Can I get my immersion heater to come on during the day?

[MartinKernick]

Hello, my first post so here goes!

I have recently inherited a flat which had both economy 7 heating and hot water on a white meter. These radiators and the long immersion element seem to be on a separate circuit from the other household appliances - as the circuit is dead during the day.

I'm intending to rent the accommodation and, because most people who would be renting it would tend to work during the day, I've replaced the heaters which were mega old, bulky and unsightly for conventional convector heaters with no night storage on the ordinary ring main. The hot water tank, however, is still on the economy 7 circuit (for the main immersion element).

So it looks to me as though my tenants would be stuck with heating their bathwater at night, even if they were only going to use it the following evening.

There an old HORSTMANN control (mechanical cam type) on the kitchen wall which offers a timed economy 7 function and a boost using the shorter element.

I've read elsewhere that devices such as a washing machine, if used at night, would operate on the economy 7 tariff even if they are plugged into the normal mains circuit. Would that be true with my setup?

If it's true, then, is there any way that I could get my HORSTMANN controller to work such that, like the washing machine, it would allow the longer immersion element to operate during the day on the normal tariff and on economy 7 during the night? I'm thinking that a tank heated during the night might be fairly cold by the evening. Also most economy 7 tariffs wouldn't be the best choice if you're only heating the water and doing no night storage would they? So if you weren't on an economy 7 tariff it'd be pretty unsatisfactory to have to think to turn on your long immersion element the night before you wanted a bath.

 

[Lectrician]

You shouldn't be putting heating loads on the ring circuit. Why not use the old storage heater points, changing the switches to FCUs if required. An electrician could alter the supply at the fuse boards to liven them on the 24hr supply.

It is usual to heat the whole tank at night, and boost the short element during the day. This works for most people. Even just heating water at night makes econ7 type tariffs beneficial. If you ditched the whole econ7 type tariff, you could liven all circuits 24/7, and remove the Horstmann controller, replacing it with perhaps just a 24hr timer, and using the short immersion as a boost, using a 1hr, 2hr press button timer.

Economy 7 is different to an old white meter setup. Photo of your metering?

 

[AndyPRK]

It doesn't sound like you are doing a very good job there.

Will the place be empty at weekends ?

 

[phatboy]

By removing the storage heaters you have instantly doubled the cost of heating the property. You have also ensured that the air is very dry and horrible to sit in due to the convectors.

I recommend buying new storage heaters, and reconnecting them to the dis-used points.

Assuming the immersion heater is reasonably modern, it will retain the heat for up to 48 hours, so heating the water at night is absolutely fine. Even better its on the cheaper rate.

I had a flat on E7 tariff, and the immersion heater was 15 years old. 2 of us lived there, and we never had to endure a cold shower.

 

[JohnW2]

By removing the storage heaters you have instantly doubled the cost of heating the property. You have also ensured that the air is very dry and horrible to sit in due to the convectors.

Your point about cost is valid, if one has an E7 or similar tariff, but I don't really understand why convector heaters should result in any dryer air than storage heaters (or, indeed, wet CH).

Assuming the immersion heater is reasonably modern, it will retain the heat for up to 48 hours, so heating the water at night is absolutely fine. Even better its on the cheaper rate.

The age of the immersion heater is obviously irrelevant (provided it still works!) - what matters is how large and well-insulated is the hot water cylinder. However, I agree that, with a well-insulated cylinder of adequate size, heating water only at night is can often be adequate. That's what I do, and we very rarely have to do any top-up water heating during the day (usually only if the house is 'full of people')

Kind Regards, John

 

[phatboy]

Your point about cost is valid, if one has an E7 or similar tariff, but I don't really understand why convector heaters should result in any dryer air than storage heaters (or, indeed, wet CH).

With convectors, the circulated air passes right across the heating element which seems to dry it. With storage heaters, the air passes over the bricks, which does not have this effect (As far as I understand, but I know the difference in feeling! Sitting in a room with a convector on makes me need to drink more water, and feels 'nasty')

The age of the immersion heater is obviously irrelevant (provided it still works!) - what matters is how large and well-insulated is the hot water cylinder

Of course, this is what I meant. The element produces the heat and is very efficient, the cylinder's insulation is the key thing.

 

[JohnW2]

With convectors, the circulated air passes right across the heating element which seems to dry it. With storage heaters, the air passes over the bricks, which does not have this effect (As far as I understand, but I know the difference in feeling! Sitting in a room with a convector on makes me need to drink more water, and feels 'nasty')

I obviously can't argue with what you say about how you feel in the presence of convector heaters, but I struggle to understand the logic of the differences you are suggesting - maybe I'm missing something.

Kind Regards, John

 

[westie101]

I think with storage heaters, that as well as the bricks they do overall warm the fabric of the house as they are on for a longer period.
Convector types are usually on as needed so whilst they do warm the air they can also dry it as well.
If that makes sense

 

[phatboy]

I think with storage heaters, that as well as the bricks they do overall warm the fabric of the house as they are on for a longer period.
Convector types are usually on as needed so whilst they do warm the air they can also dry it as well.
If that makes sense

And even when they are off, they are still providing heat. Maybe it's down to the gradual release of heat into the room?

 

[JohnW2]

I think with storage heaters, that as well as the bricks they do overall warm the fabric of the house as they are on for a longer period. Convector types are usually on as needed so whilst they do warm the air they can also dry it as well. ... If that makes sense

I won't comment on 'making sense', but I still don't really understand. If it is being suggested that convector heaters 'dry the air' (i.e. remove moisture/ water vapour from it), where is it being suggested that the moisture/water vapour goes?

Kind Regards, John

 

[phatboy]

I think I found an answer!

