Immersion losing heat

Brego888 · 25-05-2018 11:58am #1

Hi all, I'm not sure if this is a plumbing or electrical question.
Over the last couple of weeks we've notice the amount of hot water we can get for a shower from our normal immersion setting has decreased. It starts warm but becomes cold much quicker than usual.

I think I can track this back to when I removed bathroom towel radiators a couple of weeks ago for painting. I obviously had to reintroduce some water back into the system when running the gas boiler again to refill the radiators and bleed all the air out.

I used the pressure gauge near the hot water tank to refill the system. I'm regretfully not sure where the turning valve was positioned before I started the process and feel where it is now might be letting cold water into the tank when the immersion should be heating the water. The valve has an "A" turning one way and a "C" turning the other. I've tried fully turning each way and somewhere in the middle with no help each time I use the immersion.

Does it make sense that this might be affecting the water or am I way off?

http://imgur.com/WkFywLo
http://imgur.com/p0KHGg7
http://imgur.com/4AOW3bT

Sleeper12 · 25-05-2018 12:26pm

Where you run the out of of hot water in the shower do you have hot water water elsewhere?

It could be a the shower itself.

Sleeper12 · 25-05-2018 12:27pm

Can you post a photo of the shower

Brego888 · 25-05-2018 1:38pm

Sleeper12 wrote: »

Where you run the out of of hot water in the shower do you have hot water water elsewhere?

It could be a the shower itself.

Just very lukewarm water left in the taps as well.
We have 2 showers, one in the main bath and on in en suite. Both affected the same.

http://imgur.com/Nuu0gSE
http://imgur.com/qVMWMNm
http://imgur.com/yJgK3NB

John.G · 25-05-2018 9:15pm

Brego888 wrote: »

Hi all, I'm not sure if this is a plumbing or electrical question.
Over the last couple of weeks we've notice the amount of hot water we can get for a shower from our normal immersion setting has decreased. It starts warm but becomes cold much quicker than usual.

I think I can track this back to when I removed bathroom towel radiators a couple of weeks ago for painting. I obviously had to reintroduce some water back into the system when running the gas boiler again to refill the radiators and bleed all the air out.

I used the pressure gauge near the hot water tank to refill the system. I'm regretfully not sure where the turning valve was positioned before I started the process and feel where it is now might be letting cold water into the tank when the immersion should be heating the water. The valve has an "A" turning one way and a "C" turning the other. I've tried fully turning each way and somewhere in the middle with no help each time I use the immersion.

Does it make sense that this might be affecting the water or am I way off?

http://imgur.com/WkFywLo
http://imgur.com/p0KHGg7
http://imgur.com/4AOW3bT

When you say immersion are you talking about a electric immersion or the water heating from your boiler??

Brego888 · 25-05-2018 11:13pm

Electric immersion. Don't use the boiler at all this time of the year.

John.G · 26-05-2018 12:15am

Brego888 wrote: »

Electric immersion. Don't use the boiler at all this time of the year.

The pressure gauge thats showing 1.5 bar is correct and is the pressure in the boiler water/expansion vessel system and when the boiler is on it circulates water in a coil in your cylinder that heats the water in the hot water cylinder, it has no direct contact with the contents of the hot water cylinder so any adjustment to that 1.5 bar pressure wont affect it except that you have a hole in the heating coil, highly unlikely. The white Myson TVR controls the temperature of the hot water by opening/shutting a valve in the hot water boiler circuit.

Electric immersion: some cylinders have a dual immersion with a switch marked Bath/Sink and will heat depending on which is selected either 50 Lires or around 100 litres of water. I dont know what size cylinder you have or where the heating elements are but a 3 kw immersion will take 5.8 Kwh per 100 litres of water to 60C from 10C and depending on its location can take from 0.5 hrs to 3 hrs to fully heat up the water. Its likely that yours is heating at least 150 litres to 60c which will take 3 hours. This 150 litres at 60C will give you 250 litres at 40C (factor of 1.66).So if you can make sense of this and see where the heating element(s) are located you should be able to figure out how much hot water is available to you.

