What difference will tank lagging make, I have noted pre-lag kWh, what will be the result a week from now?

[ericmark]

Since I have an iboost+ I can read what energy has been used yesterday, last 7 days etc. 16.48 kWh in last 7 days, 34.64 kWh in last 28 days, but not a good reading as there was a 9-inch immersion heater, now a 27-inch immersion heater been in around 2 weeks. Yesterday 2.80 kWh, today 2.3 kWh at 5:30 pm.

With the 9-inch immersion, we were using around 4.5 kWh for 7 days, never hit the 5 kWh for 7 days, but we were not really getting much hot water, the over temperature trip was tripping 3kW it seems is too much for such a small immersion, but I use solar to heat the water, so want enough stored to bridge the bad days. OK 35p average per day to heat DHW and £20.68 for the jacket, it will take some time to break even. At least 3 months.

But most don't know how much energy is being used by the immersion, I am one of the odd few that do.

 

[Harry Bloomfield]

Eric, are you suggesting your cylinder has no insulation, or asking if it's worthwhile adding more?

 

[ericmark]

Eric, are you suggesting your cylinder has no insulation, or asking if it's worthwhile adding more?

It had the standard spray on foam they come with, but open the airing cupboard door and the heat hits you. So added one of these

Original as last picture. Not covered as neat as they show, but clearly going to retain more heat. However, as to how much it will save, that remains to be seen. So I am able to measure the kWh used, so once a week has passed I will give my findings.

I was surprised at how much more used when I went from 9" to 27" (5 kWh to 16.5 kWh) but also surprised how much quicker we seem to get hot water to the taps, and it also seems hotter, I did not expect that, the change to 27" was so it would span days with little solar.

There is nothing in the advert which gives any indication of how much energy is likely to be saved. So take a guess.

 

[polesapart]

King John, Act 4, Scene 2,

To gild refined gold, to paint the lily
To throw a perfume on the violet
To smooth the ice, or add another hue
Unto the rainbow, or with taper-light
To seek the beauteous eye of heaven to garnish,
Is wasteful and ridiculous excess.​

 

[ericmark]

You may be correct @polesapart I did not fit any extra insulation for 5 years since moving in. The change from 5 kWh to 16.5 kWh when I went from 9" to 27" was a shock, I had expected to use more but not over 3 times more.

If I keep opening the door to look, that will clearly alter how much used, so just waiting to see the results.

 

[Murdochcat]

16.5 kw sounds an awful lot fit such a small tank. Was it empty of hot water - but even then it’s still a lot.

Running hot water tap?

 

[ericmark]

Where have I said 26.5 kW? That is a 115 amp, main fuse is 60 amps, no way could I use that much power. Have I missed of a h somewhere? To heat the whole tank from cold, I would think around the 15 kWh and would take 5 hours at 3 kW. But not worried about that, clearly I do run off some hot water, but be it 9" at top or 27" the amount of hot water used is about the same. So 10 kWh per week approx extra is lost by heating the extra 16" of water, that seems a lot of extra energy.

A week today I will have answers, but until the jacket has been on a week, don't really know what it will save. I do wonder if the extra water being heated has resulted in a thermal flow though some pipework?

 

[Harry Bloomfield]

There is nothing in the advert which gives any indication of how much energy is likely to be saved. So take a guess.

I assumed those covers, were mainly intended for use where the cylinder has no insulation at all fitted? My cylinder is older than your blue one, it has yellow insulation. Rather than a stat., and immersion heater, it is gas heated - fired on 3pm to 8pm, and all digitally controlled by an actual temperature sensor, at a precise 60C. I have a Rpi, tapping into the data, so I can check minute by minute, the precise temperature of the cylinder.

The above was installed, some time after I did the following, so I wasn't able to accurately compare, but...

Before then, we were about to throw out an old bed quilt. I had also noticed our airing cupboard was rather warm, and the cylinder didn't remain that hot for as long as I would hope. So I draped the old quit fairly loosely around the cylinder, not really expecting it would make much difference. In fact it made more of a difference than I anticipated, with the hot water, still quite hot next morning after being off from 8pm, though I wasn't able to provide any numbers.

Now, I can actually provide numbers, and it generally reads above 54C, next morning. Which I think confirms an old quilt is quite effective.

It still suffers some heat loss, via convection flow, through the heating coils, if the last thing the heating system did - was heat the water in the cylinder....

I use a 3-port MOMO valve, which remains in the last position it was called to supply. If the last used was HW, then I get slight convection flow, through the coil, down and through the boiler. Cooled in the boiler. Perhaps, you have a similar loss?

