Thermal Store Cylinder on Economy 9

[Psych1965]

Dear Plumbing Community-I had my boiler replaced with a Thermal Store cylinder over two years ago and had the first servicing last week. It has prompted me to question whether it's working as it should and as cost effective as it can be, because I've noticed since my plumber serviced it, it "fires" or turns on more than 3 times/day. For example, last night I heard it "kick in" at 5AM and then again at 7AM. I was under the impression that with an Economy 9 tariff, that my cylinder should warm up 3 times/day. I may be wrong, and getting this confused with the three *time slots* (time periods) during the day/evening when the cheap rate is available, and wondered if someone could please clear this up for me.

The reason I am questioning this is because my electricity bills *are* high given I live alone, but I'm also aware that I have old storage heaters which are *not* that cost effective-they don't work well anymore; last Winter I had them on full blast. This year, however I decided to buy a portable (Dimplex) oil free heater and I just take it from room to room with me, on an as needs basis. It is fantastic and allows me to just heat up the room I'm in, while I'm in it, rather than keeping a two-bed flat warm and paying a high price for it.

I suppose my Q. is how an Economy 9 tariff is supposed to work with my Thermal Store cylinder and how do I know that it *is* coming on, only at off peak times? And is it coming on, more than it needs to? I don't remember hearing it come on at 5AM and then at 7AM before my service guy was here (but then again-I had also been sleeping with earplugs-for *years) and this week is the first week I haven't, so I'm more aware of when the cylinder is on.

I just don't want to be paying more than I need to, to heat my water up and obviously don't want the cylinder to turn "on" more often than it needs to.

I have two switches in my cupboard-Peak and Off peak, and my Peak switch is always *off*.

Many thanks for clarifying the above for me.

 

[stem]

The difficulty with Economy 9 is that your electricity supplier (the company that sends you the bill) chooses at their discretion when you get the 9 hours of off peak electricity. If you look at the details of their tariff you should get an idea. Just as an example, it might be: 5 hours at some point during the night / 2 hours at some point in the afternoon / 2 hours at some point in the evening.

Once the thermal store has heated up, its internal thermostat will turn it off, so it won't be consuming power for the whole 'off peak' period. It may cycle on and off several times depending on how much hot water you are using, and any heat losses through the insulation / pipes.

There should be two consumer units in your home. One will only be 'on' when the off peak rate is available. The storage heaters and thermal store off peak immersion heater should be wired to this, meaning they will only receive power when it's available at the off peak rate, whenever that may be.

The other consumer unit will be for everything else such as sockets, lights, etc., and will be 'on' permanently. However at certain times of the day the electricity will be charged at peak rate and other times off peak rate.

Unfortunately electricity isn't cheap*, which is why most homes have expensive boilers and radiator systems installed instead, because the running costs are about one third to half that of electricity. Electric storage heaters charge up using the 'off peak' rate so are usually half the price of standard electric heaters that run on peak rate. Be careful though because some storage heaters also have a second heater built in that can be switched on at any time so can use the more expensive tariff.

I moved from a tiny one bedroomed home heated by Economy 10 electricity to a large detached 3 bedroom house heated by gas and the running cost was about the same. Both had similar levels of insulation.

I'm a bit puzzled by some of the terms you use in your post though, electric immersion heaters as fitted to a thermal store are usually silent, so you wouldn't normally hear them "kick in" as you might with a boiler.

*Heat pumps are cheaper to run, and can claim to be up to 300% efficient, meaning 1kW of electricity can generate 3kW of heat in which case they cost about the same as a gas boiler to run. However they don't usually get hot enough on their own to heat domestic hot water, so a supplementary electric top up is also required.

 

[Psych1965]

Hi Stem-many thanks for your reply. Just to add: my storage heaters are old and I am convinced are not working as efficiently as they should be. I recently bought a portable Dimplex Oil Free Heater that I now move from room to room on an as needs basis and can pretty much keep my storage heaters OFF.

Just to clarify-when I said I can hear the Thermal Store "kick in" I meant I can hear when it's "on". You can hear it (presumably) warming the water up-it does make a sound in the same way my old heat bank did. I can video tape this next time I hear it and add it as an iCloud link if that would help-but just to say-I definitely hear it coming on throughout the day and evening time.