Brego888 · 26-05-2018 1:01am

Thanks for your reply. It is a relatively new tank only installed 4 years ago. It came with a dual bath/sink switch. During installation a timer was put in and the setting permanently fixed to bath. Never had any issues.

How do you explain the recent drop in volume of hot water though? I've only ever needed 30 minutes to heat it for a shower. Now 30 minutes gives me about half the hot water I previously had.

John.G · 26-05-2018 9:17am

Brego888 wrote: »

Thanks for your reply. It is a relatively new tank only installed 4 years ago. It came with a dual bath/sink switch. During installation a timer was put in and the setting permanently fixed to bath. Never had any issues.

How do you explain the recent drop in volume of hot water though? I've only ever needed 30 minutes to heat it for a shower. Now 30 minutes gives me about half the hot water I previously had.

Assuming you have around a "23 ins" bath element then depending on the diameter of your hot water cylinder you are probably heating around 75 litres of water and maybe up to 95 litres.
lower figure of 75 litres means that in 30 minutes will raise the water temperature by 17C which ends up as a hot water temperature of (from 10C cold water) 27C...not much good for having a shower

Higher figure of 95 litres means that in 30 minutes will raise the water temperature by 14C which ends up as a hot water temperature of (from 10C cold water) 24C...less than useless.

So I really cant comment except to say that if the sink immersion was in use for 30 mins you would heat say 40 litres to 42C, a acceptable temperature for about a 4 minute shower. I can only suggest that you leave the immersion on for at least one hour, this gives 75 litres @ 44c and 95 litres @ 37C

Sleeper12 · 26-05-2018 10:29am

John.G wrote: »

Assuming you have around a "23 ins" bath element then depending on the diameter of your hot water cylinder you are probably heating around 75 litres of water and maybe up to 95 litres.
lower figure of 75 litres means that in 30 minutes will raise the water temperature by 17C which ends up as a hot water temperature of (from 10C cold water) 27C...not much good for having a shower

Higher figure of 95 litres means that in 30 minutes will raise the water temperature by 14C which ends up as a hot water temperature of (from 10C cold water) 24C...less than useless.

So I really cant comment except to say that if the sink immersion was in use for 30 mins you would heat say 40 litres to 42C, a acceptable temperature for about a 4 minute shower. I can only suggest that you leave the immersion on for at least one hour, this gives 75 litres @ 44c and 95 litres @ 37C

Totally agree. We've a boost button on our immersion & we'd ave it on for an hour before each shower. If the tank was stone cold we'd boost for 2 hours

I'm changing my boiler soon & will have a dedicated hot water zone. Gas heats water at roughly half the price of electricity

Wearb · 26-05-2018 10:32am

Is there any chance that your boiler was contributing to your hot water cylinder heretofore? And not now that your heating is turned off.

Brego888 · 26-05-2018 6:55pm

John.G wrote: »

Assuming you have around a "23 ins" bath element then depending on the diameter of your hot water cylinder you are probably heating around 75 litres of water and maybe up to 95 litres.
lower figure of 75 litres means that in 30 minutes will raise the water temperature by 17C which ends up as a hot water temperature of (from 10C cold water) 27C...not much good for having a shower

Higher figure of 95 litres means that in 30 minutes will raise the water temperature by 14C which ends up as a hot water temperature of (from 10C cold water) 24C...less than useless.

So I really cant comment except to say that if the sink immersion was in use for 30 mins you would heat say 40 litres to 42C, a acceptable temperature for about a 4 minute shower. I can only suggest that you leave the immersion on for at least one hour, this gives 75 litres @ 44c and 95 litres @ 37C

But leaving it on for an extra half an hour doesn't explain why I haven't needed to do that previously. 30 minutes has been fine for the last 4 years.

Brego888 · 26-05-2018 6:57pm

Wearb wrote: »

Is there any chance that your boiler was contributing to your hot water cylinder heretofore? And not now that your heating is turned off.

No not really. I only use the gas to heat the water for 3 or 4 months of the winter. For the rest of the year I only use the immersion and it has never been a problem up until recently.

