New 3-phase installation with 3-phase heater

[campyk]

Hi guys!

I've got a few questions regarding a new 3-phase system setup if you don't mind.

 

Edit: I've just posted and see that there are too many questions and different topics. Should I divide it into several threads?

 

1. We plan to get an ABB distribution board
https://shop.bangkokab.com/products/DB48MC200

And in specs it says:
Rated current:
(busbar) 200 A
(outgoing) 100 A
How much power you can pull out of this board?
Is that amount per phase? As a breaker size of 200A? Which corresponds to 200+200+200? Or do I get it wrong?
Outgoing 100A per circuit, per phase or something else?

In other words, will it be enough for a 3 phase 30(100) connection?

 

2. We are going to install a 3-phase heater from Stiebel Eltron. It is 13kw - just below 20 Amp heater. (See wiring and specs attached)

In the manual it says that the recommended fuse/breaker is 20 Amp.
Our electrician has ordered (from us as we buy stuff by ourselves) a 10mm² copper wire.
His reasoning is: 3 phase wires should be thick, because 13kw is a lot. And he is scared that wires are going to burn.
In my understanding 20 Amp 3 phase is still 20 Amp and could use 2.5 or 4mm² wire. Otherwise why would manufacturer recommend 20Amp breaker? To protect what?
I've even asked an electrical shop owner about this and his recommendation was the same: 10mm².
Am I wrong here? What is the correct approach in sizing a 3 phase resistive appliance's wire?

 

3. Regarding the same heater. We've been told by service hotline support that it can work on 2 phases in the case of 1 phase failure but will deliver lower heating output.
In the case of 3 phases the current cancels out and doesn't need a neutral. But what happens with 2 phases that are 120 degrees apart? Wiring of the heater is 4 poles: 3 phases + ground. Would there be leftover current? Where would it go? Would it be safe to use the heater in this situation? Would it trip the RCBO?

 

4. Your opinion on value-oriented brands of rcd, spd etc.
Are cheaper brands worth buying? Do they work according to specs and are they reliable?
Talking about something like this:
https://shopee.co.th/product/143634292/6053181212?smtt=0.202956878-1666633208.9
Or this
https://shopee.co.th/product/303694660/6857925121?smtt=0.202956878-1666636473.9
Safe-T-Cut? CCS? Suntree? Nano?
They cost around 1000 baht for 3 phase SPD while ABB's cost 10000. ???? What's the difference if the specs are same?

 

5. Main breaker 3 or 4 poles?

 

6. How Thais call TNC-S system? Is it a standard system now or something new to Thailand?

 

Really sorry for the barrage of questions. I would really love to hear some suggestions though ????
Will be glad to thank contributors with a beer or two or another drink ????

Edited October 25, 2022 by campyk

[Crossy]

1. The current ratings of your board are per-phase. Do note that the actual rating of the main incoming MCCB will be determined by the size of the supply being provided by MEA/PEA.

 

2. I would wire the heater in 4mm² on a 32A 3-phase breaker. A 20A is just a bit close when the heater is running at full power.

 

3. There isn't any "leftover current", what you will end up with is one element running at full power with two others running in series at about 25% full power each.

 

4. I would always buy branded MCCB/MCB for the main supply, similarly for your RCD/RCBOs.

SPDs tend to be expensive from the brand names and you don't necessarily get value for money.

 

5. Main breaker will be 3-pole, you don't usually switch the neutral on a 3-phase install.

 

6. It's called TNC-S (MEN) as the neutral is grounded on every 3rd pole as well as by the rod on your property. It's a standard install here.

 

[campyk]

2 hours ago, Crossy said:

1. The current ratings of your board are per-phase. Do note that the actual rating of the main incoming MCCB will be determined by the size of the supply being provided by MEA/PEA.

 

2. I would wire the heater in 4mm² on a 32A 3-phase breaker. A 20A is just a bit close when the heater is running at full power.

 

3. There isn't any "leftover current", what you will end up with is one element running at full power with two others running in series at about 25% full power each.

 

4. I would always buy branded MCCB/MCB for the main supply, similarly for your RCD/RCBOs.

SPDs tend to be expensive from the brand names and you don't necessarily get value for money.

