Project for a Friend

[MasterBlaster]

A friend wants me to control a fan for him, such that it runs when the temperature in the room is greater than x, but only if the outside air temperature is less than y.

Obviously easy with two stats, but I'm wondering if any of you know of an inexpensive, 120vac controller with two temperature sensors and one dry contact output that will do this.

Thanks in advance!

 

[Flopro]

On the cheap...

Just wire two inexpensive mechanical relay thermostats in series - outside thermostat opens the circuit if temp above X; inside thermostat closes when temp above X...

 

[MasterBlaster]

Flopro - That is my present plan, was just wondering if there is a slightly more 'elegant' way without a massive, overkill processor. Thanks!

 

[Lancie1]

Flopro - That is my present plan, was just wondering if there is a slightly more 'elegant' way without a massive, overkill processor.

I don't think that two "line-voltage" type thermostats wired in series would be called massive overkill, nor would it use a processor.

However I once used such a thermostat that had the built in two-temperature function. I used it to control roof ventilation fans. I will see if I can find the vendor, or remember where I got it.

 

[MasterBlaster]

Lancie1 - I meant that the two 'stat method is my present plan, not that it is overkill. The overkill statement was with regard to some of the all-in-one processor/controllers I found in my search. THEY are ovrkill.

It sounds like the roof fan controller of which you skeak would be ideal.

Thanks!

 

[Ken Roach]

The four-wire, two-thermostat method for controlling vent fans is known in Northern California as the "4-2-0" controller.

And it's always "for a friend".

 

[Lancie1]

Sorry, I could not find the 120 volt temperature-ventilation controller that I remember. Maybe it is not made anymore.

 

[MasterBlaster]

Ken - This one really IS for a guy over in Napa. Wants to keep a wine room cool using outside air when possible.

Lancie - Thanks for looking. Guess I'll go for the less elegant two-'stat method. It was worht asking.

 

[Ken Roach]

I was, of course, yanking your chain in a collegial way.

It makes very good sense to limit the outdoor temperature when you're venting a wine cellar.

 

[MasterBlaster]

I knew you were, Ken. Thin skin is not one of my attributes. The wine guy actually wants three measurements, outside air greater than 32F. As I see it, that's not an issue. If the cool room gets above setpoint, run the fan even if the incoming air is very cold. The fan just won't run very long.