6000 watt water heater on 5/15 meter

[canopy]

I was summoned by a neighbor upcountry because they were having problems with their 6000W shower heater not activating. The unit looked brand new. However, the gfci test button did not trip despite there seemed to be a ground attached. I noticed a few problems at the service entry. A screw had stripped and so the wire to the heater was loosely contacting the main switch. The insulation was melted and the arcing made the contact black. Improving this connection allowed the heater to work and that's all I did for now. I also noted the wires were only 2.5mm2 on a 15M run to the shower. I also noted the meter is just a 5/15. I don't want to get overly involved in a complete redo of their house wiring nor do they have money to do much. It will probably be a tough sell as the system works, but is there anything simple that might be helpful or safer to advise in this situation.

[KhunBENQ]

Ouch! A 6 kW heater on such an antique installation at a 5/15 meter

Simple arithmetic makes clear that this can not work. Even 15A are not enough for a 6 kW heater.

Advice them on the possibility to turn in/exchange the heater for the smallest models possible (3.5 kW) which is "just about" doable.

Otherwise they will have to invest and pay for bigger meter and decent wiring/grounding.

Who had the brilliant idea to buy this???

Edited June 14, 2015 by KhunBENQ

[Crossy]

Let's shift this over to Sparking (literally it seems).

If they can swap the heater for a 3.5kW unit that will at least not risk sending the meter into orbit.

OR

New 15/45 meter (and possibly a new cable from meter to home).

Decent distribution board (only needs to be 3 or 4 way) with RCBO (Safe-T-Cut) - you can buy ready assembled units with the RCBO built-in.

4mm² cable to the heater.

3-pin outlets with connected grounds where they are needed (washer etc).

A thorough check of the existing wiring.

Doing the above will give them a system that is infinitely safer than the ancient (and fizzing) stuff they have now. Of course I strongly suspect I know who will end up paying

Purely by coincidence the local loudspeaker truck just went past offering free electrical inspections to those in the village who have older installations (everyone). Unclear if remedial work will be completely free but I suspect it will be heavily subsidised by the local government.

[canopy]

Yeah I know and gee, 6000 watts, I've never seen one that large before. A complete redo the right way crossy recommends is what I would do, but it isn't my place. And exchange isn't doable. So let me throw out another possibility. The shower is pretty low flow, driven by low psi so perhaps never pulls full power which may be the only reason worse problems haven't happened yet. What if I simply replace the faulty knife switch with a 20A RCBO and tell them just not to turn the dial up on the shower to where the breaker trips?

[attrayant]

6kW! Is that for the snowy winters we get here? I think mine is 3.5kW and I've never had it turned up more than half way.

Edited June 15, 2015 by attrayant

[Crossy]

Yeah I know and gee, 6000 watts, I've never seen one that large before. A complete redo the right way crossy recommends is what I would do, but it isn't my place. And exchange isn't doable. So let me throw out another possibility. The shower is pretty low flow, driven by low psi so perhaps never pulls full power which may be the only reason worse problems haven't happened yet. What if I simply replace the faulty knife switch with a 20A RCBO and tell them just not to turn the dial up on the shower to where the breaker trips?

That would actually work, and any form of RCBO would be better than the current knife switch.

[canopy]

Good. And what exactly is that white component on the right side of the box and does it need retained?

[attrayant]

That looks like an old style ceramic fuse. Pretty much only good for interrupting massive over-current conditions. It provides no protection against shocks or electrocution.

[Crossy]

Yup, HRC fuse.

I would retain it and just replace the knife with an RCBO, should be a drop in job, take the fuse out to isolate the system (make sure it's in the live side mind).

[IMHO]

6000w only just makes luke warm water during the cold season if you have above ground tanks guys - we actually upgraded one house to 12kW 3-phase heaters in order to make actual hot water....

Then we dumped them all for solar, and now have super hot water, 24/7/365

[KhunBENQ]

Help, where do you live?

12 kW?

Lukewarm, yes in winter. But with a 3.5 kW.

[IMHO]

Help, where do you live?

12 kW?

Lukewarm, yes in winter. But with a 3.5 kW.

The 12kW was needed in a Chiangmai house.

[KhunBENQ]

Thats an excuse

Just know through the grapevine that there are houses with heating/chimneys up in the hills.

Here in central Isan we have about two "cold" weeks around New Year (close to one digit Celsius temp. in the morning).

Showering is then postponed till noon.

Edited June 16, 2015 by KhunBENQ