LIMITATIONS FOR HOMES

LIMITATIONS FOR HOMES WITH HEAT PUMPS, ELECTRIC RESISTANCE HEATING, STEAM HEAT, AND RADIANT FLOOR HEATING

Programmable thermostats are generally not recommended for heat pumps. In its cooling mode, a heat pump operates like an air conditioner, so turning up the thermostat (either manually or with a programmable thermostat) will save energy and money. But when a heat pump is in its heating mode, setting back its thermostat can cause the unit to operate inefficiently, thereby canceling out any savings achieved by lowering the temperature setting. Maintaining a moderate setting is the most cost-effective practice. Recently, however, some companies have begun selling specially designed programmable thermostats for heat pumps, which make setting back the thermostat cost-effective. These thermostats typically use special algorithms to minimize the use of backup electric resistance heat systems.

In the summer

In the summer, you can follow the same strategy with central air conditioning by keeping your house warmer than normal when you are away, and lowering the thermostat setting to 78°F (26°C) only when you are at home and need cooling. Although thermostats can be adjusted manually, programmable thermostats will avoid any discomfort by returning temperatures to normal before you wake or return home.

A common misconception associated with thermostats is that a furnace works harder than normal to warm the space back to a comfortable temperature after the thermostat has been set back, resulting in little or no savings. In fact, as soon as your house drops below its normal temperature, it will lose energy to the surrounding environment more slowly. The lower the interior temperature, the slower the heat loss. So the longer your house remains at the lower temperature, the more energy you save, because your house has lost less energy than it would have at the higher temperature. The same concept applies to raising your thermostat setting in the summer

Zone control

Zone control works best in homes designed to operate in different heating zones, with each zone insulated from the others. In homes not designed for zone control, leaving one section at a lower temperature could cause comfort problems in adjacent rooms because they will lose heat to the cooler parts of the home. Zone control will also work best when the cooler sections of the home can be isolated from the others by closing doors. In some cases, new doors may be needed to isolate one area from another. Cooler parts of the home should be kept around 50°F to prevent water pipes from freezing. Never shut off heat entirely in an unused part of your home

GENERAL THERMOSTAT OPERATION

You can save money on your heating and cooling bills by simply resetting your thermostat when you are asleep or away from home. You can do this automatically without sacrificing comfort by installing an automatic setback or programmable thermostat.

Using a programmable thermostat, you can adjust the times you turn on the heating or air-conditioning according to a pre-set schedule. Programmable thermostats can store and repeat multiple daily settings (six or more temperature settings a day) that you can manually override without affecting the rest of the daily or weekly program.

GENERAL THERMOSTAT OPERATION

You can easily save energy in the winter by setting the thermostat to 68°F while you're awake and setting it lower while you're asleep or away from home. By turning your thermostat back 10° to 15° for 8 hours, you can save 5% to 15% a year on your heating bill -- a savings of as much as 1% for each degree if the setback period is eight hours long. The percentage of savings from setback is greater for buildings in milder climates than for those in more severe climates.

HOT WATER RADIATORS

HOT WATER RADIATORS

Hot-water radiators are one of the most common heat distribution systems in newer homes, second only to forced-air systems. They are typically a baseboard-type radiator or an upright design that resembles steam radiators. The most common problem in hot-water systems is unwanted air in the system. At the start of each heating season, while the system is running, go from radiator to radiator and open each bleed valve slightly, then close it when water starts to escape through the valve. For multi-level homes, start at the top floor and work your way down.

One way to save energy in hot-water systems is to retrofit them to provide separate zone control for different areas of large homes. Zone control is most effective when large areas of the home are not used often or are used on a different schedule than other parts of the home

In two-pipe systems,

In two-pipe systems, older steam traps often stick in either the open or closed position, throwing off the balance in the system. If you seem to have problems with some radiators providing too much heat and others providing too little, this might be the cause. The best approach is often to simply replace all the steam traps in the system.

Steam radiators located on exterior walls can cause heat loss by radiating heat through the wall to the outdoors. To prevent such heat loss, you can install heat reflectors behind these radiators. You can make your own reflector from foil-covered cardboard, available from many building supply stores, or by mounting foil onto a foam board or other similar insulating surface. The foil should face away from the wall, and the reflector should be the same size or slightly larger than the radiator. Periodically clean the reflectors to maintain maximum heat reflection.

Regular maintenance

Regular maintenance for steam radiators depends on whether the radiator is a one-pipe system (the pipe that supplies steam also returns condensate) or a two-pipe system (a separate pipe returns condensate). One-pipe systems use automatic air vents on each radiator, which bleed air as steam fills the system and then shut automatically when steam reaches the vent. A clogged air vent will keep a steam radiator from heating up. An air vent stuck open allows steam to continually escape to the living space, raising relative humidity and wasting fuel. Air vents can sometimes be cleaned by boiling them in a water and vinegar solution, but usually need to be replaced.

