Pete C wrote:
On 27 Aug 2005 14:42:19 -0700, wrote:


Pete C wrote:
On 25 Aug 2005 12:53:24 -0700, wrote:

Nothing has fixed my performace issues. HR as stating that they will
send an engineer out to test the valve out but if the shower head
itself is producing an awesome shower surely it cant be the problem.
They also said that I would be charged if it wasn't a valve issue!!!

Looks like it needs 2 bar min and 3 bar ideally, can they tell you how
many lpm it will need at those pressures?

The tech support person said I should be seeing 22 l/minute through the
jets with a 3 bar pump and I am seeing about 15 l/m

If that's through the jets alone and you're trying to run the shower
head as well, it's very likely the pressure from the pump will be too
low at the flow rate needed.


If so compare it to the 'flow curve' of the pump, and if it's way
beyond the pump's spec you're on a hiding to nothing. Either get a
bigger/another pump or reduce the amount of water the shower panel
needs.

The pump guy at Stuart Turned said the pump will only produce 9 litres
a minute though, and he managed to totally confuse the hell out of me.
He also stated that a 4 bar pump would only produce the same, and that
finished me off...........errrr.

He's right, the pump spec is for a given pressure and flow. So a 3 bar
pump will give 3 bar pressure at 9 lpm and a 4 bar pump will give 4
bar pressure also at the same flow of 9 lpm.

As the flow is increased, the higher the flow rate the lower the
pressure will be. This is what a 'flow curve' is, a comparison of pump
pressure at different flow rates

Here's a web page with the flow curves of some Stuart Turner pumps:

http://www.inspired-bathrooms.co.uk/acatalog/STUART_TURNER_SHOWER_PUMPS.html

1 bar pressure is about the same as 10 metres head of water, ie the
pressure at the bottom of a column of water 10m high.

So looking at the line for a 3 bar twin, a flow rate of 22 lpm will
give pressure equivalent to 25m head which is ~2.5 bar.

If the flow rate is 50 lpm it will a pressure equivalent to 8m head of
water, which is ~0.8 bar.

This probably assumes the same flow through both impellers of the
pump, in practice it might be a bit less if the flow is unequal.

So the pump will run the jets fine on their own but not the shower
head as well if it needs another 25 lpm.

But this is my gripe, on their own the shower jets are hardly jets. I
may be expecting too much but I was expecting to have to install grab
rails.



If they can't tell you how much flow it needs then stick a pressure
gauge on the inlet to the panel, if it's above 2 bar then the ball is
in their court as it should work fine at their minimum recommended
pressure.

Well their minimum spec is 1.5 bar.


Looking on the above chart shows the pump can give at best 38 lpm at
that pressure, maybe lower in practice if the hot and cold flow
through the pump is different.

Just concerned you might be making a lot of changes to the plumbing
when the problem is elsewhere.

Im going to digest the above with a large glass of Red wine but on your
last point:

Yes me too, I think I'm going to just accept what I've got. That said
I'm still getting a strange problem when the temp dial is set to a
specific temperature. The pump will suddenly start to cycle on and off.
This carry on until I move off the temperature.

Cheers

Richard


cheers,
Pete.