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JohnH
 
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Default Electric shower flat low pressure - options?

I've googled and checked the FAQ but not found anything specific to this
problem.

I would like fit a decent shower in my bathroom as part of a shower/bath
combination. Its a small flat with basic plumbing, 1 cold water tank and
1 hot water cylinder heated by an electric immersion heater, taps are
gravity fed (except the kitchen cold mains tap).

The problem is that the shower head height is less than 10cm below the
water level in the cold water tank and also heating the water is an
issue.

From googling it seems I would need a negative head pump like a ST
monsoon to deal with the head height. But what about heating the water?
Was thinking about some sort of electricly heated shower, but im not
sure what will work in this situation.

I dont have a gas supply so a combi boiler is not an option.

Any opinions, gratefully received.

--
JH
  #2   Report Post  
Dave Jones
 
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Default


"JohnH" wrote in message
...
I've googled and checked the FAQ but not found anything specific to this
problem.

I would like fit a decent shower in my bathroom as part of a shower/bath
combination. Its a small flat with basic plumbing, 1 cold water tank and
1 hot water cylinder heated by an electric immersion heater, taps are
gravity fed (except the kitchen cold mains tap).

The problem is that the shower head height is less than 10cm below the
water level in the cold water tank and also heating the water is an
issue.

From googling it seems I would need a negative head pump like a ST
monsoon to deal with the head height. But what about heating the water?


What's wrong with the immersion heater for heating the water?


Was thinking about some sort of electricly heated shower, but im not
sure what will work in this situation.

I dont have a gas supply so a combi boiler is not an option.

Any opinions, gratefully received.

--
JH




  #3   Report Post  
JohnH
 
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Default

In article , djones2004
@nospam.tiscali.co.uk says...

"JohnH" wrote in message
...
I've googled and checked the FAQ but not found anything specific to this
problem.

I would like fit a decent shower in my bathroom as part of a shower/bath
combination. Its a small flat with basic plumbing, 1 cold water tank and
1 hot water cylinder heated by an electric immersion heater, taps are
gravity fed (except the kitchen cold mains tap).

The problem is that the shower head height is less than 10cm below the
water level in the cold water tank and also heating the water is an
issue.

From googling it seems I would need a negative head pump like a ST
monsoon to deal with the head height. But what about heating the water?


What's wrong with the immersion heater for heating the water?


There nothing wrong with it, except I was kinda thinking along the lines
of something that you could have an 'instant' shower with. With the
immersion heater you'd have to wait till the water heated up first
before having a shower.

If I was going to use the immersion for heating is there a decent brand
of shower unit you would recommend that would do the job with the pump
attached?

Im beginning to think I could get away with this option unless the
alternative of an electric shower is not too much more expensive.

--
JH
  #4   Report Post  
Dave Jones
 
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Default


"JohnH" wrote in message
...
In article , djones2004
@nospam.tiscali.co.uk says...

"JohnH" wrote in message
...
I've googled and checked the FAQ but not found anything specific to
this
problem.

I would like fit a decent shower in my bathroom as part of a
shower/bath
combination. Its a small flat with basic plumbing, 1 cold water tank
and
1 hot water cylinder heated by an electric immersion heater, taps are
gravity fed (except the kitchen cold mains tap).

The problem is that the shower head height is less than 10cm below the
water level in the cold water tank and also heating the water is an
issue.

From googling it seems I would need a negative head pump like a ST
monsoon to deal with the head height. But what about heating the water?


What's wrong with the immersion heater for heating the water?


There nothing wrong with it, except I was kinda thinking along the lines
of something that you could have an 'instant' shower with. With the
immersion heater you'd have to wait till the water heated up first
before having a shower.

If I was going to use the immersion for heating is there a decent brand
of shower unit you would recommend that would do the job with the pump
attached?

Im beginning to think I could get away with this option unless the
alternative of an electric shower is not too much more expensive.

--

If your hot water cylinder is well insulated and your thermostat is working
ok, then using an immersion heater for primary heating, would be best left
on constantly, to be most cost effective.

Most of the decent brands would do this job and probably most of the cheap
ones too.

As for putting in an electric shower depending on if you can get a plumber
who is part P registered, or a spark who is willing to do a bit of pluming,
might cost between £250 and £350 all in.


  #5   Report Post  
Doctor Evil
 
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Default


"JohnH" wrote in message
...
In article , djones2004
@nospam.tiscali.co.uk says...

