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

[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......