Entry # 85
Gravity System Retrofit
Brief overview of the project
This was a residential retrofit job that called for replacing an old, expensive to operate heating system with a modern system which incorporated efficient hydronic equipment to deliver to the homeowner uncompromising heating comfort at a reduced annual operating cost.
Caleffi products used:
548 Hydro Separator
573 AutoFill /Backflow Preventer combo with integral pressure gauge
ZSR103 Zone Control Relay
Our design goal was to provide efficient, comfortable radiant heat in an aging home using a supply temperature of 150 degrees max on a design day of 0.
The largest challenge we expected was how to run new distribution lines up to the second floor with minimal damage and obtrusiveness.
The project concerned an old single thermostat house that had been vacant for several years and the freezing conditions had contributed to the existing boiler, cast iron radiators and gravity distribution system to form leaks. To start the project, an abatement was performed and the asbestos and distribution piping was removed.
We replaced the old boiler with a Viessman high efficiency, condensing boiler. Because we divided the house into two zones using circulators, there would be variable flow in the distribution so we needed primary/secondary piping and thus used a Caleffi hydro separator. With a temperature gauge in the hydro separator dry well, we can also monitor distribution temperature. We controlled the primary and secondary circulators using the Caleffi zone relay. For connecting the near boiler piping, we used press connections wherever possible as we have good luck and experience with press type joints.
To closely match the even, comfortable warmth the cast iron radiators had once delivered, we chose panel radiators with thermostatic radiator valves. TRVs and variable-speed circulators pair nicely together as the circulators modulate in reaction to the self-regulating TRVs. We sized the radiators to operate at the lowered distribution temperature and, together with the two zones enabling reduced temperature in the unused rooms, overall system energy efficiency was enhanced.
Running the distribution lines up to the main floor turned out to be pretty manageable after all.
The system is currently performing very well. And we were able to reduce the max supply temperature to below 150 degrees – which will help further with energy expense.