"JohnH" wrote in message
...
I've googled and checked the FAQ but not found anything specific to

this
problem.

I would like fit a decent shower in my bathroom as part of a

shower/bath
combination. Its a small flat with basic plumbing, 1 cold water tank

and
1 hot water cylinder heated by an electric immersion heater, taps are
gravity fed (except the kitchen cold mains tap).

The problem is that the shower head height is less than 10cm below the
water level in the cold water tank and also heating the water is an
issue.

From googling it seems I would need a negative head pump like a ST
monsoon to deal with the head height. But what about heating the

water?

What's wrong with the immersion heater for heating the water?


There nothing wrong with it, except I was kinda thinking along the lines
of something that you could have an 'instant' shower with.


How about doing what all people do in flats and fit a combi.


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  #6   Report Post  
Doctor Evil
 
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Default


"Dave Jones" wrote in message
...

"JohnH" wrote in message
...
In article , djones2004
@nospam.tiscali.co.uk says...

"JohnH" wrote in message
...
I've googled and checked the FAQ but not found anything specific to
this
problem.

I would like fit a decent shower in my bathroom as part of a
shower/bath
combination. Its a small flat with basic plumbing, 1 cold water tank
and
1 hot water cylinder heated by an electric immersion heater, taps are
gravity fed (except the kitchen cold mains tap).

The problem is that the shower head height is less than 10cm below

the
water level in the cold water tank and also heating the water is an
issue.

From googling it seems I would need a negative head pump like a ST
monsoon to deal with the head height. But what about heating the

water?

What's wrong with the immersion heater for heating the water?


There nothing wrong with it, except I was kinda thinking along the lines
of something that you could have an 'instant' shower with. With the
immersion heater you'd have to wait till the water heated up first
before having a shower.

If I was going to use the immersion for heating is there a decent brand
of shower unit you would recommend that would do the job with the pump
attached?

Im beginning to think I could get away with this option unless the
alternative of an electric shower is not too much more expensive.

--

If your hot water cylinder is well insulated
and your thermostat is working
ok, then using an immersion heater for
primary heating, would be best left
on constantly, to be most cost effective.


Or install a shower-coil cylinder. It has a coil at the top that high
pressure mains water runs though being instantly heated by the stored water.
Then a normal thermostatic shower mixer can be used.


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  #8   Report Post  
Stefek Zaba
 
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JohnH wrote:

I've just looked up about electric combi boilers, it seems this is what
I would need, assuming it pumps out hot water at a decent rate.

The trade does appear to use the name "electric combi boiler" for what
might be a suitable heating arrangement in your - unusual - situation. I
came across such a thing in a holiday cottage we rented a few weeks ago
(http://www.lindisfarne.org.uk/retreat/index.htm - highly recommended!
;-) As the URL suggests, it's on Lindisfarne, aka Holy Island - off the
Northumberland coast, access via causeway at low tide only. Thuz, no
mains gas; property intermittently occupied by succession of short-stay
visitors who can't be relied to light boilers, change gas bottles, or
any such; alternatives presumably oil (but no front garden and back
garden small, no access from any street!) and electric.

So they'd fitted what the mfrs literature called an "electric combi",
though more accurately it'd be an "electrically heated heatbank" -
there's a storage cylinder of (at a glance) 200? litre capacity, which
was heated through a pair of electric elements (use one for summer, both
in winter), time-controller with preference for heating during
cheap-rate night-time but would boost with pricey daytime leccy if
needed (OK for tenants paying multiple-hundreds for a week's stay).
They'd a good programmable stat, whose default setting was more or less
as a frost-stat (5 degs) with an early-morning keep-the-chill-off
period; tenant override by pushing up the setpoint (with resets to 5degs
programmed every 12h, to avoid using up the heat when the place was
empty). HW on direct-mains (unvented) heat-exchanger off the heatbank,
wasn't interested enough to work out whether the CH feed came off a
heat-exchanger or circulated the stored water - but in either case the
CH was very responsive.

