Does anybody know of a particular model of "undersink" type low-power
electric water heater which is designed for a low-pressure water system
with header tank, not mains pressure?

I seem to be struggling to see anything online which clearly states that
it is (a) for water systems at header-tank pressure only and (b) does
*not* have hot water storage but only provide instantaneously heated water.

Any particular model names much appreciated.

Michael

Michael Kilpatrick wrote:
Does anybody know of a particular model of "undersink" type low-power
electric water heater which is designed for a low-pressure water system
with header tank, not mains pressure?

I seem to be struggling to see anything online which clearly states that
it is (a) for water systems at header-tank pressure only and (b) does
*not* have hot water storage but only provide instantaneously heated water.

Any particular model names much appreciated.

Michael

Call Redring (Applied Energy Products) technical help line on 08709 000430

http://www.applied-energy.com/en/contact

and/or Heatrae Sadia Specification/Product Selection Line: 01603 420220

http://www.heatraesadia.com/hs/heatraes.nsf click on "contact us" at
bottom of page.

"Michael Kilpatrick" wrote in message
...
Does anybody know of a particular model of "undersink" type low-power
electric water heater which is designed for a low-pressure water system
with header tank, not mains pressure?

I seem to be struggling to see anything online which clearly states that
it is (a) for water systems at header-tank pressure only and (b) does
*not* have hot water storage but only provide instantaneously heated
water.

Any particular model names much appreciated.

Michael

You just need to look at the minimum pressure requirement of the heaters and
then you will see what will work...

For every 10 meters of "head" you have (The height of the cold tank in
relation to the tap) you have 1 bar of pressure.(So 10m is 1 bar, 5m is
0.5bar, 2.5m is 0.25bar etc...)

Toby...

On Tue, 26 May 2009 16:54:14 +0100, Dave Osborne wrote:

Call Redring (Applied Energy Products) technical help line on 08709
000430

http://www.applied-energy.com/en/contact

Haven't looked at the Heatrae products but noticed that Redring are pretty
keen on you only fitting their own taps or shower fittings to their
heaters. I've just been dealing with another make and model of this type
of heater which has been giving problems because it is prone to tripping
its overheat cutout thermostat. Resetting this involves opening up the box
so it's a hassle for the user. This particular unit is described as an
"INSTANTANEOUS HAND WASH WATER HEATER ... that can be used with either
taps or an open outlet sprayhead". It's actually feeding a washbasin, sink
and commercial washing machine but only seems to trip when the latter is
drawing from it (so I am told: I've never been there when this happens).

Presumably there is a certain tolerance on the sensitivity of the flow
switch that tells the unit when to switch on and off, and on the
temperature at which the overheat cutout is set. At flow rates just
above the turn-off rate (which due to hysteresis(sp?) is a bit below the
turn-on rate) I've measured the water temperature at 80C, which must be
close to the overheat trip temp. Presumably under certain circumstances
the washing machine induces the heater to get up this sort of temperature
then cuts off rapidly enough for the residual heat energy in the heating
element to take the temp up enough to trip the overheat.

Apparently the more powerful 12.5kW model in this manufacturer's range
(this is a 9.5kW unit) has a thermostat operating to cut out one of the two
heating elements at high output temperatures, but this model relies on the
flow switch alone (even though it also has two elements). I suspect the
Redring unit which stipulates you use its own taps relies on these always
providing sufficient flow rate to keep the outlet temperature down. And of
course that means you could not fit a TMV to regulate the outlet
temperature as that would throttle the heater output.

So overall I think some of these units may be a poor design for practical
use.

--
John Stumbles -- http://yaph.co.uk

Extreme moderate

Toby wrote:

"Michael Kilpatrick" wrote in
message ...

Does anybody know of a particular model of "undersink" type low-power
electric water heater which is designed for a low-pressure water
system with header tank, not mains pressure?

I seem to be struggling to see anything online which clearly states
that it is (a) for water systems at header-tank pressure only and (b)
does *not* have hot water storage but only provide instantaneously
heated water.

Any particular model names much appreciated.

Michael


You just need to look at the minimum pressure requirement of the heaters
and then you will see what will work...