John.G · 26-05-2018 7:00pm

Brego888 wrote: »

No not really. I only use the gas to heat the water for 3 or 4 months of the winter. For the rest of the year I only use the immersion and it has never been a problem up until recently.

roughly how long was the showering time and was it one or two showers

RebelButtMunch · 26-05-2018 7:03pm

The rads and taps are separate especially if your only talking about only using the immersion. In terms of heat loss

If anything you should perceive more hot water now as the cold water is milder now this time of year.

By itself Is your hot water as hot as it used to be. Can you measure it?

John.G · 26-05-2018 7:38pm

Brego888 wrote: »

But leaving it on for an extra half an hour doesn't explain why I haven't needed to do that previously. 30 minutes has been fine for the last 4 years.

You say in previous post " During installation a timer was put in and the setting permanently fixed to bath." what does this actuallu mean?. Thermodynamically the only way that I can see you reaching a showering temperature in 30 minutes is if the heating elements were wired in parallel giving 5KW or 6Kw or whatever the elements power is, but as you say why should this change if you have touched nothing in the electrical set up.

Wearb · 26-05-2018 8:07pm

Brego888 wrote: »

No not really. I only use the gas to heat the water for 3 or 4 months of the winter. For the rest of the year I only use the immersion and it has never been a problem up until recently.

When did you turn off your gas heating/ Did it coincide with your shower temp drop?

Brego888 · 26-05-2018 10:20pm

John.G wrote: »

roughly how long was the showering time and was it one or two showers

Used to get roughly 10 minutes out of either shower (but only 1 shower per 30 minute immersion use)
Now it's about 5 minutes or less

Brego888 · 26-05-2018 10:21pm

RebelButtMunch wrote: »

The rads and taps are separate especially if your only talking about only using the immersion. In terms of heat loss

If anything you should perceive more hot water now as the cold water is milder now this time of year.

By itself Is your hot water as hot as it used to be. Can you measure it?

Not sure how I'd measure it. But it feels equally as hot as previously but only lasts half the time.

Brego888 · 26-05-2018 10:26pm

John.G wrote: »

You say in previous post " During installation a timer was put in and the setting permanently fixed to bath." what does this actuallu mean?. Thermodynamically the only way that I can see you reaching a showering temperature in 30 minutes is if the heating elements were wired in parallel giving 5KW or 6Kw or whatever the elements power is, but as you say why should this change if you have touched nothing in the electrical set up.

The switch had a bath/sink switch when I bought it but the electrician but on a timer switch switch which doesnt have a bath/sink switch and he told me turning it on would heat the bath setting.
Anyway that doesn't explain why I only get half the heat that I used to get.

Brego888 · 26-05-2018 10:27pm

Wearb wrote: »

When did you turn off your gas heating/ Did it coincide with your shower temp drop?

No I haven't used the gas in 2 months. This problem only starting in last 2 weeks

RebelButtMunch · 26-05-2018 10:37pm

Anyone on the thread know if Bath means bath and sink elements and perhaps OPs bath element is gone and he's on sink power only?

corks finest · 26-05-2018 10:43pm

Brego888 wrote: »

Thanks for your reply. It is a relatively new tank only installed 4 years ago. It came with a dual bath/sink switch. During installation a timer was put in and the setting permanently fixed to bath. Never had any issues.

How do you explain the recent drop in volume of hot water though? I've only ever needed 30 minutes to heat it for a shower. Now 30 minutes gives me about half the hot water I previously had.

As a normal guy,I'd investigate if it's air locked,or needs bleeding first,then check the element on the tank itself,they do go after a few years

BaZmO* · 26-05-2018 10:52pm

RebelButtMunch wrote: »

Anyone on the thread know if Bath means bath and sink elements and perhaps OPs bath element is gone and he's on sink power only?

That’s what I was thinking. Most elements in an immersion have two heating elements, a short one for the sink which only heats the top half of the cylinder, and a long one for the bath that heats up the whole cylinder. Judging what the op said about the way the timer was wired to only have the bath element on it could be the case that the bath element going/blowing and the sink element kicking in.

