Reply to: The difference between men and women

[psychocandy]

EO, the difference between men and women is that they are right, we are wrong.

Learn to live with it and you'll lead a much happier existence

Exactly. You might win the battle but you'll never win the war!

[doodab]

True. So better turn the thermostat up a bit then.

This is what I keep telling ms doodab. Bloody freezing I am.

[mudskipper]

While we might not understand the mpemba effect we know that freezing the water in your central heating system is generally a bad thing

True. So better turn the thermostat up a bit then.

[doodab]

Sounds logical, but most women are accounting for the possible Mpemba effect. Only we don't bother trying to explain it to you boys, because, as you know, you're always right.

While we might not understand the mpemba effect we know that freezing the water in your central heating system is generally a bad thing

[mudskipper]

Unfortunately it isn't a stone hard fact at all. In fact it's as wrong as wrong thing having a wrong day in the land of wrong.

For any system e.g. your pot of water, the energy that you need to put in to restore the temperature after a period of cooling will be equal to the energy that flowed out during the cooling period, and the energy that flows out at any instant is proportional to the difference between the temperature and the ambient temperature (which is why lowering the thermostat setting saves energy).

If at any given moment you are providing energy to maintain a constant temperature you are by definition supplying the same amount of energy as is flowing out. In the "maintain a constant temperature" case this results in a greater temperature difference and hence a greater outflow of energy at any particular moment in time, than in the case if you allowed it to cool and then reheated it. Therefore the amount of energy you must supply over a given period to maintain the temperature will be greater than the amount you would use to reheat it if you allowed the system to cool over the same period.

So in the case of the pot of water, it is actually more efficient to heat it, allow it to cool, and then heat it up again than it is to heat it and keep it heated. This is fairly obvious if you look at an extreme case where you heat it, let it cool right down to ambient temperature, let it sit there for three years and then heat it up again. Clearly that uses less energy than keeping it heated for three years, but the maths applies equally well if the cooling period is only a few seconds.

Edit: And the difference between men and women is that a man will read that, check the calculation for himself, and think "yes, he's right" whereas a woman will disagree and phone 20 of her friends to get them all to agree with her thus proving that she is right.

Sounds logical, but most women are accounting for the possible Mpemba effect. Only we don't bother trying to explain it to you boys, because, as you know, you're always right.

[doodab]

It is a stone hard fact it is more efficient to heat from warm than from cold.

For example, simplifying it further, it takes medium heat on a hob and a few minutes to boil water from cold. Once boiled, you can leave it to cool to 90*c, then all it needs is minimum heat off the hob and less than a minute to start boiling again.

So if you needed to boil the same water twice, it is more efficient to boil, keep at heat until needed a few minutes later in cooking for example, rather than boiling cold water twice.

Unfortunately it isn't a stone hard fact at all. In fact it's as wrong as wrong thing having a wrong day in the land of wrong.

For any system e.g. your pot of water, the energy that you need to put in to restore the temperature after a period of cooling will be equal to the energy that flowed out during the cooling period, and the energy that flows out at any instant is proportional to the difference between the temperature and the ambient temperature (which is why lowering the thermostat setting saves energy).

If at any given moment you are providing energy to maintain a constant temperature you are by definition supplying the same amount of energy as is flowing out. In the "maintain a constant temperature" case this results in a greater temperature difference and hence a greater outflow of energy at any particular moment in time, than in the case if you allowed it to cool and then reheated it. Therefore the amount of energy you must supply over a given period to maintain the temperature will be greater than the amount you would use to reheat it if you allowed the system to cool over the same period.

So in the case of the pot of water, it is actually more efficient to heat it, allow it to cool, and then heat it up again than it is to heat it and keep it heated. This is fairly obvious if you look at an extreme case where you heat it, let it cool right down to ambient temperature, let it sit there for three years and then heat it up again. Clearly that uses less energy than keeping it heated for three years, but the maths applies equally well if the cooling period is only a few seconds.