Steam radiators can also warp the floor they are sitting on and their thermal expansion and contraction over time can dig ruts into the floor. Both of these effects can cause the radiator to tilt, preventing water from properly draining from the radiator when it cools. This will cause banging noises when the radiator is heating up. Shims should be inserted under radiators to pitch them slightly toward the pipe in a one-pipe system or toward the steam trap in a two-pipe system.

STEAM RADIATORS

STEAM RADIATORS

Steam heating is one of the oldest heating technologies, but the process of boiling and condensing water is inherently less efficient than more modern systems, plus it typically suffers from significant lag times between the boiler turning on and the heat arriving in the radiators. As a result, steam systems make it difficult to implement control strategies such as a night setback system.

The first central heating systems for buildings used steam distribution because steam moves itself through piping without the use of pumps. Non-insulated steam pipes often deliver unwanted heat to unfinished areas, making fiberglass pipe insulation -- which can withstand high temperatures—very cost-effective.

MAINTAINING AND UPGRADING EXISTING DUCT SYSTEMS

MAINTAINING AND UPGRADING EXISTING DUCT SYSTEMS

Aside from sealing your ducts, the simplest and most effective means of maintaining your air distribution system is to assure that furniture and other objects are not blocking the airflow through your registers, and to vacuum the registers to remove any dust buildup.

Existing duct systems often suffer from design deficiencies in the return air system, and modifications by the homeowner (or just a tendency to keep doors closed) may contribute to these problems. Any rooms with a lack of sufficient return airflow may benefit from relatively simple upgrades, such as the installation of new return-air grilles, undercutting doors for return air, or installing a jumper duct.

At a colder outdoor

Karlsson [8]. At a colder outdoor temperature, the supply temperature should peak; this makes the test scheme tables in EN 14511 deficient. Also other heat distribution systems, such as under floor heating, and mixed systems should be included in the model.
 Part load performance of the heat pump must be properly taken into account, and be based on relevant testing standards.
Night set back is a choice in some calculation models; this is not relevant for heat pumps and should not be a part in a new calculation model.
 Back up heaters is sometimes necessary to complete the energy demand of the house. Back up heaters should be included in the calculation model. Supplementary heating should be possible to choose between different sources of supplementary heat, e.g. electricity, solar or biomass heating.

The possibility

The possibility to include the production of domestic hot water to the SPF calculations is also a necessity in future calculation models. It should also be described how this shall be measured in tests alternatively, how the amount of produced domestic hot water shall be estimated. Today there are two main ways how to do the measurements, including the losses or not (one can measure the amount of energy that is obtained by tappings or the amount of tap water the heat pump is producing). A lot of work has already been done in this respect in the IEA HPP Annex 28 [13]. Also, there is a CEN standard on the way on how to treat DHW production. This standard however does not take into consideration combined heating and DHW production.
 Accumulators should be possible to include in the model.  
 A model must contain clear system boundaries for what is to be included in the calculations and how measurements are performed. As a basis, the system boundaries presented in the SEPEMO project [12] is recommended.
 The model must be transparent so it is possible to follow and understand the calculations. The studied models all contain parts that are more or less transparent. For example how the estimation of the number of equivalent heating hours is performed is not shown in any method

An outcome of the results

An outcome of the results should be to see that a properly sized heat pump is the best alternative to install. An oversized heat pump will result in unnecessary on/off cycling losses and an undersized heat pump will result in unnecessary high back-up heating.
For the calculation, either BIN methods or hour by hour calculations could be used. The existing calculation models based on heat pump performance testing according to standards are all using BIN models. Therefore, to keep a clear connection to existing test standards, it is the easiest to base a new model on BIN models. A hybrid model using chronological BIN’s could also be an interesting option to look into.
The drawback with this approach might be that dynamic effects, especially in cases with large or well stratified accumulators are not treated in a way that the full potential of these units are revealed. In the proposed IEA Annex, a thorough investigation of the positive and negative effects of these approaches should be performed

Conclusions

Conclusions
For a new calculation method to better represent real SPF values there is a need to rely on consistent sets of performance data acquired from lab testing. These lab testings guarantee consistency, repeatability and reliability.  
If the objective is to give better values for individual houses, more details on the building envelope, climate data etc. must be provided for the specific setup.  
If the objective is to give reliable values for typical conditions, type houses in type climates should be used, but with better details than currently used in existing model