It’s also possible that the element has just tripped. Under the plastic cap on the element there should be a reset button. Push it in to see if it resets?

Sleeper12 · 26-05-2018 10:53pm

Brego888 wrote:

The switch had a bath/sink switch when I bought it but the electrician but on a timer switch switch which doesnt have a bath/sink switch and he told me turning it on would heat the bath setting. Anyway that doesn't explain why I only get half the heat that I used to get.

Very possible electrician has it permanently on sink and not bath. This will heat less water but to the old temperature. So you will have hot water but not enough

It's a ridiculous set up limiting you to just bath. I've no idea why he'd do such a thing unless he made the mistake of putting the timer between the immersion switch and the immersion. It should be wired timer to immersion switch & immersion switch to the immersion. This will give you full control of bath and sink settings

Sleeper12 · 26-05-2018 10:55pm

RebelButtMunch wrote:

Anyone on the thread know if Bath means bath and sink elements and perhaps OPs bath element is gone and he's on sink power only?

Put any money that the electrictrican has it wired up to the sink and not the bath. I'm betting he's a handyman and not an electrician

Brego888 · 26-05-2018 11:03pm

BaZmO* wrote: »

That’s what I was thinking. Most elements in an immersion have two heating elements, a short one for the sink which only heats the top half of the cylinder, and a long one for the bath that heats up the whole cylinder. Judging what the op said about the way the timer was wired to only have the bath element on it could be the case that the bath element going/blowing and the sink element kicking in.

It’s also possible that the element has just tripped. Under the plastic cap on the element there should be a reset button. Push it in to see if it resets?

Yes this sounds like a good suggestion I might try re set it if I can get under the cap. Had watched a couple of videos of how to do this

Brego888 · 26-05-2018 11:07pm

Sleeper12 wrote: »

Very possible electrician has it permanently on sink and not bath. This will heat less water but to the old temperature. So you will have hot water but not enough

But again this in itself wouldn't explain the recent drop in amount of hot water

BaZmO* · 26-05-2018 11:07pm

Brego888 wrote: »

Yes this sounds like a good suggestion I might try re set it if I can get under the cap. Had watched a couple of videos of how to do this

If that doesn’t work I’d say the elements are wired the wrong way around.

Brego888 · 26-05-2018 11:09pm

BaZmO* wrote: »

If that doesn’t work I’d say the elements are wired the wrong way around.

But it's never been a problem over the last 4 years up until the last couple of weeks so why would being wired the wrong way round cause it?

Sleeper12 · 26-05-2018 11:27pm

The drop off in hot water is since the timer was installed. At least that's what I thought I read

Just rereading the thread now. Timers been there 4 years.

I'd get an electrician to test the voltage.

Sleeper12 · 26-05-2018 11:34pm

Another option is that the electrictrican wired in both elements instead of one. Very dangerous thing because you could have 6 or 7kw on 2.5 twin and earth. If it is wired like this then one element may have blown & it'll take twice as long to heat the water

BaZmO* · 26-05-2018 11:35pm

Brego888 wrote: »

But it's never been a problem over the last 4 years up until the last couple of weeks so why would being wired the wrong way round cause it?

Sounds strange alright, but if you were using the heating at the same time that’d contribute to heating the full cylinder.

Brego888 · 26-05-2018 11:52pm

Will try the reset option tomorrow and report back

John.G · 27-05-2018 3:38am

Brego888 wrote: »

Will try the reset option tomorrow and report back

You might also see what capacity cylinder you have, it should have a label on it, if its accessible.
Because you are still getting "1/2" heating, then I'd say again, logically, both elements are wired in parallel , the elements. I think are normally 3KW (bath) & 2KW (sink) although my 41 year old Santon is 3.5/2.5 KW, if we assume 5 KW then 75 litres will heat up (from 10C) to 39C and 95 litres will heat to 33C. (in 30 minutes), if the sink element is "blown" then 75/95 litres will heat to 27C/24C. If the bath element is blown then 40 litres will heat to 32C (I assumed 3KW sink element in my original calc). I think the advice would be get it repaired, select "bath" and set the timer to 1 hour.

