How to use Telford Tristor Thermal store economically

[Nixstar]

Hi,
Somebody please help!
I have recently moved into a home with a Telford Tristor Thermalstore used to heat the water in the flat. Problem is that after 1 and a half showers, hot water has run out. In fact, the hot water is never really that hot. A plumber has been over and changed the immersion heaters and thermostats (there are 2 on the cylinder), which has only marginally improved things. The Thermalstore is heated via an immersion heater on the Economy 7 tariff. Surely, after 7 hours of heating overnight there ought to be ample hot water in the morning. Now I've been told that the economy 7 system is not suited to the thermal store, which in fact needs to be powered 24/7 to run as its supposed to. The plumber asked me to keep the booster on for 24 hours and see if that improved things, which I reluctantly did (worried about my electricity bills) and I did have hotter water and more of it. He says the immersion connected to economy 7 needs to be rewired to receive 24/7 power. That both immersions need to be on 24/7 and this is the way a thermal store is designed to operate. Won't that mean extortionate electricity bills though? If anyone can provide any advice and expertise on the best way to use the Tristor I would very much appreciate it. So worried with the energy prices about to skyrocket.
It might help to know that the only source of heating are the 2 immersion heaters on the cylinder. It is not connected to a boiler/woodburner or solar panels and can't be either.
I look forward to any insights, thanks.

 

[JohnD]

What size is it

Post some photos please

Include the wiring, switches and timers, and the pipes.

Is the bottom heater running on the overnight supply?

Also, run your shower into a bucket and time it to full. How many litres per minute does it deliver, and how long are your showers?

 

[Nixstar]

Hi, Thanks for getting in touch.
Not sure of the size, doesn't say on the tank but its taller than me and I'm 5'3''.

The bottom immersion is connected to Economy 7 - only operates between 11.30pm and 6.30am

The upper immersion is connected to the switch pictured above, which is live 24/7 - the booster as I understand it.
The lower immersion is connected to the switch pictured below

Any help would be greatly appreciated.
Showers are short - 5 mins.

 

[oldbutnotdead]

Well that's a nasty looking piece of plumbing- all those compression fittings give it a definite builder or DIY feel. ' Just moved in'- renting or bought?
Do you have a tape measure handy to give some dimensions-height and circumference would do. That must be a very tall door if the cylinder is higher that 5'3"... It does look on the small side (maybe 200 litres?) . Are there any header tanks in the loft? (Unlikely in a flat but worth an ask).
I may be wrong (am prepare to be shot down in flames here) but it appears that the hot water (or some of it at least) is running indirect via a centre coil, which would explain the thing not providing much hot water. I'm intrigued by what looks like a motorised valve (1st pic, grey box on the horizontal bit of 22mm) on what appears to be the cold feed.
If I'm correct about the way the thing has been plumbed it is a very inefficient way to provide hot water. If the mains water supply is up to it you'd do a lot better with a pressurised hot water cylinder running direct- that thing looks as if someone has chucked it in because they had it kicking around and it was cheaper than doing the job properly. You can use a coil in a cylinder to heat hot water indirect (@bernardgreen is the source of wisdom on that one) but the coil as I understand it should (a) be designed for quite a high energy transfer rate (b) be at the top of the cylinder (so as hot is drawn off through the coil the water in the top of the cylinder cools, drops to the bottom of the cylinder pushing the warmer water below up to the top so it can continue to heat the coil). That cylinder looks as if it was designed to be heated by the coil.
Electricity per kwH is still the most expensive way to heat anything- even with the changes to the price cap, electricity per kwH is still 4 times more expensive than gas per kwH so you are going to be stuck with pricey showers unless you can sort an alternative energy source (or Plan B- join a gym an use their showers!)

 

[Nixstar]

Hi thanks for getting in touch.
I think it comes with all those bits and pieces - please see pic attached:

I'm renting so can't look into changing the cylinder unfortunately - it's also only 3 years old I believe, so doubt the landlord will appreciate being asked to look into an alternative. There are no tanks in the loft etc. So if I understand it correctly, this is how it works:the water in the tank is heated to something like 70 deg - then that temperature is to be maintained (in my case by the immersion heaters) so that anytime hot water is demanded, cold water at mains pressure is passed through a coil within, which is heated by the surrounding 70 deg tank water which in turn then heats the mains water passing through the coil which is then supposed to be delivered to the tap at about 50 deg. ??? That's what all my hours of research suggests at least and maybe I'm wrong. Sounds very complicated!
I'm in an all electric flat unfortunately, so no gas whatsoever. Showers at the gym are looking quite attractive. Now to get myself in gear and join a gym...

I think I need to find out if having the immersion heaters switched on 24/7, means they are using electricity continuously, (they're 3KW each) - or will they be governed by the cylinder's thermostat and only come on if the temperature drops below 70 deg. So they would only kick in whenever the temperature of the tank water drops below 70 deg during the day. I basically need to find out how expensive it is to maintain that temperature in the tank.
Is it sensible and more cost effective in the long run to do as the plumber has suggested and rewire the bottom immersion so it has 24/7 power and therefore is better equipped to maintain the temperature of the water throughout the day?

