Water heater is kicking out the power

[canuckamuck]

My shower water heater is kicking out the main breaker on the consumer unit. Not the ELCB, but the main off on switch for the whole unit. It did it once yesterday, and twice today so I have it switched off for now, and I will go get a new one I guess, but I would like to know what would cause that.

[eyecatcher]

Do you have a seconday breaker adjacent to the shower or just outside the bathroom?

They can allow steam to get in and you get the same nuisance factor. Mostly happens in this season when there is more steam.

New showers have their own breakers built in now so is yours due for replacing anyway?

[lopburi3]

The main breaker on the unit is the ELCB - that is what blows with a ground fault. Are you actually talking about a remote breaker? If the shower unit and blows when not using most likely lizard inside tripping it. If a remote breaker and blows when using shower most likely you are pulling more power than it can handle (cooler weather may have you using max power).

[lopburi3]

If you are talking about the main breaker in your distribution panel what is it rated? And what is the shower wattage? And is there a lot of other electric on at the same time? As said this is the time of year when you use much higher wattage setting on a water heater.

[bankruatsteve]

What is the watt rating for your shower unit? What is the breaker rating in amps? Photo of your CU uncovered would help.

Edit: What would cause that is 1) over current 2) RCD (RCBO) detecting a fault. Usually a fault related to heating unit is with the multi-point units generating steam. The single point shower units usually don't have that problem (except they may take a while to resume heating).

Edited December 31, 2015 by bankruatsteve

[canuckamuck]

The water heater has functioned fine for 4 years in the same configuration. It is only 3500 watts. The consumer unit (Distribution unit) is a 50 amp. The heater is hooked to a 20 amp breaker on the panel.

It is the main breaker in the distribution unit that is tripping. Not the ELCB or the circuit breaker in the heater.

So it knocks out power for the whole house.

I don't think it is a short or the ELCB would trip. So I think the heater itself is knackered.

Not much other power being used at the time of the outages

Edited December 31, 2015 by canuckamuck

[bankruatsteve]

Yah. Is the main breaker an RCBO (IE: does it have a "Test" button) or just over-current breaker? The "ELCB" in your shower unit is basically an "RCD" for fault protection and may not be calibrated same as RCBO in your CU. If you have short circuit, that would be over-current breaker.

Edit: Sounds like a fault somewhere. Can you take off the cover of your shower unit and look for anything between the mains connections? (turn off breaker before you do that). Could be gecko shit, sludge, stuff like that. Maybe give it a wipe and try again. Maybe your unit is screwed. But probably not from over-current or short.

Edited December 31, 2015 by bankruatsteve

[canuckamuck]

I don't know the exact terminology. But yes the Cu has the test button. The Cu has tripped a few times over the years. In all of those cases it was both switches that tripped and the little black button popped out. But this time it is only the far left switch which dropped and the little button did not pop up. Which indicates to me the RCBO did not trip. But the main breaker did.

[canuckamuck]

I will open the shower unit tomorrow

[bankruatsteve]

Hmmm. The "main" breaker is usually the RCBO (with the test button). Not sure what other button it is you talk about? Anyway... if that is 50a and your shower is connected to 20a breaker then it is not over-current (short). It would be a fault detected by the RCBO but not your shower unit. Your shower unit should also have a test button - does that work? IE: does it shut power to the unit until you re-set?

[canuckamuck]

I will send a picture tomorrow. I am probably describing things poorly.

As for the shower test button. I have never tried it. But I will in the morning.

[lopburi3]

It appears your total usage is too high for your main breaker (50 amp) - it may be defective. The fact that breaker/ELCB on unit and 20 amp breaker are not tripping seems to indicate nothing wrong with heater.

[canuckamuck]

Well that would be inconvenient. How could I find out for sure?

Edited December 31, 2015 by canuckamuck

[bankruatsteve]

Well that would be inconvenient. How could I find out for sure?

Just do the other stuff. You do not have over-current problem.

