Pete C wrote in message . ..
On 3 May 2004 15:21:20 -0700, (Rob Graham)
wrote:

I've done a trawl of the archive and I've found some answers, but in
some ways some more questions.

I've a 12 metre plus run to the kitchen sink from the HW tank with
only a 3 - 4 metre head, and have compounded the problem by fitting a
pull out mixer tap which has a high insertion loss. Various solutions
have been played with but a local heat source off the mains seems the
best option.

Just how good are under-sink heaters ? what is the storage types ?
why do they vary in power from 2.2 to 9.5Kw? What is the problem with
expansion - I would have just a short pipe run to the mixer tap ?
Would I be best to arrange a longer run ? I've seen something about
vented taps - how do these things fit in with an ordinary mixer?

Hi,

I've got one of the £90 screwfix ones, has it has 10L capacity and a
1.2kW element, comes with separate pressure release valve and is
suitable for mains pressures.

This will take about 20 minutes to heat up to 60°C from room
temperature, and I would guess about 40W/h to keep it there.

Since the pipe to the boiler contains only about 2L of water if you're
using 15mm, there is not much to worry about running out of hot water.

Another option could be to use heating tape along the pipe, this would
take about 70W/h to keep the pipe at 60°C if the pipe has 1/2 inch of
insulation.

The electricity used by both of the above would be reduced by putting
them on a time switch, adding more insulation is also a help.

cheers,
Pete.

Thanks Pete - that's quite useful. Ref. the pressure release valve -
does that avoid the use of an expansion vessel if there is inadequate
run to the hot tap. Althought there is a long run from my HW tank,
the mains feed runs passed the kitchen sink, so I was thinking if
fitting the heater quite close by. It seems that such an expansion
vessel is required if the pipe length to the tap is short (that at
least is what the Sadia web page says - see the link in an earlier
posting)

Rob