, just had a good look at the contactor and the neutral grub screw does appear to have been loose as you have all said!

My only other concern is why is the CPC in the A2 terminal on the 2nd pic, shouldn't the A1 and A2 be line and neutral respectively?
 
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Think i need to trace the CPC back to see if its been used as a neutral and not sleeved correctly and connected to a neutral some where, forgot to mention that the smaller black flex powering the contactor which is a 3 core and earth with the CPC being in A2, is supplied from the timer which is connected to a separate single phase board to the main sauna heater, surely that shouldn't be so??
 
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In that case the control box should have a warning label to isolate at two points (and preferably identifying those two points). You could isolate the main 40A and still have a live coming in from the timer.

Personally I'd have fused down from the 40A to supply the timer. It could be included in the enclosure and a 4 core run to the timer (L,N,E & SL back).

You say the box is in a humid area, but what about the 45A switch? Is that the 'cooker' type or a rotary job or something else? And is that in the humid area?

Like the others said I'd suspect a loose connection (often a neutral) but it could be some of that humidity got into the enclosure and that wouldn't have helped. So you might need to replace the enclosure.
 
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