Megaflo Cylinder for hot water

Rachel*

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. 

matelodave

Firstly, what tariff are you on. A cylinder like this is generally used in conjunction with storage heaters and on an off-peak tariff so that it can heat up overnight on the off-peak rate.

The top heater will be fed from the peak supply and the bottom from the off-peak -in which case you leave the bottom one ON and the top one OFF.

If you've got convector heaters then an off-peak tariff will cripple you as you'll be heating the place using peak rate leccy and only heating the hot water at the cheaper rates. usually the peak rate cost is about 1.5 times the off peak cost

If you've got a single rate tariff and you've got convector heaters then ideally you only turn the hot tank on an hour or so before you need hot water.
The top heater will heat around a half of the tank and the bottom one will heat all of it. Heating water with leccy is expensive.
To heat the top half (about 100litres) will take around two hours and use 6kwh = about 90p (depending on your tariff)
To heat the whole tank (about 150 litres) will take around three hours and us around 9kwh = £1.35
As hot water rises you should find that you can probably get away with an hour or so with the top heater if you don't use too much hot water

You therefore need to be fairly frugal with your use of hot water. Ideally have short showers (no more than 5 minutes) rather than baths, dont run hot water down the sink to wash stuff up (including your hands) and ideally only wash up the dishes once a day. Fit flow restrictors to the taps and the shower so you dont blast hot water down the sink or bath.

Hopefully you have opened an account with the existing energy supplier (even if you haven't actually moved in as you are responsible for the leccy used)and given them the meter readings (both registers if you do have E7). This is to ensure that you dont end up paying for the previous tenant/owners leccy and so you can change suppliers if you want to. You need to be looking for the cheapest leccy you can find because any all electric place is going to be very expensive.

Put up a picture of you leccy cupboard showing the meter and all the wiring between it and the incoming mains and the distribution boards so we can get an idea of how your place is wired. A photo or info about your heaters would also help.

Gerry1

Bottom heater should left on and be supplied be on a circuit switched by an Economy 7 meter.

Upper heater should left off and be supplied be on a 24h circuit.  Use it to get half a tank of very expensive hot water if you've messed up and run out of hot water or have been away.

That assumes your convection heaters are night storage. If they're really convectors running on daytime electricity, there's simply nothing more expensive and you'll be hit with massive bills.  If it's absolutely impossible to get gas, go for the cheapest single rate tariff you can find, and consider switching to NSHs PDQ.

Rachel*

Thanks for the replies.

I have already contacted the existing supplier (EDF) and given meter readings. I am still looking at tariffs at the moment. The previous occupants have a smart meter (Landis+Gyr E470) but when I spoke to EDF they said it was inactive? I will request an IHD so I can monitor usage more effectively anyway to help reduce my bills. 

I’ve attached pictures of the heating 

I’m fairly certain they are just convection heaters and not storage heaters. 

There is no gas supply, it may be something I look into in the future, but I can’t afford the initial outlay currently. 

*Also, I had both switches turned on from completion day (23rd Feb) until yesterday - so 5 days (as I hadn’t realised they were on) and the meter has only changed by 9 kWh. During that time I only used hot water briefly for hand washing.

knightstyle

Unfortunately those are standard panel heaters that give instant heat when required. They do not store heat obtained by using cheaper off peak electricity.
As others have said this is the most expensive form of heating you can get so expect big bills.
Look at how well insulated the flat is, one of our DDs had similar but never put the heating on as the flat below was used by a disabled person who heated their flat 24/7 to a high temp and this worked for her like under floor heating, she even had to open windows in winter to reduce the temp!

jbuchanangb

As you have panel heaters, there is no great benefit from having Economy 7, the opposite can be true because the daytime unit costs on Economy 7 are higher than the standard unit costs on a 24hour tariff. The panel heaters have their own built in timers. The important thing with those is to set them correctly and then do not switch the heater off at the wall, it will mess up the timer. Use the timer, and the override switches to suit your heating needs.

(You could of course just ignore the timer completely if you want to and operate the controls manually all the time.)

