Problems with no hot water from new tank/immersion heater

[mikenovak]

I am desperate for help with a problem I am having with my hot water system and would appreciate any advice or suggestions?

I have a hot water system that consists of an immersion heater element that is into the top of a hot water tank for the hot water in my house (I have no boiler or central heating).

5 days ago it stopped working so I called a plumber. The plumber has now replaced the hot water tank as the old one was leaking, and fitted the new tank with a brand new immersion element (27") and thermostatic control. Unfortunately, I have had to have the plumber back 7 times over the past 4 days since fitting this tank/immersion as I still do not have hot water.

After leaving the water to heat up in the tank for over 1 hour+ when you put your hand under the tap it is red-hot, but if I try to fill the bath it starts off hot but then after a minute or so it goes Luke-warm and then cold (giving me only about 2 inches of hot water..).

The plumber has replaced the thermostat (twice) and then today he replaced the immersion heater element with a new one - but yet the problem is still the same.

During the last few days we have tried to change the water temperature by turning the temperature up on the small dial on top of the thermostat on the immersion element, but if it's turned up too far the small reset button pops out to disable it - and if its set even just slightly under that point then the water doesn't get hot enough...?

Both myself and the plumber are scratching our heads as we cannot understand what is happening. I have even paid extra to get an electrician in and he has checked all of the wiring from the fuse box up to the immersion heater and also checked the voltage directly to the unit and says all is fine - so I am desperate for someone to try to offer any advice as to what is wrong here..

A family member mentioned that he had had a similar issue some years ago where the thermostat that was put in his tank was causing the same problem (not enough hot water) and he says the plumber changed it as he said he had put the wrong one in (he said he should have put a thermostat for 'hard' water rather than then one had put in - for 'soft' water).. Is this true and you have to have a thermostat for either 'hard' or 'soft' water?

I really would appreciate any help and advice on this as it's driving us all crazy!

Mike

 

[twgas]

I would be looking at a mixer tap, wasing machine or shower letting cold water into the hot supply. try isolating the cylinder and turning a hot tap on and see if it stops running.

 

[TicklyT]

Assuming the heater is almost vertical, fitted in the top of the cylinder, is the thermostat the right length for the heater?

Hot water stratifies in the cylinder, with hot water at the top and cold water at the bottom. After a short time, you only get a small quantity of hot water at the top of the cylinder, but the rest of the water is no more than lukewarm. The size of that 'bubble' of hot water grows as the heater runs for longer.

A short thermostat will switch when only the water at the top of the cylinder is hot, where a longer one will won't operate until the water lower down the cylinder has heated up.

It may take several hours for a single immersion heater to heat the entire cylinder from cold, but once it is hot, it only needs to re-heat the quantity of water you draw off. An hour is usually enough to heat water for a shower or doing the washing up, but enough water to fill a bath usually takes a lot longer.

'Hard' and 'soft' water immersion heaters are made. With hard water, limescale deposits form over time, and may cause local overheating of small sections of the heater element, so the materials used are chosen to tolerate that.

'Soft' water tends to be slightly more acidic, so heaters made from different metals are used to better resist corrosion.

The difference only shows in the price and expected life of the heater, not how effectively it heats water.

 

[mikenovak]

I would be looking at a mixer tap, wasing machine or shower letting cold water into the hot supply. try isolating the cylinder and turning a hot tap on and see if it stops running.

How do I isolate it (remember i am no plumber ) as far as I am aware there is only 2 feeds - cold in from header tank and hot out - but then it's probably best if I take a photo to put on so you could see?

Thanks for your help sofar - very much appreciated

Mike

 

[mikenovak]

Assuming the heater is almost vertical, fitted in the top of the cylinder, is the thermostat the right length for the heater?

Hot water stratifies in the cylinder, with hot water at the top and cold water at the bottom. After a short time, you only get a small quantity of hot water at the top of the cylinder, but the rest of the water is no more than lukewarm. The size of that 'bubble' of hot water grows as the heater runs for longer.

A short thermostat will switch when only the water at the top of the cylinder is hot, where a longer one will won't operate until the water lower down the cylinder has heated up.

It may take several hours for a single immersion heater to heat the entire cylinder from cold, but once it is hot, it only needs to re-heat the quantity of water you draw off. An hour is usually enough to heat water for a shower or doing the washing up, but enough water to fill a bath usually takes a lot longer.

'Hard' and 'soft' water immersion heaters are made. With hard water, limescale deposits form over time, and may cause local overheating of small sections of the heater element, so the materials used are chosen to tolerate that.

'Soft' water tends to be slightly more acidic, so heaters made from different metals are used to better resist corrosion.