When you say "it may cycle on and off...."-I think that is what I mean by kicking in-I can hear it cycling. I kept as close an account as possible over the weekend and found:

Friday night: I could hear the thermal store “on” at around 10:00PM, and I believe it was on for a few minutes. And then in the middle of the night, it was “on” at 5AM and again at 7:00AM.

On Saturday it was on at: 2:00PM, 3:25PM, 11:00PM (for 15 minutes), then again at 11:25PM, then at 3:00AM, 6:40AM and again at 7:20AM Sunday AM but only for *seconds* at 7:20AM.

Bear in mind that no hot water was being used from 10:00PM onwards Saturday night-Sunday 7:40AM. I didn’t have the taps on, or anything like that, and yet it came on at least 5 times. Is this normal, and what it is supposed to do?

The energy company I'm with are EDF and in a few Whatsapp messages over the weekend, I received 4 different replies from presumably 4 different agents re-my Q. what times am I being charged Off Peak costs and what times am I being charged Peak rates (bear in mind-my Peak switch is always OFF).

Their responses are below:

1. Product -Standard (Variable) - E9 Heating. Tariff-E9H. Unit price-12.16p. Daily Standing Charge-36.7p

1. Product -Standard (Variable)-E9 Power. Tariff-E9P. Unit price-35.79p. Daily Standing Charge-0p

1. E9H Heating-Heating 5+2 hours in 2000-0730 & 2 hours in 1300-1600 & non heating 2330-0630

1. E9P Day-Non heating 0630-2330

I want to better understand what they mean by "heating" versus "non heating". I honestly can't make sense of what they are saying in the above 4 messages. I am due a call back from the Complex Meters Team at EDF-they apprently deal with Economy 9 customers.

Thank you for clarifying that I have two consumer units in my flat-one for lights, sockets, etc. and that this one is permanently on, and the other consumer unit being for heating and my Thermal Store. That is really helpful.

I also received some information via email from the manufacturer of my Thermal Store-they said:

"The unit you have installed is known as a cylinder and more specifically a thermal store, it is not a boiler. A boiler is the appliance which generates heated water by burning gas or oil, and these come in the form of Combi, Heating only etc. However a cylinder or thermal store is the place where the heated water is stored.

In the case of your system, you don’t have a boiler to generate heated water, what you have is an electrically heated thermal store, typically referred to as a ‘Direct’ Cylinder or thermal store. The model you have is a Pandora CPC-180-ANA, there is nothing on the market that can be installed as a direct alternative, although there are one or two similar products.

The key feature of your system is that the Pandora does not require a safety relief valve, as it works like an open vented cylinder, and the water inside can expand without pressurising the cylinder or becoming dangerous. The vast majority of engineers will not have seen this type of thermal store before, however it is the most simple of units and we are always here to give anyone telephone support when needed".

I'm just trying to work out whether my Thermal Store is coming on more than it needs to (it seems to forever be warming my water)-based on the sound I hear it making, or whether the sound it makes does not = warming up, i.e., energy being used.

Even the plumber I had here last week suggested I don't need it to warm up as often as it does and perhaps I can turn "Off" the Off Peak switch at certain times in the day?

Here's a page from my Thermal Store manufacturer's website:

Most people think that the modern way to provide mains pressure hot water is using either a combination boiler or an unvented hot water cylinder. This is not usually the case however.
Combination boilers will almost always be the preferred option for properties where low flow rates are acceptable, and there is no need to run fast baths or two outlets at once. However, for properties with more than the most basic requirements, house builders and local authorities use thermal stores to provide mains hot water. Unvented cylinder do have their place, however for the vast majority of installation, a thermal store will provide everything that an unvented will, as well as more, and with none of the disadvantages of an unvented cylinder

A Thermal Store can overcome a number of problems, providing very high flow rates of hot water at FULL mains pressure (no pressure reducing valves). The utilisation of higher mains pressures also means that higher flow rates can be obtained to taps.

The question has to be, therefore, how to achieve mains pressure hot water from a hot water cylinder that is under no pressure at all ?

The water in the cylinder is used as a battery for heat. As such it never goes anywhere, certainly not to the taps, but is instead circulated through a 'heat exchanger' that transfers the heat from the hot water in the store, to heat up high pressure mains water. The water in the store and the mains water never mix, but are kept separated by stainless steel metal plates in the heat exchanger that transfer the heat. The heat exchangers are pressure tested to 72bar, far higher than will ever be encountered, and are approved.

