Adding a second chauffe-eau, using existing wiring

[Ian]

I think it'll work, but I'd like a second opinion

The current chauffe-eau is fed, (in 2.5mm) from jour/nuit unit - the main DD is rated at 20A. Circuit length is about 12m, and the chauffe is rated, I think at 2.3KW

I want to cut into the circuit at about 2m, and add another branch to feed another chauffe-eau in the opposite direction - about 10m from the split. The new chauffe-eau is a small one (15l) but still rated at 2KW - apparently, it'll only take 20 minutes to heat from cold.

Both will use off-peak, so will come on at the same time. Will the wiring and DD stand it?

I have a spare 20A DD on the tableau, so I can use that instead if there's any dubiety about plan A.

Come to think of it, I could just do that, anyway.

Any recommendations?

Thanks

[Kong]

I think the norms would suggest you need a second circuit, but judging by the numbers the cables and existing 20 amp dj would cope safely. Someone better qualified than I will come along soon.

[Quillan]

Not what you want to hear but you have to lay in a new circuit with another breaker. The current across the two for a start will be as follows.

 

2300W/220V - 10.45A plus the new one (2000W/220V = 9.09A) will be 19.54A at the breaker. Given that even more current it drawn the instance the heater coil is switched on I think firstly your running to close to the limit and on switch on the breaker will trip as both will come on together.

 

The other issue is the 2.5mm solid cable which is rated at 20A or 4.6kw. It will get warm with both heaters running at the same time and running it in trunking/conduit will not let the heat dissipate properly.

 

Then there is insurance if something does go wrong, you will probably not be covered because French regs say each heater must be fed with its own cable and breaker.

 

Personally I would also use a second Jour/Nuit unit as well although I doubt you will have to install a 2A breaker to power it. You should be able to work it out from the following.

 

http://www.installation-renovation-electrique.com/schema-electrique-chauffe-eau/

 

I have five tanks, one for each bedroom (I have a B&B with four bedrooms) and one for the rest of the house. Each is on its own circuit with its own breaker and its own Jour/Nuit breaker the latter has a single 2A breaker for all five and it works with no problem.

 

PS - You can use three core 2.5mm solid core cable just clipped with no conduit to power the heater without a problem which makes it easier to install.

 

[Ian]

Thanks, Kong and Quillan.

I hadn't realised that I was so close to the limits, so a second circuit it is.

The current chauffe-eau has a dedicated Jour/Nuit controller - it's a standalone mini tableau with a 2A breaker, a 20A breaker and the J/N unit. All controlled by the J/N switch at the compteur. I'll need to use something similar, as I've not got enough space in the tableau.

I assume I can use the J/N switch at the compteur to control the second J/N unit? It's just a switch after all.

Mind, looking at the prices (€65 just for a Legrand J/N unit alone, then there's the breakers and the case), it won't be cheap. Still, got to do it properly, I suppose.

Thanks for the help, folks - always appreciated

[Quillan]

Yes you can use the same J/N unit.

Handy in a way that you have mini tableau for the heating because you can just replace it with another. If you think about it you only want a 4 way tableau to take the J/N unit, 2A breaker and two 20A breakers. The tableau's are basically all the same and have the same rail inside. You may have to buy the rail, earth strip, live and neutral bus separately but you can get a 4 way tableau from BricDepot for €16.95 with a cover or a Legrand one with no cover for €8.40. If you swap the contents over then you will just need to get an extra 20A breaker. I think you can get all the bits for about 30 Euros.

 

Don't forget your safety when you do this. Basically switch the house off with the main EDF breaker before removing any tableau covers. Don't want your other half coming on here having a go because you didn't and ending up brown bread. Mind you you can always do what I do, get the MIL to do it with both feet in buckets of water and a metal screwdriver. [6]

[Ian]

I think I'd need another J/N unit as well.

If I follow the wiring diagram you referenced, power comes out of the 20A breaker and passes into the J/N unit at terminals 1&3. Then, if the EDF switch at the compteur is closed, power comes out of the J/N unit at terminals 2&4, and goes to the chauffe-eau.

If that's the case, I'd need another 20A breaker and J/N unit for each new chauffe-eau.

Or have I got it totally wrong?

