Hot water cylinder losing heat too fast

[mpooley]

Hi all
I have only recently realised that my Hot water cylinder is unable to keep the water hot overnight.
to be honest I'm not sure how it should perform but it seems pretty bad to me.
I have a 1200x450 indirect tank insulated with 25 foam and a tank jacket on top of that.
I have just recently tried to save money by turning the immersion off at 6pm and as we are two pensioner who don't use a lot of hot water I thought it would stay warm enough to have a wash/shower in the morning but it doesn't and I have to give it a boost up to 45c at 6:30 and then raise temp to 60c for rest of day (i did this because I thought that the hotter it was it would keep hot longer)
this is a graph of tank temp from last night can any one advise as to what might be wrong please?

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• mpooley
• 15 Apr 2014
• 1

 

[kidgreen61]

Does the vent pipe rise vertically from the cylinder, (rather than a short horizontal length before the vertical)?

If so, you may lose quite a bit of heat that way.

As regards the immersion heater, it is fitted with a thermostat, and will cut out when it reaches temp, so you may as well leave it switched on all the time.

 

[Armo74]

Some pictures of your tank would help and other info.
Sounds like your current setup needs bringing upto date so you can control what time your your hot water heats up.
Using the immersion will be costing you a fair bit.

 

[dcawkwell]

Most likely cause would you have a leak somewhere possibly under the floor or a dripping tap.
Or depending on the layout your tank and piping is acting as a heat source with the coil and is feeding the central heating circuit with some heat.

 

[mogget]

At which point on the cylinder are you measuring the temperature? Usually the cylinder thermostat is 1/3 of the way up from the bottom and is set to 60 degrees C to ensure the water is heated properly (this is important as it stops bacteria growing in the water).

 

[mpooley]

Ok thanks guys.

firstly I don't think its a control problem as I'm a bit of a computer/electronics nerd I have built my own computer controlled heating system. which has temp sensors all over the house the flow and return and the Hot water. I also wrote the program that controls the boiler / zone controls etc on a PC 24/7
That is how I got that graph.
It was only when tried to save on our electric bills I noticed this problem!
As for updating the rest of the system yes it's a nightmare. the immersion cupboard is a mess I've never seen anything like it although I bet you have seen a few as bad lol
Oh the reason I don't use the oil boiler for Hot water in summer is that I have worked it out as costing more then the immersion! I believe because of having to heat up the boiler and pipes just for hot water.

This is how it was when I moved in. The pipe work is still the same

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• mpooley
• 15 Apr 2014
• 1

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• mpooley
• 15 Apr 2014
• 1

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• mpooley
• 15 Apr 2014
• 1

 

[jeff the gasman]

Could be a convection current finding a path from cylinder and back again. It looks like you have a shower plumbed from cylinder outlet is the cold for this shower fed from cylinder feed?
The shower mixer would feel warm when not in use.

 

[Armo74]

The pumps not ideal either really,if it has to be mounted horizontally then the electrics should at least be on the top.

 

[mpooley]

Could be a convection current finding a path from cylinder and back again. It looks like you have a shower plumbed from cylinder outlet is the cold for this shower fed from cylinder feed?
The shower mixer would feel warm when not in use.

Yes you are right there is a shower on the other side of that back wall.
It looks like the shower has it's own 22mm feed down from the loft and the hot feed is 15mm
it doesn't feel warm.

 

[HERTS P&D]

It also looks like your cylinder stat is too high on the cylinder.

Andy

 

[mpooley]

It also looks like your cylinder stat is too high on the cylinder.

Andy

Ah thats interesting ! Mogget also mentioned about where I was measuring the temperature.
Now I don't use that thermostat any more since I added my computer control and it was difficult for me to put my temp sensor chip anywhere else but on the top outlet just 20mm above the tank.
But if you think that is too high then I guess you will think my new one is miles too high!
So I can see the logic that my tank is not getting hot all the way down.
so there is not enough hot water. mmmh

but I have tried increasing the temperature that my sensor will cut off the power and when I go above 65c the black reset button pops up and turns the immersion off until I reset it.
so I'm thinking it doesn't matter where the sensor is ......
Is my logic right here?

I'm no plumber so have almost zero experience

 

[mogget]

Aha! if your sensor is the same one controlling the heating your cylinder may not ever get properly hot.

The heat is introduced somewhere in the cylinder, and the hot water nearly immediately rises to the top (hot water is lighter than cold water). This forms layers of water at decreasing temperature down the cylinder, which is known as stratification.

You need to make sure that the sensor controlling the heating is placed somewhere lower on the cylinder. Then you will heat all of the cylinder above this point.

If you're switching on the immersion, the sensor at the top will very quickly register 60 degrees but just a couple of inches lower down the water may be near room temperature. So there will be very little hot water in the cylinder at the point you turn it off.

Attach another sensor 9 inches lower and you'll see the effect.

 

[mogget]

To add, I would place the cylinder thermistor for your way-above-my-head computer control system 1/3 of the way up the cylinder.

I'd love to be able to program computers, just never seemed to master coding.

 

[mogget]

...and it was difficult for me to put my temp sensor chip anywhere else but on the top outlet just 20mm above the tank

You can cut through the foam on the cylinder to gain access to the hot bit inside

 

[gas112]

first thing you want to be checking is what DCawkwell suggested