You can still do this (set the timer to 1 hour) and see what the performance is then, while you are waiting to check it out.

John.G · 27-05-2018 3:42am

Sleeper12 wrote: »

Another option is that the electrictrican wired in both elements instead of one. Very dangerous thing because you could have 6 or 7kw on 2.5 twin and earth. If it is wired like this then one element may have blown & it'll take twice as long to heat the water

and hope that he hasn't bypassed the thermostat!

Brego888 · 27-05-2018 1:25pm

OK so I took the cap off and pressed the reset button. There was no click or any feedback from the button though. Not sure it did much.
I've attached a few more photos from below the cap. Do people thing I should move the blue dial from 60 to 70?
I also attached photos of my immersion timer so you know what I'm talking about.

Heating the water now for the usual half an hour to see how I get on.

http://imgur.com/gAKFkvs
http://imgur.com/hA7jCcL
http://imgur.com/ynIQejW
http://imgur.com/qs32tjU

Does the 2/2.85kw on the cap mean that there are 2 heating elements in the tank of the same size?

Sleeper12 · 27-05-2018 1:52pm

Brego888 wrote:

OK so I took the cap off and pressed the reset button. There was no click or any feedback from the button though. Not sure it did much. I've attached a few more photos from below the cap. Do people thing I should move the blue dial from 60 to 70? I also attached photos of my immersion timer so you know what I'm talking about.

That's a good quality timer but it's not installed correctly. Power should first go to the timer. From the timer to the bath / sink switch & then on to the element itself. This way you have the option of using the bath / sink switch.

It's a dual element. 2.85kw each element.

I'm not really convinced that you would get a 10 minutes hot shower from a 30 minutes 2.85kw boost.

Do you have a pump for the shower or is it just gravity on its own?

Brego888 · 27-05-2018 2:03pm

Sleeper12 wrote: »

That's a good quality timer but it's not installed correctly. Power should first go to the timer. From the timer to the bath / sink switch & then on to the element itself. This way you have the option of using the bath / sink switch.

It's a dual element. 2.85kw each element.

I'm not really convinced that you would get a 10 minutes hot shower from a 30 minutes 2.85kw boost.

Do you have a pump for the shower or is it just gravity on its own?

I suppose for the sake of my thread you'll have to take my word for it as myself or my girlfriend have been having 10 minute showers off a 30 minute boost without issue for 4 years!

No just gravity and no pump.

I changed the dial to 70 and did the usual 30 minute boost but no change in hot water amount with my shower just now.

If it comes to it we can always start putting the timer on for an hour but that still doesn't explain this issue.

Sleeper12 · 27-05-2018 2:09pm

Brego888 wrote: »

I suppose for the sake of my thread you'll have to take my word for it as myself or my girlfriend have been having 10 minute showers off a 30 minute boost without issue for 4 years!

No just gravity and no pump.

I changed the dial to 70 and did the usual 30 minute boost but no change in hot water amount with my shower just now.

If it comes to it we can always start putting the timer on for an hour but that still doesn't explain this issue.

I wasnt doubting your honesty, I was thinking both elements might be wired together at the timer giving over 5.5KW but if is only gravity then 2.85kw is enough to give you a 10 minute shower

Brego888 · 27-05-2018 2:15pm

No worries I appreciate the replies.
Any other theories on what is going on here?

browner85 · 27-05-2018 2:21pm

Have u a back boiler in the house ? Pump could be switched on and could be cooling the water in the cylinder

Brego888 · 27-05-2018 2:28pm

No back boiler.
It's a ground floor apartment.

Wearb · 27-05-2018 2:34pm

browner85 wrote: »

Have u a back boiler in the house ? Pump could be switched on and could be cooling the water in the cylinder

Any of your main heating pipes near the heating boiler getting warm at the end of your 30 min boost?

