Hi,
My current shower is electric with a cold-water only feed and is
getting rather old. I think it is 7.5 Kw but I'm not 100% sure. We
are finding that at this time of year it is barely able to heat the
water to an acceptable temperature. We have very good mains pressure
and usually have to reduce this by running a tap at the same time as
the shower in order to give the unit time to heat the water before it
leaves the heat echanger. I am thinking about replacing it but if I do
this it would have to be like for like at the moment. By that, I don't
mean I want to replace one poor shower with another but if I do replace
it now, then the new one will also have to be electric cold-feed only.
I know people will want to try and convince me about Mixer showers and
Venturi showers but I haven't got the time to start messing around with
the plumbing at the moment. I want to take the old unit off the wall
and put a new unit in its place, otherwise the job will have to wait
for a while and we put up with cold showers.

So the question is, can anybody recommend any reasonably priced
electric cold-feed only showers which might be able to cope better than
the one we have now? I was thinking that a higher wattage shower might
have a better chance of heating the very cold water before sending it
to the showerhead. B&Q currently have a 9.5 Kw Gainsborough at =A364.98
or a 10.5 KW Gainsborough at =A389.00. Are either of these any good or
should I avoid them like the plague ? I don't mind spending more if I
have to, the momey will not be waster as whatever I install now will
almost certainly be moved into the En-suite when I eventually get
around to building it.

TIA.

Kevin.

wrote:
Hi,
My current shower is electric with a cold-water only feed and is
getting rather old. I think it is 7.5 Kw but I'm not 100% sure. We
are finding that at this time of year it is barely able to heat the
water to an acceptable temperature. We have very good mains pressure
and usually have to reduce this by running a tap at the same time as
the shower in order to give the unit time to heat the water before it
leaves the heat echanger.
?

That's what the temperature/flow control knob is for!

MBQ

Ha Bloody Ha !

wrote:
Hi,
My current shower is electric with a cold-water only feed and is
getting rather old. I think it is 7.5 Kw but I'm not 100% sure. We
are finding that at this time of year it is barely able to heat the
water to an acceptable temperature. We have very good mains pressure
and usually have to reduce this by running a tap at the same time as
the shower in order to give the unit time to heat the water before it
leaves the heat echanger. I am thinking about replacing it but if I do
this it would have to be like for like at the moment. By that, I don't
mean I want to replace one poor shower with another but if I do replace
it now, then the new one will also have to be electric cold-feed only.
I know people will want to try and convince me about Mixer showers and
Venturi showers but I haven't got the time to start messing around with
the plumbing at the moment. I want to take the old unit off the wall
and put a new unit in its place, otherwise the job will have to wait
for a while and we put up with cold showers.

So the question is, can anybody recommend any reasonably priced
electric cold-feed only showers which might be able to cope better than
the one we have now? I was thinking that a higher wattage shower might
have a better chance of heating the very cold water before sending it
to the showerhead. B&Q currently have a 9.5 Kw Gainsborough at £64.98
or a 10.5 KW Gainsborough at £89.00. Are either of these any good or
should I avoid them like the plague ? I don't mind spending more if I
have to, the momey will not be waster as whatever I install now will
almost certainly be moved into the En-suite when I eventually get
around to building it.

Basic physics prevents you getting anything massively better. Instant
electric showers are just about 99% efficient - essentially all the
electricity they consume goes into heating the water passing through,
with only small amounts lost through heating the wall they're mounted on
and the surrounding air. Given that, uprating from a 7.5kW to a 10.5kW
one is adding another (3/7.5)*100% = 40% of available power - which can
be traded off either as 40% more flow at the same temperature, or a 40%
greater temperature rise at the same flow rate, or anywhere inbetween.

Then there's upgrading the cable to supply 40% more power; it's likely
your existing cable is sized for a 7.5kw (just about 30A) load, while a
10.5kW 'monster' will be pulling about 42A. To a first approximation,
this usually means replacing a 6mmsq run with a 10mmsq one (and uprating
the MCB); proper calcs need doing to be sure, though, depending on
circuit length and routing (especially if it goes through thermal
insulation...)

Now, if a plumbing-change-free solution is all you feel up to for now,
then a heftier-rated shower with the cable upgrade is your only
solution; just don't expect magic. And you may want to look into putting
a flow restrictor in-line with the new (or even the old!) shower, simply
to reduce the flow rate through it to give it more of a chance to heat a
necessarily smaller dribble of water to a more acceptable temperature.
You may find a more modern instant-leccy shower includes an automagic
flow-rate-controller, too, so in winter you get water that's just as hot
as in summer on a given setting; just less of it.

