Select High-Efficiency
Heating & Cooling Equipment to Reduce Energy Consumption
& Demand
While Title
24 has mandatory requirements for HVAC equipment efficiency,
including furnaces, boilers, air-conditioners, heat pumps and
chillers, these can easily be bettered with thoughtful selections.
- For packaged
air conditioners and heat pumps, specify equipment complying
with the Consortium for Energy Efficiency’s minimum efficiency
standards (reprinted in Appendix D).
- For boilers,
specify Energy Star compliant equipment, which requires 85%
Annual Fuel Utilization Efficiency (AFUE) or better.
- For furnaces,
specify Energy Star compliant equipment, which requires 90%
AFUE or better.
- For all
other equipment, perform a life-cycle cost analysis as a basis
for specifications.
Life-cycle
cost analyzes consider capital, operating and maintenance costs
over the life- time of the building. The National Institute
of Standards and Technology provides a free computer program,
“Building Life-Cycle Cost” (or “BLCC”),
that helps with these analyzes, and a guide for estimating energy
costs and discount rates, “Energy Price Indices and Discount
Factors for Life-Cycle Cost Analysis”.
Air Conditioners
and Heat Pumps
High-efficiency
air conditioners and heat pumps are now widely available. Better
packaged air conditioners have cooling Seasonal Energy Efficiency
Ratios (SEERs) ranging from 12 to 15 (Energy Efficiency Ratios
[EER] of 10.6 to 11.7). Air-cooled heat pumps have SEERs ranging
from 11 to 12 (EERs of 7.8 to 12) and Heating Season Performance
Factors (HSPF) of 6.8 to 7 (Coefficient of Performance [COP]
of 3.2 to 3.5). Better water-source heat pumps have EERs of
12 to 15.8 and COPs of 4.1 to 5.3.
Ground-source
heat pumps have much higher efficiencies, with EERs ranging
from 15.8 to 22 and COPs of 3.3 to 4.1. Life-cycle costs are
typically lower than for conventional equipment, but capital
costs are high, since the wells or trenches required for the
heat sink have a large cost premium. Reducing heat sink costs
is the focus of many installations; new approaches include high-conductivity
well grouts, “slinky” coil piping, and incorporating
piping into poured foundation pilings. If trenches will be dug
for other reasons, it is often very cost-effective to also use
them for heat-sink piping.
Southern
California Edison provides financial assistance for the purchase
of high-efficiency heat pumps that replace electric resistance
heaters and air conditioners in all-electric residential renovations.
Water
Chillers
Chillers
rarely operate at full-load conditions, so manufacturers’
part-load performance data is important in their selection.
Building simulation programs such as DOE 2 make the calculation
of energy consumption considering part-load operation relatively
simple; bin method analyzes can also be used.
Centrifugal
chillers with 150 to 1500 tons of cooling capacity are now available
with full-load efficiencies ranging from 0.50 to 0.66 kW/ton
(EERs up to 9.8). Reciprocating chillers have full-load efficiencies
that range from 0.78 to 0.85 kW/ton (EERs up to 14.3 and Integrated
Part Load Values to 17.4). Screw chillers range from 0.62 to
0.75 kW/ton (EERs to 9.8).
Cost premiums
for energy-efficient chillers are typically about 6% —
quickly paid back with reduced energy costs.
CFC- and
HCFC-free chillers are now widely available. In retrofits, manufacturers
should be consulted to examine retrofit versus replacement costs.
Often replacement is less expensive even on a first-cost basis.
Boilers
and Furnaces
Even in
Santa Monica, high furnace and boiler efficiency are as critical
as cooling equipment efficiency. Forced- or induced-draft boilers
and furnaces with intermittent ignitions tend to have 80% to
86% AFUE. Condensing units that recover combustion gas heat
typically have AFUEs of 88% to 97%, but larger sizes often required
for commercial applications are available only from a few manufacturers.
When comparing
efficiencies of larger gas boilers (greater than 300,000 Btu/hr.
capacity), ratings should comply with ANSI Standard Z21.13-91
for a true comparison. 
