Hi

Just looking for a guide, not actual calcs, from someone who can give an
authoratative "yes" or "no"...

Fitted a 330l pressurised cylinder (insulated) earlier this year and to date
has been left switched on all the time due to high demand for hot water
literally 24hrs a day. Now demand is dropping off dramatically and will only
be needed Fri-Sun so...

Should the cylinder be switched off Monday - Fri am allowing the water to
cool and reheat from what I asume would be almost cold on Friday pm. Or, is
it more energy efficient to leave it on and let the thormostat regulate
power consumption to keep it up to temp throughout the week?

Any ideas...

Tony

"TonyK" wrote in message
...
Hi

Just looking for a guide, not actual calcs, from someone who can give
an
authoratative "yes" or "no"...

Fitted a 330l pressurised cylinder (insulated) earlier this year and
to date
has been left switched on all the time due to high demand for hot
water
literally 24hrs a day. Now demand is dropping off dramatically and
will only
be needed Fri-Sun so...

Should the cylinder be switched off Monday - Fri am allowing the water
to
cool and reheat from what I asume would be almost cold on Friday pm.
Or, is
it more energy efficient to leave it on and let the thormostat
regulate
power consumption to keep it up to temp throughout the week?

Any ideas...

Tony

Turn it off. It probably won't be almost cold - my brother has a 150l
cylinder in his flat which was switched off last Monday and on Saturday
the water was still warm.

As the water cools it will be losing heat more slowly than when it was
warmer (if you see what I mean). Losing heat more slowly = more
efficient. You'll have to add less heat to get it back up to temperature
than you would have lost by maintaining it over the week.

In reality there's probably not that much difference. And bear in mind
that if you are heating electrically that the cost of the energy may
vary depending on when it is consumed.

HTH

Neil

Should the cylinder be switched off Monday - Fri am allowing the water to
cool and reheat from what I asume would be almost cold on Friday pm. Or,
is
it more energy efficient to leave it on and let the thormostat regulate
power consumption to keep it up to temp throughout the week?

Definitely off, if it is for that period. If it is just unused overnight,
savings will be minimal. However, over the period of a week, you'll find it
cheaper to only heat weekends.

However, if it is electric, you may find it takes an age to reheat, so will
need to do some calculations to determine when the timer should come on.
With gas, it should only take an hour or so from cold, assuming a modern
system.

Christian.

On Mon, 6 Sep 2004 12:45:39 +0100, "TonyK"
wrote:

Hi

Just looking for a guide, not actual calcs, from someone who can give an
authoratative "yes" or "no"...

Fitted a 330l pressurised cylinder (insulated) earlier this year and to date
has been left switched on all the time due to high demand for hot water
literally 24hrs a day. Now demand is dropping off dramatically and will only
be needed Fri-Sun so...

Should the cylinder be switched off Monday - Fri am allowing the water to
cool and reheat from what I asume would be almost cold on Friday pm. Or, is
it more energy efficient to leave it on and let the thormostat regulate
power consumption to keep it up to temp throughout the week?

Any ideas...

Tony


It would really depend on how much insulation, Tony.

If you were using the system say 18 hours out of 24 every day, I would
say leave it on - it's what I do.

However, for 2 days out of 7 I would switch it off.



..andy

To email, substitute .nospam with .gl

Switch it off it is then.

Thanks guys.

Tony

In article ,
TonyK wrote:
Should the cylinder be switched off Monday - Fri am allowing the water
to cool and reheat from what I asume would be almost cold on Friday pm.
Or, is it more energy efficient to leave it on and let the thormostat
regulate power consumption to keep it up to temp throughout the week?

A little lateral thinking says that electricity used for heating water is
very nearly 100% efficient in what it does - ie there is no waste heat, as
there might be with a less direct method, ie a gas boiler.

However, no insulation can be 100% efficient, so there will be some heat
loss. So switching off when not required must be the cheapest option. It
might not be the most convenient, though, given the time needed to re-heat.

--
*I took an IQ test and the results were negative.

Dave Plowman London SW
To e-mail, change noise into sound.

"Neil Jones" wrote in message
...
Should the cylinder be switched off Monday - Fri am allowing the water
to
cool and reheat from what I asume would be almost cold on Friday pm.
Or, is
it more energy efficient to leave it on and let the thormostat
regulate
power consumption to keep it up to temp throughout the week?

Turn it off. It probably won't be almost cold - my brother has a 150l
cylinder in his flat which was switched off last Monday and on Saturday
the water was still warm.

What cylinder is this ? Our cylinder goes cold in 2 to 3 days. It also
costs about 10p/day just to keep the water warm without using any. Even
tried adding a standard cylinder jacker over the spray foam but that didn't
make a major difference - temperature between the jacket and the foam was
about 2 to 3 deg above ambient.

TonyK wrote:
Hi

Just looking for a guide, not actual calcs, from someone who can give an
authoratative "yes" or "no"...

Fitted a 330l pressurised cylinder (insulated) earlier this year and to date
has been left switched on all the time due to high demand for hot water
literally 24hrs a day. Now demand is dropping off dramatically and will only
be needed Fri-Sun so...

Should the cylinder be switched off Monday - Fri am allowing the water to
cool and reheat from what I asume would be almost cold on Friday pm. Or, is
it more energy efficient to leave it on and let the thormostat regulate
power consumption to keep it up to temp throughout the week?