 

5. Main breaker will be 3-pole, you don't usually switch the neutral on a 3-phase install.

 

6. It's called TNC-S (MEN) as the neutral is grounded on every 3rd pole as well as by the rod on your property. It's a standard install here.

 

Thanks a lot! Everything is much clearer now.

I just got a reply from ABB seller from bangkokab.com and it seems these boards only support Formula A1 range devices which is very limited and exclusive of 4-pole RCBO's, SPD's and any other line-up devices, not to mention  any other third-party devices like relays, timers, etc.

Is it possible that board with a din rail mounting would be butchered to such a degree? Is that because of unremovable (non-standard?) connectors?

 

3. There isn't any "leftover current", what you will end up with is one element running at full power with two others running in series at about 25% full power each.

 

The wiring scheme looks like there are 3 separate 1-phase heating elements. If it's correct, what type of dedicated RCBO would I need to use here?

[Crossy]

I would certainly avoid any boards the need "special" devices.

 

The Schneider/Square-D boards, although not DIN mount, have the advantage of being readily available and being able to accept both 3-phase and single-phase MCBs and RCBOs in any position. There are other manufacturers of plug-in MCB/RCBOs that fit too.

 

I wouldn't go with Schneider surge protection (it's crazy $$$), definitely add a small DIN box and use the lower cost option.

 

It may also be worth considering using sub-boards rather than packing everything into one central board. Of course, that depends upon the layout of the property, but any place that needs a >60kW supply is going to be pretty substantial.

 

It may also be worth looking at your hot water plans, is one big heater or several smaller (single-phase) heaters more practical?

 

Also, if you really need a massive heater (the biggest single-phase unit I've seen is 8kW) then do look at gas heaters, they are low cost and really blast the heat without killing your power supply.

 

 

[carlyai]

For the 3 phase water heater, should you use a 3 phase RCB, or wouldn't it work in this application as there is no dedicated neutral to the heater? It seems from the wiring diagram that the active to one end of the heater returns via the earth, which is connected at the CU to the neutral. Maybe reading the cct wrong.

So the question is  should you use a 3 phase RCB?

[Crossy]

32 minutes ago, carlyai said:

For the 3 phase water heater, should you use a 3 phase RCB, or wouldn't it work in this application as there is no dedicated neutral to the heater? It seems from the wiring diagram that the active to one end of the heater returns via the earth, which is connected at the CU to the neutral. Maybe reading the cct wrong.

So the question is  should you use a 3 phase RCB?

 

That heater does look a bit odd, but it's certainly not earth return on one element. Just how the 3 incoming phases map to what appears to be 4 elements in a star arrangement is unknown.

 

It will certainly need a 3-phase RCBO which could be 3 or 4 wire (if it has a neutral just connect to the neutral bar so the Test button works).

 

I'm still not convinced that a 3-phase heater is actually needed, particularly on such a massive supply.

 

EDIT A quick scan of the available plug-on accessories doesn't reveal a 3-phase RCBO, which surprises me somewhat.

 

[carlyai]

21 hours ago, Crossy said:

 

That heater does look a bit odd, but it's certainly not earth return on one element. Just how the 3 incoming phases map to what appears to be 4 elements in a star arrangement is unknown.

 

It will certainly need a 3-phase RCBO which could be 3 or 4 wire (if it has a neutral just connect to the neutral bar so the Test button works).

 

I'm still not convinced that a 3-phase heater is actually needed, particularly on such a massive supply.

 

EDIT A quick scan of the available plug-on accessories doesn't reveal a 3-phase RCBO, which surprises me somewhat.

 

I think the heater is wired in a Wye configuration. I have found a couple of 3 phase, 3 pole RCBO's with Neutral connections.

I presume the neutral would go from the junction of the Wye back to the CU neutral bus.

 

3 phase, 3 pole RCBO, something like this in the picture?

 

[SomchaiDIY]

23 hours ago, Crossy said:

That heater does look a bit odd, but it's certainly not earth return on one element. Just how the 3 incoming phases map to what appears to be 4 elements in a star arrangement is unknown.

possible steibel use same heat core for low and high power model

 

high power model have 4 element in the star low power have 3 element in the star

 

here is circuit for high power model

 

[carlyai]

2 hours ago, carlyai said:

I think the heater is wired in a Wye configuration. I have found a couple of 3 phase, 3 pole RCBO's with Neutral connections.

