I've recently complete an addition to our home and now have two different type of radiators – low mass and high mass.
1) Low mass boiler w/outdoor reset
2) existing system (2/3 of the house) has large cast iron radiators (high mass) - 2nd floor rads have thermostatic radiator valves (TRV)
3) 1st floor of the old system does not have TRV and is where the main thermostat is located
4) new radiators are runtal baseboards (low mass) and runtal towel (low mass) radiators all with TRV
5) new zone pump is a taco variable speed
6) new zone has outdoor reset mixing valve - to allow a lower temp than boiler min.
7) new zone is set up using primary/secondary loop configuration
1) Run the new zone as continuous circulation, low water temp, letting the variable speed pump control the flow
2) prevent boiler flashing when most of the runtal TRV are closed - old slant fins had this problem
3) Use main thermostat and 1st floor loop as the reference zone - area of greatest heat loss in house
4) fire the boiler using reference zone only
5) I believe I should add a buffer tank to the mix to both prevent the flashing when only a couple of runtal TRVs are open - low pump flow / speed
6) A buffer would also allow for a degree of decoupling with the TRVs decide to open when the main zone is still open
1) Could an electric water tank (unwired) be used as the buffer tank?
- stainless buffer tanks are rather pricey and 30+ gallon in size
- I would like to use a 10 -20 gal tank
- since it's a closed system I would think a glass lined tank would hold up just fine
2) Should the sacrificial anode still be left in the tank?
3) Could the buffer tank be placed in series with the secondary loop
- avoid the cost and energy use of another circulator, controls etc.
Thanks for any input