'O'-level physics follows: pushing the temp of 1 litre of water up by 1
degree Celsius needs 4.2kJ. A kJ is 1 kW/second; so, over a minute, each
kW of shower-rating can raise a litre through about 15 degrees (since it
takes 4.2, call it 4, seconds to raise it through each degree), or more
usefully for back-of-the-envelope purposes, half a litre through the 30
degrees needed to take 'cold-but-not-freezing' (10 degrees C) to 'warm
but not hot especially by the time it's been through the air and hits
your skin' (40 degrees). Which gives us the rule-of-thumb that flowrate
of showerable-temp water in litres/minute is half the kW rating of the
heater - whether that's an instant-electric or a combi (after exhausting
any pre-stored reserve). Of course, shower and combi mfrs play fast and
loose with their 'flow rate' figures - even if they do give one, it's
almost always for an unrealistically low temperature rise (assuming,
say, a 20-degree feed - "it's summer!" - and a 35-degree output "it's
summer, you *want* a refreshing, cooling, not-too-hot shower!". (Indeed,
one of our regular physics-defying brochure-regurgitating posters will
be along soon to p-d and b-r; let's not encourage him by arguing.)

HTH - Stefek

"Stefek Zaba" wrote in message
...
wrote:
Hi,
My current shower is electric with a cold-water only feed and is
getting rather old. I think it is 7.5 Kw but I'm not 100% sure. We
are finding that at this time of year it is barely able to heat the
water to an acceptable temperature. We have very good mains pressure
and usually have to reduce this by running a tap at the same time as
the shower in order to give the unit time to heat the water before it
leaves the heat echanger. I am thinking about replacing it but if I do
this it would have to be like for like at the moment. By that, I don't
mean I want to replace one poor shower with another but if I do replace
it now, then the new one will also have to be electric cold-feed only.
I know people will want to try and convince me about Mixer showers and
Venturi showers but I haven't got the time to start messing around with
the plumbing at the moment. I want to take the old unit off the wall
and put a new unit in its place, otherwise the job will have to wait
for a while and we put up with cold showers.

So the question is, can anybody recommend any reasonably priced
electric cold-feed only showers which might be able to cope better than
the one we have now? I was thinking that a higher wattage shower might
have a better chance of heating the very cold water before sending it
to the showerhead. B&Q currently have a 9.5 Kw Gainsborough at £64.98
or a 10.5 KW Gainsborough at £89.00. Are either of these any good or
should I avoid them like the plague ? I don't mind spending more if I
have to, the momey will not be waster as whatever I install now will
almost certainly be moved into the En-suite when I eventually get
around to building it.

Basic physics prevents you getting anything massively better. Instant
electric showers are just about 99% efficient - essentially all the
electricity they consume goes into heating the water passing through,
with only small amounts lost through heating the wall they're mounted on
and the surrounding air. Given that, uprating from a 7.5kW to a 10.5kW
one is adding another (3/7.5)*100% = 40% of available power - which can
be traded off either as 40% more flow at the same temperature, or a 40%
greater temperature rise at the same flow rate, or anywhere inbetween.

Then there's upgrading the cable to supply 40% more power; it's likely
your existing cable is sized for a 7.5kw (just about 30A) load, while a
10.5kW 'monster' will be pulling about 42A. To a first approximation,
this usually means replacing a 6mmsq run with a 10mmsq one (and uprating
the MCB); proper calcs need doing to be sure, though, depending on
circuit length and routing (especially if it goes through thermal
insulation...)

Now, if a plumbing-change-free solution is all you feel up to for now,
then a heftier-rated shower with the cable upgrade is your only
solution; just don't expect magic. And you may want to look into putting
a flow restrictor in-line with the new (or even the old!) shower, simply
to reduce the flow rate through it to give it more of a chance to heat a
necessarily smaller dribble of water to a more acceptable temperature.
You may find a more modern instant-leccy shower includes an automagic
flow-rate-controller, too, so in winter you get water that's just as hot
as in summer on a given setting; just less of it.

