Electric Shower Overheating issue

newbie13

Hi All,

I have the Galaxy G9000 Electric wall shower in my bathroom since the house was built.

It always turn on the " Overheat Increase Flow " light after I turn off the shower.Most of the time the "Light" stays on with Overheat Increase flow. There are two light on the shower 1 is for the POWER 2nd for Overheat.

It doesnt come up during I have bath.After I finish my bath,I turn off the shower in 4-5 second I hear something inside boiling then this light come up.

I have tried to cool down the water flow before I turn off,then turn off the switch.

I turn off from main switch from which is on the ceiling.Is this dangerous to do it ?
I dont know how to deal with. Is there anyone with experienced with these Electric Power showers. ?
thanks

Sir Arthur Daley

There could be alot of reasons for that behaviour, have you checked the filter?

newbie13

Sir Arthur Daley wrote: »

have you checked the filter?

I am not experienced with electric related products & works! be honest scared off electricity.

Sir Arthur Daley

newbie13 wrote: »

I am not experienced with electric related products & works! be honest scared off electricity.

Ok, it may be the filter. One thing you could elimate before you get someone is that the shower head is free from lime scale and the shower flexible hose is not kinked/restricted.

newbie13

Sir Arthur Daley wrote: »

Ok, it may be the filter. One thing you could elimate before you get someone is that the shower head is free from lime scale and the shower flexible hose is not kinked/restricted.

Good idea thanks, I believe that it quite old hose& head.

Sir Arthur Daley

newbie13 wrote: »

Good idea thanks, I believe that it quite old hose& head.

If they are in good condition they be fine. The age of the shower would question the economics of getting it repaired versus buying a new one. Im not familier with that model but last time i fitted a galaxy was over 7-8 years ago.

Sleeper12

newbie13 wrote: »

Hi All,

I have the Galaxy G9000 Electric wall shower in my bathroom since the house was built.

It always turn on the " Overheat Increase Flow " light after I turn off the shower.Most of the time the "Light" stays on with Overheat Increase flow. There are two light on the shower 1 is for the POWER 2nd for Overheat.

It doesnt come up during I have bath.After I finish my bath,I turn off the shower in 4-5 second I hear something inside boiling then this light come up.

I have tried to cool down the water flow before I turn off,then turn off the switch.

I turn off from main switch from which is on the ceiling.Is this dangerous to do it ?
I dont know how to deal with. Is there anyone with experienced with these Electric Power showers. ?
thanks

NEVER turn off the electric shower by the pull cord switch. They are not designed for this & you'll burn it out.

The boiling noise you hear is called kettleing. The noise is thousands of air bubbles around the element. This is a sure sign that your element is caked with limescale. No limescale, no kettleing noise. You need a new element or shower if your old shower is old. The limescale is the reason the warning light comes on.

If getting the shower replaced try go for a Mira or Triton. Most of the other brands are rubbish

Bruthal

Any electric shower has a lot of residual heat in the element at the moment it is turned off, as well as the water in the heating can also hot.


In my own t90, the overheat stat clicks most times it is used, just after it is switched off, and resets when it cools. Likely some limescale not helping matters.

Also if the element has any limescale on it, it wont get the full cooling effect of the water on it during use, so when you turn it off, the element will already be a bit hotter than if it had no scale on it.


All in all, the nature of electric showers means there is a lot of heat in the element at the moment of switch off, and water in the heating can at around 40c or so now not flowing, which then gets the heat from the element transferred into it.

Turn the shower to the cold setting after each use with the heat selector before switching off, and let run for 20 seconds or so, which can avoid the problem.

Bruthal

Sir Arthur Daley wrote: »

Ok, it may be the filter. One thing you could elimate before you get someone is that the shower head is free from lime scale and the shower flexible hose is not kinked/restricted.

If they alone where the problem, the shower would be too hot to use properly.

Bruthal

newbie13 wrote: »

Hi All,
I have tried to cool down the water flow before I turn off,then turn off the switch.