The difference only shows in the price and expected life of the heater, not how effectively it heats water.

Hi TicklyT

Thanks for the info.

I have been leaving the immersion switched on all the time for a number of hours to test that theory (i.e. to heat the whole tank it would take a couple of hours or more) - yet even after 3 - 4 hours of being on all the time I only get 2" of hot water in the bath when I run it before it goes cold.

Regards

Mike

 

[mikenovak]

I would be looking at a mixer tap, wasing machine or shower letting cold water into the hot supply. try isolating the cylinder and turning a hot tap on and see if it stops running.

Here are some photos that might be of help in identifying something obvious that I cannot see?

Untitled

• mikenovak
• 6 Mar 2011
• 1

Untitled

• mikenovak
• 6 Mar 2011
• 1

Untitled

• mikenovak
• 6 Mar 2011
• 1

[/img]

 

[TicklyT]

With the power safely isolated (preferrably at the consumer unit), disconnect the red and brown wires from the thermostat (white plastic bit in inmmersion heater). the thermostat should then just lift out so you can check the length of the one fitted. It should be about the same length as the pocket it sits in. No need to turn any water off - the thermostat just sits in a dry pocket.

If a short one is fitted, it will only respond to the water temperature at the top of the cylinder, not the temperature lower down.

 

[mikenovak]

With the power safely isolated (preferrably at the consumer unit), disconnect the red and brown wires from the thermostat (white plastic bit in inmmersion heater). the thermostat should then just lift out so you can check the length of the one fitted. It should be about the same length as the pocket it sits in. No need to turn any water off - the thermostat just sits in a dry pocket.

If a short one is fitted, it will only respond to the water temperature at the top of the cylinder, not the temperature lower down.

Just found the end of the box with the label on that the plumber brought with the latest immersion (including thermostat) - it's a 27" immersion element with an 18" thermostat - model number is HS27 and supplied by Banico Controls. The copper cylinder that the plumber put in is a 36 x 18 direct cylinder with envirofoam by Gledhill.

Thanks for your help so far - appreciate your taking the time to think about my problem

 

[xr4x4]

I would be looking at a mixer tap, wasing machine or shower letting cold water into the hot supply. try isolating the cylinder and turning a hot tap on and see if it stops running.

Here are some photos that might be of help in identifying something obvious that I cannot see?

Untitled

• mikenovak
• 6 Mar 2011
• 1

That wire from the immersion looks like it doesnt go direct to the switch, do you have a timer on the immsersion circuit?

 

[mikenovak]

I would be looking at a mixer tap, wasing machine or shower letting cold water into the hot supply. try isolating the cylinder and turning a hot tap on and see if it stops running.

Here are some photos that might be of help in identifying something obvious that I cannot see?

Untitled

• mikenovak
• 6 Mar 2011
• 1

That wire from the immersion looks like it doesnt go direct to the switch, do you have a timer on the immsersion circuit?

Hi

Yes- the wall switch cable goes to a timer on the wall, then another cable goes from the timer to the top of the tank. The electrician I had in checked all of the voltage etc from the switch on the wall to the timer and then from the timer to the tank - so all should be ok. Plus I got him to check that the plumber had wired it correctly and he confirmed he had.

Regards

Mike

 

[xr4x4]

Er....ok,

So how long is the immersion actucally on for? According to the timer?

Sounds like its not for long enough.

 

[mikenovak]

Er....ok,

So how long is the immersion actucally on for? According to the timer?

Sounds like its not for long enough.

Think we have sussed the problem out.. I have just had a friend around who is an electrician - he checked the power into and out of the thermostat - and guess what.. it's only intermittently working, and then whilst doing it it started arcing inside - so it's definetely a faulty thermostat.. He thinks the suppliers have had a faulty batch - hence the plumber changing it and it still not working properly. I will get another thermostat in the morning and hopefully resolve the problem Well, at least I know what it is now!

Thanks for your help - it's been very much appreciated.

Mike

 

[Nige F]

Ah so - another Chinese thermostat - allegedly

 

[mikenovak]

Ah so - another Chinese thermostat - allegedly

I bet it bl**dy is too lol - it's got to be a bad batch of these as the plumber replaced it with a brand new one from the same supplier - so will be making sure I tell him tomorrow so he can tell the supplier - otherwise there will be a lot more postings to this forum from people in the same situation as I was.

Thanks for your help though - very much appreciated

Mike

 

[DAMackinnon]

Replaced bottom emersion heater elements in hot water tank is not heating the 24hrs tank system but top emersion element does work when we use the booster system, but that cost money.

So we're asking what could be the possible cause of this problem plz help.