 

[ericmark]

I have a coil, and it is C Plan, and no way to turn the hot coil off, so 16:54 yesterday and 14:16 today, clearly 2 hours still to go, and it does not take into account any hot water used, rather disappointing, I had hoped for a greater saving, but time will tell.

 

[flameport]

Most heat loss is from the pipes. Insulating an already insulated cylinder will achieve very little.

 

[ericmark]

Most heat loss is from the pipes. Insulating an already insulated cylinder will achieve very little.

So it seems, but only £20.68 so no great loss, I will report as to what saving I do get, as to loss in pipes, that is why I am using an immersion heater rather than the oil boiler, which I had to run 4 times a week ½ hour a time, although after 20 minutes it would turn off due to hot water return, a 20 kW boiler, so I would guess around 25 kWh to heat with oil (C Plan) and the water was only just warm enough.

But the old 9" immersion heater was letting the water go cold if we had a dull day, so change to 27" which is far better, however weekly energy use went from under 5 kWh to 16.5 kWh for the 7 days, so I assumed loses due to heat from the tank in the main. About the same amount of hot water to that using oil, so it does seem loosing over 10 kWh per week heating up the boiler and pipe work, and this time of year don't want those pipes heating my living room, so moving to electric is going to save money, as will not need to run the AC in the living room for as long.

So 2.3 kWh to 1.8 kWh yesterday until 4:40 pm to today 4:40 pm, but one day is not long enough to be sure it is a true reading. If it drops to 10 kWh for the week, I will be satisfied.

 

[Johntheo5]

Where have I said 26.5 kW? That is a 115 amp, main fuse is 60 amps, no way could I use that much power. Have I missed of a h somewhere? To heat the whole tank from cold, I would think around the 15 kWh and would take 5 hours at 3 kW. But not worried about that, clearly I do run off some hot water, but be it 9" at top or 27" the amount of hot water used is about the same. So 10 kWh per week approx extra is lost by heating the extra 16" of water, that seems a lot of extra energy.

A week today I will have answers, but until the jacket has been on a week, don't really know what it will save. I do wonder if the extra water being heated has resulted in a thermal flow though some pipework?

At a present 20C mains temperature, it requires, 4.65kWh to heat 100L to 60C, ((100*(60-20)/860)) so 9.3kWh to heat a 200L cylinder and 13.95kWh to heat a 300L cylinder, etc.
If you start off with a fully heated cylinder and finish up with the cylinder again reheated to 60C then your daily usage, litres, is the measured kWh/0.0465

 

[ericmark]

What I use is not important, what I lose is, two reasons, one it costs to heat it, and two more important, don't want to heat the house. Nothing I can do about the pipes, but not getting pipes hot boiler to storage tank to start with makes sense, so better to use an immersion heat to the boiler.

But my calculations were clearly flawed. I had assumed losses from a 9-inch immersion heater and a 27-inch immersion heater would not be that much different once the tank had been heated. But the loses were three times greater, so it seems the loses must be from the tank.

A small change I would have accepted, but three times seemed a bit OTT, so Screwfix had opened a new store in Welshpool so 10% off, so the jacket was £20.68 not a huge amount so felt worth fitting one. But since I can monitor immersion heater use, due to having an iboost+ fitted, it seemed prudent to measure before and after "Saving" the unit calls the power used a saving as should come from the sun. It does not consider I would get 15p/kWh for export, and off-peak costs 8.5p/kWh, so a simple time switch would save more, but not worth the cost to swap it. At 6.5p/kWh, gain would be looking at years. Which it seems may also be the case with the jacket.

 

[Harry Bloomfield]

What I use is not important, what I lose is, two reasons, one it costs to heat it, and two more important, don't want to heat the house. Nothing I can do about the pipes, but not getting pipes hot boiler to storage tank to start with makes sense, so better to use an immersion heat to the boiler.

I assume, by 'pipe losses', that means the heating pipes between boiler and cylinder. In winter, those 'losses' will be welcome, and contributing to heating the home, assuming the pipe run is entirely internal. My boiler to cylinder pipe run, is around 3m of 22mm flow, 3m return.

 

[ericmark]

I assume, by 'pipe losses', that means the heating pipes between boiler and cylinder. In winter, those 'losses' will be welcome, and contributing to heating the home, assuming the pipe run is entirely internal. My boiler to cylinder pipe run, is around 3m of 22mm flow, 3m return.

Yes, three-story house, so a lot of pipe work, all hidden, and most impossible to reach to lag, in winter does not really matter, it is still heating the house, but not wanted in summer. Since C plan, the bore is large, also the boiler its self need to get hot. And with at least 24 hours between burns, it fully cools before the next burn.