Cooling it using the temperature dial wont do much. Try turning the selector switch to cold while its still running, and let run for 20 or 30 seconds before switching off.

Sir Arthur Daley

Bruthal wrote: »

If they alone where the problem, the shower would be too hot to use properly.

What point are you referring to the filter or hose or head?

Bruthal

Sir Arthur Daley wrote: »

What point are you referring to the filter or hose or head?

Both. If the filter is clogged, flow is reduced. User will turn the temperature dial to cooler (increase flow), to attempt to have the usual temperature shower.

If they are able to have the usual temperature shower by doing this, then no overheating due to water flow problem.

If the filter/shower head is clogged to the extent that its bringing on the overheat light after the shower is turned off, then the shower will be noticably hotter than normal during use.

The likely cause is limescale on the actual element, which insulates it from the cooling effect of the water flowing over it, so the element gets hotter than normal. Of course, the same thing would happen with a clogged filter, but the user would likely notice the shower being too hot during use.

We often see the other symptoms of scaled up elements as well, with showers cycling from hot to cold.

Id say the overheat light coming on is probably possible in a normal functioning shower as well, especially if the user likes very hot showers, but definitely much more likely with scale on elements.

Sir Arthur Daley

Bruthal wrote: »

Id say the overheat light coming on is probably possible in a normal functioning shower as well, especially if the user likes very hot showers, but definitely much more likely with scale on elements.

Power to the element would get cut off until unit cools, so wouldn't you get the situation of it cycling?

Bruthal

Sir Arthur Daley wrote: »

Power to the element would get cut off until unit cools, so wouldn't you get the situation of it cycling?

Cycling starts when the limecale reaches a certain thickness, and for people who tend to take quicker showers, the scale buildup would have to be even thicker.

Overheat cutout after switching off after use happens earlier in the limescale buildup stage, and since the shower is now off, no cycling happens. I can hear my t90 overheat cutout click after every use. People wont pay much attention to it, or even notice it, unless there is a light coming on beside an overheat sign such as in the OP case here.

Its still a fair point that cycling would be expected though. But that seems to happen with very badly scaled elements anyway.

Sir Arthur Daley

I am of the thinking if the shower was running and if the Overheat Increase Flow light comes on the power gets cuts to the element until it cools sufficiently.

Bruthal

Sir Arthur Daley wrote: »

I am of the thinking if the shower was running and if the Overheat Increase Flow light comes on the power gets cuts to the element until it cools sufficiently.

You would be correct. If it is overheating during normal use.

The OP said it happens after use, after the shower is switched off.

Any electric shower transfers residual element heat to the now non flowing heating can water, water which is likely at least 40c. So that water increases in temperature. Does`t take much for it to go over the cutout temperature, even on a perfectly functioning shower.

On an element with limescale, the element itself will reach a higher temperature during use. Making the overheat trip more likely.

Like I said, my t90 trips the overheat stat after every use, yet works perfectly fine during use.

Sleeper12

If you cut the element in half with a hacksaw you'd find so much limescale that there is only room in the heating can for half the amount of water it's supposed to have. This is why the water continues to heat up so much after it is turned off.
The only thing that can create the kettleing is limescale. The heating can will weigh almost twice as much now as a new one.
The shower is doing exactly what it is supposed to do when the warning light is on.
Only 2 options. Replace the heating can or the shower.

Bruthal

Sleeper12 wrote: »

If you cut the element in half with a hacksaw you'd find so much limescale that there is only room in the heating can for half the amount of water it's supposed to have. This is why the water continues to heat up so much after so much.

Id say the main reason the overheat trips is because the can itself overheats due to the elements being insulated from the cooling effect of the water. The overheat stat is actually in contact with outside of the can itself.

The water in a brand new shower will heat up quite substantially after it is switched off too. Long showers cause cans to overheat too. There is a duty cycle to stick to.

Sleeper12

Bruthal wrote: »

Id say the main reason the overheat trips is because the can itself overheats due to the elements being insulated from the cooling effect of the water. The overheat stat is actually in contact with outside of the can itself.

