3 phase immersion heaters in star (no N) or delta

[vitoboy]

Hi all
Been to a micro brewery today .

They have 2 water boilers with 3 phase immersion heaters in them (ie 3 x elements)
Originally they were wired to run single phase will all the lives and neutrals linked out and a 32A single phase supply connected to them.
Now they are wired in a star configuration. .. but with no neutral at the star point.
All cable sizes seem very large to me at 6mm.
The heaters are of the type sold by RS ..or look to be so.
I can't see any part numbers to know their rating .. but im guessing 4 - 6 kw or 12 even.
Now looking at this I was thinking that they should have a neutral to the star point..?.
Then i thought why not change it to delta configuration. ..no neutral needed .. and greater heating capacity. ..I think..
I'm used to star delta for motor starting etc but not really as a heating load.
Some advice would be appreciated.

Cheers

Vito

 

[westward10]

Is each of the three elements actually single phase.

 

[Bobster]

Quite a common design, draw it out you'll see why they need no neutral. Do not change it to a delta configuration. You'll change the characteristics.

Ensure they have adequate load monitoring protection, as if one heating element fails an it becomes unbalanced the other 2 will quickly fail too.

Seen this install numerous times on bitumen heating tanks. Although it is a rather old fashioned way of doing things.

 

[telectrix]

if each element is a 240V jobby, wire in delta and you'll fry them with 415V across each.

 

[Pete999]

Hi all
Been to a micro brewery today .

They have 2 water boilers with 3 phase immersion heaters in them (ie 3 x elements)
Originally they were wired to run single phase will all the lives and neutrals linked out and a 32A single phase supply connected to them.
Now they are wired in a star configuration. .. but with no neutral at the star point.
All cable sizes seem very large to me at 6mm.
The heaters are of the type sold by RS ..or look to be so.
I can't see any part numbers to know their rating .. but im guessing 4 - 6 kw or 12 even.
Now looking at this I was thinking that they should have a neutral to the star point..?.
Then i thought why not change it to delta configuration. ..no neutral needed .. and greater heating capacity. ..I think..
I'm used to star delta for motor starting etc but not really as a heating load.
Some advice would be appreciated.

Cheers

Vito

If the heaters are rated at 400Volts and connected across 2 phases they won't require a Neutral. Balanced load no N

 

[Toneyz]

It's not an electrode boiler by any chance did about them at college years ago but never seen one to this day.

 

[Bobster]

It's not an electrode boiler by any chance did about them at college years ago but never seen one to this day.

Doubtful in a brewery, they'd ruin the taste.

My guess is ceramic wire wound heater elements. Imagine they are installed in an orifice within the bottom of the tank.

 

[telectrix]

Doubtful in a brewery, they'd ruin the taste.

My guess is ceramic wire wound heater elements. Imagine they are installed in an orifice within the bottom of the tank.

wouldn't be much use outside of the tank, would it? .

 

[telectrix]

i am now getting bombarded with huge ads top of page. everything from motorcycle boots to google gadgets. even got one from cheat-a-trade. what's the crack?

 

[Pete999]

It's not an electrode boiler by any chance did about them at college years ago but never seen one to this day.

Used to have three to look after on a large A/C installation, they were providing humidity to a large computer suite,

 

[vitoboy]

Is each of the three elements actually single phase.

I guess..they were running single phase at one time...
I imagine 3 x 2kw or 3kw or 4kw Immersions ..

 

[vitoboy]

Doubtful in a brewery, they'd ruin the taste.

My guess is ceramic wire wound heater elements. Imagine they are installed in an orifice within the bottom of the tank.

Yeh but no but ..
Ceramic wire wound I think ..just like a standard immersion but x 3 .
But the elements are in a sleeve..maybe stainless looking at it.

 

[vitoboy]

OK I'm still not sure about star without a neutral.
I understand that they may not be designed to have 400 v across them ... but maybe they are ... but I can't tell without a part numbe ..I see from rs that some are and some arnt .

But I guess in the end it's in star now..it works..with no neutral so it's ok.
If you have an unbalanced load in star and there is no neutral then what happens to the unbalanced portion of the load..?.
The Brewery does require fast heat up times as this would mean they can do more brews a day..at the moment only 1 ...hence I wondered about the delta connections.
But without the part numbers to guide me I think I can't risk finding out..!

Thanks all for the good stuff.

Vito

 

[Toneyz]

Did you get any freebies?

 

[vitoboy]

Did you get any freebies?

Not yet...but as you can tell I'm keen to help them out.!

 

[Bobster]

If they end up unbalanced the voltage will change over the 2 remaining elements and they'll go pop pretty quickly.

Just think of it as a 3 phase motor in star, but it has no motive force.

Could be possible to connect in delta, but the current will increase.

An yes, I've seen similar before, they'll be kept in stainless tubes considering it's food produce.

 

[vitoboy]

Thanks for that contact.
As I said they appear to be of the type sold by RS ..
And looking at the rs wiring diagram they may or may not be suitable for delta connection depending on the part no. So far I can see none.
Maybe I should introduce a neutral. .. to the star point ... but there is not enough cores for this at the moment. .
Or I could use earth .. it's a pme system after all. .
There is a neutral at the controls .. but I think it's only used for 230v coils and thermostats. .