With only two bedrooms and a bathroom upstairs, and a largish open-plan
living area downstairs, this arrangement was perfectly adequate to keep
the place toasty-warm on its own - though we dig bring up three
office-moving crates full of wood for the multifuel stove for the
prettiness off it, and in case of powercuts. The tenant instructions
asked us not to fiddle with any of the controls, and so I avoided the
temptation to switch to the 'winter' position (both heating elements). I
believ therefore that the heating (and the bath filling) was done with a
single 6kW element; if one was living there permanently, with more of an
eye on the running costs, I think you'd want to make use of the 'winter'
position to get both elements going in winter, purely to get the bulk of
the energy consumption done on cheaprate. The place was reasonably
insulated - gert thick walls, well-fitting windows - and being terraced
had only the front and rear exposed; but exposed to seriously chilling
winds - this being an island in the North Sea, after all!

What kW would be needed for an acceptable shower and for running a bath?
(won't be used for heating as there are electric rads here).
I've seen some boilers on discountedheating.co.uk from 2kW to 12kW.

Hope the thumbnail above suggests hope, in that case - 2kW sounds
stupidly small, 12kW may be overkill (but would give you relatively fast
recovery, at the cost of needing a hefty feed (50A circuit, may need to
get yor supplier to uprate their incoming fuse).

Can anyone recommend any decent plumbers in high wycombe?

Rocking-horse droppings come to mind ;-)

Ob. thread-drift (but still d-i-y): we drove onto Lindisfarne on a
Saturday, parked the car, and didn't try to move it till the Friday.
Started just fine, but wouldn't move - felt as if it'd been clamped;
well, it *would* move, but only by dragging the non-rotating rear
driver's-side wheel over the gravel! Turned out the sal****er spray +
damncold winds (this was February) had made the handbrake shoe seize up
(big clue: handbrake handle inside the car wouldn't come back up once
released). While waiting for the RAC to show up (hey, it's paid for, may
as well use it) tried - on the suggestion from the man in the Local
Shoppe ;-) - tapping it free with a suitable hammer substitute (wheel
wrench, since you asked - I'd jacked up that wheel and taken it off, for
better access and trying to work out Wot Wus Going On. A couple of
non-vicious taps, a satisfying 'ping' of releasing spring, and the wheel
turned freely! Result! RAC callout cancelled, off to Berwick...

Cheers, Stefek
  #10   Report Post  
Stefek Zaba
 
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JohnH wrote:

Thanks for the info there Stefek. After some consideration I think going
for one of these "electric combi boilers" is not really what I need. A
gas jobbie would be perfect, unfortunately no gas here.
So what someone else suggested on uk.rec.motorcycles was to use a mains
electric shower. They are cheap and should be simple enough to install
without the hassle and expense of ripping out the old tank etc..

They're certainly straightforward to install. (Don't, though, make the
allegedly common balls-up of trying to run them off an existing socket
circuit! They need their own, dedicated circuit, most often run in
10mmsq cable with a 40A breaker.) I find them fine for showering under,
but plenty of others prefer much more of a downpour for their shower.

An instantaneous heater just can't produce the hefty flow which some
people like (basic physics intervenes: water just takes a lot of energy
to heat up!). So, with a 9kW electric-instant, you're not going to get
more than a 'few' (can't be bothered doing the calculations yet again!)
litres/min; with a combi which goes up to say 24kW you'll get more -
about enough for most people's idea of a decent shower, but still
relatively slow to fill a bath and a PITA if other people are using hot
water at the same time. The effect is more pronounced in winter - to get
from incoming temp of say 5 degs up to comfortable showering temp of
about 40 is nearly twice the stretch than from a summer pipe-temp of
15-20 degrees. Hence the use of some sort of storage arrangement, so the
heating can happen over a longer time than the usage - whether that's a
conventional hw tank, heatbank, or the built-in small storage which some
combis have to give a higher initial flowrate...

Thanks for the tip about the handbrake on the car by the way, never
realised that could happen!

Nor did I, but I do now. Apparently it's common practice Oop Their Way
to leave the car in gear but handbrake off - though the island's not
quite pancake-flat, the bits with the roads all are...


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Dave Plowman (News)
 
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In article ,
Dave Jones wrote:
If your hot water cylinder is well insulated and your thermostat is
working ok, then using an immersion heater for primary heating, would
be best left on constantly, to be most cost effective.