I presume the neutral would go from the junction of the Wye back to the CU neutral bus.

 

3 phase, 3 pole RCBO, something like this in the picture?

 

Which is what @Crossy said yesterday. 

Sorry for that. ????

[bluejets]

For final sub-circuit wiring size one needs to know both the current draw and the length of the run from the main board.

As quoted above, 4sqmm may be sufficient up to approx. 25 metres.(assuming copper)

Installs also would normally require a lockable isolator, (lock in off position naturally) in this instance 3 phase, located right beside the heater unit for maintenance purposes.

Edited October 27, 2022 by bluejets

[carlyai]

55 minutes ago, bluejets said:

For final sub-circuit wiring size one needs to know both the current draw and the length of the run from the main board.

As quoted above, 4sqmm may be sufficient up to approx. 25 metres.(assuming copper)

Installs also would normally require a lockable isolator, (lock in off position naturally) in this instance 3 phase, located right beside the heater unit for maintenance purposes.

Thanks. In my case the multi-point heaters are in a domestic house. 

Heaters are fed from the house CU, which has a lockable door. The heaters are mounted under the kitchen bench and under the laungry bench. Next to each heater is another 3 phase breaker. I don't have an actual lockable isolator next to the heater unit.

I read that now (in Aus) each sub-circuit final must have a RCB/RCBO. Does that mean each seperate feed from the CU must have a RCBO?  Eg.  Stove, kitchen.

[carlyai]

I just had a phone call from Steibel Thailand. Previously I'd made enquiries about installing an RCBO on the 3 phase water heaters. 

They ensured me that if the heater has a ground wire, it doesn't need an RCBO.

I asked them to check again with the technical department and they said 100% sure.

So does the water heater need an RCBO?

[Crossy]

1 hour ago, carlyai said:

So does the water heater need an RCBO?

 

That would depend upon how long you want to live for in the event of a L-E fault.

 

In reality, with a properly implemented TNC-S (MEN) system you could probably get away without. But ...

 

[carlyai]

12 minutes ago, Crossy said:

 

That would depend upon how long you want to live for in the event of a L-E fault.

 

In reality, with a properly implemented TNC-S (MEN) system you could probably get away without. But ...

 

That's what I thought.

I know it happens, but It's pretty disturbing when the company technical division gives very bad advice. 

Makes you wonder if any water heaters of this brand have RCBO protection.

If you can just bear with me a little longer. ????

The 3 phase water heater is earthed, about 3 m away from the shower, connected by PVC pipes to the metal shower taps, set in bricks and mortar, not physically tied back to the earth system. The water is very pure (lots of filtering). I have an MEM system.

Just say one element developed a short to ground. How's them there deadly electrons going to get to me, enough to ruin my shower? (Go easy, it's Friday).

[SomchaiDIY]

2 hours ago, carlyai said:

I just had a phone call from Steibel Thailand. Previously I'd made enquiries about installing an RCBO on the 3 phase water heaters. 

They ensured me that if the heater has a ground wire, it doesn't need an RCBO.

I asked them to check again with the technical department and they said 100% sure.

So does the water heater need an RCBO?

many steibel 3 phase heater have bare type heat element

 

possible some country have the special safety regulation require for this type system

 

i think for sure good ground is important and best include some earth leak protection at supply

 

 

some information about bare wire heater from stiebel company

The water in an instantaneous water heater is heated either by a tubular heater system or a bare wire heating system.
Most STIEBEL ELTRON instantaneous water heaters heat water using bare wire heating elements. The live heating conductors are located directly in the water to be heated. The bare wire heater spirals are set into a pressure-tested insulating block. Pipes in the insulating block house the heater spirals. The insulation resistance is assured by upstream and downstream devices, even if the earth conductor is interrupted. The insulation resistance depends in part on the properties of the water flowing through. For this reason, the electrical resistance and conductivity of the water at the installation location must be taken  into consideration. Bare wire heating elements are also especially suitable for use in hard water. The very small amount of water inside the appliance and the low-mass heating system mean there is hardly any post-heating after the appliance has been switched off – an important factor in the reduction of scale build-up.