Most of these "fan heaters" heat through convection, they create an air current, displacing cold air with warm air... the dewpoint inside of your room changes, and the cool air which falls to the ground, brings much of the moisture down there with it. Or it will condense on the walls or ceiling... anyplace where the air temp is cooler than the created heat.

So it puts the moisture on the floor

 

[JohnW2]

I think I found an answer!

Most of these "fan heaters" heat through convection, they create an air current, displacing cold air with warm air... the dewpoint inside of your room changes, and the cool air which falls to the ground, brings much of the moisture down there with it. Or it will condense on the walls or ceiling... anyplace where the air temp is cooler than the created heat.

So it puts the moisture on the floor

However, that's all very well, but they are describing how a heater which "heats through convection" can result in water vapour condensing on surfaces (walls, ceilings, floors) which are cooler than the heated air. However, both convection/fan heaters and storage heaters heat almost exclusively by convection, as, to a substantial extent, also do CH radiators (particularly the efficient 'finned' ones) - so I'm still not sure that I necessarily see the difference.

I suppose it's possible that convection heaters raise the temperature of the air to a greater extent than do storage heaters (thereby enhancing the above effect), but those bricks in storage heaters seem to get mighty hot!

Kind Regards, John

 

[MartinKernick]

Thanks for all the replies.

My comments about Economy 7 tariffs were based on some things I read on the U Switch site.

http://www.uswitch.com/gas-electricity/guides/economy-7/

They say:

As a general rule of thumb you would need to use more than 40% of your electricity at night to make Economy 7 cost effective. Some Economy 7 plans charge almost twice the standard night rate for any electricity used in the day, which can cancel out the benefits of the cheap electricity you get at night.

An Economy 7 tariff is best suited to people who have electric storage heaters and a hot water tank.

Now I don't know who to believe, but I'm heartened by the hope that the hot water would stay hot over, say, a 12 hr period.

As regards the convectors on the ring main, it's only a small flat, suitable for a single person or a couple at most. If one were to turn all three of them on at once they would amount to 3.8kw. Would that be a problem? The cooker is, of course on its own circuit. You might plug in a kettle run a microwave run a TV and still have considerable headroom. I too am not convinced that convectors dry the air any more than storage radiators would.

However I think, if the white meter can't supply electricity outside the night hours, reinstating the circuit on the normal meter might be a goer. I'll definitely explore that suggestion.

Most people in the block who rent, work during the day. So, for those sorts of people, the flat would be empty during the day and, possibly some of the evening too. While there have been major advances in storage radiators I'm not convinced that they offer the flexibility that many tenants will want, though I agree there are arguments on both sides.

If I were to get an electrician to reinstate economy 7 circuit on a normal meter, I'm guessing that the Horstmann controller would work fine as a 24hr timer for the water - just not on the economy 7. Anybody know if I'd have any problems with this? The existing economy 7 circuit could also easily feed one of the convectors too. So I like this suggestion.

 

[endecotp]

Most people in the block who rent, work during the day. So, for those sorts of people, the flat would be empty during the day and, possibly some of the evening too.

I lived in a similar flat in about 2000. My experience was that the storage heaters were great for the living room; they could easily retain heat during the day while I was working and keep the room warm in the evening. For the bedroom I had a non-storage convector with a built in timeswitch that came on for a short period late in the evening.

As a potential tenant, I would be put off by a property with only electric convectors due to the potential cost. How well insulated is the flat?

 

[JohnW2]

They say: "As a general rule of thumb you would need to use more than 40% of your electricity at night to make Economy 7 cost effective. Some Economy 7 plans charge almost twice the standard night rate for any electricity used in the day, which can cancel out the benefits of the cheap electricity you get at night. ... An Economy 7 tariff is best suited to people who have electric storage heaters and a hot water tank."
Now I don't know who to believe ....

What that says is roughly true. E7 etc. tariffs vary, but daytime units usually cost more than twice (not "almost twice") the night rate, such that the break-even-point is usually between 30% and 40% night-time usage (it's about 34% with the tariff I have). As a consequence, it is rarely cost-effective to have E7 unless one has night storage heaters.

As regards the convectors on the ring main, it's only a small flat, suitable for a single person or a couple at most. If one were to turn all three of them on at once they would amount to 3.8kw. Would that be a problem? The cooker is, of course on its own circuit. You might plug in a kettle run a microwave run a TV and still have considerable headroom.

Even though it is not generally regarded as good practice to have heaters on a ring circuit, numerically speaking what you describe does not sound unreasonable. However, are you sure that you are going to heat a whole flat satisfactorily with only a total of 3.8 kW? Many people would have that much heating in a single room.

I too am not convinced that convectors dry the air any more than storage radiators would.

As you will have seen, nor am I.

However I think, if the white meter can't supply electricity outside the night hours, reinstating the circuit on the normal meter might be a goer. I'll definitely explore that suggestion.

AFAIAA, most/all current E7 installations (like mine) simply meter all electricity usage in the installation at either peak or night rate, according to the time of day - i.e. there are no parts of the installation that only gets electricity at night (unless one deliberately installs time switches to achieve that, as one generally would with storage heaters).

If I were to get an electrician to reinstate economy 7 circuit on a normal meter, I'm guessing that the Horstmann controller would work fine as a 24hr timer for the water - just not on the economy 7. Anybody know if I'd have any problems with this? The existing economy 7 circuit could also easily feed one of the convectors too. So I like this suggestion.

You really need first to decide whether you want E7 (at all) or not - and, if not, get it changed to a single tariff supply. As above, in the absence of storage heaters, E7 is likely to result in higher electricity bills.

Kind Regards, John