Megaflo Cylinder for hot water

QrizB

AliceBanned said:

Mmm I live in an all-electric flat with E7 and NSH. Not sure of the brand of immersion but it has two elements and a timer. I find if I put it on during the later hours of the tariff eg 6am for 1.5 hours, I have enough hot water though not always piping hot as with a nice combo boiler😕. Currently that costs me about £1 a day and I no longer use the boost but I used to if I wanted an evening bath. I have only morning bath or shower (I don’t have an electric shower).

@AliceBanned does your timer control the upper immersion heater or the lower one? Conventionally it would be on the upper heater (with the lower one switched by the E7 supply) but that isn't always the case.

Is your morning shower early enough that you're within the E7 period?

AliceBanned said:

I am wondering whether I should put it on for any longer than this during off-peak hours as given that the water will be heated does it continue to use more electricity than needed to keep it hot? Unfortunately I can’t access the thermostat so would need to get a plumber in to check it and adjust. It’s ok as it is, not ideal and will cost me closer to £2 a day soon. I presume on days I don’t have a bath it costs a bit less? I went through a phase of turning it off every other day and having cool shower but that’s ridiculous. This energy crisis just makes me frugal though I will be able to afford the bills. I guess it’s mild panic at horrific costs as it’s all electric. I’m sellyup next year anyway and want to go back to GCH (want to move for other reasons). 

If you run the immersion for longer it should get to "piping hot" just like a gas combi, then the thermostat will cut out and (after that) it won't cost you appreciably more. Once my tank is up to the thermostat temperature my immersion cycles in and out uses about 100 watts on average to keep it warm.

k_man said:

Apodemus said:

Maybe someone can check my maths, but my calculation suggests that 4.5kWh would deliver 925 degree/Litres of heating - so if the incoming water was 20C (which its probably not) and the output temp was 45C (and it may be higher), then you are only heating 37 L of new water each day?

I think you are out by a factor of about 4.
4.5kWh will heat approx 150l of water from 20C to 45C

Yes, I agree with k_man's number.

• Heat capacity of water =4.2 kJ / litre-K
  
• 4500 W x 3600 s = 16.2 MJ
• Amount of water heating provided = 3860 degree-litres

AliceBanned

[Deleted User] said:

AliceBanned said:

sebtomato said:

Rachel* said:

I’ve recently purchased a 2 bedroom flat, which has electric convection heaters and a Megaflo Unvented Direct Cylinder for hot water. 

I’ve been trying to read up about the Megaflo cylinder but just end up confusing myself so was hoping someone can help me. 

1. Is it cheaper to leave this switched on all the time, or just when I want hot water? (I work different shifts each week, anything from 6am to 7pm over Mon - Sun)

2. I noticed there is two switches on the wall, and from my research I believe it is a 2 immersion system? So it is better to leave one on and the other one off unless I want a bath or will be using a lot of hot water in one go? 

I haven’t actually moved into the property yet as I’m still decorating, buying furniture etc. so I have turned it off unless I’m actually at the property and needing hot water. But just want to be prepared for when I move in. 

I have pretty much the same model.

Typically, your flat should have an economy 7 meter, as that cylinder is designed for off-peak use.

During off peak hours, the off peak circuit should be active. This should power the switch going to bottom cable, to heat up water during the night when it's cheap (cheaper rates). The bottom cable leads to the bottom heating element that heats the water...from the bottom.
Off-peak should be 7 hours during the night. Currently 23:30 to 01:30, and then 03:30 to 08:30 with EDF energy in London (other areas may have different hours).

The switch leading to the top cable should only be used for top-ups (only heating up the top of the cylinder, shallow water), when you have used all hot water and needs some more on that day. Don't leave that switch on all the time, only one hour or two should be sufficient, only when you need additional hot water.

If you don't have economy 7, then maybe only switch on for a few hours before you need hot water, or get an electrician to install a timer on the "non-top" up socket, so that you can hot water in the morning when you need it (so for instance switch to be one from 05:00 to 08:00). 

Given the high electricity prices, you don't want those switches to be on all the time. One of my neighbour made that mistake and had a £400 bill...per month.

Mmm I live in an all-electric flat with E7 and NSH. Not sure of the brand of immersion but it has two elements and a timer. I find if I put it on during the later hours of the tariff eg 6am for 1.5 hours, I have enough hot water though not always piping hot as with a nice combo boiler😕. Currently that costs me about £1 a day and I no longer use the boost but I used to if I wanted an evening bath. I have only morning bath or shower (I don’t have an electric shower). 

