Time clock stopped working

[uksparks]

Hi,

any ideas chaps? Got the time clock below, was working fine 12 months ago before works started, just gone to power up and am getting no voltage on the output, wound it up etc...

 

[uksparks]

No, the two immersion supplies are on different phases, I hve a proper change over switch for this, properly labelled for400v and dual feeds and points of isolation...

The only fuse that I am aware of that would blow should it be overloaded is in the bck of the time clock across the outer pairs, so between L1 from top of Contactor and A1.

 

[davesparks]

Why not put them both on the same phase? I know what you have done is strictly right, but does not common sense dictate that you avoid having 415V in an enclosure if possible, especially in a domestic environment!

And why did you think the 400V labels were necessary?

I don't follow the bit about the fuse? What do you mean the only fuse you are aware of? Have you not designed the coil cct with appropriate fusing?

 

[uksparks]

I appreciate what you are saying about avoiding having 400v in an enclosure, but by having them on different phases you are less likely to be left without water should you lose a phase.

the 400v sticker, I was under the impression that you had to label anything above 230v...no?

the fusing, so what would you do then? Please explain, I have only replaced the contractor so not strictly speaking changed the bit before it, but should you be able to advise as to the best setup I'll happily incorporate it.

 

[davesparks]

Interesting point, but is be looking to consider the chances of a diyer working on that versus losing a phase of a three phase supply for a significant length of time.
Losing one phase of a small TP supply is pretty rare in my experience, especially for the length of time it takes a cylinder full of hot water to go cold.
Think about what the loss of a phase would entail, if it's a supply issue the DNO will be on it pretty quickly I'd have thought!

It could be the fuse in the head which goes I guess, but since it would be the fuse for your SP supply which goes then the whole house will be off so the hot water not heating will be secondary to the lack of lights and power.

Yes you have to label anything with a Uo above 230V where you would not normally expect it to be, but nothing in your install has a Uo above 230V
I agree that the changeover switch should be labelled regardless of that reg, due to fact anyone could open it up unwittingly.

You must have done more than change the contactor, the old one worked and this one didn't initially.
But regardless of that if the coil cct is unfused and just tapped off of the L1 terminal then you have the cables running to the timeswitch fused at 63A (in the exel) they don't look like 16mm to me
Obviously you don't always fuse down a coil cct, think about a basic DOL starter, but in this situation I would expect to see the coil cct fused down.
It's din mount contactor in a din rail enclosure so you could have easily popped a 1A MCB in there for the coil cct.

I'll see if I can post a pic of a recent lighting control I put together to illustrate this setup.

 

[uksparks]

I see what you mean about fusing it, I can probably stick a breaker in there, just fiddling the tails a bit, the excel is at 32A and the time switch claims it can take 78A according to the sheet in the back of it, I suppose its just the cable that can only take 26A being 2.5, hmm you have got me thinking.

I agree, there's nothing Uo @ 400v.

 

[davesparks]

Yeah the timeswitch will be able to switch high load, on a SP supply the tails would go straight through it without a contactor.

Is 32A enough for that many storage heaters? But I guess with that many they may not all be the usual 3.5KW jobbies?

 

[davesparks]

As mentioned earlier, a little box I had to put together recently to replace a defunct working light control in a theatre.




Reading from the right we have
-Main switch
-Outgoing cct MCBs
-Contactor
-1A MCB for control cct
-Impulse relay
-24V Impulse timer (for switch debouncing)
-24V PSU

24V cct works like this:
pushbuttons are N/O and trigger the impulse timer, the impulse timer switches its contacts for the specified time then resets.

240V control cct:
The timer switches a 240V supply to the coil of the impulse relay, the relay switches 240V to the contactor coil.

All of the control ccts are fed via the 1A MCB, including a 240V remote override (the red one coming out of the 1A MCB)


And yes there are a few things there which you could call in to question, feel free to question me on them and I will endeavour to explain when I get back from work later, hopefully be home by 3AM.

 

[uksparks]

Thanks or this Dave, looks good, and I do appreciate your comments, I don't have a great deal of experience in this side of things, nothing to hide, I'll be quite honest but we all have to learn / start somewhere.

I think I'll squeeze a mcb in next to the Contactor.

Well it's 32A per phase and there's only 4 heaters per phase max, the heaters only draw approx 1.5kW each some are more, but I did balance it so that each phase draw was under 32A.

I suppose my only concern would be any earth leakage, the accumulation of 12 heaters, hopefully it won't be so much it trips the RCD, otherwise I'll be having to rethink things and incur a fair bit of cost.

 

[davesparks]

Go on, play spot the deliberate mistake with those pics!

Well you see I am far more used to the big jobbies at 3.5KW and 16 sodding bricks each to carry up flights of stairs. But then they were usually 1 or 2 in the whole property which were expected ted to heat the whole house. One in the hallway, one in the living room and maybe one upstairs, plus the bottom immersion makes a 4way board nicely.

Assuming the heaters are new there shouldn't be any earth leakage on them. Old ones may have a bit of leakage but that's likely to be the elements which are easily replaced and pretty cheap.
Personally I'd have found a way to not need an RCD for them, steel conduit in the chases would probably be my first choice. But then that is my first choice of wiring system on any surface work anyway. Ran a bond to a gas pipe in it the other day just to prove to a plumber that it is possible to get three 90degree bends into a pipe accurately without having to cut and join the pipe.

Did you consider the normal installation in your balancing calculations? Doubt it will have much effect during the off peak hours but if it has afternoon boost it may skew your balance a bit
But don't worry about that, in the grand scheme of things it won't cause anyone any problems.