Brego888 · 27-05-2018 2:44pm

Wearb wrote: »

Any of your main heating pipes near the heating boiler getting warm at the end of your 30 min boost?

No all pipes cold around the gas boiler.

Only pipe that is warm around the water tank is the one coming out of the top in the below photo. Should the middle or bottom pipe be warm too?

http://imgur.com/57CiPj4

John.G · 27-05-2018 2:53pm

Brego888 wrote: »

No all pipes cold around the gas boiler.

Only pipe that is warm around the water tank is the one coming out of the top in the below photo. Should the middle or bottom pipe be warm too?

http://imgur.com/57CiPj4

Is it warm/hot at the Myson TRV (white valve), if so or even if not just turn the white knob clockwise to its stop,this will prevent any chance of losing heat through the coil and boiler system, put it back to its original setting (5?) when you flash up your boiler again.

John.G · 27-05-2018 3:02pm

Sleeper12 wrote: »

That's a good quality timer but it's not installed correctly. Power should first go to the timer. From the timer to the bath / sink switch & then on to the element itself. This way you have the option of using the bath / sink switch.

It's a dual element. 2.85kw each element.

I'm not really convinced that you would get a 10 minutes hot shower from a 30 minutes 2.85kw boost.

Do you have a pump for the shower or is it just gravity on its own?

how do you know its 2.85Kw/element

Brego888 · 27-05-2018 3:06pm

John.G wrote: »

Is it warm/hot at the Myson TRV (white valve), if so or even if not just turn the white knob clockwise to its stop,this will prevent any chance of losing heat through the coil and boiler system, put it back to its original setting (5?) when you flash up your boiler again.

So is that valve only relevant when the boiler is being used to heat the water? And no the pipe around that valve is stone cold.

Brego888 · 27-05-2018 3:09pm

John.G wrote: »

how do you know its 2.85Kw/element

Assume because of the cap photo I put up earlier

http://imgur.com/qs32tjU

John.G · 27-05-2018 4:14pm

Brego888 wrote: »

Assume because of the cap photo I put up earlier

http://imgur.com/qs32tjU

Sorry, I didnt pick up on that photo so it all goes back to your original query of why things have changed. (the reason I asked you to check the white myson valve was in case there was any reverse circulation induced in the coil from the hot water in the cylinder) Now that we know the exact immersion element power ratings we can do a few more calcs to try and figure out the mystery. If the electrician wired as he said..ie bath element only on then that will heat 75 litres (from 10C) to 26C or 95 litres to 23C in 30 minutes, both of those temperatures are only tepid and you would notice it straight away, now maybe he wired the sink immersion in permanently and if he did then this will heat (from 10C) 40 litres to 41C which is grand for showering and this would explain what is going on if you now had just cold water from the immersion if the sink element has failed BUT you still have hot water but it only lasts half the time. The only fit for all this is that the two elements are wired in parallel (both on) and the bath element has failed or there is no power to it. Assuming you had both elements working together for the last four years then they wold have heated (from10C) 75 litres to 43C or 95 Litres to 36C, in practice the amount of water being heated is probably somewhere between 75 & 95 litres as we dont know the diameter of the cylinder so the temperature was probably some way between the two, say 40C which was perfect showering temperature and you had somewhere around say a volume of 85 Litres at this temperature. Now you are gone to "1/2" so it can only mean to me at any rate that you are now running on the sink element only with the water temperature around the same at 41C but only with a volume of around 40 litres.
The sink element will heat 40 litres to 60C in 49 minutes and give you 67 litres of water at 40C when mixed with cold water at your shower, so again I would advise to set your timer to 1 hour and see what happens until you can get the wiring checked out.

It should be relatively easy to see what way the elements are wired up.

Brego888 · 27-05-2018 4:24pm

Cheers for that.

Heating it for an hour definitely works and is certainly enough for a shower. That's what the missus has been doing now the past 2 weeks where as I can just about get away with a really really quick shower with the 30 minutes!

So when you say I need the wiring checked what exactly needs checking or what do I need to ask an electrician to do?

Immersion losing heat

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