 

[carlyai]

2 hours ago, SomchaiDIY said:

many steibel 3 phase heater have bare type heat element

 

possible some country have the special safety regulation require for this type system

 

i think for sure good ground is important and best include some earth leak protection at supply

 

 

some information about bare wire heater from stiebel company

The water in an instantaneous water heater is heated either by a tubular heater system or a bare wire heating system.
Most STIEBEL ELTRON instantaneous water heaters heat water using bare wire heating elements. The live heating conductors are located directly in the water to be heated. The bare wire heater spirals are set into a pressure-tested insulating block. Pipes in the insulating block house the heater spirals. The insulation resistance is assured by upstream and downstream devices, even if the earth conductor is interrupted. The insulation resistance depends in part on the properties of the water flowing through. For this reason, the electrical resistance and conductivity of the water at the installation location must be taken  into consideration. Bare wire heating elements are also especially suitable for use in hard water. The very small amount of water inside the appliance and the low-mass heating system mean there is hardly any post-heating after the appliance has been switched off – an important factor in the reduction of scale build-up.

 

Thank you for this detailed response and the unit sounds safe.

I got a quick phone call response from Thailand but no response from Germany.

Maybe some of us Falangs get a bit carried away with safety, but it is hammered into us when we did our tech training.

When I started on my 5 year Telecommunications traineeship in 1963, some trainees were cutting their hand, so eventually they banned the use of knifes. Also later on a couple of trainees were electrocuted working on live switchboards, so they banned us working on power. And so it goes. ????

 

[carlyai]

Reply from the company in Germany.

'You cannot connect RCBO for Steibel eltron 3 phase water heater. As they require wiring of 3 phase + Earth. RCBO will not operate since there is no Neutral connection. Would Suggest connect TP MCB for protection. 

Ideally we suggest individual MCB's to be fitted in the Main DB box for respective equipment and an Isolator switch be installed for maintenance inline near to the equipment.'

[Crossy]

19 minutes ago, carlyai said:

Reply from the company in Germany.

'You cannot connect RCBO for Steibel eltron 3 phase water heater. As they require wiring of 3 phase + Earth. RCBO will not operate since there is no Neutral connection. Would Suggest connect TP MCB for protection. 

Ideally we suggest individual MCB's to be fitted in the Main DB box for respective equipment and an Isolator switch be installed for maintenance inline near to the equipment.'

 

Schneider seem to disagree. https://www.se.com/ng/en/faqs/FA282621/

 

Note that if there is a neutral available on the supply side, just connect it to the N terminal of the RCD and it will work fine.

 

Connnection in 3P RCCB.pdf

[bluejets]

18 hours ago, SomchaiDIY said:

The water in an instantaneous water heater is heated either by a tubular heater system or a bare wire heating system.
Most STIEBEL ELTRON instantaneous water heaters heat water using bare wire heating elements. The live heating conductors are located directly in the water to be heated. The bare wire heater spirals are set into a pressure-tested insulating block. Pipes in the insulating block house the heater spirals. The insulation resistance is assured by upstream and downstream devices, even if the earth conductor is interrupted. The insulation resistance depends in part on the properties of the water flowing through. For this reason, the electrical resistance and conductivity of the water at the installation location must be taken  into consideration. Bare wire heating elements are also especially suitable for use in hard water. The very small amount of water inside the appliance and the low-mass heating system mean there is hardly any post-heating after the appliance has been switched off – an important factor in the reduction of scale build-up.

 

I would like to see a reference to this .....either your explanation is out of wack or the way you read the data is incorrect.

There is no way bare resistance wire would be placed directly in the water for instance.

 

What was a common arrangement some 40 odd years ago, was to have a heater tube fitted into the water chamber.

Inside this was the heater wire wound on a ceramic insulated bobbin. 

 

No idea what you are on about with your upstream and downstream protection devices.

 

 

 

[carlyai]

15 minutes ago, bluejets said:

I would like to see a reference to this .....either your explanation is out of wack or the way you read the data is incorrect.

