Our heating and hot water run off a solid fuel Rayburn, which gives us an
enormous amount of very, very hot water. I've just fitted a shower running
off the hot cylinder and cold header tank (which is approx 10' up from the
shower in the loft). The shower is a simple thermostatic mixer valve with
an 8" soaker head on it, but the flow is a little disappointing and you
have to have the mixer turned practically all the way to cold to get it
cool enough to use. By way of comparison, we have a shower hose on the bath
taps which runs off the rising cold main and you get good pressure and mix
through this - it's just not safe if someone else turns a cold tap on.

I was planning on boosting the shower's cold supply by using a single
impeller pump mounted by the tank in the loft so the cold has a lot more
pressure. The reason for only pumping the cold is I've been told that the
hot water from a Rayburn ruins pumps very quickly because of the
temperature, and also it would balance up the mix at the shower because
there would be more cold coming through.

Am I on the right track here and does anyone have a recommendation for a
pump and the size that is likely to be best?

Cheers

Danny Monaghan wrote:
Our heating and hot water run off a solid fuel Rayburn, which gives us an
enormous amount of very, very hot water. I've just fitted a shower running
off the hot cylinder and cold header tank (which is approx 10' up from the
shower in the loft). The shower is a simple thermostatic mixer valve with
an 8" soaker head on it, but the flow is a little disappointing and you
have to have the mixer turned practically all the way to cold to get it
cool enough to use. By way of comparison, we have a shower hose on the bath
taps which runs off the rising cold main and you get good pressure and mix
through this - it's just not safe if someone else turns a cold tap on.

I was planning on boosting the shower's cold supply by using a single
impeller pump mounted by the tank in the loft so the cold has a lot more
pressure. The reason for only pumping the cold is I've been told that the
hot water from a Rayburn ruins pumps very quickly because of the
temperature, and also it would balance up the mix at the shower because
there would be more cold coming through.

Am I on the right track here and does anyone have a recommendation for a
pump and the size that is likely to be best?

Cheers

I wonder if you might be better off with a larger bore cold feed to the
shower so the mixer working point is more in the middle of its range.
Also the position of the control on your mixer should be purely a
function of the output water temperature and not needing to be set as
you suggest. It would appear that the thermostatic bit is not
controlling the temperature.
Or may you could consider reducing the temperature of your general
hot water supply. I'm not suggesting going down the route of the recent
'nanny state' thread but it does sound like there are some safety issues
with your very hot water supply.
just my 2p

Bob

On Sun, 24 Aug 2008 05:10:36 -0500, Danny Monaghan wrote:

I've just fitted a shower running off the hot cylinder and cold header
tank (which is approx 10' up from the shower in the loft).

I assuming that the HW system is the normal open vented type.

What size pipe did you use to bring the cold water down to the shower
mixer? I suspect the HW feed and distribution will be 22mm, the cold feed
to the shower also needs to be 22mm and from the same header tank, not the
one for the primary circuit... (I think you would have noticed if you'd
done that though). The available flow and pressures at the shower mixer
need to be fairly closely matched.

--
Cheers
Dave.

"Danny Monaghan" wrote in message
. 109.144...
Our heating and hot water run off a solid fuel Rayburn, which gives us an
enormous amount of very, very hot water. I've just fitted a shower running
off the hot cylinder and cold header tank (which is approx 10' up from the
shower in the loft). The shower is a simple thermostatic mixer valve with
an 8" soaker head on it, but the flow is a little disappointing and you
have to have the mixer turned practically all the way to cold to get it
cool enough to use. By way of comparison, we have a shower hose on the
bath
taps which runs off the rising cold main and you get good pressure and mix
through this - it's just not safe if someone else turns a cold tap on.

I was planning on boosting the shower's cold supply by using a single
impeller pump mounted by the tank in the loft so the cold has a lot more
pressure. The reason for only pumping the cold is I've been told that the
hot water from a Rayburn ruins pumps very quickly because of the
temperature, and also it would balance up the mix at the shower because
there would be more cold coming through.

Am I on the right track here and does anyone have a recommendation for a
pump and the size that is likely to be best?

From the cold tank run a dedicated 22mm pipe to the cold on the shower
mixer.