Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site oberon.UUCP Path: utzoo!watmath!clyde!burl!ulysses!gamma!epsilon!zeta!sabre!petrus!bellcore!decvax!ittatc!dcdwest!sdcsvax!sdcrdcf!oberon!blarson From: blarson@oberon.UUCP (Bob Larson) Newsgroups: net.consumers Subject: Re: Heat pump/water heater energy conservation Message-ID: <169@oberon.UUCP> Date: Sun, 15-Dec-85 15:53:56 EST Article-I.D.: oberon.169 Posted: Sun Dec 15 15:53:56 1985 Date-Received: Wed, 18-Dec-85 04:47:05 EST References: <237@neurad.UUCP> Reply-To: blarson@oberon.UUCP (Bob Larson) Organization: U. of So. Calif., Los Angeles Lines: 79 In article <237@neurad.UUCP> donn@neurad.UUCP (Donn S. Fishbein) writes: >Is it more economical to set back the >temperature at night, and during the day when no one is home, or to leave >the temperature adjustment alone? Is there something unique to heat pump >technology in this regard? (I am assuming the heating case, most things also apply to cooling with oposite temperature directions.) In many cases it is more economical to set the temperature down at night, but not all. Heat pumps heat most eficently when it is warm outside. However, when there is a large temperature change to be made, or the heat pump alone cannot handle the heating, electrical heating elements will also be used. (Lower efeicency.) Avoid a large setback at night or else raise the temperature gradually. Since the heat pump heats most efiecently durring the day, a day setback may not be a good idea. (It probably isn't a good idea to set the thermostat up at night when cooling.) Changing thermostat settings should not be done often. Compressors in heat pumps and air conditioners cannot restart immediatly after shutting off. (5 minutes is ususally recomended.) Better systems have special timers to protect users from this mistake, cheaper ones tend to use circut breakers for this, (often auto reset type) but occasionaly the circut breaker won't act fast enogh to save the compressor. >I have noticed that nearly all of the automatic thermostats available >specifically say "NOT FOR HEAT PUMPS". I recomend following such advice unless you realy know what you are getting into. The warentee won't cover specificly prohibited use, and it is possible to damage the heat pump. >the major problem seems to be that the heat pump >contains two thermostatic switches; one for the heat pump compressor, and one >for the aux. heating coils. Some contain more than this. Changeover (heat to cool) and several stages of additonal heating are sometimes used. >The heating coils are activated if one changes >the temperature set point abruptly eg. from 55 F to 68 F. Does this occur >simply to decrease the time it takes to achieve the new temperature, >or is the heat pump incapable alone of affecting the change? Mostly to decrease the time. >Is it more economical to allow the heat pump to operate alone? In most cases, yes. Heat pumps are most eficent at higher outdoor temperatures. Below a certain outdoor temperature, the auxilery heaters are more efficent. (Usually in the 0-20 F range, depending on many factors. (humidity, heat pump design, air circulation around heat pump, etc.) >Is there a solution to this problem of automatic thermostats being unable to >control an essentially two-stage system? There are automatic thermostats for heat pumps. It's mostly a matter of the mass produced thermostats only fit the most common case. (After all, it might cost a couple of dollers more to put in the extra parts to handle a heat pump.) Improving the air circulation around the outdoor side of a heat pump or air conditioner is an often overlooked way to improve their efficency. Placement also makes a big difference, a warm in winter cool in summer location is prefered. >Finally, with regards to the hot water heater, is it advisable to install a >timer so that it only runs when people are likely to be home. >In other words, is the energy needed to reheat the water more or less >than that required to maintain the water temperature for a prolonged period of >no hot water use. My hot water usage is quite modest, yet I think this >appliance is quite an energy hog. It depends on the length of your "prolonged period". For less than a day at a time, it probably isn't worth the bother. -- Bob Larson Arpa: Blarson@Usc-Ecl.Arpa Uucp: ihnp4!sdcrdcf!oberon!blarson __________________________________ Unix: An operating system similar to Os-9, but with less functionality and special features designed to soak up excess memory, disk space and CPU time on large, expencive computers. -- Os-9/68000 operating system users manual