Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!linus!decvax!harpo!seismo!hao!hplabs!sri-unix!STEINBERG@RUTGERS.ARPA From: STEINBERG@RUTGERS.ARPA Newsgroups: net.physics Subject: Re: Why don't thermostats work? Message-ID: <16544@sri-arpa.UUCP> Date: Wed, 8-Feb-84 13:19:24 EST Article-I.D.: sri-arpa.16544 Posted: Wed Feb 8 13:19:24 1984 Date-Received: Sat, 11-Feb-84 05:49:35 EST Lines: 18 From: Lou> Richard M King: > Assuming that the difference between the indoor and outdoor >temperatures is large compared to the width of the hysteresis band, we >observe that the temperature will fall at a constand rate within that band >when the furnace is off, following which it will rise at a constant rate >when the furnace is on. Yes BUT: The rates of rise and fall depend on the outside temperature. When it is colder, the house cools faster and warms slower. Thus when it is colder outside the average temperature is indeed lower. Also, since there is some delay between the time the thermostat turns on and the time the heat effectively reaches the room (due, e.g., to the heat capacity of radiators), the bottom of the hysteresis band will be lower when it's colder. However, these effects may be less significant than the other effects that have been mentioned, such as radiation and evaporation. -------