Economy 7 - Help!

Naf

When you'd shower after getting home did you have to physically switch the heater back on to get more hot water?

DJ_MPH

HappyMJ wrote: »

Not much difference at all. The water would not have been very cold it would have still been warm at the top of the cylinder.

The usage to me seems low but as you say you didn't use any heating so could be high. Are you aure there wasn't a storage heater turned on giving you a small amount of background heat not requiring you to turn on any additional heating. It does get quite cold in the evening how did you keep warm?

We lived in a block of flats, with neighbours either side, and above and beneath us. I made sure all the storage heaters were switched off, and the place was still really warm. I think we got conductive heat from the surrounding flats? Either way storage heaters were never on. We tended to be out of the flat from 6am til 8pm most days (barring days off) - It has just worried us about having the boost switched on constantly for so long. We received a final bill which was over 300% more expensive than what we had been paying each month direct debit. As I said we only had one reading when we moved in and one when we moved out so its possible that the large bill is an accumulation of "un-estimated" usage throughout the year. But we questioned how much of that could be attributed to the boost switch being active.

Naf wrote: »

When you'd shower after getting home did you have to physically switch the heater back on to get more hot water?

No, we left the switch on permanently as advised by the electrician and plumber.

I had thought it would be cheaper to just switch it on when needed but this went against the advice of the pro's

HappyMJ

DJ_MPH wrote: »

We lived in a block of flats, with neighbours either side, and above and beneath us. I made sure all the storage heaters were switched off, and the place was still really warm. I think we got conductive heat from the surrounding flats? Either way storage heaters were never on. We tended to be out of the flat from 6am til 8pm most days (barring days off) - It has just worried us about having the boost switched on constantly for so long. We received a final bill which was over 300% more expensive than what we had been paying each month direct debit. As I said we only had one reading when we moved in and one when we moved out so its possible that the large bill is an accumulation of "un-estimated" usage throughout the year. But we questioned how much of that could be attributed to the boost switch being active.



No, we left the switch on permanently as advised by the electrician and plumber.

I had thought it would be cheaper to just switch it on when needed but this went against the advice of the pro's

You didn't take regular meter readings so you are never going to know.

It's a very reasonable bill. I don't see how you can say you used less than 1,565kWh over the year during the day on the fridge, cooking, washing, tv, lights etc and then trying to say a large portion of that was used on hot water heating during the day. The average usage for the UK is 3,300kWh and that figure excludes all hot water heating and heating.

Richie-from-the-Boro

A day rate, a non E7 water cylinder will use considerably more electricity like with like than an E7 cylinder when used as an immersion heater.

The non E7 cylinder will use more electricity, but will give like with like proportionally more hot water.

The E7 cylinder will use more electricity, but will not give like with like proportionally more hot water.

Naf

DJ_MPH wrote: »

No, we left the switch on permanently as advised by the electrician and plumber.

I had thought it would be cheaper to just switch it on when needed but this went against the advice of the pro's

Sounds to me like it heated pretty much exactly what you used, then; maybe slightly more. But some at the wrong rate.
Overnight it heated enough for you both to shower; no way to make that cheaper. Then while you were at work it heated water for our shower when you got home, perhaps a little more than you needed, but you used it, so couldn't transfer that onto the night rate either. Unfortunately after your shower it also continued to heat water before your night rate kicked in.
Say from 6 'till midnight you used 3kW each day on day rate instead of night (the water it heated then would still have been heated overnight, and the cylinders do a pretty good job of insulating) that's 24kWhrs per day; at 9p extra each (rough figures based on your post earlier) makes £2.16 per day extra. So could have made almost £130 difference across the two months. - less if you showered later than 6.

HappyMJ

Naf wrote: »

Sounds to me like it heated pretty much exactly what you used, then; maybe slightly more. But some at the wrong rate.
Overnight it heated enough for you both to shower; no way to make that cheaper. Then while you were at work it heated water for our shower when you got home, perhaps a little more than you needed, but you used it, so couldn't transfer that onto the night rate either. Unfortunately after your shower it also continued to heat water before your night rate kicked in.
Say from 6 'till midnight you used 3kW each day on day rate instead of night (the water it heated then would still have been heated overnight, and the cylinders do a pretty good job of insulating) that's 24kWhrs per day; at 9p extra each (rough figures based on your post earlier) makes £2.16 per day extra. So could have made almost £130 difference across the two months. - less if you showered later than 6.

It's not 24kWh each day. The annual day peak rate usage is only 1,565kWh...daily that's only 4kWh per day. 24kWh multiplied by 60 days is 1,440kWh that only leaves 125kWh for the rest of the year. No chance..

Naf

HappyMJ wrote: »

It's not 24kWh each day. The annual day peak rate usage is only 1,565kWh...daily that's only 4kWh per day. 24kWh multiplied by 60 days is 1,440kWh that only leaves 125kWh for the rest of the year. No chance..

Mine was the worst it could have caused in extra charges. Clearly it didn't. Comparing the readings to my calculation, it doesn't seem that it was the boost that was permanently on, just the standard heater. Unless the OP got home very late and wasn't showering until very close to midnight, then the boost heater ought to have used more than 4kWh every evening after their shower, but before the night rate kicked in.

DJ_MPH

I'm not complaining about the bill, obviously whatever we've used we've been billed for - not disputing that. Just trying to establish roughly how much more expensive it is to run the boost all day every day, as opposed to only using the overnight heating switch.