 

[Nixstar]

Also I think its either 150 or 200 litres. I'll check measurements once I've located my tape measure

 

[Nixstar]

Hi thanks for getting in touch.
I think it comes with all those bits and pieces - please see pic attached:

I'm renting so can't look into changing the cylinder unfortunately - it's also only 3 years old I believe, so doubt the landlord will appreciate being asked to look into an alternative. There are no tanks in the loft etc. So if I understand it correctly, this is how it works:the water in the tank is heated to something like 70 deg - then that temperature is to be maintained (in my case by the immersion heaters) so that anytime hot water is demanded, cold water at mains pressure is passed through a coil within, which is heated by the surrounding 70 deg tank water which in turn then heats the mains water passing through the coil which is then supposed to be delivered to the tap at about 50 deg. ??? That's what all my hours of research suggests at least and maybe I'm wrong. Sounds very complicated!
I'm in an all electric flat unfortunately, so no gas whatsoever. Showers at the gym are looking quite attractive. Now to get myself in gear and join a gym...

I think I need to find out if having the immersion heaters switched on 24/7, means they are using electricity continuously, (they're 3KW each) - or will they be governed by the cylinder's thermostat and only come on if the temperature drops below 70 deg. So they would only kick in whenever the temperature of the tank water drops below 70 deg during the day. I basically need to find out how expensive it is to maintain that temperature in the tank.
Is it sensible and more cost effective in the long run to do as the plumber has suggested and rewire the bottom immersion so it has 24/7 power and therefore is better equipped to maintain the temperature of the water throughout the day?

Read more: https://www.diynot.com/diy/threads/...rmal-store-economically.588427/#ixzz7NTc1EW1e

 

[oldbutnotdead]

Your description is pretty much what that setup looks like. The insulation on modern cylinders is pretty good, yes the immersion heaters should be controlled by their thermostats so they won't be sucking up 3kw all day.
Because of the way your hot water is plumbed you do need to keep the whole tank hot - some experiments might be worth while but it depends how beneficial the E7 tariff is after April 1. E7 used to be a good deal but think it no longer is- have you had notice of what you'll be paying per kWh after April? (Both peak and off-peak rates). If there isn't much difference you may be better on a standard tariff BUT if you have night-storage heaters it all gets more complex.

 

[Nixstar]

Night rate is going up from roughly 13p to 19p per kWh and day rate from 24p to 35p or thereabouts. And I do have storage heaters

 

[algas]

Hi Nixstar, in the picture there is a grey knob in the middle of the pipework,it may be a blending valve. Thermal stores should be kept at about 70 deg which would scald so a blending valve is in place to inject some cold water into the hot as it leaves the cylinder on way to taps, its a safety feature.
Look on the front of the grey knob there may be a + or - with a directional arrow, usually anti clockwise for hotter water, clockwise for cooler, just check yours hasn't been set for cool which will be aprox 50 deg, max + should be 60 deg, if you cant turn the valve it may be siezed, then its a repair or replacement. Hope this helps.

 

[oldbuffer]

1. The immersion heaters will switch off automatically once the set temperature is reached.
2. If you feel comfortable doing so you could check the temperatures to which the immersion heaters are set. However to do so requires you to remove their covers, and underneath the covers are mains voltage electric cable terminals. I would:
2a. Turn off the power at the switches to which the cables from the immersion heaters run. This looks to be the left and centre of the three switches in your first photograph.
2b. I would also switch off all the power to the house at both normal rate and Economy 7 consumer units.
2c. Undo the small nut holding each immersion heater cover on, and don't lose them.
2d. Inside there will be a small dial, often triangular with rounded corners, with a pointer in the middle. The pointer should be set to around 73, representing 73 degrees. Make sure they are set correctly. It won't matter if the bottom one is a little over 73 degrees. You may need a medium size flat bladed screwdriver to adjust them.
2e. If they are wildly out of setting, make sure you are reading them correctly. On some makes it is particularly difficult to make out where the point of the pointer is.
2f. Each heater will also have an overheat thermostat. This trips out if the water gets too hot, and must be manually reset. Usually a small button, sometimes requiring a pin or similar through a small hole, to be pushed. Will click if it had triggered as you reset it.
2g. Replace the covers, put the small nuts back on and tighten securely enough to prevent small fingers fiddling.
2h. Switch the power back on.

 

[Madrab]

Unfortunately, given the way electricity costs are increasing a direct thermal store like that is going to cost a fair bit to run, no getting away from it.
A store has to be kept hot all the time, it is the only way it will work properly. Once the store is up to temp (up to 130mins for the 200l) then the immersion heaters will shut off but the minute you use hot water they will kick back in again to maintain the temp.

Do you have a single output meter that clicks to economy 7 overnight then the immersion heaters should be wired so the economy 7 powers the both to heat the whole cylinder on cheap rate overnight and then the bottom one is shut off and just the middle one is then the booster to keep it topped up when the temp drops when it's used during the day at peak rate. Or is it a dual meter with 2 outputs and the consumer unit is split to only certain things that run on economy 7 overnight? You need quite a comprehensive understanding on how your electrical system in set up.

The only real option, I would suggest, that will allow a semblance of control is to fit a mains power monitor, that way it allows an eye to be kept on real time costs, so at least the budget can be controlled accordingly.

 

[Madrab]

Having another look at the pictures too, the overfill controls for that cylinder (that controls the 2 port valve etc) are powered from the switch marked 24hrs and they need a permanent power. I would hope that they are wired into the live side of the switch and not the switched load side.