three phase board separation

[Vinnie2020]

hello everyone, I have a little problem. I've got a three phase board, it has the three phase sauna, one phase lighting and sockets connected to it. The problem i am facing right now. This is a comercial unit. So the problem is that the sauna makes the RCD trip every so often. And the board is protected by only1 RCD as a main switch. So when RCD trips the whole lighting and other circuits will be disconnected. This is causing a lot of hassle for the customer. And he's wondering if there is anything to do, add additional RCD or do something else without spending a fortune on this.
I have attached a photo so you could better understand what I mean

 

[davesparks]

And he's wondering if there is anything to do, add additional RCD or do something else without spending a fortune on this

That depends on what the customer considers to be a fortune, some people would consider a £100 solution to be a fortune whilst others would be happy to pay £1k/£1.5k to replace the DB with one which would better suit the requirements.

What does, or does not, actually require RCD protection in this installation?
How many circuits are there in total?

 

[James]

I would start by looking into WHY the rcd is tripping.

it would be better to find a potential fault that is developing than find a way to avoid it tripping.

 

[Vinnie2020]

I would start by looking into WHY the rcd is tripping.

it would be better to find a potential fault that is developing than find a way to avoid it tripping.

RCD is tripping when people pour too much water on the sauna stones. And that's for protection obviously. So I qas thinking if I could separate sauna circuit and the rest of premises, so if the sauja trips, it wouldn't take the power out in the whole board.

 

[westward10]

What make and type is the board as you may be able to replace the main switch, fit rcbos for the single phase circuits and a separate rcd for the sauna but as @James says solving the tripping issue is what you should be looking at.

 

[davesparks]

RCD is tripping when people pour too much water on the sauna stones. And that's for protection obviously. So I qas thinking if I could separate sauna circuit and the rest of premises, so if the sauja trips, it wouldn't take the power out in the whole board.

Then there is clearly a potentially dangerous fault with the sauna which needs fixing.

 

[pc1966]

Is the main board RCD at 30mA type? They are prone to tripping on cookers, etc, with a small amount of damp absorbed by the element so it would not be very surprising if they go on a sauna!

 

[Vinnie2020]

Then there is clearly a potentially dangerous fault with the sauna which needs fixing.

Thank you

Is the main board RCD at 30mA type? They are prone to tripping on cookers, etc, with a small amount of damp absorbed by the element so it would not be very surprising if they go on a sauna!

On the RCD it says 100A 3P

 

[pc1966]

On the RCD it says 100A 3P

It should also say the trip current (30mA, 100mA, 300mA typically). That photo is not detailed enough to see that.

 

[Vinnie2020]

It should also say the trip current (30mA, 100mA, 300mA typically). That photo is not detailed enough to see that.

I'll take a new photo tomorrow.

Thank you for your help

 

[davesparks]

It should also say the trip current (30mA, 100mA, 300mA typically). That photo is not detailed enough to see that.

It's 30mA, if you zoom in a bit you can see it.

 

[pc1966]

It's 30mA, if you zoom in a bit you can see it.

OK, that sort of confirms it.

The best suggestion is from @westward10 and as it looks like a Hager board you can probably get RCBO for the single phase circuits easily enough. However, I'm not sure you will find a RCBO to replace the 3-pole MCB in that board (and no space for another pole beside it) so your best/cheapest option might be:

1. Replace the RCD incomer with a switch (4P matches, but 3P might be fine).
2. Replace the single pole MCBs with RCBOs for all circuits needing that protection (sockets, lights, etc)
3. Put the RCD incomer from (1) in to a "garage CU" enclosure to provide separate protection for the 3-phase supply to the sauna.

Maybe others will have better ideas?

It might be worth inquiring of the sauna company what sort of RCD protection the recommend, as 30mA might be less than normal for that sot of load (assuming cable route does not require it).

 

[Vinnie2020]

OK, that sort of confirms it.

The best suggestion is from @westward10 and as it looks like a Hager board you can probably get RCBO for the single phase circuits easily enough. However, I'm not sure you will find a RCBO to replace the 3-pole MCB in that board (and no space for another pole beside it) so your best/cheapest option might be:

1. Replace the RCD incomer with a switch (4P matches, but 3P might be fine).
2. Replace the single pole MCBs with RCBOs for all circuits needing that protection (sockets, lights, etc)
3. Put the RCD incomer from (1) in to a "garage CU" enclosure to provide separate protection for the 3-phase supply to the sauna.

Maybe others will have better ideas?

It might be worth inquiring of the sauna company what sort of RCD protection the recommend, as 30mA might be less than normal for that sot of load (assuming cable route does not require it).

Thank you very much for your answers. That helps a lot to understand which is the best option. And if anyone else has any other options i would like to hear them please.

 

[westward10]

This is what you need to replace the rcd switch.

JK11004S - Hager 100A 4 Pole Mains Switch Incomer Kit, JK11004S Four Pole Switch Disconnector / JK1 Isolator Kit

Buy this Hager Hager 100A 4 Pole Mains Switch Incomer Kit, JK11004S Four Pole Switch Disconnector / JK1 Isolator Kit JK11004S online from Sparks Direct at our low price of £53.87. Archway, London UK.

www.sparksdirect.co.uk

 

[Vinnie2020]

This is what you need to replace the rcd switch.

JK11004S - Hager 100A 4 Pole Mains Switch Incomer Kit, JK11004S Four Pole Switch Disconnector / JK1 Isolator Kit

Buy this Hager Hager 100A 4 Pole Mains Switch Incomer Kit, JK11004S Four Pole Switch Disconnector / JK1 Isolator Kit JK11004S online from Sparks Direct at our low price of £53.87. Archway, London UK.

www.sparksdirect.co.uk

So I have to replace all mcb's to rcbo's and replace rcd to this switch? What about the 3P mcb?

 

[pc1966]

This is what you need to replace the rcd switch.

That is a good price. I was going to say you can probably buy just the switch on its own, but depending on your local trade outlet stock/staff levels, that might be the best option.

 

[davesparks]

Maybe others will have better ideas?

Yeah, my idea would be to find the fault that causes it to trip when water is poured on the stones in the sauna. This sounds like a definite link has been made between this action and tbe tripping of the RCD, so it needs to be investigated.

 

[pc1966]

Yeah, my idea would be to find the fault that causes it to trip when water is poured on the stones in the sauna. This sounds like a definite link has been made between this action and the tripping of the RCD, so it needs to be investigated.

Yes, a couple of things to find out, such as did it always do this? (i.e. is a 30mA trip too low for that sort of installation) or has something changed.

It might not be the actual sauna heater of course, it could be that a light in the sauna is letting steam in and causing the earth leak. Maybe someone put in a replacement without suitable IP ration, or maybe it has special seals around them that have degraded with time, etc.?

That is the problem with a single RCB and intermittent trip - they might find it is actually a light circuit or similar that is causing it to trip.

Maybe @Vinnie2020 can get them to run it and make it trip then quicky isolate all the MCBs and see if an insulation tests reveals a leaky circuit before it dries out.