The reason we got the plumber and electrician out was because the overnight switch stopped working so we'd wake up with no hot water for showers. They came to "fix" it but the problem persisted so we had to continually use the boost switch instead

Richie-from-the-Boro

DJ_MPH wrote: »

I'm not complaining about the bill, obviously whatever we've used we've been billed for - not disputing that. Just trying to establish roughly how much more expensive it is to run the boost all day every day, as opposed to only using the overnight heating switch.

The reason we got the plumber and electrician out was because the overnight switch stopped working so we'd wake up with no hot water for showers. They came to "fix" it but the problem persisted so we had to continually use the boost switch instead

- I disagree with a lot that's posted here
- it would cost a minimum of the % difference between your day & night rate
- and a maximum of the day / night % difference plus the cost of the infinity cycle of the artificially induced convection current
- plus a factor of 9 [ish] because you have to reapeat this 9 more times if you want the same 100% volume of hot water

Assume any size you like the outcome will be the same, for the purpose of this post lets assume its a 200 litre E7 Part L compliant cylinder.

Your E7 standard Part L cylinder will be more than capable of keeping the external losses down to a minimum regardless of which of the two inputs you use so the losses will be the same. Your Part L cylinder is designed using the bottom stat & element to heat & hold a cylinder full of the cheap stuff for 24 or more hours.

Using a Part L cylinder as an immersion heater with the top stat & element will result in heating only about 10 % of the volume of the cylinder. That top 10% will have the heat constantly diluted by the 90% of the cold water underneath. At that point the stat kicks back in and a second round of unnecessary extra costs are incurred reheating the top 10% until it reaches the predetermined temp then the stat switches of the top element .. .. .. and then it does this again and again and again .. .. its now an infinity cycle.

That's why an immersion heater has a single stat & element at the middle or bottom and an E7 Part L has two stat elements at the middle and top.

Liquid, such as water, is heated from the bottom, the layer of water closer to the heat source expands and hence becomes less dense compared to the water layer above it. Expanded water is less dense than the surrounding water and therefore it rises. The cooler regions of the water in the upper part of the flask, being denser, sink. This movement of liquid due to a difference in density sets up a convection current.

So the heated [ hot ] water pushes up and forces the cooler water down over the thermostat which in turn is heated until the whole volume of the tank reaches your pre determined setting then the stat switches the leccy off. Its a bit atomic science and the random motion of atoms and all that, but sufficient to say that's why the top down element on an E7 cylinder is both rubbish at heating a full tank of water and why the induced infinity cycle adds to the cost of the minimum of the % difference between your day & night rate.

#32

NOTE : All trad immersion [direct] heater cylinders were bottom only, I haven't included coil combos because this is an E7 debate. These days is difficult to find a direct bottom stat & element replacement, most are replaced with a middle stat & element with the above results for the householder.

DJ_MPH

Richie-from-the-Boro wrote: »

- I disagree with a lot that's posted here
- it would cost a minimum of the % difference between your day & night rate
- and a maximum of the day / night % difference plus the cost of the infinity cycle of the artificially induced convection current
- plus a factor of 9 [ish] because you have to reapeat this 9 more times if you want the same 100% volume of hot water

Assume any size you like the outcome will be the same, for the purpose of this post lets assume its a 200 litre E7 Part L compliant cylinder.

Your E7 standard Part L cylinder will be more than capable of keeping the external losses down to a minimum regardless of which of the two inputs you use so the losses will be the same. Your Part L cylinder is designed using the bottom stat & element to heat & hold a cylinder full of the cheap stuff for 24 or more hours.

Using a Part L cylinder as an immersion heater with the top stat & element will result in heating only about 10 % of the volume of the cylinder. That top 10% will have the heat constantly diluted by the 90% of the cold water underneath. At that point the stat kicks back in and a second round of unnecessary extra costs are incurred reheating the top 10% until it reaches the predetermined temp then the stat switches of the top element .. .. .. and then it does this again and again and again .. .. its now an infinity cycle.

That's why an immersion heater has a single stat & element at the middle or bottom and an E7 Part L has two stat elements at the middle and top.

Liquid, such as water, is heated from the bottom, the layer of water closer to the heat source expands and hence becomes less dense compared to the water layer above it. Expanded water is less dense than the surrounding water and therefore it rises. The cooler regions of the water in the upper part of the flask, being denser, sink. This movement of liquid due to a difference in density sets up a convection current.

So the heated [ hot ] water pushes up and forces the cooler water down over the thermostat which in turn is heated until the whole volume of the tank reaches your pre determined setting then the stat switches the leccy off. Its a bit atomic science and the random motion of atoms and all that, but sufficient to say that's why the top down element on an E7 cylinder is both rubbish at heating a full tank of water and why the induced infinity cycle adds to the cost of the minimum

NOTE : All trad immersion [direct] heater cylinders were bottom only, I haven't included coil combos because this is an E7 debate. These days is difficult to find a direct bottom stat & element replacement, most are replaced with a middle stat & element with the above results for the householder.

Well I'll be honest, lot of that went over my head - but you seen to know what you're talking about when it comes to boilers.

Yes, the element that we were "forced" into using was the top one which i refer to as the "boost". The switch for this element was on 24 hours a day 7 days a week for around 2months. I'm assuming this cost us considerably more than using just the bottom element during off peak hours. Would it be reasonable to assume that it would be around 4 times more expensive to heat the water in this way?

Sorry, I'm still REALLY confused about this. I just want to be able to approach the landlord and request that he reimburse us for undue water heating costs and to be able to explain as simply as possible how a reasonable estimation can be made.

I appreciate everyone's input so far, thankyou.