There is no way bare resistance wire would be placed directly in the water for instance.

 

What was a common arrangement some 40 odd years ago, was to have a heater tube fitted into the water chamber.

Inside this was the heater wire wound on a ceramic insulated bobbin. 

 

No idea what you are on about with your upstream and downstream protection devices.

 

 

 

I think this is a direct quote from the information sheets from the company. 

[bluejets]

22 hours ago, carlyai said:

I read that now (in Aus) each sub-circuit final must have a RCB/RCBO. Does that mean each seperate feed from the CU must have a RCBO?  Eg.  Stove, kitchen.

Largely correct.

Hotplates must also have isolators (not ovens though)

There are alternatives to using RCD's such as the placement and protection of wiring in such a way as to negate the use of any residual current device.

Usually with fixed installed devices such as water heaters and electric stoves this normally presents no problem in theory so long as the earthing system is initially in place and tested on occasion.

However, the whole exercise was to give an alternative in case anyone was opposed to the extra cost of the RCD BUT as it turned out, guessing by common sense approach, much better to use the RCD to begin with, as the wiring conditions are rather expensive to implement.

All lighting and GPO's must be covered by RCD anyhow. So basically everything on RCD, or rather RCBO units preferred.

 

Where any mains enter an installation in out of sight arrangement i.e. inside a wall cavity, the cabling must be protected by an earthed sheet metal cover the entire length. Assumind the distance from the inner wall sheet and the cable is 75mm or less, which is probably 99.9% of buildings in Aus anyhow.

So again, just do it they way the SAA rules suggest.

 

The incentive not to take short cuts by the way, is the way the authorities can come back at a lecky up to some 7 years later, even if retired and business is closed.

Hence many lecky's have found, by others bad misfortune not to realise, insurance cover needs to extend 7 years into retirement.

Just a by-the-way bit of dribbling on.........????

[Crossy]

@bluejets

 

From here instructionandinstallationmanual_doc-00060852.pdf (page 29)

Sorry about the wiggly hilite, it's early ???? 

 

[Crossy]

It's important to note that electrical regulations and installation practices do vary around the world. What would be perfectly acceptable in the UK may be totally prohibited in, say, Australia.

 

I will say that AS3000 is actually a pretty good fit for Thailand whereas BS7671 has some things which maybe don't work quite as they would "back home".

 

When I lived in Seoul our local pub (yes, The Seoul Pub https://www.trazy.com/spot/2982/seoul-pub-서울펍-nightlife-bar) had the pool rules on the wall, the top line read "We don't care what they do where you come from, this is what you do where you are!".

 

[KhaoYai]

None technical answer here but I was a little confused as to why you needed a heater in Thailand.  Then as the discussion continues it seems this heater may actually be a water heater.

 

Why not consider an Air Source Heat Pump? I have one with a 200L tank and my house has a simple 30amp supply.  These water heaters are incredibly efficient - from memory mine consumes 1.4kw but puts out 4kw. Mine cost me 50,000 4 years ago.

 

I can put you in touch with the supplier in Pattaya if you want.

 

As for usage in the real world, I think I made a mistake buying an ASHP.  If I needed 200L of hot water, it absolutely would be the way to go.  But I don't, I only need hot water for showers really.  I had no idea that the ASHP actually heated 200L in its storage tank - I hadn't even considered that its a storage based system, not instantaneous.  My fault for not doing my homework but I still don't really regret it.  When I change over to Solar Energy, it won't matter anymore.

 

Still, both my showers get used at the same time on occasion and 2 x 3.5kw electric showers running at the same time as everything else may well have been pushing it a bit.

 

Overall I'm happy with the ASHP but I'll be a whole lot happier when I'm on solar.  I talked to a restaurant owner who has the same ASHP as I do and says its cut his electric bills by 75%.

[carlyai]

1 hour ago, KhaoYai said:

None technical answer here but I was a little confused as to why you needed a heater in Thailand.  Then as the discussion continues it seems this heater may actually be a water heater.

 

Why not consider an Air Source Heat Pump? I have one with a 200L tank and my house has a simple 30amp supply.  These water heaters are incredibly efficient - from memory mine consumes 1.4kw but puts out 4kw. Mine cost me 50,000 4 years ago.

