Hi.

I've spent a few hours recently up in the loft, trying to understand how
my central heating/hot water plumbing works. One point that baffles me
is a copper pipe connecting the flow pipe (from the boiler) back to the
return pipe (to the boiler), situated about a meter before the two pipes
enter/exit the (indirect) copper tank. This "connection" has a
wheel-handled valve half-way along it (I assume, from the wheel-handle,
that it's a gate valve).

In case it helps, here's a poor quality ascii-art picture, with
connection to feed/expansion tank and overflow pipe omitted (it should
work with a fixed-width/monospaced font):


To Rads
^
^
Flow from boiler---+---Pump---Diverter Valve---Into Copper Tank
|
Valve
|
Return to boiler---+-------------------------------From Copper Tank



My questions a what's the purpose of the pipe, should the valve be
open or closed during "normal" operation, and why would I ever want to
change the valve's setting (open/closed)?

Many thanks, Jaime

Paul wrote:
jaime wrote:

Hi.

I've spent a few hours recently up in the loft, trying to understand how
my central heating/hot water plumbing works. One point that baffles me
is a copper pipe connecting the flow pipe (from the boiler) back to the
return pipe (to the boiler), situated about a meter before the two pipes
enter/exit the (indirect) copper tank. This "connection" has a
wheel-handled valve half-way along it (I assume, from the wheel-handle,
that it's a gate valve).

In case it helps, here's a poor quality ascii-art picture, with
connection to feed/expansion tank and overflow pipe omitted (it should
work with a fixed-width/monospaced font):


To Rads
^
^
Flow from boiler---+---Pump---Diverter Valve---Into Copper Tank
|
Valve
|
Return to boiler---+-------------------------------From Copper Tank



My questions a what's the purpose of the pipe, should the valve be
open or closed during "normal" operation, and why would I ever want to
change the valve's setting (open/closed)?

Many thanks, Jaime

Don't buy anything from Maplins. My broadband started to go slow and my
ISP said I needed a new filter. Maplins said I needed new cable. I
bought new cable but the broadband speeded up again - must have been
BT. So I took the cable back. But because it had been machine packed
there is no way I would return it "in the same condition". The cable
WAS "in the same condition". But the idiots said the packing had to be
the same -- impossible!

If they want to get things back "correctly" they should use packing it
is possible to pack.

Every other company I've taken anything back to, in living memory has
accepted it back with full refund.

Except Maplins.

Don't even think of shopping with them.

is the right answer !! lol

jaime wrote:

Hi.

I've spent a few hours recently up in the loft, trying to understand how
my central heating/hot water plumbing works. One point that baffles me
is a copper pipe connecting the flow pipe (from the boiler) back to the
return pipe (to the boiler), situated about a meter before the two pipes
enter/exit the (indirect) copper tank. This "connection" has a
wheel-handled valve half-way along it (I assume, from the wheel-handle,
that it's a gate valve).

In case it helps, here's a poor quality ascii-art picture, with
connection to feed/expansion tank and overflow pipe omitted (it should
work with a fixed-width/monospaced font):


To Rads
^
^
Flow from boiler---+---Pump---Diverter Valve---Into Copper Tank
|
Valve
|
Return to boiler---+-------------------------------From Copper Tank



My questions a what's the purpose of the pipe, should the valve be
open or closed during "normal" operation, and why would I ever want to
change the valve's setting (open/closed)?

Many thanks, Jaime

Don't buy anything from Maplins. My broadband started to go slow and my
ISP said I needed a new filter. Maplins said I needed new cable. I
bought new cable but the broadband speeded up again - must have been
BT. So I took the cable back. But because it had been machine packed
there is no way I would return it "in the same condition". The cable
WAS "in the same condition". But the idiots said the packing had to be
the same -- impossible!

If they want to get things back "correctly" they should use packing it
is possible to pack.

Every other company I've taken anything back to, in living memory has
accepted it back with full refund.

Except Maplins.

Don't even think of shopping with them.

On Mon, 4 Dec 2006 16:06:27 UTC, "Paul" wrote:

Don't buy anything from xxxxx.

Oh, for God's sake...

--
The information contained in this post is copyright the
poster, and specifically may not be published in, or used by
Avenue Supplies, http://avenuesupplies.co.uk

On Dec 4, 3:56 pm, jaime wrote:
Hi.

I've spent a few hours recently up in the loft, trying to understand how
my central heating/hot water plumbing works. One point that baffles me
is a copper pipe connecting the flow pipe (from the boiler) back to the
return pipe (to the boiler), situated about a meter before the two pipes
enter/exit the (indirect) copper tank. This "connection" has a
wheel-handled valve half-way along it (I assume, from the wheel-handle,
that it's a gate valve).

Do you have thermostatic radiator valves (TRVs) on all your radiators?
The pipe is a bypass to allow some flow when all of the TRVs are closed
but the boiler hasn't realised yet. The alternative is to have one
radiator (e.g., in the bathroom) that is always on and doesn't have a
TRV.

It needs to be open a little. I can't tell you how much "a little" is,
but I'm sure someone will be along shortly.

MBQ

On Mon, 04 Dec 2006 09:56:57 -0600 someone who may be jaime
wrote this:-

I've spent a few hours recently up in the loft, trying to understand how
my central heating/hot water plumbing works. One point that baffles me
is a copper pipe connecting the flow pipe (from the boiler) back to the
return pipe (to the boiler), situated about a meter before the two pipes
enter/exit the (indirect) copper tank.

I doubt if you have a copper tank. You probably have a copper
cylinder.

This "connection" has a wheel-handled valve half-way along it

It is a bypass.

My questions a what's the purpose of the pipe,

It could be to keep the boiler back end temperature up, in order to
reduce corrosion. It could be to provide a water path when
thermostatic radiator valves and the cylinder thermostat have shut
off. Otherwise the pump may be pumping against a closed system. The
bypass could be for both reasons.

We would need more details on the system to give much more advice.

should the valve be open or closed during "normal" operation,

Probably neither. It should probably be partly open.

and why would I ever want to
change the valve's setting (open/closed)?

We can't read your mind and thus can't even guess why you might want
to move the valve. Why do you want to fiddle with it?

It should have been set up by whoever installed it and they should
really have removed the handle to stop people fiddling with it.

If you are feeling keen you could replace it with a modern automatic
valve.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54