3 phase conundrum

[PatsPatter]

It won't be low voltage - it's switching the contactor using 240V remember. The main thing is that it's a dry contact, so the installer can use the contacts in pretty well any way they want as long as they stay within the current switching capability. Ie, if they want a switched live feed, connect one side to a live supply; want a switched neutral (as in this case), connect one side to neutral; want to switch a customer circuit*, connect the customer circuit to it. It may be relatively low current - but I'd guess they'd not have it rated less than at least a few amps…
……..

OK, understood. Mine operated with 12 volts because the reed switch could only handle about 1/2 amp at less than 50 volts………..and to avoid any significant voltage being allowed to get mixed up with a domestic water supply system.
In my house wiring case it isn't a problem.

 

[Spark123]

... and then, of course, there are those items which are provided with some sort of removable/replaceable link, which turns dry/volts-free contacts into "non-dry/volts-free" contacts (do they have terminology for that?), without the contacts having been changed in any way!!

Kind Regards, John

Wet contact

 

[JohnW2]

Wet contact

Indeed. However, I was actually thinking of the other phrase ("volts-free") - what is the opposite of that? "Volts-present", or what?

Kind Regards, John

 

[EFLImpudence]

Don't know.

Live ?

 

[PatsPatter]

I know it's a while since this thread was active, but:
The Acti9 TP board is installed and (mostly) tidied up. It looks a whole lot better and the next phase of the upgrade is underway. There will be two 3.2Kw storage heaters in an area of the new build where I couldn't install an extension of the ducting for the current blown air system.

L1 is the source of the supplier's radio switch 'dry contact' trigger circuit for the existing off peak blown air system and immersion heater. Post 6 shows a picture of the old setup.
Each heater is to be fed, via a RCBO, from a different phase on the Acti9 TP board, L2 and L3, in this case.
I would have thought it would have been simpler to have a couple of dual function contactor/RCBOs within the Acti9 board, triggered by the Supplier's switch circuit - but I can't seem to find any such animal. Maybe I'm looking for the wrong thing. If they don't exist:
What sort of contactors and enclosures should the storage heaters be given to bring them into circuit when the off peak is 'ON'?
My thoughts went down two routes, as follows:
1. One enclosure with a 4 pole (NO) contactor. I say 4 pole because it seems to be the most readily available multiple pole contactor and generally cheaper than two single pole units.
2. One enclosure with two (NO) contactors, separated (by a blank) to stop any mutual interference - which shouldn't be a problem as they are both doing the same thing at the same time, anyway?
Will

 

[SimonH2]

The usual way of handling this is to have an enclosure alongside the dist board and put a contactor in that. A single 4 pole will do just fine - route the live from the MCB/RCBO via a pole on the contactor and then on to the device being controlled. Switch the contactor with the "off peak" output/contact from the dual rate meter.
Some dist boards have optional extension cabinets available that are useful for this, or you just plonk some random enclosure alongside the board.
EDIT: BTW, I think you'll find that many contactors aren't actually "4 pole" but 3 pole plus a control contact which may not be the same rating (esp on larger sizes). They'll have 3 poles for switching the load, plus the fourth which is for the control circuit (hold in circuit on a basic "press green to start, red to stop" setup.)

 

[PatsPatter]

The usual way of handling this is to have an enclosure alongside the dist board and put a contactor in that. A single 4 pole will do just fine - route the live from the MCB/RCBO via a pole on the contactor and then on to the device being controlled. Switch the contactor with the "off peak" output/contact from the dual rate meter.

Thanks for the response. That's pretty much the answer I'd hoped for and not some added complication this job seems to have produced - in spades.
I assume the 4 pole will still be OK used to switch 2 feeds from 2 separate RCBOs mounted on 2 different phases on the TP board? I wasn't quite sure if you noted it was my intention to use separate lives for each heater. I'm trying to split and balance the load between the phases as best I can. The main blown air system is 15 Kw, so with these two added to the rest, it's a fairly hefty drain. The induction hob (3.5 Kw) is on L1, with all the rest of the potential loads balanced as much as reasonably possible.