If you decide you want a 24hour tariff, even though you have an Economy 7 meter, and several energy companies will allow you to do this, then the advice regarding the hot water tank rather depends on how much hot water you are likely to need. You can heat just the top half of the tank as and when you know you will need it for a bath for example.

Gerry1

Rachel* said:

There is no gas supply, it may be something I look into in the future, but I can’t afford the initial outlay currently.

It would be worth finding out whether gas might be available.  Obviously not if it's a village miles away from the nearest supply, but it's a no-brainer if it's available nearby and can be installed.  It would massively reduce your energy bills and add significant value to your flat, especially after 2025 when new builds can't have gas boilers.  It would also make your flat sell more easily and more quickly.

You certainly won't want to use daytime electricity for heating after your first cold winter, you'll have been freezing or been hit with massive bills, probably both.  You'd have to get NSHs but although the better ones (e.g. Dimplex Quantum) have high heat retention and don't waste money heating rooms when you're not there, they're not cheap.  Far better and more cost effective to go for a gas boiler with wet radiators if it's feasible, even if it means a slightly bigger mortgage.

Bacman

The Megaflow has the main heating element on the top, the bottom is for "boost" if needed. The bottom one itself will not provide hot water due to convection, the top one is the one to use. Get an electrician to install an electric timer so you can set it to come on for a few hours to heat up the boiler rather than being on all the time as the unit uses a lot of power.

The radiator is nothing to do with the Megaflow, it is a stand-alone electric heater. They do dual systems, this is not one of them.

Google "Baxi Megaflow system" and learn about the unit. Normal plumbers in practice do not know how the Megaflow works or how to repair them, although will pretend they do and charge for it. Baxi will refer you to a monthly direct debit with Domestic General, or alternatively if you have a problem phone Baxi directly for them to arrange a qualified plumber to visit.

Also research into "replenish the bubble" if you get water going through the turnish.

If you have general questions, you can message me if you like; we have had a Megaflow for a few years now and had to learn stuff about it (I suggest you do too).

matelodave

Bacman said:

The Megaflow has the main heating element on the top, the bottom is for "boost" if needed. The bottom one itself will not provide hot water due to convection, the top one is the one to use. Get an electrician to install an electric timer so you can set it to come on for a few hours to heat up the boiler rather than being on all the time as the unit uses a lot of power.

The radiator is nothing to do with the Megaflow, it is a stand-alone electric heater. They do dual systems, this is not one of them.

Google "Baxi Megaflow system" and learn about the unit. Normal plumbers in practice do not know how the Megaflow works or how to repair them, although will pretend they do and charge for it. Baxi will refer you to a monthly direct debit with Domestic General, or alternatively if you have a problem phone Baxi directly for them to arrange a qualified plumber to visit.

Also research into "replenish the bubble" if you get water going through the turnish.

If you have general questions, you can message me if you like; we have had a Megaflow for a few years now and had to learn stuff about it (I suggest you do too).

WRONG info. The Megaflow cylinder shown is made by Heatrae Sadia and is an Unvented Direct Cylinder. It does not have a bubble and is designed for off-peak use (thats why its got a lower immersion, to heat the whole tank on off-peak leccy).

I guess yours was something from the Ark (or even Baxi), when combination cylinders were fitted

Bacman

Nope. Ours is unvented. These have a bubble, it's how you get the pressure. It's only 6 years old. Info is not wrong. Bottom element does not heat up the whole boiler, our top one failed a couple of years back and until the enginner came and fixed the issue our water was warm only, and the Baxi enginner told me the above. Anyway, the original poster can research from Google easily, I had to originally.

matelodave

Apologies, the Megaflow HE does have an inbuit expansion facility rather than needing an external expansion vessel. So I apologise.
However the tank that the OP has, does not have an heating coil for use with an external boiler, its just electrically heated and therefore the lower immersion is there to heat the whole tank (usually on an off-peak supply) and the upper immersion is for peak time boosts if you run out.  Although hot water rises, the lower down then the lower heater will heat more water than the top one (I'm guessing that if yours had a lower element then it wasn't connected as it shouldn't be necessary if you've got a gas boiler)