"Kalico" wrote in message
...
On 27 Oct 2005 03:31:12 -0700, "Jon" wrote:

I'm new to all this so please bare with me...

I'm having a problem with a combi-boiler and need help trying to
identify the problem -

The boiler appears to be working fine - i.e. it's able to heat the
radiators and water. However when heating water for the shower it seems
incredibility sensitive to changes in water pressure, if someone were
to turn the tap on in the kitchen the hot water flow in the shower
completely stops. Also, if the heating is on it seems to frequently
cause the hot water in the shower to fluctuate.

I'm wondering is it possible to control the boiler so that it gives
priority to heating water? Also, is it possible to prevent the affect
of turning on a tap in another room?

TIA

What type of shower valve do you have? A thermostatic valve would
help.

Not sure, but getting a 22mm pipe for the hot as near as possible to
the shower, with other services branching off in 15mm, might make a
difference.

My plumber disagrees, saying that it makes no odds since it is only
15mm coming from the boiler, but to me it seems common sense that it
would help smooth the flow of hot from the boiler. Sure someone will
tell us either way.

The best thing to do is run a dedicated 22mm pipe from the stopcock to the
combi, even if the mains is 15mm. Tee off the cold to shower just before
the combi on this 22mm pipe. At the stopcock tee off to all the other cold
outlets and insert a controlling gate valve here. Also insert in-line
service valves at taps and throttle them back. Then the combi and shower
will get priority.

Putting 22mm on the outlet side can work but only when feeding the shower,
and 22mm must be on the combi feed. Again this makes sure the shower gets
priority.