Indeed...but a lot of the listings online don't give full information.
Can't see the wood for the trees.

There will be a fairly low head. It's a bungalow.

I'll explain - we insist on having a *proper* bidet in our new en-suite.
Not those stupid over-rim fill units but a proper ascending spray bidet.
There used to be one in the old main bathroom fed from the vented hot
water cylinder sytem and the cold water tank. That gave a perfectly
adequate head for the spray.

Unfortunately the ridiculously overbearing regulations make it very
difficult to fit a proper bidet these days - and our new heating/water
system features an unvented hot water cylinder which of course is
coupled directly to the mains.

In order to fit a proper bidet we would need to install a small header
tank in order to have an air-gap isolated water supply, and in order to
get hot water for the bidet therefore the only practical option is to
have a small electric heater fed from that header tank. A storage heater
would be a waste of energy given the low frequency of use. The amount of
hot water use is minimal, so something that is a 5kW instant heater is
all that is required.

Seems difficult to find something as simple as this!

Michael

Michael Kilpatrick wrote:
Toby wrote:

"Michael Kilpatrick" wrote in
message ...

Does anybody know of a particular model of "undersink" type low-power
electric water heater which is designed for a low-pressure water
system with header tank, not mains pressure?

I seem to be struggling to see anything online which clearly states
that it is (a) for water systems at header-tank pressure only and (b)
does *not* have hot water storage but only provide instantaneously
heated water.

Any particular model names much appreciated.

Michael


You just need to look at the minimum pressure requirement of the
heaters and then you will see what will work...

Indeed...but a lot of the listings online don't give full information.
Can't see the wood for the trees.

There will be a fairly low head. It's a bungalow.

I'll explain - we insist on having a *proper* bidet in our new en-suite.
Not those stupid over-rim fill units but a proper ascending spray bidet.
There used to be one in the old main bathroom fed from the vented hot
water cylinder sytem and the cold water tank. That gave a perfectly
adequate head for the spray.

Unfortunately the ridiculously overbearing regulations make it very
difficult to fit a proper bidet these days - and our new heating/water
system features an unvented hot water cylinder which of course is
coupled directly to the mains.

In order to fit a proper bidet we would need to install a small header
tank in order to have an air-gap isolated water supply, and in order to
get hot water for the bidet therefore the only practical option is to
have a small electric heater fed from that header tank. A storage heater
would be a waste of energy given the low frequency of use. The amount of
hot water use is minimal, so something that is a 5kW instant heater is
all that is required.

Seems difficult to find something as simple as this!

Michael

What a pain!!

Wouldn't they be happy with a double check valve on both the hot and
cold supply to the bidet to prevent anything nasty getting back into the
mains supply? Seems pretty OTT if not to me, as as far as I am aware,
you can fill your pond with the hose if you have a double check valve!

Toby...

Toby wrote:

Michael Kilpatrick wrote:


In order to fit a proper bidet we would need to install a small header
tank in order to have an air-gap isolated water supply, and in order
to get hot water for the bidet therefore the only practical option is
to have a small electric heater fed from that header tank. A storage
heater would be a waste of energy given the low frequency of use. The
amount of hot water use is minimal, so something that is a 5kW instant
heater is all that is required.


What a pain!!

Wouldn't they be happy with a double check valve on both the hot and
cold supply to the bidet to prevent anything nasty getting back into the
mains supply? Seems pretty OTT if not to me, as as far as I am aware,
you can fill your pond with the hose if you have a double check valve!

Toby...


Yes, it's all a load of tosh if you ask me. A bidet is a "category 5"
fluid risk, and for some reason a double check valve is not sufficient.
You have to have an air gap e.g. cistern with ball cock valve. Or
something called a type DC pipe interrupter, but I'm not really sure
about those when attached to a bidet.

Absolute twaddle, it really is! Anyway, I never had a double check valve
on our outside tap, as it wasn't a requirement when the house was built.
And I've connected it directly to a hose whose outlet is submerged in
the fish pond.

