attic fan thermostat recommendation

[Vintage Veloce]

My garage attic fan is about 5 years old. It runs lots of days here in San Diego.
Recently, it seems that the "hysteresis" has become too large.
In non-geek: I mean it goes on at 100°F and goes off at 80°F, a 20° difference. Way too big, it used to be around 5°!
Ideally, I'd like an accurate digital control thermostat for the fan that allowed me to set both the high and low temperature and could handle around 10A.
Also, it would be great. but not required, if it was z-wave or some other protocol that I could control from my hubitat.
Any recommendations / ideas?

The old thermostat:

 

[gagecalman]

This is what I use on my attic fan.

RANCO ETC-111000 Digital Cold Temperature Control New: Tools Products: Amazon.com: Industrial & Scientific

RANCO ETC-111000 Digital Cold Temperature Control New: Tools Products: Amazon.com: Industrial & Scientific

www.amazon.com

 

[tool_scrounge]

Digital controls are nice if you want to program the thermostat hysteresis. For attic fans, the passive bi-metalic switch type work fine for me. If you are in fire country, some folks wiring a firestat switch in series to shut off the attic fan if the temperature goes over a very high threshold. If the neighborhood is on fire you do not want to be sucking embers into your attic. You can find them on Amazon & Ebay.

 

[Vintage Veloce]

I bought this thing... I'm testing it on the bench now and it works fine there. I'll try and put it in the attic later this week.

 

[Vintage Veloce]

New thermostat and fan installed. I figured I'd replace the fan while I was doing the project (trying to fend off murphy's law).
I left the fan's built-in mechanical thermostat in place and just set it at it's minimum.
I also put a screen on the fan to protect against wasp entry and accidental injury. I just used some silicone caulk to stick the screen on.
I'm a little concerned about the durability of the thermostat, especially operating in the hot environment. It will be interesting to see how it lasts.
Currently showing 84.5 degrees in the attic. The fan is set to turn on at 85 degrees F and off at 80. It is running in the picture because the temp had hit 85 a few moments before I took the picture. (I tested it by holding the probe in my hand to heat it above 85.)

 

[LS6 Tommy]

What's wrong with just using the OEM stat? Been using them for decades with no issues to date. Motors go bad before the stats do.

Tommy

 

[Vintage Veloce]

What's wrong with just using the OEM stat? Been using them for decades with no issues to date. Motors go bad before the stats do.

Tommy

Read the top post, the OEM stat went bad.

 

[LS6 Tommy]

Read the top post, the OEM stat went bad.

Weird, when I opened the thread it started with post #5, where he says he left it in place, set at the lowest setting. I didn't notice until I read your reply...

Tommy

 

[CraigStu]

Is there any concern that the on and off temps being so close means there will be a lot of on and off cycles of both the T-stat and the fan? Lots of things from car engines to light bulbs wear more via start/stop than via longer run times.

 

[Vintage Veloce]

Is there any concern that the on and off temps being so close means there will be a lot of on and off cycles of both the T-stat and the fan? Lots of things from car engines to light bulbs wear more via start/stop than via longer run times.

So that hasn't been a problem. Typically the fan goes on in Late morning as the temperature is increasing and stays on till evening when it falls.
But it could be a problem when it isn't so warm... we will see. If it is I'll make the hysteresis wider.

 

[K'ledgeBldr]

You have radiant barrier sheeting/decking- how hot could it get?

 

[Vintage Veloce]

You have radiant barrier sheeting/decking- how hot could it get?

My thermometer only reads to 120... so hotter than that.

 

[Jeepster04]

Its always confused me that we build homes that have a 120F+ hot box above them... Then try to insulate and keep the inside of the house cool...

 

[Vintage Veloce]

Its always confused me that we build homes that have a 120F+ hot box above them... Then try to insulate and keep the inside of the house cool...

Much modern construction now considers the attic a conditioned space. Especially with the ductwork and blower up there, there seems to be an advantage for many buildings to insulate the actual roof and then air condition the attic as well as the house underneath.

In my case, I use the attic for storage, my goal for the fan is for hot days: to keep it close to the temperature of the outside. Otherwise it gets really hot up there could potentially damage stuff over long storage.