Edit: And the difference between men and women is that a man will read that, check the calculation for himself, and think "yes, he's right" whereas a woman will disagree and phone 20 of her friends to get them all to agree with her thus proving that she is right.

[wim121]

Why would I ask a plumber a maths / physics question?

Is it more energy-efficient to keep the heating on all the time?

if you leave your heating on 24/7, you will typically end up using more fuel in a like-for-like situation. This is because some heat loss will always occur due to the difference between the temperature outside your house and the temperature you are trying to keep on the inside. So if you have your heating on all the time, your heating system will be using energy on an ongoing basis to maintain the inside temperature, even when you are tucked under your duvet.

That's why ensuring your home is well-insulated and draught proofed is vital to minimise this heat loss. Taking steps to improve insulation is a good way to save on your energy bills; this can include insulated cavity walls, a well-insulated loft, double-glazing (or heavy curtains) and draught proofed doors, floors and skirting boards.

If your home is insulated well enough, you dont have to worry about heat loss so much. Heat loss can happen to such an extent in a non insulated home that the home wont ever warm up properly.


It is a stone hard fact it is more efficient to heat from warm than from cold.

For example, simplifying it further, it takes medium heat on a hob and a few minutes to boil water from cold. Once boiled, you can leave it to cool to 90*c, then all it needs is minimum heat off the hob and less than a minute to start boiling again.

So if you needed to boil the same water twice, it is more efficient to boil, keep at heat until needed a few minutes later in cooking for example, rather than boiling cold water twice.



I've worked with numerous well versed plumbers who agree on a modern system, in a modern house, with the heating being controlled by the thermostat switching it on and off when required, rather than the antiquated method of one or two heating cycles per day.

[escapeUK]

Now let us assume you have a house to heat in winter and get to 20*c, especially while you relax in the evening and get up in the morning. If you set your heating times for two times a day, they may need to go for a couple of hours each full blast, just to heat the home up, so four hours or so. That expends a massive amount of energy, heating a home from cold to warm.

Why would I ask a plumber a maths / physics question?

Is it more energy-efficient to keep the heating on all the time?

if you leave your heating on 24/7, you will typically end up using more fuel in a like-for-like situation. This is because some heat loss will always occur due to the difference between the temperature outside your house and the temperature you are trying to keep on the inside. So if you have your heating on all the time, your heating system will be using energy on an ongoing basis to maintain the inside temperature, even when you are tucked under your duvet.

[wim121]

Id hate to see your heating bill if you believe nonsense like that.

Isn't nonsense, ask your plumber. Or do the maths.

For example, most leave their boiler on, ready for hot water, etc etc, as running on just the pilot light doesnt use much gas or electric.

Now let us assume you have a house to heat in winter and get to 20*c, especially while you relax in the evening and get up in the morning. If you set your heating times for two times a day, they may need to go for a couple of hours each full blast, just to heat the home up, so four hours or so. That expends a massive amount of energy, heating a home from cold to warm.

Whereas if you let the thermostat do its job and turn your heating on and off automatically, once you house is to temperature, it will switch itself on when it needs to, maybe for half an hour every four hours, keeping your radiators almost constantly warm. That equates to three hours every 24hr cycle. That is a pessimistic estimate though, you could save a lot more.

[Old Greg]

What happens is the female of the species destroys the males brain cells, except for those that need to be passed on to the children.
When the last child is born, the male is left a mindless husk of a worker, that serves the nest and follows direction of the queen/female

And rightly so.

[Diver]

With two young kids.

What happens is the female of the species destroys the males brain cells, except for those that need to be passed on to the children.
When the last child is born, the male is left a mindless husk of a worker, that serves the nest and follows direction of the queen/female

[Old Greg]

ah! a married man then

With two young kids.

[Diver]

I'm way beyond thought.

ah! a married man then

[Old Greg]

You Think?

I'm way beyond thought.

[Diver]

You have created a paradox. Admin will now overheat and explode.

You Think?