As stores are filled up once only, there is no need for a permanent connection for filling the store, and hence no need for an overflow or discharge pipe. As such, systems can be as simple as cold in and hot out, with no other pipework connections.

They can also be DIY installed by anyone competent - you don't need to be a registered installer. Nor do they need regular preventative servicing - the only component that may need servicing is the pump, a standard circulator that should last many, many years (and is simple to change).

As the water in the store remains the same, there is no introduction of limescale or other salts. The water in the store should be protected with standard corrosion inhibitor for central heating systems, as this will ensure continued operation of the system, keeping it clean years to come. Anti-freeze can also be added, making this system suitable for dwellings that are left unheated in the cold weather.

The picture to the left shows a standard indirect Stowaway Heat Bank Thermal Store.

END OF EXCERPT

Stem-I'm just trying to work out whether my Thermal Store is working as it should (the plumber who was here last week seems to think it is)-but I couldn't help being more attuned to how often it fires/cycles since his visit and I want to know whether it's doing so more than I need it to.

Many thanks and best wishes,
Psych.

 

[stem]

my storage heaters are old and I am convinced are not working as efficiently as they should be. I recently bought a portable Dimplex Oil Free Heater that I now move from room to room on an as needs basis and can pretty much keep my storage heaters OFF.

Electric 'resistance' heaters are all 100% efficient. No matter their age. The energy they take in is what they give back out. The difference is that storage heaters use electricity when it's cheaper, so cost less to run per unit of heat. Having said that, in your case if you are only heating one room at full price electricity occasionally, then it could well work out cheaper than heating the whole property for longer periods of time but using a cheaper rate.

I'm just trying to work out whether my Thermal Store is working as it should (the plumber who was here last week seems to think it is)-but I couldn't help being more attuned to how often it fires/cycles since his visit and I want to know whether it's doing so more than I need it to.

If it's connected to an off peak consumer unit and powered accordingly, then yes it will be working properly, there's not much else you can do other than reduce your hot water consumption and check the insulation, more about that later.

Think of the thermal store like your phone battery. You charge it up and then as you use the phone it discharges. The more you use it the quicker it discharges, but it will still discharge very slowly even if you don't use it. But when it's fully charged it won't charge anymore for quite a while.

Sometimes the immersion heater isolator has a pilot light so you can see when the off peak consumer unit is on.

So in the picture above both switches are in the 'on' position. The full rate one is lit showing it has power, but the off peak isn't showing that it isn't getting any power at this point in time.

If yours doesn't have a light on, you could replace it for one that does, or as a test you could turn off the off peak consumer unit for a day or two and if the thermal store goes cold, you will know it is only being charged during the off peak rate.

Bear in mind that no hot water was being used from 10:00PM onwards Saturday night-Sunday 7:40AM. I didn’t have the taps on, or anything like that, and yet it came on at least 5 times. Is this normal, and what it is supposed to do?

To a certain extent yes, because there will be some losses from the thermal store itself, and the hot pipes going from it, but good pipe insulation without gaps will help. [the picture below is not not a thermal store but to show good pipe insulation]

Also, warm water rises to the top of the thermal store and as it cools it sinks so there will be some internal convection taking place inside which can trigger the heater to come on, but it if no water is being used then it shouldn't be on for very long [unless the 'off peak power' has just started and it has to catch up for previous usage] and not very frequently. Unless there is a leak or dripping tap somewhere.

If the thermal store itself has good insulation, it shouldn't feel warm to the touch.

 

[Psych1965]

Thanks very much, Stem. So, I do have two light switches in what I call my "boiler" room but the only one with the light is the Peak, and as I mentioned above, it's always "OFF". I'll see over the next day or so whether the Thermal Store is warm to the touch-I know that the pipes do get hot because I accidentally touched one (it may have been a valve) but nonetheless, it was very hot.

When you say "The more you use it the quicker it discharges"-does the act of discharging=the sound it makes when it is warming up? I am presuming that the sound it makes when it's doing whatever it's doing is "warming" the water?

I, myself can't comment on how well insulated the pipes/Thermal Store is but when the plumber attended last week he commented on how professionally my Thermal Store was installed (he wasn't the one who installed it).

I really appreciate your detailed and helpful replies. It has put my mind to rest re-a lot of my concerns.

I'm now awaiting a call from EDF's Complex Meter Team over the next few days as I'd like to know the precise times I am paying for Peak Heat, etc. and hot water.