Cheers

[Quillan]

What I meant was you don't need a second 2A breaker to power the J/N device. However you are right, you need two J/N devices, one 2A breaker and two 20A breakers making five. Sorry about that, seem to have lost the ability to count. I think the next size up in boxes is six but it's not that much more.

[Ian]

It was as much the way  read it, as what you wrote. Thanks for the guidance, I'll visit Leroy Merlin tomorrow.

Cheers

[Quillan]

I just went down to turn off one of my rooms for winter and checked. The setup is as we agreed except the breakers for the heaters are all 16A. Might save you a Euro or three on the cost for installing the new heater.

[Ian]

I had a look in Leroy Merlin yesterday. They do a complete mini-tableau, like the one I already have, for about €45. Contains a 2A, 20A and N/J unit. Made by Lexman, rather than Legrande or Debflex or whoever, but what the heck.

I think I'll use one of these, alongside the existing one, and just split the signal feed from the compteur.

Thanks for all the help - as ever, it's appreciated.

Cheers

[Quillan]

The comteur just has contacts so there is a live in and a live out to the 2A breaker then on to the J/N device. So you want two wires out (you can remove the plate covering the contactor connections, there should be no seal and it is on the consumer side) each to a 2A breaker then on to the respective J/N device. I guess the box is pre-wired anyway so I guess it makes it a lot easier and cuts down on time plus it is probably only a few Euros more than buying all the bits on their own so probably the best way to go. Don't forget to mark up which one is for which tank. Good luck.

[Ian]

I don't even need to meddle with the compteur.

I have extended the wires from the compteur (in the barn) to the tableau (in the house), so I just need a couple of wagos in a small JB, and the job's a good' un.

Good idea, by the way, about labelling the two units.

Cheers

[Ian]

You wouldn't believe it!

All the plumbing done last week, plus the electrical connection at the chauffe-eau (C-E).

This morning, I fitted the new J/N unit, and wired it all in to the tableau. Switched on all the interrupteurs, then switched the J/N unit to "manual" Bang! DD tripped!

I checked all my wiring - OK - so I disconnected the supply at the C-E and replaced it with a light bulb. Tried again - bingo! - no tripping, the bulb lit.

So, I measured the resistance of the C-E element. It was zero. I think that means a short circuit in the C-E?

Three steps forward, two steps back......

Cheers

[Quillan]

Don't assume anything including that the internal wiring of your new 'box' is correct. It sounds to me as if there is a wire somewhere that either shouldn't be there or it's in the wrong place. Do the old 'divide and divide again' fault finding technique. Assuming you wired everything up including the new tank try disconnecting the tank from your new 'box' (at the box end) and try again. If it still does not work try disconnecting the cable that goes from N/J output to the relay. That said the first thing I would do is have a nice cup of tea, relax and look at the drawing for the box then go back ten minutes later and go through it wire by wire.

[Ian]

As soon as the DD tripped, I went and compared the wiring diagram that somebody (you?) provided a link to, with the wiring diagram that came with the J/N unit, with what I've actually wired . They all seem to match (but yes you're right, check and check again).

I have left the light bulb at the end of the feed, and the N/J unit set to "auto". If the bulb lights up at 10:30 PM tonight, I'd be inclined to think that the wiring was OK, and it IS the C-E at fault. However, I'll re-check the logic again tomorrow - I don't want to have to dismount the C-E, only to find the fault lies elsewhere.

But if the C-E resistance shows as zero ..... (OK, it could be better if I'd used an AVO, rather than a cheap multi-meter, but even so....)...

Cheers

[Ian]

Well, the lamp lit up, which made me more convinced than ever the C-E was at fault.

However, I decided to try one last test this morning. I plugged the C-E into a socket and it worked! So I tried the full set-up again, with the same result - the DD tripped. Only, this time, I noticed the 2A IDs had also tripped. Must be a problem with the EDF signal switch, I thought, and it was. When I disconnected the connection to the new NJ unit, all was well.

I had a suspicion what the problem was so I decided to look for a two C-E circuit diagram, which confirmed it. Only ONE live feed to the EDF switch is needed (you can use the switched return to control as many  NJ units as you like) and I'd connected BOTH live feeds. So, I disconnected the new live feed, and everything seems OK.

The final test will be tonight - both should switch on automatically at 10:30PM. Fingers crossed.

[Ian]

Me again.