 

I can put you in touch with the supplier in Pattaya if you want.

 

As for usage in the real world, I think I made a mistake buying an ASHP.  If I needed 200L of hot water, it absolutely would be the way to go.  But I don't, I only need hot water for showers really.  I had no idea that the ASHP actually heated 200L in its storage tank - I hadn't even considered that its a storage based system, not instantaneous.  My fault for not doing my homework but I still don't really regret it.  When I change over to Solar Energy, it won't matter anymore.

 

Still, both my showers get used at the same time on occasion and 2 x 3.5kw electric showers running at the same time as everything else may well have been pushing it a bit.

 

Overall I'm happy with the ASHP but I'll be a whole lot happier when I'm on solar.  I talked to a restaurant owner who has the same ASHP as I do and says its cut his electric bills by 75%.

The 3 phase multi-point heaters are great. Fairly instantanious full flow hot water, but I wouldn't install them again.

Before I built the house we had a 3 phase supply close by from a de-commissioned rice mill, so we just asked PEA if we could move the meter and use it.

Very difficult then to get a real electrician that knew about 3 phase installations. We eventually got someone who installs power in factories and he was the one that said to install the 3 phase heaters.

 

[carlyai]

KhaoYai said: 'I was a little confused as to why you needed a heater in Thailand.'

Gets cold in Isaan near Lao. Gets down to 4 to 6 degrees C.

So the other heater was a water heater but this one in the picture is the house gas log fire. 

Sit around in your undies, drinking red, watching the flames flicker. ????

[SomchaiDIY]

3 hours ago, bluejets said:

I would like to see a reference to this .....either your explanation is out of wack or the way you read the data is incorrect.

There is no way bare resistance wire would be placed directly in the water for instance.

 

What was a common arrangement some 40 odd years ago, was to have a heater tube fitted into the water chamber.

Inside this was the heater wire wound on a ceramic insulated bobbin. 

 

No idea what you are on about with your upstream and downstream protection devices.

 

 

 

my english is not good but not difficult to understand for most people

 

out of wack i need the lookup

 

-----------------------------------------------------

 

----------------------------------------------------

 

 

best if you make the contact with steibel company about this out of wack info

 

web link to stiebel company writing i copy at my post

 

https://www.stiebel-eltron.com/en/home/service/faq/what-heating-systems-are-used-in-instantaneous-water-heaters.html

 

 

tech document for bare wire heating element

 

23_Janzen.pdf

 

 

[SomchaiDIY]

fun with bare element heater sometime called suicide shower

 

some idea about how the steibel product can protect user from the dangerous current

 

resistance of water at shower flow tube makes current limit to water output 

 

also show problem with rcd device using this heater type

 

 

some suicide shower video
part 2 show the leaking current test

 

 

 

 

 

part 2

 

 

 

[carlyai]

Thanks @SomchaiDIY

I hope the moderator doesn't mind me saying this but you are a welcomed addittion to this brilliant forum. Not detracting from the other posters (except the guy redoing his condo who rubbished posters). ????

[bluejets]

8 hours ago, KhaoYai said:

Why not consider an Air Source Heat Pump

Don't touch those things with a 40ft pole.

 

They brought them in down under about 20 years ago and not worth a cracker.

 

If it breaks down, you first need to contact(not necessarily in this order)

a refrigeration mechanic.

Then, a plumber,

Then a lecky

Then a computer programmer

 

If you're lucky, one may be able to find the solution.

Most of the info is kept secret by the manufacturers and only released to "service agents".

If the night falls below 5 degrees C , they don't work at all.

Needless to say all the yuppies bragged about how fantastic they were, and now not one to be seen anywhere, gone the way of the Dodo ( thankfully)

 

I'm wondering why the Op needs a whopping great 3 phase system for a hot water system (no idea why instantaneous also)

There are single element single phase storage systems out there that have done the job extremely well for the last 80 years or more, and they would be reasonably efficient.

Power requirements perhaps 3600w , (250 litre) can be run off a single solar panel array direct (no inverter required)  to boot.

 

Edited October 29, 2022 by bluejets