That's fighting talk. ;-)

--
*When everything's coming your way, you're in the wrong lane *

Dave Plowman London SW
To e-mail, change noise into sound.
  #12   Report Post  
Stefek Zaba
 
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An instantaneous heater just can't produce the hefty flow which some
people like (basic physics intervenes: water just takes a lot of energy
to heat up!). So, with a 9kW electric-instant, you're not going to get
more than a 'few' (can't be bothered doing the calculations yet again!)
litres/min; with a combi which goes up to say 24kW you'll get more -


So here's the amazingly detailed back-of-an-envelope calc. Takes
4.2kJoules to raise 1 litre through 1 degree C. A reasonable midpoint
for how much temp rise you want is 30 degrees - from 10 to 40; so
handwave it to 120kJ for each litre. A nice round number, that, since we
want our final answer in litres/minute - since 1kW means 1kJ/sec, to get
120kJ in a minute we want 2kW.

Thus, rule-of-thumb-close-enuff-for-jazz says 'shower delivery rate, in
litres/min, = half of kW rating'.

Sanity-check: that says a 9kW leccy shower puts out 5L/min. That's
rather below the mfrs advertised figures - e.g. Goolgle says
dealtime.co.uk describe several 10.5kW showers asdelivering "up to"
14L/min. Either there's a mistake in basic physics... or, the "up to"
figure is for a lukewarm shower (30mumble) in summer (incoming at
20mumble, at least until the prewarmed water in the house cold water
pipes has all come through and you drop back to the underground temp
closer to the low teens). Second sanity-check: 1min for a litre through
30degs with 2kW input says a 2kW kettle will take 3 mins to boil (90
degs rise needed) - yup, that's consistent with normal experience. Third
sanity-check: combi specs at the top of my Google results for 'combi
"litres per minute"' say '28kW 11.4 lpm' and '27kW 11 lpm', for a
35degree rise; perfeckly in line with the rule-o-thumb derivulated above.

So that's two-out-of-three sanity checks in line with Normal Fizziks,
and one out in creative-marketing-specmanship land. Pretty normal, then ;-)
  #13   Report Post  
Andy Wade
 
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Stefek Zaba wrote:

Takes 4.2kJoules to raise 1 litre through 1 degree C.


As the final answer to this sort of calculation is usually needed in kW
or kWh I find it useful to remember the heat capacity of water as 1.16
Wh per litre per degree. 1.2 Wh is near enough for most purposes.

--
Andy
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Stefek Zaba
 
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Andy Wade wrote:


As the final answer to this sort of calculation is usually needed in kW
or kWh I find it useful to remember the heat capacity of water as 1.16
Wh per litre per degree. 1.2 Wh is near enough for most purposes.

Cool (or, more exactly, warm ;-) For litres/min we transform 1.2Wh to
72, well, 70 Wmins; which tells us that for a 30 degree rise we need
70x30 = 2.1kWmins, agreeing with the previous sketch.

The best aide-memoire I've come across (and therafter remembered!) for
such "cached" intermediate results is "pi seconds is a nanocentury" -
i.e. in a year there's 3.gubbins x 10e7 seconds. Useful when you're
roughing out 'X things/sec, how many X in a year?' or similar.

Then there was Grace Hopper's visual-aid-memoi in some of her talks
she handed out 'nanoseconds' - one-foot lengths of wire, for such is a
(useful approximation to) the speed of light/electrical-signal
propagation - the relatively small (10-20%) differences between speed of
light in a vacuum, and electrical signal in copper, don't matter much
for these rule-o-thumb mnemonix; and it's kinda instructive to realise
that as memory buses in ordinary PCs approach GHz speeds, the distance
on the motherboard from CPU to RAM is 'significant' - half a cycle or
more...

Stefek
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Andy Wade
 
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Stefek Zaba wrote:

The best aide-memoire I've come across (and therafter remembered!) for
such "cached" intermediate results is "pi seconds is a nanocentury" -


For pi itself everybody knows 22/7, but far fewer can recall 355/113 -
remember it as 11-33-55, split in the middle with the first half as
denominator - and that gets you within 0.1 ppm or 6 decimal places of
the real true pie.

Then there was Grace Hopper's visual-aid-memoi in some of her talks
she handed out 'nanoseconds' - one-foot lengths of wire, [...]


Funny, before I even got as far as that paragraph I was thinking "one
foot per nanosecond"...

For something slightly more on-topic, how about 60 bricks per square
metre (for half-brick thick stretcher bond)? Or ten ft^2 in a m^2 -
that's about 7% out but still useful for rough estimating or heat loss
calculations.

--
Andy
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