While the second C-E controller works, it all looks untidy. So, I've decided to replace the two standalone C-E control units (mini-tableaux) with a new, single range, secondary tableau. This will control the two chauffe-eaux

The first question is, are the rails standard between manufacturers? In other words, can I combine the two sets of disjoncteurs and J/N units in one new tableau, even though they come from two manufacturers?

Cheers

[Chancer]

Yes and no, all DIN rail mounted disjoncteurs should be standardised the world over, and indeed they are except for the French manufacturers that want to sell you a tableau and then make it as difficult as possible for you to add stuff from their competitors whilst massively hiking the prices of the essential Equipment like 2a disjoncteurs that they dont include in their tableaux pré équipés.

 

In practice they will fit on the din rail, they respect all the dimensions for width, projection etc but you will find that the bit that projects through the slot in the cover will be higher or mower meaning you have to start cutting. 

 

Also the pitch, offset and orientation of the contacts will be different meaning that if you want to use peignes to make a neat job you either cant or have to start filing them down and bending them.

 

It gets even worse when you start mixing and matching platines, disjoncteurs, compteurs, and habillages from the 3 manufacturers which are all supposed to be standardised and interchangeable in order to carry the ERDF part number, I had a right old time with the 8 derivation individuelles from my colonne collectif, it took a lot of patience but looks just fine now and saved shedloads of money.

[Ian]

Thanks, Chancer, that's what I suspected.

I'll try and re-use the bits - if it just won't work, I'll bite the bullet and buy new. That'll hurt, but at least the installation will be right.

Cheers

[Chancer]

Try and buy a tableau nu that is the same make as one of the standalone ones, that way half of the stuff will fit, if you are Lucky the rest will as well, if not its only a bit of trimming and bidouillage.

 

Totally unecessary and against all the well intentioned aims of standardisation but I just come to expect pettiness and spite these days.

[Ian]

Unfortunately, that's not possible. One is 8 years old, and I can't even see a name on it, while the latest one is "Lexman" and they don't seem to make IDs (and I need one for the new tableau).

BD offer IDs from €20 (Debflex) to €110 (Legrande). Having used almost totally Legrande kit when I wired the house, I was/am impressed by it, so that's my choice. Especially for something like an ID - there are no bargains in safety equipment.

Mind, at that price, BD are having a laugh. Leroy do the same for €68, not much more than Siemens or Schneider at BD.

So long as the existing components fit on the DIN rail, I'll manage to wire them somehow.

Thanks for the help, it's appreciated.

Cheers

[Chancer]

When you have 6 flats to do the collective savings cant be ignored, I bought 3 rangé tableau équipés with smoked glass covers over each rangé  for €60 each on promo, I actually got up early for that one! On that purchase alone I saved a couple of thousand Euros. Actually just the ID's alone at the price you quote would have been €1320 [:-))]

 

I saved close to €10000 Euros on the colonne collectif but it took a lot of battling with the ERDF and I nearly lost big time, in the  400 amp street connection for 8 dwellings cost only €910 and as compensation for their malpractice they 8 installed meters and disjoncteurs that I would have had to pay for as part of each mise en service saving me another few thousand euros, now I pay just €40 for each mise en service.

[Ian]

I'm in a different league - only a few bits required, so if I need to buy new, it's not the end of the world.

Cheers

[Quillan]

[quote user="Ian"]I'm in a different league - only a few bits required, so if I need to buy new, it's not the end of the world.

Cheers
[/quote]

 

Here is a thought, take one of the breakers with you to BricoDepot because they sell all the bits, including the rails, seperatly so you could 'try before you buy'.

[Ian]

Too late, I'm afraid.

I decided to spend on a Legrange tableau nu, plus ID, from Leroy. All the other bits fitted (though the Lexman bits were decided shoogly - I don't think  I'll use their stuff again). Mind,as Chancer said, none of the connections were in line, so I couldn't use peigns - had to do it the old fashioned way, with wire.

Much tidier now, all full protected with a good earth, etc. No blue flashes when I switched on, and at least one C-E works when I switch to manual (it has a light that comes on).

The proof of the pudding will be tonight, at 10:30 - if both come on (and stay on....), I shall go to bed a happy man.

Thanks to you all for the advice - I don't know where we'd be without this forum.

Cheers