Some dist boards have optional extension cabinets available that are useful for this, or you just plonk some random enclosure alongside the board.
EDIT: BTW, I think you'll find that many contactors aren't actually "4 pole" but 3 pole plus a control contact which may not be the same rating (esp on larger sizes). They'll have 3 poles for switching the load, plus the fourth which is for the control circuit (hold in circuit on a basic "press green to start, red to stop" setup.)

I understand. Assuming my question above comes out as 'Yes', that will still leave me a pole to use if any more heaters get added.
Schneider/Merlin-Gerin seem to have plenty of options for an enclosure without breaking the bank.
Will

 

[SimonH2]

I assume the 4 pole will still be OK used to switch 2 feeds from 2 separate RCBOs mounted on 2 different phases on the TP board?

Yes, that's not a problem.

 

[scousespark]

I'm pretty amazed that anybody would think a 3 phase installation would be something that could be undertaken with a bit of research. What testing have you done, and what did your LABC say when you notified them you were doing this yourself? I'm just a bit curious.

 

[PatsPatter]

I'm pretty amazed that anybody would think a 3 phase installation would be something that could be undertaken with a bit of research. What testing have you done, and what did your LABC say when you notified them you were doing this yourself? I'm just a bit curious.

Errrrr....
Have you looked back at all the previous posts on this? Perhaps you should.
It has been a long, ongoing, well advised project, with the installation, if not the provision of components, undertaken by a local firm of experienced, well respected electricians, with over 50 years experience of 3 phase work.
If you do look back, you will see that the problem came about because of the efforts of a professional who, it turns out, wasn't.
My reason for coming on here and asking the questions in the first place was to avoid being left in the lurch again by a 'professional' who cost me a lot of money correcting mistakes.
Contrary to a belief commonly held in some quarters, there are those who understand principles and practicalities outside of their chosen profession and choose to expand that understanding in order that they don't end up being taken for a (very expensive) ride by incompetent tradesmen. You don't have to be a rocket scientist to understand what a rocket does.
For my own part, I'm well acquainted with the principles - and more importantly, the dangers - of poking a screwdriver into a three phase supply.
That's why the work is now undertaken by someone I trust. I simply keep myself advised, so I understand what is needed. If a professional tells me I have to do something, I have every right to ask him why. I'm paying.
Will

 

[scousespark]

In 6 pages asking for advice you have not mentioned any firm. Surely a firm with 50 years, who are on site, should be answering your questions. I posted after reading the last bit in your original post.

 

[PatsPatter]

In 6 pages asking for advice you have not mentioned any firm. Surely a firm with 50 years, who are on site, should be answering your questions. I posted after reading the last bit in your original post.

OK, I jumped down your throat and I apologise. It's a very touchy subject for me because I'm out of pocket to the tune of £1,000+ and there is a relative involved. A difficult situation which has made me determined to understand what is going on.
You're right, I didn't mention any firm but that is what has happened and that's who has done the installation work. I went to school with the guy and he would tell me, straight to my face, if he thought my ideas were wrong. He's quite happy for me to provide the equipment, then fill gaps between jobs with my bit as my renovation progresses. The last stage was done when they got pushed off a big job because of a customer scheduling cock-up. A benefit to both of us.
There is surely nothing wrong with wanting to know exactly how a considerable amount of my funding is spent, is there?
That apart, electrics/electronics interest me a lot. When you're not well heeled and 3 phase machine tools appear at half the price of single phase items, learning how to build converters is a way of making use of them. Imagine my joy at finding the house I was going to buy had 3 phase. The only down side came when it was realised what a mess it was in - and then it was made worse.
As regards the added dangers of 3 phase, I'm pretty sure I understand the implications. I know about danger. I lived and worked in a dangerous profession for many years. Low level flying down to 100 feet, over the ocean, is not without risk. You only get one chance to mess it up - for yourself and anyone else with you.
Either way up, isn't that why we come on here? To look for advice from professionals? If you asked me, I'd happily tell you how not to fly into an oil rig in low cloud.
Will