Michael

On Thu, 28 May 2009 00:08:50 +0100, Michael Kilpatrick wrote:

Yes, it's all a load of tosh if you ask me. A bidet is a "category 5"
fluid risk

because basically you could crap[1] into the bidet pan and it'd be
equivalent to a fresh, potable water supply pipe, shared with the
neighbours's drinking water taps, submerged in your khazi.

... and for some reason a double check valve is not sufficient.
You have to have an air gap e.g. cistern with ball cock valve. Or
something called a type DC pipe interrupter, but I'm not really sure
about those when attached to a bidet.

Loadsamoney, but probably in the Reliance Water Controls catalogue.

Absolute twaddle, it really is!

Maybe not if you're the neighbour whose drinking water tap is on the same
supply as your bidet/khazi.



[1] or more politely, and realistically, faecal matter could get into it.

--
John Stumbles -- http://yaph.co.uk

My other sigs are posh

YAPH wrote:
On Thu, 28 May 2009 00:08:50 +0100, Michael Kilpatrick wrote:


Yes, it's all a load of tosh if you ask me. A bidet is a "category 5"
fluid risk


because basically you could crap[1] into the bidet pan and it'd be
equivalent to a fresh, potable water supply pipe, shared with the
neighbours's drinking water taps, submerged in your khazi.


... and for some reason a double check valve is not sufficient.
You have to have an air gap e.g. cistern with ball cock valve. Or
something called a type DC pipe interrupter, but I'm not really sure
about those when attached to a bidet.


Loadsamoney, but probably in the Reliance Water Controls catalogue.


Absolute twaddle, it really is!


Maybe not if you're the neighbour whose drinking water tap is on the same
supply as your bidet/khazi.

I know peoples' gas boilers can explode. I know houses can catch fire
(I've seen it happen in front of me). I know radiators can leak and ruin
a carpet or worse.

The thing is, I've never heard of anyone who has experienced, or indeed
has ever told me of anybody else who has experienced, backsiphonage
through the water mains.

Furthermore, whilst I might occasionally leave a tap running in a
basin, it's rather a different matter to leave an ascending spray bidet
running inadvertently and unattended, which is when a risk of
backsiphone might be present.

Michael





[1] or more politely, and realistically, faecal matter could get into it.

On Thu, 28 May 2009 09:36:55 +0100, Michael Kilpatrick wrote:

Furthermore, whilst I might occasionally leave a tap running in a
basin, it's rather a different matter to leave an ascending spray bidet
running inadvertently and unattended, which is when a risk of
backsiphone might be present.

You might be using the bidet when Fireman Sam comes along and attaches his
water pump to the hydrant down the road, dropping the pressure to your
house and sucking the water and unmentionables back out of your pipework
into the common main. Then Sam turns his pump off and Mrs Jones down the
road finds she can fill a glass of water again ...

You might (fairly reasonably) say what are the chances of that happening,
but from the point of view of the makers of the regulations, if there
weren't such a restriction and, say, ascending spray bidets became popular
and common over the country there could be a pretty good probability of it
happening from time to time. And given the consequences (Mrs Jones isn't
too healthy and if she gets topped by the public water supply someone's
head's going to be on a pike) it's a reasonable position for the regulators
to say: "this water supply, provided at public expense, is intended to be
safe for drinking under all circumstances: if you want to wash your botty
in it, fine, but you must make doubleplus sure - at your expense - that
your botty washings don't get back into the public supply".

--
John Stumbles -- http://yaph.co.uk

Many hands make light work. Too many cooks spoil the broth.

On 28 May 2009 09:26:33 GMT someone who may be YAPH
wrote this:-

You might be using the bidet when Fireman Sam comes along and attaches his
water pump to the hydrant down the road, dropping the pressure to your
house and sucking the water and unmentionables back out of your pipework
into the common main. Then Sam turns his pump off and Mrs Jones down the
road finds she can fill a glass of water again ...

The chances of this happening when the bidet is fed from the mains
and a double check valve is fitted to the hot and cold supply are, I
suspect, so small as to not be worth considering. Mrs Jones' house
is probably more likely to be destroyed by an aeroplane falling out
of the sky.

Is the water supply often contaminated in this way in comparable
places with a more relaxed attitude to such things?



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54