Axel Berger  wrote:
> "Michael J. Mahon" wrote:
>> My solution was to install a simple timer switch in the thermostat
>> circuit that switched on about 4pm and off about midnight.
>
> Sounds reasonable. The point I'm thinking about is sensitivity. The
> current thermostats are in closed plastic cases, that's how the internal
> feedback through a heating resistor works. It means they're shielded
> from rapid changes. If I have a sensor with small thermal mass it will
> see a large drop every time someone passes throught the door. So a low
> pass is the absolute minimum.
>
>> it is important to anticipate a future need
>
> Not necessarily. With the afternoon sun coming in it tends to get warmer
> than the set point. When it cools down, it does so very slowly. After
> switching on the floor becomes very comfy in much less than an hour.
> Turning off again in time is the more important bit as you have found.
> That's the part the internal feedback in those cheapo units supplies.
>

Your floor responds much faster than mine did.

Our slab was heated by embedded copper tubing with circulating hot water.
Although one could notice a slight increase in temperature after the heater
and pump were on about an hour, it took about three hours before
significant heating. Similarly, the slab stayed warm several hours after
the heat was turned off--it was still very comfortable to the feet at 8am
after being shut off at midnight!

The vented, metal thermostat had no anticipator heater, since providing a
time constant comparable to the slab would have been impractical.

--
-michael - NadaNet 3.1 and AppleCrate II:  http://michaeljmahon.com

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