- Author
-
Liu, S. T.
|
Kelly, G. E.
- Title
- Predicting the Energy Performance Ratings of a Family of Type I Combination Appliances.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Sponsor
- Department of Energy, Washington, DC
- Report
-
NISTIR 5250,
August 1993,
27 p.
- Distribution
- Available from National Technical Information Service
- Keywords
-
Annual Fuel Utilization Efficiency
|
ANSI/ASHRAE standard 103
|
ASHRAE standard 124-1991
|
boilers
|
building technology
|
combination appliance
|
combined annual efficiency
|
DOE water heater test procedure
|
energy factor
|
linear interpolation
|
rating
|
space heating
|
tankless coil
|
water heating
- Abstract
- ANSI/ASHRAE Standard 124-1991 specifies the laboratory tests and the calculation procedure for estimating seasonal and annual performance of combination appliances which are designed to provide both space heating and water heating. A boiler that includes a tankless coil for water heating is covered by those sections in ASHRAE Standard 124 that pertain to Type I combination appliances. In an effort to minimize the test burdens on manufacturers, a computer simulation study was conducted to determine if a subset of a family series of Type I combination appliances could be tested and used to predict the performance of the rest of the appliances in the family. Computer simulation was conducted on a family of five different size boilers with an identical tankless coil to calculate their Combined Annual Efficiency (CAE) as specified in ASHRAE Standard 124. To this end, the Energy Factor (EF) for water heating and the Annual Fuel Utilization Efficiency (AFUE) for space heating were calculated. For the water heating test that was simulated, daily hot water draw volumes of 243.4 liters (64.3 gal.) and 454.2 liters (120 gal.) were used. The results showed that for the five boilers, the AFUE for space heating differed by less than 1 percent. On the other hand, the EF for water heating depended strongly on the size of the boilers for the same daily hot water drawn and on the volume of daily water drawn for a given size boiler. However, for the same daily hot water drawn volume, the EF was an approximate linear function of the boiler size. The results also showed that the CAE varied by slightly over 1 percentage point among the five boilers when the same daily water drawn volume was used and by less than 0.8 percentage points for the same boiler when the two different hot water draw volume were used. Thus a single linear interpolation based on either water drawn volume appears adequate for determining the Combined Annual Efficiency CAE.