The water in a brand new shower will heat up quite substantially after it is switched off too. Long showers cause cans to overheat too. There is a duty cycle to stick to.

That quite possibly contributes to the problem.
The biggest problem I have after replacing a shower like this (even with the same model is quite often the client feels that the damaged shower was better than the new one. This is because Less water fits into the scaled heating can. Obviously if the can holds only half the amount of water as the new one then it heats the water quicker. This means you get a much quicker flow of water & therefore much better pressure while still getting hot water.

Bruthal

Sleeper12 wrote: »

That quite possibly contributes to the problem.
The biggest problem I have after replacing a shower like this (even with the same model is quite often the client feels that the damaged shower was better than the new one. This is because Less water fits into the scaled heating can. Obviously if the can holds only half the amount of water as the new one then it heats the water quicker. This means you get a much quicker flow of water & therefore much better pressure while still getting hot water.

I'm not convinced of that.

If the element is that badly scaled, it won't transfer as much heat to the water, hence the extra heat transfer to the can and stat.

The electric shower can only transfer a certain amount of heat to a given quantity of water per minute. This can't be increased using the same kW elements, no matter what else is done. Temperature of output depends on input temperature and elements kW and flow rate. A higher flow rate at same output temperature requires either a bigger element, or a higher initial water temperature.

The can being of less volume means it changes water more often. It does not mean more water is actually flowing. And it cannot mean more heat is transferred to the water.

It cannot transfer more heat to a given volume of water per minute than when new. So user imagination might be the answer there.

Sleeper12

Bruthal wrote: »

I'm not convinced of that.

If the element is that badly scaled, it won't transfer as much heat to the water, hence the extra heat transfer to the can and stat.

The electric shower can only transfer a certain amount of heat to a given quantity of water per minute. This can't be increased using the same kW elements, no matter what else is done. Temperature of output depends on input temperature and elements kW and flow rate. A higher flow rate at same output temperature requires either a bigger element, or a higher initial water temperature.

The can being of less volume means it changes water more often. It does not mean more water is actually flowing. And it cannot mean more heat is transferred to the water.

It cannot transfer more heat to a given volume of water per minute than when new. So user imagination might be the answer there.

I'm not sure you are following me on this.
Shower puts 8.5kw into element or 8.5kw worth of heat into heating can. Let's say new can holds a pint of water. The 8.5kw element has to heat a pint of water. Now let's say Heating can caked in limescale can only hold a half pint of water put it is still 8.5kw of energy / heat going in. Obviously now you have to increase the flow of the water (pressure). If you don't do this then the Tco will come into play & you'll get cycling scalding, freezing.

This is where clients think new shower isn't working properly. They have to reduce the pressure to get the same heat their old shower. If you were to put the old heating can in they would the pressure they have gotten used to.

Bruthal

Sleeper12 wrote: »

I'm not sure you are following me on this.
Shower puts 8.5kw into element or 8.5kw worth of heat into heating can. Let's say new can holds a pint of water. The 8.5kw element has to heat a pint of water. Now let's say Heating can caked in limescale can only hold a half pint of water put it is still 8.5kw of energy / heat going in. Obviously now you have to increase the flow of the water (pressure). If you don't do this then the Tco will come into play & you'll get cycling scalding, freezing.

You will have to think about that now.

Assume flow rate is 10 pints per minute
Can holds a pint. There for can water changes 10 times per minute. If the can volume reduces to 0.5 pints, it is correct to say that can will heat in half the time.

But..... The same 10 pints per minute flow rate causes 20 changes of water in the can per minute. Same heat input. Same temperature change. Same flow rate. And can volume is heating faster. But it's being refilled twice as often.

A 10 pint can will still work perfectly, but would require a longer initial startup time to be ready to use.

You can not change physics laws. 8.5 kW will increases a given flow rate temperature. Changing can volume can't change that.

If what you say is true, then surely designing cans half the size would require half the element kW. But its simply not correct.

The only other difference possible is a different shower head with less or smaller holes on the older shower, causing a faster water jet. But higher water volume with same element kW and same temperature change can't happen. That's certain.

