Conventional Propane Boiler

ScottMcNab

Hi
I have a low mass Biasi conventional propane boiler. It doesn’t have any special controls so need help with what I currently have. Right now it’s set up as a cold start boiler which Biasi recommends. Here’s how it works - Thermostat calls for heat and boiler fires, water temperature reaches a certain temperature and aquastat tells circulator pump to kick on, boiler keeps firing until thermostat is satisfied and the burner shuts off. Circulator pump runs until water temperature cools. Aquastat that controls the circulator has a differential of 30. What should I set the water temperature at on the aquastat to start circulating water? Keep in mind it’s a cold start boiler.
Thanks

Jamie Hall

The water temperature for your system depends entirely on the type of system and the way it's piped and pumped and beyond that on the ability of the system to heat the structure. If it's being varied in some way -- such as with outdoor reset -- it also depends on the outside air temperature.

So... there is no one right answer. One system might run just fine at 120 circulating, with the boiler being held at say 160 return to avoid condensation and using primary/secondary. Another might need 180 circulating...

STEVEusaPA

I’d prefer to protect the boiler with a 3 way or 4 way thermostatic mixing valve over turning the circulator on and off.
With a system especially with large water content, the circulator (relay) will constantly be engaging/disengaging.