Connection between flow and return pipes between boiler and copper tank

[jaime]

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 |

[.]

is the right answer !! lol

[Paul]

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.

[Bob Eager]

Oh, for God's sake...

[manatbandq]

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

[David Hansen]

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

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

It is a bypass.

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.

Probably neither. It should probably be partly open.

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.