[net.consumers] flash water heaters

king@kestrel.ARPA (09/29/85)

Most water heaters have a tank inside them which holds as much water
as you are likely to use at one time (say 40 gal.), and a small heater
to let it heat a new batch of water after you have used up the old
one.  I have heard that there are a few that work differently - they
have a small heat exchanger, and a big burner that lets them heat the
water as you use it.  There was an article in February 1982 Pop
Mechanics. 

Does anyone have any experience with a flash water heater?  I like the
idea for two reasons:  

1> It's usually the tank that died when a water heater has to be
thrown out.

2> Heat escapes out the side of the tank 24 hours per day.

thanks in advance


-dick

hollombe@ttidcc.UUCP (The Polymath) (10/03/85)

In article <1424@kestrel.ARPA> king@kestrel.ARPA writes:
> ...  I have heard that there are a few that work differently - they
>have a small heat exchanger, and a big burner that lets them heat the
>water as you use it...
>
>Does anyone have any experience with a flash water heater? ...

I put up with these for about two years when I was living in London,  about
10  years  ago.  In general, I don't think they're worth the bother.  Water
temperature depends on flow  volume.  You  may  have  trouble  getting  the
temperature you want for high volume applications (taking a shower, running
a dishwasher, etc.).  At low volumes, I've seen some of them generate  live
steam through a kitchen faucet -- dangerous, especially if you have kids to
worry about.

If you're concerned about heat leaking from a tank heater,  wrap  it  in  a
fibergalss  blanket  (some  local  gas  companies will supply these free of
charge).

-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
The Polymath (aka: Jerry Hollombe)
Citicorp(+)TTI                    Common Sense is what tells you that a ten
3100 Ocean Park Blvd.             pound weight falls ten times as fast as a
Santa Monica, CA  90405           one pound weight.
(213) 450-9111, ext. 2483
{philabs,randvax,trwrb,vortex}!ttidca!ttidcc!hollombe

ray@othervax.UUCP (Raymond D. Dunn) (10/07/85)

In article <1424@kestrel.ARPA> king@kestrel.ARPA writes:
>
>...... I have heard that there are a few that work differently - they
>have a small heat exchanger, and a big burner that lets them heat the
>water as you use it....
>
>Does anyone have any experience with a flash water heater? ....

This type of water heater has been in use in the UK for many years, gas
fired, and was commonly known as an 'Ascot' (the manufacturer's name).  Very
often in small hotels, boarding houses etc, you had to put a shilling in its
meter to provide hot water to take a bath!

This type was normally connected to only one tap.

Prior to leaving the UK ten years ago I installed a more modern gas system
which replaced the hot water tank heated by a coke (ie solid fuel) furnace.
It fired automatically whenever any hot tap was turned on.  The only
disadvantage was the rather low flow rate even though it was 70,000 BThU
(took about 15 minutes to fill a bath) - it also made a disconcerting *boom*
whenever it came on!

Currently, electric models (15amps at 240volts - 3.6kilowats) are very
popular in shower outlets and kitchen sinks, but these have very low flow
rates - these are beginning to be advertised here in Canada, but 110V is a
big limitation.

It is interesting to note that the UK, if not all Europe, is light years
'ahead' of North America in all forms of energy conscious gadgets, driven
presumably, by the high relative cost of energy.

In particular, gas fired systems of all types have for many years been in
the 90%+ efficiency range, with *plastic* balanced flues - a balanced 'flue'
(chimney) is one in which the air inlet to the heater is a pipe concentric
with the exhaust outlet, thus both preheating the intake, and ensuring no
pressure differential problems - plastic can be used because virtually all
the heat is extracted in the burner (similar heaters are becoming available
here now).

Gas fired hot-water house heating systems use *1/4"* micro bore piping
which can be retrofitted to a house more easily than re-wiring! (I'm stuck
here in Montreal with mammoth 3" cast-iron piping!).  A major advantage of
these systems is the speed they come up to heating temperature.

Incidentally, two relatively simple things can be done to minimise the cost
of running a conventional electric hot water heater:-

1) Turn down the thermostats so that you normally do not have to add much
cold water to the hot to get a working temperature.  Unfortunately, if you
have a dishwasher, this usually requires very hot water (again, in the UK,
most dish-washers and washing machines have their own built in heaters).

2) Fit a time switch to the *lower* heating element, so that, although the
upper element will continue to provide hot water on demand, the heating of
*bulk* hot water will be timed to your consumption, i.e. showers, baths,
washing etc.  Alternatives are to switch the whole thing off when you are
away from home!

By the way, it is interesting to note that in winter (certainly here in
Montreal!) the power used for water heater inefficiencies, cooking,
refridgerators, lighting etc, can be regarded as being virtually *FREE*,
because every kilowatt-hour of energy used for them would otherwise have to
be used directly by the house heating system!

Sorry this turned into a text-book, hope it is of interest.

Ray Dunn   ...philabs!micomvax!othervax!ray

PS - smug look - electricity costs only 3.5 (Canadian) cents per kilowatt
hour here!