On Thu, 08 Feb 2007 17:04:26 +0000, Roger Mills wrote:

In an earlier contribution to this discussion,
curiousdog wrote:

I have what I think is a conventional heating system (perhaps, maybe)
and have had several challenges over the years, must to do with the
motorised flow-control valve breaking.

More recently I have a concern with the pump. It's installed
vertically pushing against gravrity up to the valve where it splits to
the heating and the storage tank. On setting 1 it runs very quietly
but the pressure seems to be very low and the radiators don't really
heat up as they should. The water in the storage tank also takes
forever to re-heat. I am pretty sure there are no airlocks anywhere.

So, logically, I tried to set the pump speed to 2. The pump speed
picks up and makes a lot more noise and then stops and restarts
itself. There also seems to be a lot more noise in the pipes, water
sounds. But the end result of all this is a lot of air that I have to
keep\bleeding out every 15 minutes.

So, is the pump faulty?

I doubt it.


Should it be installed vertically pushing against gravity?


Yes, that's fine!


There is only a 4" run of pipiong between the pump and the valve.
Could this be a problem?


No, that's fine!


thanks for any assistance/advice anyone can offer

Is it an open vented system (with a small fill & expansion tank in the
attic)? If so, it's very likely that the higher pump speed is causing it to
'pump over'. This means that, when the pump is running, there is a constant
flow of water out of the up and over vent pipe back into the tank. This is
very bad, and will result in a lot of air being introduced into the system.
It usually results from the vent and fill pipes not being connected into the
system in the right way, and is likely to need some pipework changes to
fix - or conversion to a non-vented (pressurised) system if your boiler is
suitable.


Just as likely is that thew higher speed is causing air to drawn down into
the circuit.

Unless the positioned of the vent and feed pipes are known relative to the
pump we can only speculate.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
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