 

[westward10]

Connect the star point to earth!!
Have you been asked to look at these heaters?

 

[davesparks]

Maybe I should introduce a neutral. .. to the star point ... but there is not enough cores for this at the moment. .
Or I could use earth .. it's a pme system after all. .

Why do you want to add a neutral connection? All it will do is waste cable as it won’t do anything in normal operation.

I assume you are joking about using the earth?

 

[Bobster]

Thanks for that contact.
As I said they appear to be of the type sold by RS ..
And looking at the rs wiring diagram they may or may not be suitable for delta connection depending on the part no. So far I can see none.
Maybe I should introduce a neutral. .. to the star point ... but there is not enough cores for this at the moment. .
Or I could use earth .. it's a pme system after all. .
There is a neutral at the controls .. but I think it's only used for 230v coils and thermostats. .

What have they asked you to do with the heaters?

An please, please tell me you're kidding about thinking of using the cpc as a neutral.

In any form of installation this is prohibited and potentially very dangerous!

 

[AJshep]

I work in a unit that has uses large ovens to cure latex. Each oven was handbuilt in Poland, and each is slightly different

They have the same configuration as the OP, with the 3 elements with the outputs connected to a star point, so it's not particularly uncommon.
Like Rob said, just make sure you have some sort of phase monitoring protection, but I suspect if it has its original control panel then it should already be in place. if its been modified then you may want to take a closer look.

I've been installing these "Europa ECPF05" to the supply of each oven, and switching the coil circuit through it.
It just adds additional phase failure/undervoltage protection to the each of the ovens I work on because quite often the whole Industrial estates incoming 3Phase supply is unbalanced, they get alot or surges and the DNO are always out at the transformer.

 

[vitoboy]

Sorry guys..don't know what I was thinking there..I would no more use a cpc as a neutral here than anywhere else..
Must stop drinking red wine on Monday nights.

Ajshep.. Yes just looked these europa ecpf05 .. I don't believe there is any protection apart from a 3ph mcb for each heater ... but I will check...if not it would be easy to add one of these units to the contactor coil if there is room to fit them in the panel. ..as usual it's pretty rammed in there.
At the price its cheap insurance on the cost of an immersion...

 

[Bobster]

The cheapest way I've seen of offering protection in these scenarios is a motor overload that fits to the bottom of the contactor. It will detect no load on a phase an trip, protecting the others.

Be aware, if you start modifying this. You will have to make sure the control system is compliant with all relevant standards under CE.

 

[ElectroChem]

@Rob you keep mentioning the other 2 elements blowing if one goes open circuit. Won't a 2-wire load through two elements in series give 200V across each? No reason a resistive load would be damaged there. I can see monitoring for element loss as the power would be halved so you'd lose heat though.

 

[Bobster]

@ElectroChem

You're correct in what you say. I should have been clearer in my earlier posts.

I've made the assumption that these heaters are the same as all the others I've worked on. That they aren't just 3 resisistive elements. More like 9 (3 in parrallel) all to male the Y config. If one fails in a leg, the Y becomes unbalanced, causing the others to fail in a run away effect.

On my phone currently so that still may not be the clearest of answers.

 

[Bobster]

I'd never make a teacher!

 

[ElectroChem]

@Rob Very interesting setup, took me a bit to wrap my head around how a cascading failure would work there. With the potential for run away burnout, running a neutral to the star point would start to look attractive.

 

[Bobster]

@Rob Very interesting setup, took me a bit to wrap my head around how a cascading failure would work there. With the potential for run away burnout, running a neutral to the star point would start to look attractive.

That would stop the run away problem.

It's an old setup, not something I would imagine is installed as new anymore.

Any tank heater designs I've done in recent years involve thyristors to control the heating output from a 4-20mA signal.

 

[davesparks]

The three phase immersion’s I’ve worked on before have been a single unit where if any one element fails the whole lot has to be replaced anyway.

 

[Bobster]

They're babies Dave

 

[davesparks]

They're babies Dave

I’m sure they are, but the OP mentioned that they were linked out and running on 32A single phase, so presumably they are only going to be this kind of size.

 

[Bobster]

I’m sure they are, but the OP mentioned that they were linked out and running on 32A single phase, so presumably they are only going to be this kind of size.

Must've skipped over that bit of info.

 

[Marvo]

OK I'm still not sure about star without a neutral.
I understand that they may not be designed to have 400 v across them ... but maybe they are ... but I can't tell without a part numbe ..I see from rs that some are and some arnt .

But I guess in the end it's in star now..it works..with no neutral so it's ok.
If you have an unbalanced load in star and there is no neutral then what happens to the unbalanced portion of the load..?.
The Brewery does require fast heat up times as this would mean they can do more brews a day..at the moment only 1 ...hence I wondered about the delta connections.
But without the part numbers to guide me I think I can't risk finding out..!

Thanks all for the good stuff.

Vito

It's not just about whether the elements are rated to run at a higher voltage, there's an implication for the product being heated. If you increase the element voltage you effectively increase the heat density of the tube which means higher temperatures at the interface with the product. The product may burn on the surface of the tube causing taste problems etc.

......Maybe I should introduce a neutral. .. to the star point ... but there is not enough cores for this at the moment. .
Or I could use earth .. it's a pme system after all......

Rather use a smiley emoticon to show when you're joking......