Thermal store & Boiler Temperature

[rick]

Have just had the boiler changed to a Viessmann OV 32 kW

Its primaries connect direct to a thermal store, and the thermostat at the bottom 1/3rd of the store sets the temp of water within.

The stat is set to 60 and a baffle just below halfway gives stratification. (schematic below)

Heating coil is taken off the bottom half and mains pressure DHW of a heat exchanger in Top half

What would be ideal temp to run boiler at ..... Viessmann has digital controls so can set to what I want, previous boiler had only a rotary knob, with no temperature setting or display. ( was set to 3/4 on)

Wondering what is best to benefit from as much condensing mode as is possible.

Only information I can find is a post which states to run boiler at about 10C higher than store stat temp, (i.e. 70C) to stop boiler cycling. Does this seem about right.

[John Rumm]

If you run at a 20 degree delta, then a flow temp of about 70 with a store temp of 60 might be ok. That would keep it in condensing more most of the time (assuming there is enough load to keep the boiler running)

In the bounds of reasonable, yup.

IIRC I run about 74 degrees flow when reheating my cylinder to 60 normally, but also to 70 once a week. he bulk of the reheat happens with the boiler close to full output. (my cylinder coils is rated up to about

22kW, and it is a 24kW boiler)