Boiler replacement in Acalanes Ridge, CA built around your radiators and piping

Choosing and installing the right boiler

Many existing boilers are larger than the homes they heat. Original equipment may have been sized generously, and insulation or window upgrades since then have reduced heat loss further. Replacing a boiler based on the old nameplate carries that oversizing forward. We calculate your home heat loss and compare it with the heat your radiators or baseboard can deliver, which gives a far better basis for sizing.

For hot water systems, the main choice is between a conventional boiler and a condensing boiler. Condensing boilers, often called mod-cons because they modulate their firing rate, recover additional heat from exhaust gases. They achieve their highest efficiency when water returning from the radiators is cool enough for condensation to occur. That is where outdoor reset control matters: it adjusts water temperature based on the weather, running cooler in mild conditions and hotter only when needed.

Outdoor reset control is what lets a condensing boiler live up to its efficiency rating. We set the curve to match your home.

Whether a condensing boiler fits well depends on your heat emitters. Radiant floors and generously sized cast iron radiators work well at lower water temperatures. Small baseboard systems may need higher temperatures, which reduces condensing benefit. We evaluate your emitters and explain realistic performance rather than quoting the best case.

Near-boiler piping is where many installations succeed or fail. Modern boilers often require hydraulic separation, such as primary and secondary piping or a low loss header, so the boiler and heating circuits each get the flow they need. We also plan for air elimination, expansion tank sizing and a dirt separator, often magnetic, to protect the new heat exchanger from sludge carried over from old piping.

Venting and drainage are different for condensing boilers. They typically vent through approved plastic or stainless materials and produce acidic condensate that should pass through a neutralizer before draining. If the old boiler vented into a chimney shared with other appliances, we review how those appliances will vent once the boiler is disconnected.

Steam systems are a separate case. Steam boilers are sized to the connected radiation rather than heat loss alone, and piping near the boiler must follow manufacturer requirements closely. Converting steam to hot water is rarely simple, so most steam homes replace with a new steam boiler. For homes that also want domestic hot water from the boiler, combination units or indirect water heaters can be considered.

Before starting up a new hot water boiler, we flush the system and add appropriate treatment where recommended. Commissioning includes combustion analysis, setting the outdoor reset curve and verifying heat delivery. If repair might still be an option for your current equipment, compare with our Boiler Repair page before deciding.