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

Bobster · Jun 18, 2018

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 · Jun 18, 2018

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 · Jun 18, 2018

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

davesparks · Jun 18, 2018

vitoboy said:
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 · Jun 19, 2018

vitoboy said:
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 · Jun 19, 2018

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 · Jun 19, 2018

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 · Jun 19, 2018

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 · Jun 19, 2018

@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 · Jun 19, 2018

@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 · Jun 19, 2018

I'd never make a teacher!

ElectroChem · Jun 21, 2018

@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 · Jun 21, 2018

ElectroChem said:
@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 · Jun 21, 2018

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.

[ElectriciansForums.net] 3 phase immersion heaters in star (no N) or delta

Bobster · Jun 21, 2018

They're babies Dave

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

Bobster

vitoboy

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westward10

davesparks

Bobster

AJshep

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vitoboy

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Bobster

ElectroChem

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Bobster

Bobster

ElectroChem

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Bobster

davesparks

Bobster

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