Best wishes,
Psych.

 

[stem]

So, I do have two light switches in what I call my "boiler" room but the only one with the light is the Peak, and as I mentioned above, it's always "OFF"

Typical yes the 'peak' switch should normally be 'off' It's only there to allow you to get hot water if the thermal store has run out and the 'off peak' rate isn't available.

I know that the pipes do get hot because I accidentally touched one

Then it will be loosing heat, cooling the thermal store and cause the electric heater to come on when you've not used any hot water. Foam pipe insulation is cheap available at DIY stores and easily installed, you can cut it with scissors

"The more you use it the quicker it discharges"-does the act of discharging=the sound it makes when it is warming up? I am presuming that the sound it makes when it's doing whatever it's doing is "warming" the water?

When I say the more you use it, I mean when you use a hot water tap and hot water leaves the thermal store causing it to cool. The sound I imagine is, as you say, the heating element coming on to heat it back up again.

 

[Psych1965]

Super-thank you.

 

[Psych1965]

Stem-I've just had an email from a really helpful person at EDF (I'm still waiting to speak with the Complex Meter team)-apparently the hours for cheap electricity are on the last page of my bill and state:

What times do the different prices for my electricity apply?

All times are not GMT

Meter: H11**** Tariff: Standard (Variable) - E9 Heating
Heating 5+2 hours in 2000-0730 & 2 hours in 1300-1600 & non heating 2330-0630

All times are not GMT
Meter: H11**** Tariff: Standard (Variable) - E9 Power
Day: Non heating 0630-2330

I am trying to make sense of this and the fact that "all times are not GMT" doesn't help at all.

Stem-am I right in assuming that my portable Dimplex heater would fall under Power, as opposed to Heat? I think the only appliance at home that would fall under Heat are my storage heaters, correct?

Effectively, and if I am correct in my interpretation of the above (and as per the email that my EDF contact sent me):

"My understanding is any usage between the times mentioned above would be charged at the lower rate so even washing machines plug sockets etc as long as it is within the time frame above".

So, if he is correct, any heating used between 8:00PM-7:30AM would be charged at the lower rate and any lights on between 11:30PM-6:30AM would also be charged at the lower rate? That's a bit silly, isn't it? Why provide the lower rate when most of us are asleep? Unless I've got that wrong way round. But the EDF guy said that any usage between those times would be charged at the lower rate.

I'm also confused as to why "non heating" is mentioned twice-under both Heating and Power. So, say a washing machine falls under "non heating"-why are there two different hours (ranges)-one under Heating and one under Power? This is doing my head in.

Let's say I'm doing a load of laundry at 8:00AM-according to E9 Heating, I'd be paying a higher rate (11:30PM-6:30AM), but according to E9 Power, I'd be on a lower rate (6:30AM-11:30PM). I am so confused.

 

[stem]

No wonder it's called "Complex" I'm not too sure, but here's my understanding:

It looks to me that you have 9 hours of 'off peak' power for the storage heaters and hot water heating that comes as:
A 5 hour period, plus a 2 hour period overnight at EDF discretion somewhere between 20:00 and 07:30
A 2 hour period in the afternoon somewhere between between 13:00 and 16:00

The everything else is 24 hours, i.e.: Non heating 2330-0630 + Non heating 0630-2330 = 24 hours. I would expect this to move between the two tariffs....or maybe it doesn't and it's always 'peak'

I believe that 'heating' means the devices connected only to the off peak tariff, so as you say storage heaters, and also the 'off peak' hot water heating. And that 'power' is everything else that can be used at any time. So that covers everything.......then there's the term 'non heating' possibly the same as 'power' who knows?

Regarding the "All times are not GMT" possibly it could move to "BST" when the clocks change, but again only my guess.

Hopefully the helpful person at the EDF 'Complex Meter Team' can enlighten you.

 

[Psych1965]

Thanks very much, Stem. It's reassuring to know that even you can't make sense of what they're saying. Seriously-it's a bit confusing and left for us, the customers to draw our own conclusions. I'm hoping I do get a call back from the Complex Meter Team by the end of the week, otherwise it may not be until January that I can speak with them due to family commitments, etc. I'll update here just in case this is of interest to anyone else.

Thanks again for all of your help thus far and happy holidays in case I'm not back here before Christmas.

Psych.