Chapter 3 - Hydronic Heat Sources

Conventional gas- and oil-fired boilers are currently used in the vast majority of residential and light commercial hydronic systems in North America.

The cast-iron sectional boiler is currently one of the most common boilers used in residential and light commercial buildings in North America.

If a cast-iron boiler is significantly oversized and experiences long off-times between firing cycles, much of the heat stored in the boiler's thermal mass can be carried up the flue by air currents passing through the combustion chamber.

Many boilers currently used in North America were designed with the intent that flue gases would condense within the boiler.

Condensing boilers are designed with large heat exchanger surfaces capable of extracting more heat from the exhaust gases compared to the heat exchangers in conventional boilers.

In full storage ETS systems, all energy used during the subsequent on-peak period is purchased and stored during the peak cycle.

The term "hydronic heat pump" always refers to a heat pump that delivers heat to a flowing stream of water.

The heating capacity of the heat pump drops rapidly with increasing source water temperature.

It is not advisable to maintain water flow through the condenser whenever the heat pump is operating.

The decision to use a wood-fueled boiler involves a time commitment much more demanding than for conventional heat sources operating on natural gas, propane, fuel oil, or electricity.

Most cast-iron sectional boilers are limited to use in __________ hydronic systems.

The combination of metal and water weight gives cast-iron boilers the ability to absorb a significant amount of heat. Such boilers are said to have a high __________.

One type of boiler design surrounds the combustion chamber with a water-filled heat exchanger. This arrangement is called a __________ boiler.

Analysis of combustion processes reveals that significant amounts of heat can be recaptured from the exhaust stream if the water vapor it contains can be _________.

Boilers with low thermal mass tend to have __________ cycle efficiencies due to lesser amounts of heat remaining in the boiler following burner shutdown.

A boiler operates at __________ efficiency only when it is being fired continuously under nonvarying conditions.

A __________ is a device for converting low-temperature heat into higher temperature heat.

A flow restriction or stoppage in the __________ can lead to rapid formation of ice crystals on the cold heat exchanger surfaces separating the water and refrigerant.

In solar anti-freeze based combisystems, the outside heat dump provides a way for the system to shed excess heat. It is activated if the temperature of the thermal storage tank reaches a _________ upper limit.

It is vital that the solar collectors and all exposed piping in a drain-back system be pitched a minimum of __________ toward the storage tank to allow complete drainage.