Water heater wiring?

Mark wrote on Monday (23/02/2004) :

It sounds most likely to be a poor and high resistance connection, the connection to which the blue is connected. Blue is (or should be) nuetral not live BTW.

| I've got hot water tank that has an economy 7 (night time) heater. But it | keeps burning the insulation on the live (blue) wire. When I rewire it'll | work fine before the insulation burns again and disconnects the wire. | | Have I faulty wiring or a faulty heater?

That depends on where the heat causing the burning is coming from. If it is coming from the heater's heating elements, the heater is at fault for not protecting the wiring. If it is coming from the wire itself, then it could be either the wire (such as it has been damaged and has a hot spot) or the heater (it's drawing too much current and overheating the wire). In the latter case, your breaker should be tripping, too, which means it is either faulty or incorrectly sized. If you are putting in all new wire each time, that sounds like an overcurrent situation, unless you are using the wrong wire size.

Tell us more. What is your supply voltage, heater current, breaker rating, and wire gauge?

Depends on which side of the Atlantic you are on.

On Mon, 23 Feb 2004 16:36:19 GMT Harry Bloomfield wrote: | Mark wrote on Monday (23/02/2004) : |> I've got hot water tank that has an economy 7 (night time) heater. But it |> keeps burning the insulation on the live (blue) wire. When I rewire it'll |> work fine before the insulation burns again and disconnects the wire. |>

|> Have I faulty wiring or a faulty heater? | | It sounds most likely to be a poor and high resistance connection, the | connection to which the blue is connected. Blue is (or should be) | nuetral not live BTW. | | -- | | Regards, | Harry (M1BYT) (L) |

So I see you have a UK callsign. So what are the wiring color standards over there? You say neutral is blue? What are the hot colors (up to 3 for 3 phase power)?

If you look his original post started with UK.

Fads

Economy 7 indicates UK :-)

Neutral is blue over there, hot (single phase) is brown. I believe 3 phase hots are brown, black & grey.

On Mon, 23 Feb 2004 19:44:22 +0000 (UTC) Michael Moroney wrote: | snipped-for-privacy@ipal.net writes: | |>So I see you have a UK callsign. So what are the wiring color standards |>over there? You say neutral is blue? What are the hot colors (up to 3 |>for 3 phase power)? | | Neutral is blue over there, hot (single phase) is brown. I believe 3 | phase hots are brown, black & grey.

And what about (safety) ground?

Do you know if the rest of Europe is the same?

On Mon, 23 Feb 2004 12:14:58 -0000 Mark wrote: | UK | | I've got hot water tank that has an economy 7 (night time) heater. But it | keeps burning the insulation on the live (blue) wire. When I rewire it'll | work fine before the insulation burns again and disconnects the wire. | | Have I faulty wiring or a faulty heater?

OK, now that I know what colors the wires should be over there, tell me what colors are actually present on the wiring. The other wire is brown?

I'm assuming 1 phase power. If both wire gauges are the same, then what is most interesting here is that the other wire is not burning up. Since blue is supposed to be neutral, but you are saying "live", I'm wondering if it's wired backwards, and is drawing extra current because it has the terminal for the blue wire connected to the water piping or other ground, and is losing current to that. If this were the case your breaker should still be tripping off if it is connected on the blue side, but that would not normally be the case.

Another possibility is that some other power source is energizing the water piping and it's coming back into the water heater which has connected it to the blue wire. If the wiring is connected but the heater is shut off, do you still get the blue wire burning up?

There are other tests that are more dangerous, so I'll just say you need to get a professional electrician to look into it if some simple problem is not found.

It's either green or green with a yellow stripe.

This is a newish standard, at least for some countries. I believe all of Europe uses this for new stuff but old stuff in some countries is different.

England may have used blue for a hot for the old standard, leading to a lot of confusion! (One European country did, anyway) So the original post may be talking about a hot, not a neutral.

On flexible cables....

Blue = Nuetral Brown = Live Green/yellow = Earth or ground

On non-flexible cable...

Black = Nuetral Red = Live (single phase) On three phase.. Red, Yellow, Blue

Sorry about the blue (live) confusion folks, I meant to type neutral but in my haste to fix the problem I typed it and didn't check afterwards.

The wiring and the element has been fine for 15 years.

I've just reconnected it again and will check in a few days to what it's like. It never blows the fuse.

Sorry about the blue (live) confusion folks, I meant to type neutral but in my haste to fix the problem I typed it and didn't check afterwards.

****************************************** Good Morning Mark,

You may have a short between the heater element and Ground on the neutral side, which may be providing a ground path for some other device on your overall wiring layout, or, possibly the heater is not grounded, and there is return to ground path for something else back through the water heater circuit.

I have seen this in the past when the ground on the main panel was bad, but the ground through the water pipes was good, and all the neutral currents went through the path of least resistance back to ground, the hot water heater wiring.

Sneak ground paths, and overloaded neutrals are hard to find, and a very common problem, especially on older wiring systems.

Check this with an Ohmeter, ( with the heater element disconnected, ) read between the neutral side, ( Blue ) wire and Ground. If you find a short, ( unless the Neutral is grounded deliberatly at this point ) This is your problem. But you have another problem that you are not seeing, and that the Neutral return to ground either at your main sevice panel, or at your meter is open. This must be a very small hot water heater, as all heaters I am used to are 240vac, not 120vac..

Have a great day .

| Sorry about the blue (live) confusion folks, I meant to type neutral but in | my haste to fix the problem I typed it and didn't check afterwards. | | The wiring and the element has been fine for 15 years. | | I've just reconnected it again and will check in a few days to what it's | like. It never blows the fuse.

If current is flowing only on the neutral (from somewhere else), then of course the fuse on the hot won't blow.

The "somewhere else" could be something else that has a broken neutral but is well grounded to the water than the heater is grounded do, where the water ground doesn't have a good path back to the transformer ground.

There could be other causes, but the dangerous ones come to me first.

| This must be a very small hot water heater, as all | heaters I am used to are 240vac, not 120vac..

He's in UK. Single phase, single pole, 220-240 some volts. They won't get the problem of phases out of balance with an open neutral like we would in the US (and can thus see something is wrong sooner), but it can still happen in various forms, which seems very plausible for this.

Perhaps, but the capital 'UK' on the first line certainly does :-)

daestrom

You have probably the combination of poor thermally rated supply cable, a relatively poor cable connection (which with a little oxidation due to heat causes higher than normal resistance & further heat ) & ppssibly also a high power thermal heating element, Remedies include better connection, tinned bigger cable witrh higher thermal rating of insulation, & lower wattage element. I have had similar problems with everything apparently "within spec", my burnouts developed about six month intervals.

Pete