"Christian McArdle" wrote in message
et...
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.
This is a DHW only heat bank. So you will be having a diverter valve for
either CH & DHW, with the CH running directly from the condensing boiler. A
condensing boiler with load compensation control will reduce the rad temps
for the vast majority of operation, except on warm up in winter which will
be rather high. You can have a high temp limit on some boilers, so no over
hot rad temps.
A blending valve can reduce max rad temps, but there is other ways of doing
it. What you want is the boiler at full temp when DHW is being called and
then a lower temp for the CH mode. In a simple boiler this is achieved by
having the boiler stat on full, and a pipe thermostat on the boiler flow.
When calling for DHW the pipe stat is switched out, when CH is called it is
switched in. Very simple, and very effective.
To keep the return temps cool you could have:
1. Oversized rads
2. Install a plate heat exchangers on the return to the boiler with the
cold water mains entering this first. It will act a pre-warmer when the
boiler is operational either for DHW or CH and hot water is being drawn off.
It will also reduce the return temp into the boiler. It will also impove
the flow rate when the boiler is operational. You could have the control
system so that the boioer always fires on DHW when water is drawn-off, as a
combi does. Plate heat exchangers are not that expensive.
What make & model of cylinder thermostat is DPS using on the Pandora heat
bank?
What kW rating is the coil?
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