On Wed, 1 Oct 2003 09:18:20 +0100, "Christian McArdle"
wrote:

What is your spec? Does it have a blending valve on the flow and return?

No blending valve. The indirect coil comes unadorned. There is a
thermostatic mixing valve on the DHW outlet, though.

I'm certainly interested in anything that can reduce the return temperature,
though. I wouldn't mind reducing the radiator flow temperature, too, for
safety reasons. I have a five year old, whose bed is adjacent to a radiator.
Can blending valves achieve this?

Christian.


Are you running the radiators from the store as well, Christian?

Otherwise, if it's a condensing boiler, does it have separate
temperatures of operation when in DHW mode vs. CH?

On mine, there are zone valves on the feed from the boiler - there
being one quite close to it for a new radiator. There is then the
original 22mm feed to the airing cupboard where there is one zone
valve for CH and one for the cylinder.

When the CH demands, the valves for that open and the flow is limited
to 70 degrees. When the cylinder demands, these valves close and
the DHW one opens. Then the boiler will run at 82 or even 85 degrees
flow.

If your boiler doesn't do this but modulates based on the return
temperature, then adding a blending valve to the radiator circuit to
feed some water back to the return, the effect would be to reduce the
heat output because the boiler will see it as reduced load.

Then you have to think about whether the radiator sizes are adequate
at the reduced temperature to give the heat output you need.


..andy

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