I have made an outdoor heated shelter for my cat. It works great but would work better with heat control. On below 20C, off above. No adjustability required. +/- 2C acceptable. Reliability critical as death may result from malfunction.

I have circuit board soldering experience and some electronics training and experience but I am lost at how to make this happen.

The heater itself is a 240 volt, 100 watt light bulb running on 120 V (~40 W). It is embedded in the base and relies on convection air currents to deliver the heat to the cabin which is then ventilated through a small hole at the top. The structure is made from 4" foam (R-20). There is nothing like it on the market, that's why I built it.

Pictures available by email, you are then welcome to post them on this forum. I was unsuccessful in my attempts.

Thanking you in advance,
Tom
Victoria BC Canada

 

Any possibility of using 120VAC? Some voltage drop on a long wire run won't bother the light bulb.

Line voltage thermostats (available at building supply places like Home Depot or Lowes in the US) do exactly what you are asking for but the ones I'm familiar with switch only one line (the black hot wire in 120Vac residential US wiring), and I suspect that your 230V supply needs both lines switched on or off.

There are low voltage thermostats that can switch a 230Vac relay, though.

 

google a device called "thermocube"

 

Go to any hardware store and ask for a baseboard heater thermostat or line voltage thermostat. These are fairly cheap (the baseboard units) mount on a standard electrical box and should do the trick. Some of the line voltage thermostats even have a remote sensing bulb that you can put in the enclosure and keep the wiring outside. The baseboard units would have to be mounted inside as they sense temp at the thermostat. They are reliable and should work for decades with a tungsten load. Google line voltage thermostat for examples. Crude, but effective.

Regards
cww

 

I made a similar shelter for my cat. For heat I used a heating pad here:

http://www.amazon.com/Outdoor-Heate...WJRE/ref=sr_1_1?ie=UTF8&qid=1291151411&sr=8-1

and a thermostatically controlled outlet here:
http://www.amazon.com/WIN100-Heating-Cooling-Programmable-Thermostat/dp/B000E7NYY8/ref=pd_sim_ol_27

This solution has worked great for me for over a year now, and the cat is quite happy!

 

> There are low voltage thermostats that can switch a 230Vac relay, though. <

Let me re-state that:

There are low voltage thermostats that can switch a low voltage relay (coil) whose contacts can handle the load at 230Vac.

 

From the original post....I got that Tom was indeed using 120vAC to power the 240 volt bulb. This would certainly give an extended life to the heating source.

As for baseboard thermostats, my experience would place them in a range way above that which Tom is looking for. I would guess that as soon as you go past the off position, anywhere below +5C would turn it on. He is looking for something with a range down to -20C.....He wants to cultivate a cat with a good fur coat!

Household variety thermostats generally do not go that low.

Cheers all
Gerald Beaudoin

 

"He is looking for something with a range down to -20C.....He wants to cultivate a cat with a good fur coat!


Looked to me like he said +20C (68F)

 

>Looked to me like he said +20C (68F)

Geeze...you're right....I live in Quebec so the minus temperatures and the impending winter comes to mind first! I'd say his cat is living in the lap of luxury at +20C.

 

Then you expand the search to Granger etal. they have line voltage thermostats for freezers. Or you can recalibrate the cheap items. They generally have a screw for that purpose and the principle is the same. I've set one to work around 0 F for heat tapes. Throw it in the freezer set to mid range and back the screw off until it opens.

Regards
cww

 

Thank you ccw, you hit the nail on the head.

I was hoping to get something smaller, but this will certainly do.
It even worked on a 10 watt load!

-Tom

 

I spoke with Honeywell today to inquire if they might have something smaller available.

No.

Thanks again everyone.

-Tom

 

I had no clue that there was sufficient adjustment range to do that. Thanks for mentioning it.

 

It would be hard to say for sure that any one tstat does. I've seen several different designs. The crudest ones with a short bimetal strip are the most adjustable as there is less bend over the range so a given adjustment will cover more range. These also have the widest differential as a clue. But what can't be done with the screw can typically be done with a little bending of the non-bimetal part. Indeed that is how some of these are "calibrated".

Regards
cww

 

Okay, further to my search, I am now trying to get a smaller unit (line voltage controlled) and preferably one that doesn't "click".

Again, the parameters: "on" below 68F, "off" above, +/- 5 degrees, load may vary from 10 - 100 watts at 120 volts.

Thanks again for your assistance,

-Tom

 

Finding electronic versions is easy. The size is a problem. As these are used with regular wiring devices, they are sized to fit outlet boxes. You might try Omega and the lab supply houses. They might have something, but it will probably be pretty spendy. Actually, it's likely that anything using line voltage will need to have connections in boxes by most local codes anyway.

Regards
cww