I am wondering whether I should put it on for any longer than this during off-peak hours as given that the water will be heated does it continue to use more electricity than needed to keep it hot? Unfortunately I can’t access the thermostat so would need to get a plumber in to check it and adjust. It’s ok as it is, not ideal and will cost me closer to £2 a day soon. I presume on days I don’t have a bath it costs a bit less? I went through a phase of turning it off every other day and having cool shower but that’s ridiculous. This energy crisis just makes me frugal though I will be able to afford the bills. I guess it’s mild panic at horrific costs as it’s all electric. I’m sellyup next year anyway and want to go back to GCH (want to move for other reasons). 

The photo above shows a well-lagged unvented cylinder. I have a 250L unvented cylinder that we heat throughout the day using diverted solar electricity. The daily heating requirement averages 3kWh/day during the Winter season. Adjusting the immersion heater thermostat is a simple and safe operation if you turn the power off. Some cylinders have visible adjusters on the face of the immersion heater: others have a cover which is screwed on. Behind the cover, you will see something like this:


For an unvented cylinder, the temperature should not be set below 55C.

Don't be seduced into thinking that gas re-heating of a cylinder will always be cheaper. Re-heating my cylinder by gas uses an average of 7kWh/day: why?

1.  The boiler goes to its maximum flow temperature so it is not that efficient (ie; no condensing so gas efficiency will be c.80% of electricity)).

2. The boiler water flow through the cylinder initially removes heat from the cylinder.

3. The pipes between the boiler and the cylinder will also be emitting heat. (clearly, this contributes to heating the home)

Thanks but I was thinking in terms of price of gas per kw. Used to be about 4x that of electricity so I was shocked at how much more it cost when I first moved. I will take a look at thermostat and turn off mains - mine is a hidden one. 

The problem is with E7 the water is heated during the night so by mid afternoon it’s not hot. I’ll see what my tariff is in October with E.on Next. 

I could put an electric shower in but I’m moving soon - think that would be the cheapest option otherwise and forget about baths.

sebtomato

QrizB said:

AliceBanned said:

Mmm I live in an all-electric flat with E7 and NSH. Not sure of the brand of immersion but it has two elements and a timer. I find if I put it on during the later hours of the tariff eg 6am for 1.5 hours, I have enough hot water though not always piping hot as with a nice combo boiler😕. Currently that costs me about £1 a day and I no longer use the boost but I used to if I wanted an evening bath. I have only morning bath or shower (I don’t have an electric shower).

@AliceBanned does your timer control the upper immersion heater or the lower one? Conventionally it would be on the upper heater (with the lower one switched by the E7 supply) but that isn't always the case.

Actually, it would make sense also to have a timer controlling the heating time during the off peak hours too.

In my case, the bottom heating element is only live during off peak hours (5 pole smart meter), but then it means water starts heating up at 23:30 in the evening, and then through the night on and off until 08:30 (end of off peak).

I would much prefer for water to heat up only from 05:00 or 06:00 (for a shower from 07:30), as I am not going to use hot water between 23:30 and 07:30 anyway. Otherwise, it goes through the cycle of water heating up, cooling down, heating up etc. Probably not that efficient.

Next time I have an electrician coming in, I will ask to rewire the bottom element to a standard/peak supply socket, and have a timer on it to control better the usage. 

AliceBanned

I think my timer controls both elements. I can set the time for off peak use or to heat during peak or use boost function. I’m not sure which element beats up on E7.

the previous owner had E10 so maybe that’s why the timer can control both elements and both rates? So complicated! I had it changed to E7 as it was not reasonable having 2 standing charges and the NSHs don’t need additional tariff into the evening. On very cold days I boost them with convector heat but don’t often need to if I have enough stored heat. It’s such a minefield and faff, have to have a crystal ball to manage this set up.🙈😅

AliceBanned

On previous post I meant electric 4x that of gas. Sorry for confusion!😌

sebtomato

AliceBanned said:

I think my timer controls both elements. I can set the time for off peak use or to heat during peak or use boost function. I’m not sure which element beats up on E7.

the previous owner had E10 so maybe that’s why the timer can control both elements and both rates? So complicated! I had it changed to E7 as it was not reasonable having 2 standing charges and the NSHs don’t need additional tariff into the evening. On very cold days I boost them with convector heat but don’t often need to if I have enough stored heat. It’s such a minefield and faff, have to have a crystal ball to manage this set up.🙈😅

One thing to clarify: all electricity you use during off peak hours are at off peak rate, regardless of the sockets being used.

However, some flats like mine have a circuit only live during off peak hours. Typically because of off peak water heating and/or storage heating.

At the end of the day, if your timer guarantees that water heating only happens during off peak hours, you are fine.