As others have said, it's best to turn it off.
However, if it's in a place where this is possible, you'll get a significant
increase in time to cool down if you get a 5 quid roll of loft insulation and
pack it (loosely, but leaving no air gaps) round the cylinder.

"Ian Stirling" wrote in message
...
TonyK wrote:
Hi

Just looking for a guide, not actual calcs, from someone who can give an
authoratative "yes" or "no"...

Fitted a 330l pressurised cylinder (insulated) earlier this year and to
date
has been left switched on all the time due to high demand for hot water
literally 24hrs a day. Now demand is dropping off dramatically and will
only
be needed Fri-Sun so...

Should the cylinder be switched off Monday - Fri am allowing the water
to
cool and reheat from what I asume would be almost cold on Friday pm. Or,
is
it more energy efficient to leave it on and let the thormostat regulate
power consumption to keep it up to temp throughout the week?

As others have said, it's best to turn it off.
However, if it's in a place where this is possible, you'll get a
significant
increase in time to cool down if you get a 5 quid roll of loft insulation
and
pack it (loosely, but leaving no air gaps) round the cylinder.


Coincidentally was thinking about the same question only this only this
morning. Would there be any economy in switching the water heater
tank/cylinder off for certain periods, especially since now only one person
(me) living in this house?

Talking to myself driving to technical college, went like this. Self, I
said;

"Normal practice here is to leave the hot water heater, which is typically
30 imperial gallons with upper and lower 3000 watt heaters with individual
thermostats in a flip-flop arrangement, on, all the time".

BTW we went on vacation on one occasion for a couple of weeks and switched
off the hot water circuit breaker; when we returned the tank water was still
tepid! So have always assumed that heat loss to the ambient surroundings in
our unheated average 55 to 60 degrees F. basement, is very small?

" What about temporarily hooking up an electric clock to the heaters. Then
see how long the heaters came on while domestic hot water use was zero, to
maintain the set temperature.
If the clock ran for say ten minutes during a ten hour period.
Then electric consumption would-be 10/60 * 3 = 0.5 Kilowatt hours or units
per 10 idle/quiescent hours. An average of 0.05 units per hour?
Electricity here now costs about 9 cents (Canadian) or roughly 4 pence per
unit all charges, such as sales tax included
Using these hypothetical numbers; then if unit left on for 24 hours, with no
use of domestic hot water, 24 * 0.05 * 0.04 = approximately 5 pence per
day?".

For a two week holiday I would in fact shut off the water pressure and
switch off the hot water heater and, unless mid winter, the electric heat;
otherwise for a quiescent two weeks it might cost, theoretically, about 14
* 5 = 70 pence! Does this make sense or have I slipped a decimal place
somewhere?

Cheers.

"TonyK" wrote in message ...
Hi

Just looking for a guide, not actual calcs, from someone who can give an
authoratative "yes" or "no"...

Fitted a 330l pressurised cylinder (insulated) earlier this year and to date
has been left switched on all the time due to high demand for hot water
literally 24hrs a day. Now demand is dropping off dramatically and will only
be needed Fri-Sun so...

Should the cylinder be switched off Monday - Fri am allowing the water to

Sunday - Thursday. That way it will be hot for you on Friday and you
can use up what you've already heated on Sunday.

MBQ

Terry wrote:

"Ian Stirling" wrote in message
...
TonyK wrote:
Hi

Just looking for a guide, not actual calcs, from someone who can give an
authoratative "yes" or "no"...

Fitted a 330l pressurised cylinder (insulated) earlier this year and to
date
has been left switched on all the time due to high demand for hot water
literally 24hrs a day. Now demand is dropping off dramatically and will
only
be needed Fri-Sun so...
sniip
As others have said, it's best to turn it off.
However, if it's in a place where this is possible, you'll get a
significant
increase in time to cool down if you get a 5 quid roll of loft insulation
and
pack it (loosely, but leaving no air gaps) round the cylinder.

Coincidentally was thinking about the same question only this only this
morning. Would there be any economy in switching the water heater
tank/cylinder off for certain periods, especially since now only one person
(me) living in this house?

Talking to myself driving to technical college, went like this. Self, I
said;
snip
Then electric consumption would-be 10/60 * 3 = 0.5 Kilowatt hours or units
per 10 idle/quiescent hours. An average of 0.05 units per hour?
Electricity here now costs about 9 cents (Canadian) or roughly 4 pence per
unit all charges, such as sales tax included
Using these hypothetical numbers; then if unit left on for 24 hours, with no
use of domestic hot water, 24 * 0.05 * 0.04 = approximately 5 pence per
day?".


Based on cooldown rates, for my admittedly well insulated cylinder, I believe
it's about 80W or so.
So, at 4p/unit, that's be around 8p/day.

For a two week holiday I would in fact shut off the water pressure and
switch off the hot water heater and, unless mid winter, the electric heat;
otherwise for a quiescent two weeks it might cost, theoretically, about 14
* 5 = 70 pence! Does this make sense or have I slipped a decimal place
somewhere?

It's within a factor of 10, so I'll not disagree.

Either measuring the on-time, or measuring the temperature drop with an
accurate thermometer after 12 hours switched off would work, if you know the
cylinder capacity.