[lopburi3]

Believe you have a main panel breaker that is not an RCD but only a breaker and that is tripping? So the problem is either excessive total current or defective breaker. An electrician could use an ammeter to measure the total current but try to think of other heavy electric usage at the same time as your shower. Anything new? Electric ovens? Large refrigerators? Air conditioners? Something other than heater might be using more current than normal and not tripping its breaker but total too much for main feed. Turn of of selected other breakers when using shower can be used in attempt to find - but if intermittent may not be easy.

[canuckamuck]

Nothing new, and not much running at the time. I will try to get a bunch of high demand devices running at the same time tomorrow. Kettles, power tools and such. And see if I can trip it without the heater running. There are no air con units here.

[cornishcarlos]

Nothing new, and not much running at the time. I will try to get a bunch of high demand devices running at the same time tomorrow. Kettles, power tools and such. And see if I can trip it without the heater running. There are no air con units here.

If you get in the shower with a kettle and power tools, it won't be just the main breaker trippin'

[Foozool]

Just replace it with a new one and not taking a chance of electric shock.

[RichCor]

From what the OP has so far described, if the main breaker is popping then it could be

• over-all power demand on main breaker too great (but system working as designed)
• main breaker has lost rating capacity, main breaker needs replacement
• electrical load of water heater greater due to L/N fault (wouldn't trip RCD/ELCB), MCB or ELCB capacity not yet exceeded, main breaker capacity exceeded
• electrical leak in water heater, ELCB or RCD may not be functioning (has it been tested recently), main breaker acting as the functioning RCD.

[Crossy]

If it really is opening the main breaker on over-current with no other loads on at the time it's shot.

If it's opening the main breaker on earth-leakage it's shot.

To be honest, particularly where shower heaters are concerned, if it's doubtful replace it. Ensure the new one is grounded.

[canuckamuck]

From what the OP has so far described, if the main breaker is popping then it could be

• over-all power demand on main breaker too great (but system working as designed)
• main breaker has lost rating capacity, main breaker needs replacement
• electrical load of water heater greater due to L/N fault (wouldn't trip RCD/ELCB), MCB or ELCB capacity not yet exceeded, main breaker capacity exceeded
• electrical leak in water heater, ELCB or RCD may not be functioning (has it been tested recently), main breaker acting as the functioning RCD.

Please help me understand an L/N fault.

The load on the electrical system, at the times it has kicked out, has been very low. Just fridge, freezer, PC, a couple of fluorescents and two small pond pumps. So it can't be overall load on the system. It's a 50 amp set up. Unless the unit is faulty. It is 4 years old.

A problem I noticed today is that when the shower head is left hanging to the ground, air is being sucked in through the inlet tap at the base of the heater and into the heating reservoir. You can actually see it happening with the cover off because the internal pipes are slightly transparent. My people like to fill a bucket with the shower head hanging in the bucket and leave it there with very low flow through the head. Every time it has tripped it has been in this situation, where the shower head was hanging to the ground and barely running. I haven't been able to make it trip with the shower head in the normal high position. And air doesn't suck in when the shower head is high either.

I am tempted to just replace the cheap tap (which leaks anyway) and see if that fixes it. Don't worry about safety, I have the breaker switched off when I am not there testing it, and the ELCB on the heater works (I tested it today). No one is having showers in there at the moment

[canuckamuck]

While we are on this topic, I do expect I will be replacing the heater. I want to get a 4500-5000w type. What breaker and wire will I need?

[Crossy]

While we are on this topic, I do expect I will be replacing the heater. I want to get a 4500-5000w type. What breaker and wire will I need?

If your existing wiring is 2.5mm² you'll be ok with a 20A breaker so long as you don't take 1/2 hour showers.

If you are replacing the wiring go for 4mm² and a 30A breaker.

[canuckamuck]

While we are on this topic, I do expect I will be replacing the heater. I want to get a 4500-5000w type. What breaker and wire will I need?

If your existing wiring is 2.5mm² you'll be ok with a 20A breaker so long as you don't take 1/2 hour showers.

If you are replacing the wiring go for 4mm² and a 30A breaker.