'O'-level physics follows: pushing the temp of 1 litre of water up by 1
degree Celsius needs 4.2kJ. A kJ is 1 kW/second; so, over a minute, each
kW of shower-rating can raise a litre through about 15 degrees (since it
takes 4.2, call it 4, seconds to raise it through each degree), or more
usefully for back-of-the-envelope purposes, half a litre through the 30
degrees needed to take 'cold-but-not-freezing' (10 degrees C) to 'warm
but not hot especially by the time it's been through the air and hits
your skin' (40 degrees). Which gives us the rule-of-thumb that flowrate
of showerable-temp water in litres/minute is half the kW rating of the
heater - whether that's an instant-electric or a combi (after exhausting
any pre-stored reserve). Of course, shower and combi mfrs play fast and
loose with their 'flow rate' figures - even if they do give one, it's
almost always for an unrealistically low temperature rise (assuming,
say, a 20-degree feed - "it's summer!" - and a 35-degree output "it's
summer, you *want* a refreshing, cooling, not-too-hot shower!". (Indeed,
one of our regular physics-defying brochure-regurgitating posters will
be along soon to p-d and b-r; let's not encourage him by arguing.)

HTH - Stefek

Now that you have absorbed all that "claptrap and disposable technical
rubbish" Perhaps you should consider that the old unit is completely furred
up and can't be compared to the current selections. Maybe you should
consider putting the 9.5 kw unit in. Then have a nice shower--a strong
tipple--and invite your now cleaner maiden in for the finale. If you are
lucky--maybe your own fuse is the only one to blow.

My current shower is electric with a cold-water only feed and is
getting rather old. I think it is 7.5 Kw but I'm not 100% sure.

It is unlikely that the electric feed will support a large increase in
power. Your choices are probably to install a new 7.5kW shower, mess around
with the electrics to get a 10.5kW, or mess around with the plumbing to get
a decent shower.

If you post the length of the cable run, the cross sectional area of the
cable and the way the cable has been installed into the building (i.e. run
between floor boards, buried in an insulated wall etc), then it can be seen
if the circuit is already large enough. However, determining the cross
sectional area isn't necessarily very easy. It is probably 6mm2 or 10mm2
cable. It might be as small as 4mm2.

Christian.

Christian
When I posted I was still at work so couldn't be certain about any of
these things but now that I'm home I have some of the answers. The
current shower is on a 40amp MCB with 6mm2 cable. The cable run is
slightly more difficult to determine but the shower unit is relatively
close to the consumer unit on the floor above. I would guess that it's
no more than 8m long in total and runs under floorboards and up through
studded plasterboard. I don't believe any of the studded walls in the
house contain insulation but I canot be 100% certain. As it happens I
would be much more inclined to upgrade the electrics if needed as this
would be much easier given the current state of the rest of the work
I'm doing in the house. That said I was rather hoping for the straight
swap of one unit for the other. Any opinion as to the largest rated
shower I can safely install without running a new cable ?

wrote in message
oups.com...
Christian
When I posted I was still at work so couldn't be certain about any of
these things but now that I'm home I have some of the answers. The
current shower is on a 40amp MCB with 6mm2 cable. The cable run is
slightly more difficult to determine but the shower unit is relatively
close to the consumer unit on the floor above. I would guess that it's
no more than 8m long in total and runs under floorboards and up through
studded plasterboard. I don't believe any of the studded walls in the
house contain insulation but I canot be 100% certain. As it happens I
would be much more inclined to upgrade the electrics if needed as this
would be much easier given the current state of the rest of the work
I'm doing in the house. That said I was rather hoping for the straight
swap of one unit for the other. Any opinion as to the largest rated
shower I can safely install without running a new cable ?


We had a mira sport 8kw running on 6mm cable for about 10 years till I
finally bit the bullet and put in powershower. Although you can't compare
the two my wife was always happy with the leccy 1. I think if you got to
stay with the 6mm cable you and need to just swap shower units, try a modern
8kw 1 and we never had a problem with the mira.

wrote:
B&Q currently have a 9.5 Kw Gainsborough at =A364.98
or a 10.5 KW Gainsborough at =A389.00. Are either of these any good
or
should I avoid them like the plague ?

I had no end of grief with a Heatrae Sadia, so I replaced it with a
Gainsborough on special offer from a shed. *Then* I found out that
Gainsboroughs are yesteryear's Heatrae Sadia designs with the casing
tarted up and the price dropped to fit on the shelf in a shed.

