[Greenbuilding] Triac Thermostats

Corwyn corwyn at midcoast.com
Mon Dec 19 17:13:43 PST 2011


On 12/19/2011 5:32 PM, John Straube wrote:
> You cant use a normal on-off thermostat with a modulating control.
> The simplest thermostat for use with an SCR or TRIAC would have what is
> called proportional control.
> For example, if the temperature fell below 68F by 0.1 F, 100W would be
> delivered to the heater, of the temperature dropped to 67.8F, 200W would
> be provided and if it dropped to 67F, 1000W would be delivered.
> Because a smaller amount of heat is added with small temperature drops,
> the temperature does not oscilate as much as an on-off control with a 3F
> deadband as described in the example.

But, it isn't, in fact, delivering 100W to the heater.  It is delivering 
1000W to the heater for 1 second out of 10.  Or perhaps 0.1 seconds out 
of 1 second.  I guess that is the point I am trying to make.

Since I have trouble believing that anyone *needs* within 0.1F stability 
in their house temperature; a thermostat upgrade will get most of the 
accuracy improvement anyway; and since no one has shown energy savings, 
I would recommend these only if the lifecycle benefits make them cheaper.


Thank You Kindly,

Corwyn

-- 
Topher Belknap
Green Fret Consulting
Kermit didn't know the half of it...
http://www.greenfret.com/
topher at greenfret.com
(207) 882-7652



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