[time-nuts] Temp/Humidity control systems?

jimlux jimlux at earthlink.net
Thu Oct 27 10:51:37 EDT 2016

On 10/27/16 7:37 AM, Bob Camp wrote:
> Hi
> Ok, take this with a bit of caution ….
> Your “time cave” does not have a specific spec on temperature or on humidity.
> You get to pick a number for either one. Anything in the “non condensing” (let’s
> call it < 80%) range for humidity is likely ok. Temperature up to 40C is probably
> ok for any gear that I can think of. As long as you *never* go in and out of the
> cave, comfort in the cave is a non-issue.

This is an interesting point.. basically you'd turn your DOCXOs into a 
TOCXO where the third oven is your time cave.. you make the set point 
*above* the surroundings, so all you need to do to hold temperature is 
to add heat - which is much, much more controllable in a gradual way 
than removing heat.

The "two radiators and a pump" approach is appealing - you could set it 
up so that the pump is variable speed. That said, there's a fair amount 
of "custom fabrication" involved: you have to find some suitable 
radiators, make the appropriate fittings and connections to your pump 
and hoses, and arrange for fans to blow through them.  You might be able 
to find something off the shelf - Grainger and McMaster are full of 
interesting things - and things to cool hot water using air blowing 
through the coils are probably a fairly off the shelf item.

And, would using a liquid thermal transfer path be any different than a 
variable speed air vent between inside and outside?

What I'm looking for right now is a suitable controller that will run an 
exhaust fan that fits in a 12x12" (approx) opening when the outside 
temperature is "closer" to my target set point than the inside temp:

In Southern California, the outside air temp moves quite a bit during 
the day and rapidly at the day/night transition, so when the garage is 
hot, and outside is cooler, I'd like to exchange air.  Likewise, if the 
garage is cold (cooled down overnight) and outside is warmer, I'd like 
to exchange air to warm it up.

The standard "differential thermostat" seems to only do one of the 
directions (turn on/off load when T1 -T2 > setpoint and T1 > setpoint), 
and I suppose I could "wire or" two of these,  but it seems there should 
be a 'More clever" off the shelf solution.

(and frankly, if someone made something that opened/closed my windows, 
I'd love that too, for the same reason.. I can cold bias the house in 
the morning, leave the AC off all day with the windows closed, and then 
automatically open the windows in the afternoon/evening when the outside 
temperature drops below the inside temperature setpoint)  In combination 
with Time-of-Use electricity rates (something you should consider in 
temperature regulation of your time cave - "store cold at night"), one 
can cheaply pre-cool the house in "super off peak" time.

(Yes, I could program an Arduino to do this, but then I have to cobble 
up a AC relay, a DC power supply, etc., etc....)

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