On Sat, 20 Nov 2004 17:22:55 +0000, Simon Hawthorne wrote:

On Sat, 20 Nov 2004 17:13:56 -0000, "IMM" wrote:

It almost certainly has gravity hot water with an old cast iron boiler like
that. At least it has zoning of upstairs and downstairs.

Thanks IMM

Should the pump always run then - even when the room stats have closed
the zone valves?



My guess is the CH timer drives the pump and boiler. The wall thermostats
drive the zone valves. The timer is probaby set so the HW heating is
always implied with any heating ("10" or gravity mode).

Very likely the flow to the HW coil is also the vent pipe pipe.
Likely with this type of installation the feed pipe (if it not combined
with the vent ) goes to somewhere near the boiler returns from the HW
coil.

With care it might be possible to make this system fully pumped using two
pumps and an extra zone valve. It shouldn't matter if a pump is running
in a stalled condition, but graeat care has to be taken to make sure that
pumping over or sucking air won't happen.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html