Sir Arthur Daley

Is the shower head that may be partially blocked with scale be ruled as not being a part of the problem that the op has?

Sleeper12

Bruthal wrote: »

You will have to think about that now.

Assume flow rate is 10 pints per minute
Can holds a pint. There for can water changes 10 times per minute. If the can volume reduces to 0.5 pints, it is correct to say that can will heat in half the time.

But..... The same 10 pints per minute flow rate causes 20 changes of water in the can per minute. Same heat input. Same temperature change. Same flow rate. And can volume is heating faster. But it's being refilled twice as often.

A 10 pint can will still work perfectly, but would require a longer initial startup time to be ready to use.

You can not change physics laws. 8.5 kW will increases a given flow rate temperature. Changing can volume can't change that.

If what you say is true, then surely designing cans half the size would require half the element kW. But its simply not correct.

The only other difference possible is a different shower head with less or smaller holes on the older shower, causing a faster water jet. But higher water volume with same element kW and same temperature change can't happen. That's certain.

I can't speak about physics laws but if the can heats up twice as fast & you don't increase the flow and water then the water in the can will get too hot & the Tco will cut in.
CCan you explain that?
My brain hurts here thinking about this!

Bruthal

Sir Arthur Daley wrote: »

Is the shower head that may be partially blocked with scale be ruled as not being a part of the problem that the op has?

If that is part of the problem, the shower would be too hot to use. They didn't seem to indicate that was happening.

Head partially blocked = reduced flow rate = hotter shower during use.

Sleeper12

Sir Arthur Daley wrote: »

Is the shower head that may be partially blocked with scale be ruled as not being a part of the problem that the op has?

It could be blocked. In fact with the amount of limescale on his element I would think he'd have to clean the head every few weeks. It may contribute to the problem but once you hear kettleing you know it's the element. For kettleing the water is coming close to boil.

Sir Arthur Daley

The heating can must be the culprit so.

Bruthal

Sleeper12 wrote: »

I can't speak about physics laws but if the can heats up twice as fast & you don't increase the flow and water then the water in the can will get too hot & the Tco will cut in.
CCan you explain that?
My brain hurts here thinking about this!

1 pint heating can.
Shower pump running.
Temperature dial set so 10 pints per minute flows.
Heat can empties and refilled 10 times a minute. 10 pints a minute passes through it.

0.5 pint heating can.
Shower pump running.
Temperature dial set so 10 pints per minute flows.
Heat can empties and refilled 20 times a minute. 10 pints a minute still pass through it.

100 pint heating can.
Shower pump running.
Temperature dial set to 10 pints per minute.
Heat can empties 1/10th volume per minute. So it can still heat and supply 10 pints per minute the same as other 2 cans. But it would take a few minutes to initially get to operating temperature, and it would no longer be an instant shower.

In all 3 cases, 8.5kw heat put into water. And that is fixed. No way to increase pints per minute heated by certain temperature.

Sleeper12

Sir Arthur Daley wrote: »

The heating can must be the culprit so.

It is & you weren't far off the track. First thing I'd always tell the client is take the head off. If that fails next likely thing is filter. I've rarely seen the hose being the problem but it does happen. If shower is too hot & it's not these then it has to be element. But there is also a tiny chance that the flow valve has failed.

Bruthal

Sir Arthur Daley wrote: »

The heating can must be the culprit so.

Its likely. But as I was saying, my shower trips its overheat stat after every switch off. I'd say there is some scale built up. But the temperature in the heating can always soars up in any shower switched off from full on. At switch off, flow has ceased, but element still at operating temperature.

Just try switching one off, and back on 20 seconds later. It will be roasting for a few seconds. So I'd say it happens on properly working showers sometimes too.

Sir Arthur Daley

Bruthal wrote: »

Just try switching one off, and back on 20 seconds later. It will be roasting for a few seconds. So I'd say it happens on properly working showers sometimes too.

In old showers this would be true but the ones with phased shutdown elimates this.