Thanks Crossy

[RichCor]

From what the OP has so far described, if the main breaker is popping then it could be

• over-all power demand on main breaker too great (but system working as designed)
• main breaker has lost rating capacity, main breaker needs replacement
• electrical load of water heater greater due to L/N fault (wouldn't trip RCD/ELCB), MCB or ELCB capacity not yet exceeded, main breaker capacity exceeded
• electrical leak in water heater, ELCB or RCD may not be functioning (has it been tested recently), main breaker acting as the functioning RCD.

Please help me understand an L/N fault.

The load on the electrical system, at the times it has kicked out, has been very low. Just fridge, freezer, PC, a couple of fluorescents and two small pond pumps. So it can't be overall load on the system. It's a 50 amp set up. Unless the unit is faulty. It is 4 years old.

A problem I noticed today is that when the shower head is left hanging to the ground, air is being sucked in through the inlet tap at the base of the heater and into the heating reservoir. You can actually see it happening with the cover off because the internal pipes are slightly transparent. My people like to fill a bucket with the shower head hanging in the bucket and leave it there with very low flow through the head. Every time it has tripped it has been in this situation, where the shower head was hanging to the ground and barely running. I haven't been able to make it trip with the shower head in the normal high position. And air doesn't suck in when the shower head is high either.

I am tempted to just replace the cheap tap (which leaks anyway) and see if that fixes it. Don't worry about safety, I have the breaker switched off when I am not there testing it, and the ELCB on the heater works (I tested it today). No one is having showers in there at the moment

In this instance, a L/N fault condition would be one where a device design has failed and higher power is being drawn as a result, usually the extra load being converted into heat, eventually causing an upstream breaker to open. This type of fault wouldn't trigger an RCD device as the current isn't being leaked away from Load / Neutral wiring.

Sounds like you've pinpointed the conditions that lead to the fault condition arising.

If your water heater is designed to deliver a set water temperature then having air backflow into the thermal vessel could cause the power/heat regulation system to pull maximum current as it attempts to have the water sensor reach desired temperature. Though it seems odd that no other breaker and only the main breaker is affected.

If you water heater is just the variable percentage type then the power load should be fixed and the air backflow shouldn't have any effect on the total power draw -- though this condition could lead to damage of the thermal vessel or heater element connection as they then become the thermal coupler dissipating the generated heat.

I would thing allowing air to backflow into a running water heating system isn't a good thing.

[canuckamuck]

On Monday I'll change that valve and see if it stops the problem. We will still probably get a new heater anyways

[canuckamuck]

How would I know, until I replace it or fix it and see a difference in the bill?

[lopburi3]

It is not clear if you are turning heating unit off when you say running water at low volume with shower unit to floor. Heater should only be turned on when actually needing hot water for shower - if just using to fill buckets and such turn the heating off. Low volume of water with heater on can cause boiling (which your mention of air bubbles in line seems to be happening) and this is a serious concern in all manuals and units have a built in volume control to actually prevent operation of heater but that could have failed (and should never be relied on).

[canuckamuck]

It is not clear if you are turning heating unit off when you say running water at low volume with shower unit to floor. Heater should only be turned on when actually needing hot water for shower - if just using to fill buckets and such turn the heating off. Low volume of water with heater on can cause boiling (which your mention of air bubbles in line seems to be happening) and this is a serious concern in all manuals and units have a built in volume control to actually prevent operation of heater but that could have failed (and should never be relied on).

They fill the big bucket and have a bucket shower, so the heater is on. Always at max too, because it is a weak heater and we live at 700 meters altitude.

I am pretty confident now that it is the air leak and the low flow usage that is causing the issue. A normal shower can be had without knocking out the power. We will be buying a new one and this might get moved to be a kitchen water heater. Or it might get tossed.

[bankruatsteve]

Uhm - if you or yours needs to have a hot/warm water bucket splash, BOIL some water and add it to the bucket. Using the shower unit for that at low flow (like others say) is probably causing your problem and not the way to do it. It would be much more efficient to heat water in the kettle or over the coals in a pot. C'mon... THINK.