Within the first year that Gainsborough shower needed a new solenoid
valve, the shower head was too restrictive (replaced it with a French
one) and it developed a dangerous fault in that one of the crimps of
the heater connections was badly made and overheated, which heated the
hefty copper cable, which in turn nearly melted through the top of the
casing. Gainsborough flat out refused to supply me a spare and instead
sent me a fitter who did the job FOC, who mentioned that he saw this
fault a lot, and who was under instructions to take the old part away
with him. If that doesn't reek of a product liability problem I don't
know what does. The solenoid valve is getting noisy again, btw.
Short answer to your question: Avoid.

wrote:
Hi,
My current shower is electric with a cold-water only feed and is
getting rather old. I think it is 7.5 Kw but I'm not 100% sure. We
are finding that at this time of year it is barely able to heat the
water to an acceptable temperature. We have very good mains pressure

the one we have now? I was thinking that a higher wattage shower might
have a better chance of heating the very cold water before sending it
to the showerhead. B&Q currently have a 9.5 Kw Gainsborough at £64.98

I also have this problem. The big problem is that the wiring feeding my
20 year old Triton T80 won't take a higher load.
I considered rewiring but that is just too much trouble in a flat. So
I've decided I may as well install a gas combi instead. (May as well
replace the 20 yr old boiler before it fails catastrophicaly one day.
Besides reclaiming the area occupied by tanks etc adds at least 5% extra
space to a tiny flat).

So my advice, check that a higher rated heater won't overload your wiring.


--
David Clark

$message_body_include ="PLES RING IF AN RNSR IS REQIRD"

Calculator here
http://www.tlc-direct.co.uk/Technica...ltageDrop.html
10 kw showers are OK giving adequate shower but I would have thought
7.5 kw just too small to be any good. If you are putting in a cable why
not go next size up - 10kw needs 10mm cable, go for 16mm and be covered
for a bigger shower.
I find electric showers very handy - cheap to buy and fit (depending on
cable and pipe route) reliable, quick response and always available,
but if you want the best then go for mains pressure via combi boiler ,
but then combis come with a whole load of problems of their own.
cheers

Jacob

size up - 10kw needs 10mm cable, go for 16mm and be covered for a bigger
shower.

Jacob

You don't run 16mm2 very often in a domestic situation then do you !!

Dave

--
For what we are about to balls up may common sense prevent us doing it
again
in the future!!

On Fri, 28 Jan 2005 22:56:50 GMT, quisquiliae
wrote:

wrote:
Hi,
My current shower is electric with a cold-water only feed and is
getting rather old. I think it is 7.5 Kw but I'm not 100% sure. We
are finding that at this time of year it is barely able to heat the
water to an acceptable temperature. We have very good mains pressure

the one we have now? I was thinking that a higher wattage shower might
have a better chance of heating the very cold water before sending it
to the showerhead. B&Q currently have a 9.5 Kw Gainsborough at £64.98

I also have this problem. The big problem is that the wiring feeding my
20 year old Triton T80 won't take a higher load.
I considered rewiring but that is just too much trouble in a flat. So
I've decided I may as well install a gas combi instead. (May as well
replace the 20 yr old boiler before it fails catastrophicaly one day.

When you remove your 20 year old T80 could I have it as spares for my
15 year old one please ;-)

Mind you, the last time it went wrong I got a new part straight from
Triton?

As posted already it does run out of 'ooommpf' in the coldest weather
but is still pretty stable temperature wise and serves it's purpose
(heating water to allow us to wash) pretty well.

All the best ..

T i m

T i m wrote:

When you remove your 20 year old T80 could I have it as spares for my
15 year old one please ;-)

Mine had most of its insides replaced ~12 years ago. The local plumbers
merchant suggested contacting Triton direct. I did and was able to
replace the heating element and valve assembly for about £40 inc vat,p&p
etc

It needs more replacement parts now. Switching to the off position there
is a sound of water boiling although switching to cold/low/high settings
is ok. For the past few months I have been leaving it on the cold
setting and switching off at the isolator.

That and a combination of winter weather was about to motivate me to
rewire and replace. Then the plumber who came during my kitchen
renovation suggested a combi. Which makes sense, with the kitchen done
converting the shower room/WC (170cm x 90cm) into a wet room is the
nextgreat renovation project. But quote for new HE combi (central London
prices) £3,000. Still awaiting the wet room quote... oh and the car
service estimate is over £2000 (which must be more than a ten year old
Twingo is worth). Sigh -- I need to get out of academia and get a proer
paying job; or move somewhere sane and sensible.

As posted already it does run out of 'ooommpf' in the coldest weather
but is still pretty stable temperature wise and serves it's purpose
(heating water to allow us to wash) pretty well.

Yes in summer setting it at 8/12 is hot enough and reasonable pressure.
This week though its at 12/12, and just adequate.

[excuse typos, keyboard needs cleaning]

--
David Clark

$message_body_include ="PLES RING IF AN RNSR IS REQIRD"